You can contact me through the contact form below. Or you can browse the questions that
other people have asked and read my answers below.
Hello I have at spa/hot tub which holds approx. 1000ltrs water just wondering if you think it viable to incorporate a heater to the system to keep water temperature at a set temperature . the system has a 1.5kw heater witch switches on and off automatically when temperature drops 1 degree . full system running consumes 2.5kw (pumps and lights etc. ). Rather than having a 1.5kw heater switching on and off when needed I thought a smaller heater running continuously from free power might be worth doing even if it only helps a little. Any help or suggestions would be most welcome. Thanks for your time, Steve.
Stephen Mellenthin, August 2, 2009
Solar power can definately help you here... but I would not recommend solar electricity: you would be better off investigating solar hot water systems.Photovoltaic panels (which generate electricity from sunlight) tend to be between 6% and 15% efficient whereas solar hot water systems can be up to 70% efficient and tend to be cheaper to buy as well - at least in DIY form, especially if you spend some time shopping around for the best prices.
A solar hot water system incorporating a thermal switch should go a long way towards reducing your energy consumption. Exactly how big your system would need to be would depend on a number of factors - specifically whether your spa is indoors or outdoors; what months of the year you want to use your spa; where abouts in the world you are based.
Meanwhile, you can reduce your current electrical consumption by using energy saving lighting - I recently saw a swimming pool lit by LEDs which looked stunning and are extremely energy efficient.
Dear Mr. Michael Boxwell
Many thanks for the good book, but i have one question, which is in page 15 and 16. You wrote that when connecting in series, we add the voltages of panel together and add the power( in watts)of each panel together you calculate the max. amount of power and voltage the solar will generate, and in page 15 you wrote that 4 panels, each on have 12V and power 20W and when connect in series it will be 48V, 80W array. I think in this case, we have to connect in parallel with another 4 panels with the same V and W to get 48V and 80W.
Best regard
Rasool Ali, August 4, 2009
Thanks for the comments about the book.With regards to your question, when you connect solar panels in series, both the voltage and the power increase, whilst the current remains the same. When you connect solar panels in parallel, the power and the current increase, whilst the voltage remains the same.
Let me explain another way, using the example of a 12v 12w solar panel (I'm using 12w because this equals 1 amp at 12v, which makes the maths easier).
If you take one 12v 12w panel, your solar panel provides 1 amp of current at 12 volts. If you take four 12v 12w panels and connect them in series, the power and the voltage is multiplied by four - so you have 48v at 48w, but your current remains the same - 1 amp.
If you then take four 12v 12w panels and connect them in parallel, the power and the current is multiplied by four - so you have 12v at 4 amps, but your voltage remains the same - 12v.
I hope this answers your question.
Is it possible to incorporate PV panels into a south facing conservatory roof?
Michael Churchman, September 2, 2009
Yes it is possible, but of course that will cut down on the amount of sunlight shining into your conservatory roof.It also depends on the amount of panels you plan to fit to your roof. A large panel weighs in the region of 18kg and so there may be weight limits if you wish to fit lots of panels.
To secure the panels to the conservatory roof, you would probably be best to bond them to the roof although it may be possible to have special mounts fabricated for the purpose.
Your best bet would be to choose which solar panels you want to work with, get the physical specifications of the panels (height, width, depth and weight) and speak to your conservatory supplier to see what they recommend.
Is there an inexpensive way I can heat my two 16-gallon water tubs for my horses using solar?
barb henderson, September 5, 2009
Yes there is, but I wouldn't recommend solar electric for heating water.Instead, I'd recommend a solar hot water system. Depending on what your exact requirements are will depend on the best solution, but if you want to keep to a budget I'd either recommend a simple swimming pool solar heater (typically available on eBay from around £100/$150) or build your own from plans freely available on the web (start at www.instructables.com).
Just wanted to say thanks for your website. I just used your Project Analysis report and it really is excellent. I just wanted a rough guide to see if a potential project was feasible and approximate costs and the report did just that, plus provided some extra tips. If we go ahead with a solar installation, I will definitely buy your book.
One comment, any chance of adding more countries to the Project Analysis? Our planned project will be in Spain, so I had to find the Latitude for our area and then find a place in the USA at the same latitude. Which also meant that the prices given in the report were in US dollars instead of pounds.
thanks again, Rob
ps I found your site through A1 Business Forum.
Rob, September 22, 2009
Dear RobThanks for your comments. the publishers are adding new countries to the project analysis tool at the moment: by Christmas we should be covering most of Europe as well as India, the Middle East and parts of Africa.
We will also be providing prices in a number of other currencies as well.
Best Regards
Michael
What do you think about feed-in tarrifs?
John Newman, September 26, 2009
Now there is a big question. How long have you got?I question what the Government hope to achieve with feed in tarrifs in terms of overall carbon reduction. I also feel that with the proposals as they stand, the 'early adopters' who have already installed solar stand to loose significantly, which is unjust.
However, from the model seen in countries like Germany and Spain, it is clear that a feed in tarrif this scheme will encourage the short term take up of solar for grid-tie applications. Whether that is the best application for solar depends on a number of factors, such as geographic location and how the local electricity is generated on the national grid.
Personally, I believe the plan is flawed and a better solution would have been to boost the renewable obligation certification scheme (ROC) by improving the funds available and reducing the paperwork and administration for solar home owners to go through.
This would also have been of much greater benefit for off-grid solar systems, which have a much greater potential to reduce carbon emissions over grid-tie systems.
Mr Boxwell,
I'm working on a school project for which I plan to design a solar photovoltaic system to power a small boat (this is one the projects that you talk about on Apendix E of your book). Do you have any additional information on this type of project? Any links, articles, etc would be helpful. I have found some internet sites that have some information on these type of projects but the info is very superficial and does not provide any tecnical details on the design.
Thanks.
Julio Hernandez
Julio Hernandez, October 2, 2009
My little boat is a small inflatable with an electric outboard motor. The motor is from a company called Minn Kota (other brands are Shakespeare and E-Thrust). I've had it for a number of years and have found it to be a very good little setup for inland waterways (lakes and rivers).The outboard is a 12v 100w motor. I have an 85 amp 12v leisure battery and charge it using a 20w solar array. This configuration allows me around eight hours of continuous use on a single battery charge, which is far more than I need. The 20w solar array is a bit too small - from a flat battery it would take almost two weeks to fully charge the batteries - but because I don't use the boat that often, this isn't a problem.
Because I only have an inflatable boat, the solar panels aren't actually mounted to the boat itself and I charge the batteries up when the boat is moored rather than all of the time.
All of the other solar boats that I have looked at in detail use a very similar setup to mine - outboard motor, large leisure battery and a small solar panel (plus solar charge controller and battery cut-off switch). You can also add a 12v battery charge gauge if you wish - you can find these easily online or at car accessory outlets.
The total cost of my setup (electric motor, battery, solar charge controller and solar panels) has been comparable to the cost of a petrol-powered outboard motor on its own. For that I have a virtually silent powered boat with no virtually no running costs.
I have no experience of converting a petrol outboard engine to electric power, nor do I have any experience of inboard electric boats. If you are specifically after information like that, I would recommend that you visit the Electric Boat Association web site at http://www.electric-boat-association.org.uk
Mr. Boxwell
Thank you for your prompt response to my previous question. Your answer was very helpful. As a follow up question, I was wondering how the motor speed is controlled? Does the motor you use have its own power electronics to control the speed?
Thanks.
Julio Hernandez
Julio Hernandez, October 2, 2009
With the electric outboard motor, there is a speed controller built into the outboard motor itself. If you were planning to build your own electric boat from raw components you would need to purchase your own motor controller, along with a potentiometer to work as a throttle and a three way switch to allow you to select forward, reverse or neutral.The best known make for motor controllers is Curtis Instruments (http://www.CurtisInst.com) and they can supply the motor controllers, the instruments and all the ancillary components you would require. You will require a different type of controller depending on whether you buy a brushed motor ('DC motor') or a brushless motor ('AC motor') - for cost and simplicity, you probably want to stick with a brushed motor design if this is your first electric vehicle.
If cost is an issue, the cheapest way to get the electrical equipment you need would be to buy a second hand electric scooter from eBay - that will give you everything you would need except a solar panel and charge controller: batteries, mains charger, controller, motor and ancillary components.
I am planning a grid tie system/small battery back up system, I have come across some Suntech 200w 18v panels, do you see any problems using 18v panels?
Thanks
Paul, October 19, 2009
No, there will not be any trouble using 18v solar panels. In order to charge a 12v battery, you need a higher voltage going into the battery in order to charge it up. 18v is fine, so long as you have a charge controller to stop the batteries from being overcharged.With regards to your charge controller, the most efficient controllers are MPPT (Maximum Power Point Tracker) controllers which will reduce the voltage coming from the panel going into the battery without reducing the wattage. Other controllers will reduce the voltage and truncate the wattage, which in effect means you are likely to loose around 25% efficiency from the panel.
HOw do you calculate the total irradiance foe total solar spectra? i need to know the basic calculations for energy exoposed to object
Prashant Gharal, October 20, 2009
You can find out all this information on the NASA web site. Start here: http://edmall.gsfc.nasa.gov/inv99Project.Site/Pages/science-briefs/ed-stickler/ed-irradiance.html
What is your advice regarding using a solar panel INSIDE a caravan while on a storage site.
Mrs Kelly Henderson, October 27, 2009
I do this with my caravan! It depends on what you want to achieve, but if you just want to keep the battery topped up (i.e. not recharging it from being flat) between uses, a solar panel will work reasonably well, so long as it is left in a south facing window and the panel is not completely shaded.I've got a 10w solar panel for this purpose (its around 30cm square) which cost me £35 on Amazon. It's small enough to prop up inside the window and big enough to provide a reasonable current - even during the winter months - to make it worthwhile having.
I would avoid the very small panels (1.5 - 3 watt panels) for this purpose however as they simply aren't big enough to do anything worthwhile.
If you want to do something a little more ambitious - like recharge the batteries from flat between uses - you would probably be better off fitting a larger solar panel to the roof of the caravan and installing a charge controller to ensure the batteries never get overcharged.
Hi Mike,
I just got your book today I bought last week through Amazon.com. Great piece of work and easy to read. I will probably ask more questions in the future. For now, could you please provide solar irradiance in Nigeria (all states) and Cameroon (all main cities? Why you did not cover many countries in Africa?
Great job,
Alain
Dr. Alain Nkoyock, November 2, 2009
Thank you for your comments. I am adding new countries all the time - around 10 countries a month. I will update the web site with the solar irradiance figures for Nigeria and Cameroon in the next week. My intention is to cover the whole of Africa, but this will take a little time to achieve!
Hi Michael -
I came across your website after hearing about your book on amazon.com. I intend to order a copy next payday!
I have been to other websites that claim you can construct your own solar panels from materials ready available at local hardware stores. Is this true? If yes, do you address it in the book?
Thanks.
Bob
Bob Jewell, November 6, 2009
Thanks for your message. I know the web sites you refer to - avoid them. Visit www.diysolar.com and then ask whether the risks associated with home made solar panels are worth taking.Professionally built solar panels are dropping rapidly in price at the moment. You aren't going to save any money by building your own.
You cannot build a solar panel at home to anywhere near the same quality of a professionally manufactured unit. At best your home made panel won't provide much power and will degrade rapidly. At worst it could end up being a fire hazard.
hi, michael I have a project that I could use your advice on, i have a 20x20 building
it does not have a hot water heater but it does have a small window unit and 2, 8foot for resident lights and it also has two plug-ins on each wall. my deep well pomp is a one horse motor.075kw that I would like to run also.
My question is, what type of inverter should I use? do they make inverter's four 220 outlets. In this building I have had the power company to cut my power off. I would like to run pv and also win power. This building is my office
so I would like enough power to operate this small build. my last KWH USAGE WAS 600
And also thank you for your book it is a good one, as you can tail I am just an amateur at this thank you and God bless.
larry, November 7, 2009
You can get 220v inverters without a problem - there are lots of different makes and models. I'd recommend a pure sine wave inverter and my personal recommendation for make would be 'Sunny Boy' - they're good quality, reliable units that won't let you down.You will need to work out your wattage use on a daily basis, as described in my 'Scoping the Project' chapter. This will give you a much better idea of what you will need. At a guess I would suggest that if you used 600kWh of electricity in your last quarter you are going to need to look at reducing this load first.
I am doing an assignmint at college on, reducing the average energy bill of a household. I have chosen solar power and have to go into great detail about what solar power is, how it works, optimum angles, light intensity at my longditude etc. two other solutions were required, i chose wind and solar-wind hybrid. any insight you could give on household solar power would be greatly appreciated. thanks
Ryan Daly, November 10, 2009
You've got yourself a big subjecct there! The first thing about reducing the average energy of a household is making sure you do the obvious things first - low energy lighting, low energy appliances, making sure everything is switched off if you're not using it, switching off equipment at the wall socket and not leaving them on standby.Once you've done that, you then need to look at house insulation - making sure your not loosing heat through windows, doors, walls and the roof.
Then you need to look at your heating and hot water. You want the most efficient heating system available in order to keep your heating costs low. A solar hot water can help here, heating the water up that can be used for washing and - in some cases - for household heating as well (especially with underfloor heating systems, where excessively high water temperatures are not required).
Finally, you can look at solar electricity to generate some or all of your electrical energy.
Why do it all in that order? Quite simply, although the insulation and investigating the electrical usage are boring, its where you can make the greatest savings - an average household can save 30% of their bill by doing the simple stuff, and quite often for a very modest amount of money. All those savings can go towards paying for your solar equipment later on.
I'd suggest you use the online calculators on this site, and the solar project analysis tool to help you get some of the core information you are after.
Good luck with your assignment.
I have a photovoltaic system with battery charging and backup that uses TRAC inverters. The system is far too complicated for me to understand or deal with. When I have blown circuits during holiday festivities the battery backup is a failure and requires "resetting" which I, to this day, don't understand. I have no way of knowing how much my system produces and everyone, starting with the installer, says "well, you produced the difference between how much you used last year and this year". My system was inoperable for a 3-6 month period due to fried junction box on the roof that had filled with water. I had no idea it wasn't producing and no measurable way to know. What's the big mystery. Why can't I have a flow meter, just like the one coming IN from the grid, installed coming IN from the solar panels, so that I can see the volume of production. This system is 7 years old and I've spoken with 3 solar installers who all blow me off similarly. I'm a terrible salesman for the solar industry and I'm constantly asked "how's your system working out?" I'd love to be able to tell them. Can you answer this question?
charles young, November 10, 2009
First of all, congratulations on taking the step seven years ago on installing a solar electric system. I'm sorry to hear you've had problems with it - it does sound like you need somebody to have a look at your configuration. It does not sound right if your battery backup system needs resetting every time you need to rely on it, but without knowing the intracies of your system, it is hard to comment in more detail.With regards to the information you can get from your system, the technology has moved on in the past few years and most particularly it has moved on in terms of the information you get from the systems. There are two answers - the expensive one is to replace your inverter with a newer model. This will give you all the information you could ever want, but at a cost of a new inverter.
If it were my money though, I'd go for a much cheaper solution and fit a standard utility electricity meter between your inverter and your load. This will give you a flow reading from your photovoltaic system into your home. Nice and simple to install and it will give you the basic information you want, plus change from $100. Some battery powered meters don't even need you to cut the wire, but clamp around it, which makes it really simple to install.
You will be able to buy a suitable meter from your local electrical hardware store, or you can buy online from companies like http://www.kwhmeters.com.
Are solar panels better than wind turbines
Anonymous, November 11, 2009
I answer this in my article 'Wind Turbines vs Solar Panels', which you can read at http://www.solarelectricityhandbook.com/Solar-Articles/wind-turbines.html.Unfortunately, there is no clear answer to the question - wind turbines can work extremely well if you have the perfect site for them - if you have a site with higher than average wind speeds, a clear air flow with no obstructions and no turbulance, wind turbines can be hard to beat.
The problem is, very few people have the ideal site for a wind turbine, and if you don't have a good site for a wind turbine, you are going to be very disappointed with the performance of your wind system.
How much is it to get solar panels?
autumn, November 11, 2009
Prices are coming down all the time - a 5w solar panel can cost around $30 and capacities and prices go up from there.There is a Solar Project Analysis tool on the web site that can give you some indicative prices for your project based on how much power you wish to generate. I'd suggest you work out what power you need, then fill in the questionnaire on the project analysis web page. That should give you a reasonable idea of what your system will cost you.
Hi Michael,
I have not got a question as yet but know I will have soon but I just wanted to congratulate you on the best book I have ever read! Your style is so easy to understand so practical and so honest and as a heating engineer with a reasonable knowledge of solar for hot water and a good basic knowledge of electricity you are not patronising. Brilliant well done.
I lied about no questions, can you write a book, like this one, about wind turbines and other forms of power generation please.
Best wishes,
Martin Downes
Martin Downes, November 12, 2009
Thank you Martin, I really appreciate your message - I've had a tough day today and your comments have really cheered me up!A book on wind turbines is on the cards... but that is going to be a little while away yet: my next book is on electric cars, and that one is coming out early next year.
how many kilowatt hours per month with 30 200 watt sanyo panels with 3 2500 watts sma inverters in las Vegas with ajustment in tilt thank you
Roger Cooley, November 14, 2009
That is quite some setup! Assuming you have a site without any shading issues, I would expect an average daily figure of around 17½kWh +/- 20% at this time of year. That will drop to around 15kWh a day in December.During the height of summer, I'd expect you'd be generating around 37-42kWh +/- 20% a day, although because of the intense heat you get in the summer, you'll find you'll generate more power on cooler days than on the very hottest.
Hello Michael, thanks for writing the book, it's got a lot of useful advice in it and is written in a accessible style - Hooray!
My dilemma is two-fold; I'd like the government grant to help pay for the solar panels, so that rules out installing it myself (for a system just over 1kw, which is all I have room for, the grant is a sizeable percentage of the cost) and secondly I'd like a back up supply in case of a power failure. Page 137-8 (Appendix E) describes a back up system but it doesn't spell out if this works with a grid-tie inverter.
As a follow on to the second question, I have heard that in the US inverters exist that can send power back to the grid but which don't shut down when there is a power cut - I presume they have an isolator switch which stops the flow of electricity out of the house - can an isolator of some sort be fitted to a UK-style grid-tie system at a later date, if the system in Appendix E doesn't work with a grid tie inverter?
Gary Miller, November 18, 2009
Dear GaryThanks for the comments about the book. You are right about the current grant system in the UK - you're going to have to get a professional installation in order to get access to these funds.
With regards to a power backup system, there are grid-tie systems that now include a power backup system as well: in effect, these work like uninterruptable power supplies (UPS's) so that power to the building continues even if there is a mains power failure.
You are also right about the US inverters that do not shut down when there is a power cut. As far as I am aware (and I could be wrong on this count), there is no such inverter yet available in the UK. Of course, a manual isolator could be fitted, but getting approval for this for a grid tie installation could be tricky.
Hello Michael,
I got your book for Christmas and it was the first thing I read.
Examples and calculations are excellent as is the total book & website content. Could not recommend it highly enough.
Just a quick question regarding the feed in tariffs.
We are being offered (relatively) high tariffs but the system compels you to use a Microgeneration Certification Scheme approved installer.
This means that you have to pay 'top dollar' for the installation, parts etc. with no choice of components at all. This outweighs most of the cost benefits of installing solar PV in the first place and really puts back the payback period.
Do you know whether any of the schemes are being expanded to allow inclusion of DIY systems? These are just as valid, especially as the final mains connection has to be done by a qualified electrician.
Thanks a lot.
Best Regards
Mike Norton
Mike Norton, January 7, 2010
Dear MikeThanks for the comments about the book. It is much appreciated.
Typical for the UK, the Microgeneratoin Certification Scheme insists that you use registered installers. Like the solar hot water systems this then means that instead of having a solar hot water system installed for under £1000, it costs you three to four times as much.
The old scheme that they have phased out allowed for DIY installation, and worked extremely well. The new scheme that is now coming in penalises people who have already put in solar power and dramatically increases the cost for installing solar in the UK: I suspect the scheme will actually mean less solar power is installed in the UK rather than more.
Solar electricity is a very simple form of power generation that is easy to install, so long as you follow some basic rules. Unfortunately, the bureaucrats have got it badly wrong, and as ever, the rest of us have to suffer.
However, there is an answer. I think we'll see a lot more 'small scale' solar in housing from ingenious DIYers - powering the lighting system in a home, for instance, is a straightforward thing to do and can be done entirely independently of the main power in your home. It depends what you want to achieve - and how much you want to spend - but my advice would probably be to start with a small stand-alone system and then build that up over a period of a few years.
In my small off-grid system, I would like to provide the ability to charge the battery bank from the grid during prolonged cloudy periods. Is there a way to automatically do this without damage to the Morningstar MPPT controller?
Emery Mitchamore, January 7, 2010
There are controllers around that will allow you to do this automatically - but they aren't cheap.I don't know the Morningstar MPPT controller so I am not entirely sure what would be the best and most cost effective way of achieving this. I'd recommend talking to MorningStar to see what they suggest.
Two options come to mind - both of which would require further investigation. The first is to install a small transformer to bring mains voltage down to an appropriate voltage and feed the power into the system as if it were a solar array. Check with MorningStar before you go this way.
You would still need to manually switch the transformer on and off - you could partially automate it using a timer switch - but making a fully automatic system could be very complex - unless you are handy with electronics.
The second alternative would be to charge the batteries directly when they run low. Again, check with MorningStar to see whether you would need to disconnect the controller if you went this route.
Creating a manual transfer switch would be very straight forward, but an automatic transfer switch would be much more difficult: you would need to have another controller that is measuring the charge from the batteries, measuring the amount of power coming from the solar array and then switching across to the mains supply if the solar power and the batteries are both low, and then switching back again afterwards. If you're handy with electronics, it could easily be done, but otherwise I think you would struggle.
So sorry - I can't give you a full and complete answer, but I hope that will give you something to go on.
Thanks for the great book (2010 edition). I need to build some grid fallback systems for a construction site. I was thinking about using an inverter/charger. As you probably know, these act like UPS systems where AC is the priority source. I was thinking about using an automatic switch so turn off and on the AC supply to the inverter. If the batteries deplete the Inverter/Charger turns on, charges the batteries and supplies grid power. If the sun comes out then the panels can aid the charge. Once the batteries have reached their full charge voltage (or some set voltage you have selected) the switch disconnects the grid source. I want to know if there is such a switch? And where do I find one? I think they are like a generator auto start switch but I need one used for grid source instead. Appreciate any insite or ideas you may have.
Dean Sala, January 11, 2010
There are solar controllers available that will do exactly what you want. Alternatively, all you are actually after is a relay between the mains supply and the battery charger, which switches on and off depending on whether your solar inverter is running or not.There is an excellent introduction to relays here: http://www.reuk.co.uk/Relays-and-Renewable-Energy.htm
Depending on how your system works and how much electricity you need, your other alternative may be to fit a timer to the charge controller so that it only charges at night. This could be done either in conjunction with a relay or separately.
The benefit of this is that you can then use cheap rate electricity (if you have a night tariff) and the carbon footprint of the National Grid at night is much lower than it is during the daytime. If you are based in the UK, you can actually monitor the carbon footprint of the National Grid in real time: http://www.owningelectriccar.com/national-grid-electric.html
Hi Michael,
Can I ask - have you investigated the use of parabolic mirrors to focus light sources onto solar panels?
If so, can you comment as to whether this increases their power generation?
Thanks!
Nathaniel Trevivian, January 12, 2010
Yes I have, and yes it works... but proceed with caution.I have only experimented with parabolic mirrors for fun and never in a live installation. The issue is that although it increases the intensity of the light and thereby increases the power generation, it can also burn the solar panels and destroy them if you end up with too much intensity.
I have experimented with parabolic mirrors in the winter months, and I have also experimented with them at night (to see how much power I could get from the moon!) and they can be quite fun, but I would not recommend them for a serious application.
Dear Michael,
Many thanks for the great book.
I have a quick question about inverter sizing for a grid-tied system. How close to the maximum power rating of an inverter is it advisable to go ? For example an SMA Sunny Boy 3000 has a max DC power-rating of 3,200W (http://www.sma.de/en/products/solar-inverters/sunny-boy/sunny-boy-1100-1200-1700-2500-3000.html), could I install panels with a nominal power rating of 3.2kWp (or even higher given that actual power generation is never likely to hit this particularly in the UK), or is it advisable to leave a 'safety margin' for the inverter to ensure maximum relaibility/lifespan - e.g only install a maximum of 3kWp of panels with a 3200W rated inverter ?
Many thanks
Bill
Bill, January 13, 2010
Dear Bill,Thanks for the compliment.
Inverters are funny things. They're not so fussed about the power coming into them as they are the power going out of them.
So you'll wear out an inverter quicker by using all 3.2kW of electricity than you will 'over feeding' the inverter in the first place.
You really want to match your inverter to your solar array as well as you possibly can. The reason for going for a bigger inverter than your array can handle is really down to whether you can forsee wanting to expand your array in the future.
As a rough rule of thumb, you should be aiming to use no more than 50-70% of your inverter capacity as 'constant' power - so your 3.2kW should be a peak rather than a constant load. Do that, and your inverter should last you a very long time.
Q.1 I would like to install a solar panel on my RV unit(recreational vehicle); Do you have some detailed instructions how that could be done specifically on an RV.
Q.2 I have read somewhere that the "Peel and Stick" solar panels are more efficient than glass panels, shatterproof, flexible and easy to apply.? What are your thoughts on these flexible panels? And especially how these would work on the roof of an RV?
Thank you,
Alex. Sztogryn
Alex., January 15, 2010
I have fitted solar panels to my caravan and it is very easy: use an exterior grade bond such as mastic to fix the panel onto the roof of the RV making sure you seal all the way around the panel.If you drill a hole in the roof to feed the cables through, make sure you also seal this with the same method.
As an aside, make sure the panel you choose uses toughened glass. The vast majority of them do, but there are a few of the cheaper panels that don't.
The peel and stick panels are shatterproof, flexible and easy to apply, but they are not as efficient as the glass panels. The panels I have come across have all been amorphous panels providing around 5% efficiency. They are great at what they do - they are widely used by river boats because you can even walk on them - but they are not cheap. For an RV, I'd recommend a glass covered panel every time.
Dear Michael,
I just read you book (2010 edition). I found it really good.
I am in Buenos Aires, Argentina.
I started a solar company three months ago and I need to find information about solar insolation in my region (Argentina, Uruguay, Bolivia, Peru, etc). I couldn't find any information of those countries in your website.
Could you help me with this ?
Best Regards,
Maxi
Maxi Postigo, January 19, 2010
Of course I can. I shall update the solar insolation tables and solar angle calculators with information for Argentina, Uruguay, Bolivia, Peru and Costa Rica this afternoon.If you check the web site in two hours time, you should have all the information you need.
All the best,
Michael
Dear Michael,
I am just reading your book and i wanted to simulate with your online calculator. I am from italy and there is not italy between the countries for irradiance and tilt calculations.
Is it possible to add?
thanks
giulia suriano, January 22, 2010
My apologies - I cannot think how Italy has been missed. I have got the data for Italy and will update the web site in the next half hour.
We are thinking about installing rooftop solar wall panels in order to prewarm outside air for a set of commercial air handlers. The installation requires multiple rows of solar heat panels and ducting. The panels in each row are approximately 3 ft high. We do not want the panels to steal sunshine from each other. Would you please tell me the mean sun angle for Seattle Washington so I can properly space the rows for optimal performance?
Thank you for your time and I look forward to your reply.
Regards,
John Payne
John Payne, January 24, 2010
Thanks for your e-mail. 'Optimal performance' will vary at different points throughout the year. Are you looking to provide optimal performance during the winter months, the summer months or an average that will work throughout the year?If you want to achieve optimal winter performance, I would suggest an angle of 26 degrees from vertical. For optimal summer performance I would suggest an angle of 58 degrees and for all year round performance I would suggest an angle of 42 degrees.
Can you tell me what to spend for annual maintenance? Should I budget 5% of the system cost? What is likely to break? Other than break/fix, are there additional maintenance tasks that need to be done?
John Parlapiano, January 28, 2010
Annual maintenance is very cheap unless something actually fails. Excluding failures, budget $10 a year and an hour of your time every three months or so for regular maintenance. That maintenance consists of checking electrical connections, checking the batteries and topping up with water (if using 'wet' batteries) and making sure the solar panels themselves are clean and in good condition.The most likely thing to fail is the battery pack, although it is not unknown for controllers or inverters to break down.
If you have a battery based system, you will need to replace the batteries at some point during the lifetime of the system: how long the batteries last will depend on your system setup - see the section on Batteries in the chapter on Component Selection and Costing for more details. As a rough rule of thumb, I'd suggest you need to budget for a complete change of batteries every four years if you're using cheap batteries or every seven years if you're using good quality batteries.
how much energy does an average home 1500 sqft require? in kwh
my bill says 856kwh in this period. do i average that by 30 then know the actual daily demand and from there determine the equipment sizes
geo, January 30, 2010
Yes - that is absolutely right. Devide the number of units of power used by the number of days.In the UK, the average home uses 0.8kWh of electricity each hour. In the US, the average home uses 1.2kWh of electricity each hour. Of course, these figures will depend on how you heat (and/or cool) your home, how many people live in your home and so on.
To get the best out of solar power, you need to see how you can reduce your demand for power: it is more cost effective to halve your power usage than it is to buy a more expensive solar system.
Hi
Firstly, thanks for the book
I need some advice, and would be grateful if you could help.
I am beginning to design a PV system for a beach hut, which will power fridge, lights etc.
I envisage using a MPPT controller, and a 24v system, which I believe will be more efficient, however the recommendation seems to be to take the DC load from the MPPT. Whilst I would take the 24v fridge load from the MPPT, i would need to take the 12v light load direct from one of the two 12v batteries, would this be OK?
Thanks for your help.
Andrew Britten
Andrew Britten, January 31, 2010
You would be better off connecting two 12v lights in series rather than powering the lights from one of the batteries. Otherwise you will end up with an unbalanced battery pack which will reduce the lifespan of the batteries.If you would prefer not to run two lights in series, you can get a voltage converter to drop the voltage from 24v to 12v. These aren't expensive and can be purchased from any electronics shop or truck-stop (most trucks run on 24v and an adaptor to run 12v car accessories in the cab is a popular piece of kit).
Hello Michael i have a quick question for you..i bought your book off of amazon and its a great read so far..i have a photovoltaic installation class coming up monday and your book has helped me prepair...anyways i have the 2010 edition and it says its internet linked..could you send me the URL for the website? or explain how i can use the internet and my book together. thanks mike ttyl
Hans Van Houten, February 4, 2010
Dear HansThanks for your message. You've found the web site - www.SolarElectricityHandbook.com. The web site has lots of resources which will be useful if you are looking to put together a photovoltaic system:
The 'additional resources' section includes lists of web sites, many of which change too rapidly to be worth putting in the book directly.
There is a news section, which reports on interesting news in the solar sphere and new articles that I write on a regular basis.
The most important part is the Online Calculators. These calculators allow you to look up solar insolation and angles for installations across the world - if I put them in book form there would be over 350 additional pages of information! Finally, the solar project analysis tool allows you to enter your power requirements and have a custom produced 11 page report detailing the configuration and likely cost of a photovoltaic system.
Good luck with your installation class!
Hello there, bought your book and am doing some research on your website. I live in Melbourne Australia and was trying to use your calculator to get an idea of my system requirements. I got unstuck at the insolation figures - Can you change the website so that I can enter my latitude and insolation values if I know them (I do..). At the moment picking the "pre-canned" values for the UK, USA, Canada, India/Sri Lanka, etc doesn't help me at all. Thanks kindly. Matt
Matt, February 6, 2010
Dear MattThanks for your e-mail. I shall have a word with the web designers and ensure that Australia is added to all our calculators. I'll do my best to get this sorted as quickly as possible after the weekend.
Mike
I have a remote cabin that gets maybe 2 weeks of use during a year - one month max - in the summer. Usually there is 2+ weeks between <7 day uses giving plenty of time to recharge batteries via solar panels. We currently have propane lights, refridgeration and stove, so running out of power is not the end of the world. I would like to have better lighting and the option of not having to run a gas generator to vacuum, use power tools, etc. It gets extremely cold there during the winter (-30F or more). I did not see in your book how I would calculate the size of a solar array required for a 2 week recharge of battery power that would give me ~7 days of power. Any word of wisdom on things that I need to consider?
John Simons, February 11, 2010
That is an interesting project you have there. In essence, what you need to do is work out your power requirement on a daily basis when you are on site. You then need to calculate the size of the battery so that you have seven days of reserve in your batteries.The good news is that you'll need a solar panel approximately one third of the size of the panel you would need if you were using your cabin all the time, which really brings your costs down.
Hi,
I'm looking at installing a solar pv system around 2KW to take advantage of the government feed in tariff and grant, before it disappears. My research leaves me wanting a system I can add to using distributed inverters, like the SolarEdge Inverters. Is there any equivalent system in the UK?
Anthony
Anthony Sumner, February 13, 2010
I like what I see of the SolarEdge inverter system, although I have to confess I haven't seen one in real life. For larger solar PV installations looks like a great solution. The concern I would have is the cost - the extra efficiencies of the system are countered by the cost of the additional hardware and I'm not currently convinced that the system has an improved payback as a result.I'd like to be proved wrong though! There has been some clever thinking going into this system and any way of optimising power generation from solar should be encouraged.
Unfortunately the SolarEdge system is not available in the UK and I am not aware of any other system that is available in the UK that does the same thing.
How many solar pv panels would be needed to provide 2.8 killowatts of electricty thank you
Ian Antonio, February 15, 2010
I need a bit more information before I can answer that! The size of solar array you need will depend on where you live and what months of the year you want to use your system.If you can tell me where you are based and what months of the year you want power, I'll let you know what size system you will require.
Hi there.
I'd just like to say that your book has been great in setting a few ideas firmly in my mind for my next project. I'm part of an expedition team set for Borneo, and we're planning on using solar power to enable us to use laptops and LED lighting, as well as charging camera equipment.
The section on irradiance simplified things for me and I now think I've got the numbers and the plan right in my head:
4x40w solar panels, should give us 640Wh of energy per day.
6 hours of 50w laptop use, and 6 hours of 20W worth of LED lights should take us to 420Wh of use per day, plus the camera equipment should be less than 50Wh roughly. We'll also have a small generator in case of emergencies or lack of sun.
I'm thinking adding another 40w panel would be enough to account for 10% loss using an AC invertor, plus another 20%(ish) from a charge regulator - and we can always be flexible with our laptop use too if we're using a bit too much.
So if there are any problems with this plan, it'd be great to hear from you! I just want to double and triple check everything. Any help would be appreciated and we'd love to credit you on our website. The blog is ready at www.fxpedition2010.com and soon we'll have another website up that we'll use to give free resources to schools.
Thanks for the great book.
Kind Regards
Dan
Dan Sargison, February 15, 2010
Wow! What a wonderful project. I've enjoyed looking at your web site.My concern with the solar side of things is that you are going to spend a lot of your time in the shade out of direct sunlight, which would severely reduce the amount of power you can generate.
In order to give you the best advice, I'd like to find out more about your project - I'll send you an e-mail with my phone number on it in a few minutes so we can discuss your needs in more detail.
Hello,
Thank you for posting the solar irradiance on the website. The solar irradiance fluctuates all year round and therefore solar module efficiency is directly proportional to solar irradiance. However, could you tell us which period these solar irradiance covers?
Thank you very much
Glenn
Glenn Miniscloux, February 18, 2010
The information on solar irradiance comes from NASA and is based on satellite monitoring. Solar irradiance measurements are taken every three hours, every single day. The figures shown on my web site are based on the average readings over an entire month, in turn averaged over 22 years of readings.On any one day there will be fluctuations in the amount of irradiance - often as high as 20%. Within an average day, irradiance figures change throughout the day, with the best figures at solar noon.
If you know your latitude and longitude, you can see the underlying data for yourself here: http://eosweb.larc.nasa.gov/cgi-bin/sse/grid.cgi
on the flat roof, can i install collector flat?
Arun Bapat, February 23, 2010
Yes you can. You will find, however, that you will have significantly less power from your system - most noticeably in winter, spring and fall. In the middle of winter, the difference can be as much as 50%.
To set up solar panels (probably foldable flex panels) to recharge an e-bike battery at 36Volts 10 Ah, what type of controller do I use? Do I need anything else? Is it easy to set up?
Ellen, February 26, 2010
An ebike solar charger is a great application for a small solar system. There are a couple of ways of carrying this out.If you are looking for a fixed system - mounted to the roof of a shed, for instance - your best bet would be to have two sets of batteries, so that one battery pack can always be charging whilst the other set is in use.
If you are looking for a system to take with you, you'll find that the solar panels themselves are going to be too bulky - either that, or you'll end up with a very small amount of power generation that will give negligable benefit.
The biggest issue is going to be finding a suitable charge controller that runs at 36v. The majority of controllers run at 12v, 24v or 48v and whilst some 36v controllers do exist, you may have to do some hunting to get one at a good price. MorningStar do an excellent MPPT controller that can handle 36v. However, these are really aimed at bigger systems and may not be cost effective. The Al-Samawa ASG6001SC controller is another option, which is much cheaper but can be difficult to get hold of.
The actual wiring up is simple - you'll need to modify your battery box so you can plug the solar array into it, you'll need to connect three solar panels together in series to give you the voltage you need, and then you run everything through a solar controller so the batteries don't overcharge. With the right equipment to hand, that bit should only take you an hour or so.
A few years ago, a friend of mine who doesn't own a car and uses his 24v bicycle to go everywhere, modified a bicycle trailer to build in a solar charging system into the lid of the cargo box on the trailer. From memory, he had around 80w of solar panels, charging a second set of batteries in the trailer. The combined battery pack gave him a range of about 50 miles and in the height of summer the system could completely recharge the entire pack every day.
Good luck with your project. It sounds fun.
Hi I have just bought your book, very informative.
My question is:- How do you measure a gable roof from the ground to work out how many sq meters are available for mounting PV solar panels using just one side of the gable roof.
John
John Bate, February 27, 2010
How come the solar angle calculator shows a greater angle from vertical in June than January. Surely the angle from vertical should be less in June as the sun is higher in the sky then ( i.e nearer vertical )? Doesn't seem right to me. Based on United Kingdom, Birmingham.
Cheers, - Nick
Nick, March 5, 2010
Hello Nick, thanks for your message.Are you mixing up your horizontals and verticals? In June, the panel needs to be closer to horizontal than vertical, so based on this there is a larger angle from vertical.
The confusion may well be because many solar experts quote the angles based on a horizontal plane rather than vertical.
All the best
Hi Michael,
I found your book very interesting. I understand that from April 1st consumers can sell excess energy back to the national grid, can you advise me of the tarriff please? Or point me in the right direction.
regards,
Lance
Lance Feller, March 9, 2010
Dear LanceYou've always been able to sell your energy back to the National Grid, but now the Government has published new feed in tariffs for new systems that guarantee a good return over the lifetime of the system.
This particular scheme is only available for systems that have been installed by accredited installers - DIY installations are not elegible. If you are interested, shop around for a good price: most accredited installers are charging a significant premium which wipes out much of the cost benefit of using them in the first place.
You can find the details at http://www.pv-tech.org/news/_a/uk_feed-in_tariff_announced/
There is also a good web site at http://www.fitariffs.co.uk/
Hi Michael,
Great Book - working through a simple 'lighting'-'stand alone' system for a Hunting Hut in New Zealand - would you have the 'Solar Insulation Values' for New Zealand?
Cheers
Matt
Matt Coombes, March 11, 2010
Fantastic. I have updated the solar irradiance figures to include New Zealand. You can find the updated table here http://www.solarelectricityhandbook.com/solar-irradiance.html
So far, I've only put in ten locations to start with (the ten largest cities in N.Z.) and I'm guessing there isn't much call for Hunting Huts in large cities! If you need a more accurate set of figures, let me know your nearest town/village or lat/long and I'll get it for you.
What is the most optimum fix angle for pv in Los Angeles California?
Yildirim Arkun, March 15, 2010
As you are aware, the height of the sun varies at different times of the year, so the comprehensive answer is that it depends on when you want to optimize power generation - during the summer, during the winter, or at an average throughout the year.If you have the potential to adjust the angle of your solar panel throughout the year, even better, but for most people that is not practical.
If you want to optimize your energy production in the winter, you should angle your solar array at a 40 degree angle to vertical (i.e. 50 degree from horizontal). To optimize energy production in the summer, you should angle your solar array at a 72 degree angle to vertical (18 degree from horizontal). For the best average throughout the year, I would recommend a 56 degree angle from vertical.
I hope that helps.
Good day,
I have recently purchased your book, and am slowly reading through it.
Yesterday I tried to locate South Africa, on your data, but could not find it.
Is it possible to give me some idea of the Solar Angles and Solar Irradiance for South Africa, Bloemfontein, 29° 36' 43.17" South & 26° 03' 42.94 East?
Hannes Coertzen, March 17, 2010
Thank you for your message. I will add South Africa to the online calculators later on this week for you.
I HAVE NO EXPERIENCE IN SOLAR ENERGY FIELD. I READ THIS BOOKS SO MANY TIMES; WATCH DVDs. HOW CAN I GET THE JOB IN THIS FIELD IF THEY WANT EXPERIENCED PEAPLE?
THANK YOU!
EVERALDO SILVA
EVERALDO SILVA, March 17, 2010
This is always a difficult issue: once you have some experience, finding a job in the solar sphere is easy. Getting started is not.Without knowing where abouts you live in the world, it is difficult to provide specific information. There are training courses you can go on to get you professional qualifications, including some PC based courses so you can learn directly from wherever you are. There is a basic free one available here: http://www.aeesolar.com/trainings/solar-training-webinars.html, which may be worth signing up for.
If you have some money that you can use to buy a solar panel, a controller, a battery and an inverter, you can start working with the equipment for yourself - if you have a project that you can use the parts for, even better as you can then at least include this as work experience.
Other than that, all I can suggest is keep trying. Good luck.
Hi, I live in Los Angeles CA,do you know if there some store in LA, to buy some Cell,Bat... or Solar Panel. Can you help on this please.
Jimmy, March 17, 2010
I don't live in Los Angeles so I have no personal experience of any local shops in your area. Real Goods Solar has a site in Los Angeles - look at their web site at http://www.RealGoodsSolar.com.
I have read your excellent book, and want to calculate the Solar insolation values. I live on the mendip Hills (Altitude 900ft)which is 20 miles south of Bristol (UK). The area is subject to low cloud, mist or fog on numourous days of the year. Can you advise or provide a link where I can factor your Solar insolation values for this area for these weather conditions. During the summer (July and August)periods we do experience quite a lot of rain and where here in the mendips we can often also be in cloud for quite a lot of the time.
Thanks in anticipation
stuart mcmanus
Stuart McManus, March 21, 2010
I have lots of happy memories of walking the Mendip Hills and I have been lost in low cloud on at least one occasion!You can get this information from NASA. Go to http://eosweb.larc.nasa.gov/cgi-bin/sse/grid.cgi and create a new account. Then enter your Latitude and Longitude (I looked up 'Mendip' on www.Multimap.com and got the figures 51.126 and -2.65) and select insolation values and cloud cover. You'll then get the solar irradiance figures and a percentage of cloud cover for each month.
hello Michael,
How can I calculate the min distance between collectors to avoid shading of one over the other and as a function of the slope of the collector.
Jose M. Gonzalez, March 23, 2010
Measure the height of the top of the panel from the ground when placed at the optimum angle you have chosen - it doesn't matter if you use inches or centimetres. Then look up the solar angle from vertical for December for your area using the Solar Angle Calculator on this site.Then visit this web site: http://www.carbidedepot.com/formulas-trigright.asp
The height of the top of the panel from the ground is 'side a', angle 'B' is the solar angle from vertical. Enter this information and click on the Calculate button. The figure they provide for side 'b' is the distance you should place between your first row of solar panels and your second.
Hi Michael
Have your book and was trying to get a project analysis, live in Phoenix,AZ, the information I have is KW/day usage from my electric bills, but I can't use that with the form that is provided on site - any suggestions/solutions ?
Thanks
Dennis Pullaro, April 4, 2010
The answer is to put a single reading for your whole site and put it down as one hour.i.e. if you are using 20kWh of electricity a day, put it down as follows:
Device Description: HOUSE
Voltage: MAINS VOLTAGE
Power (watts): 20000
Hours of use per day: 1
However, I'll warn you now - if you are planning to simply move everything across without looking at what you can reduce, you're going to be looking at a very big bill to transfer to solar!
can a solar panel used in Central America get too hot ? what happens if gets too hot ..is is bad for system ?
David Ellis, April 7, 2010
If a solar panel gets too hot the efficiency of the panel drops. Some amorphous panels have been known to be damaged by very hot temperatures but crystalline panels should be fine.
Hi Michael,
I read your blog article on Solar Generators. I want to make (or buy) a solar generator capable of running an A category ice cream freezer on a UK 240v plug. It uses approximately 18kw per hour. I have absolutely no idea where to start. How much roughly can it be done for? I want the green credentials but haven't got unlimited funds!
I'd appreciate any advice you have for me.
Kind Regards,
Philip
Philip Barnes, April 19, 2010
How big is this ice-cream freezer? 18kW hours of electricity is enough to run 24 homes on average!If you've got a big industrial freezer unit, then unfortunately I have to tell you that you're not going to be able to afford a solar system to run it - at a rough guess you are going to be looking at a bill the wrong end of £100,000. Technically it can be done, and there is a video on YouTube about a company who has done it. Have a look at it here to see the scale of what is involved: http://www.youtube.com/watch?v=Y2PeHjmhl1U
Small freezers are a very different story. I would recommend changing your freezer though because in solar terms, an 'A' rating is not actually that good.
You can actually buy very, very efficient 12v freezers which are specifically designed to be powered by solar. They're not cheap - prices start from around £400 - but they are somewhere in the region of ten times more efficient than A+ rated freezers. The cost of running one of those on solar power is likely to be in the region of £250-300.
There are several suppliers of solar freezers. The most popular is Sundanzer (http://www.sundanzer.com).
Solar angle and solar irradiance for Bangladesh are not included in the calculator drop-down box.Where can I find them?
Thank you for offering an awesome book for the beginners.Most of the urban housing are pencil-structure(Flat-roof) and quite dense.Power requirement is high in comparison to the available roof area.Will appreciate your views.
Ahmad Elahi, April 25, 2010
Bangladesh is currently not included in our solar calculators. I shall speak to our programmer and ask him to add Bangladesh to the system for you. If you check in a couple of days you will find everything you need.With regards to your power requirements, solar does require a large amount of surface area to generate electricity. Unfortunately there is no easy answer to that: either you need to find some more space to put panels or you need to reduce your power requirement.
I have a Xantrex hybrid system. My problem is not with that, but with the panels.
They are stationary roof panels rated at 4950W. Professional installer says they're at optimum tilt. Ten strings of three. I've watched them for several months now and have yet to see them exceed 4000W. Inverter output a little over 3K. Should I expect more?
John Stewart, April 30, 2010
You don't say where you are based. You will only find you get optimum power in the summer months when the sun is directly overhead. If you want, you can buy a solar irradiance monitor which will tell you the strength of the sun.There are some other things to check - obviously keep your panels clean as dirt does build up on the panels and will have an effect. There is the possibility that you have a poor connection or a rogue cable somewhere in your solar array that is increasing resistance.
Hi Michael
I recently bought the 2010 version of your book from Amazon, very clear & readable. I tried to fill in some electrical usages in the calculator but it didn’t give a very sensible result. This was because I didn’t fill in the details for each of the dozens of electrical devices in our home but tried to add them together and guessed (wrongly) the hours of us. It’s kind of difficult to know how many hours they run as so many devices switch off or go on standby most of the time.
Can I do it a different way? I know my home consumes 5,350 kWH per year or 14.625kWH per day on average which excludes heating. So I know we use an average of 0.61kWH each hour. I was thinking about a ground mounted array of say 22 Mitsubishi 180Wp PV panels feeding in a grid tied system via an inverter.
What would that set up typically cost and how much of my annual usage could I expect it to cover?
Ray
Norwich, UK
Ray Spreadbury, April 30, 2010
I appreciate the difficulty in calculating the electrical requirement for each device in your home. The reason for suggesting that this is a good approach is to help you evaluate each device individually. For instance, some PCs use twenty times as much power as others and if you find 'power hungry' equipment when you audit your house, you can start seeing straight away where you can make savings.For a 'quick and dirty' approach, the best way to use the calculator would be to enter 14625 watts for one hour on the solar calculator - that would give you the figures you need.
If you shop around for the best price and you're doing the work yourself, I would suggest a system with 22 Mitsubishi 180Wp panels would cost you in the region of £10,000.
In the depths of winter, I would anticipate that system providing an average of 2½kWh per day, whilst in the summer months, the system would generate 17-19kWh per day.
I would anticipate your suggested system providing pretty much all of your energy for around 5 months of the year - from mid April until the middle of August.
I have been trying to figure out if I can use a $300 inverter purchased at a store like Canadian Tire but nobody at the store knew. I called Sonny Boy and compared a similar size inverter at $3000 but they couldn't explain what was special about their inverter that would make it required for a grid tie. Have you ever done a grid tie and what inverter did you use?
Darren Anderson, May 18, 2010
All you are getting for $300 is a basic inverter that you cannot use for grid tie: for grid tie you needs lots of other clever electronics to synchronise your power with the grid's. A lower cost inverter is fine for powering stuff in your house though. Check that it is a pure sine wave inverter and that it includes a voltage cut out so that it doesn't completely kill your batteries.
I saw an article in Ottawa Metro paper which quoted you as saying solar panes cost 150 per. At that point I'm interested
When I go to one of my local suppliers, they suggest they are around 600 for a 120 v panel (Qualicum Beach BC).
So where are you getting your panels from (manufacturer or retailer). Do you recommend one manufacturer over another?
In my case I'm looking to reduce my electrical consumption from BC Hydro. I run a seasonal house and heating is all electric. What total costs should I expect as an entry point? What about solar versus wind? Maintenance is an issue as no one is in the house
9 months of the year, yet I maintain heat to prevent mold.
Thanks
Barry Morton, May 20, 2010
Solar panels are dramatically dropping in price and in the next few years you can expect to pay much less for them than you do now. CAN $600 is pretty expensive for a 120w panel though. If you shop around you should be able to get one for under CAN $400. The next generation of solar panels are likely to be an order of magnitude cheaper, however. A 120w panel in a couple of years time could cost as little as CAN $50-75.I'm based in the UK, so I get my panels from different sources: I tend to go for Kyocera, although more recently I've been experimenting with the lower cost panels from China which are giving near-identical results for a lot less money.
Electric heating consumes a lot of electricity and for that reason, you will probably find you'll need to find a different heating system for your home - especially as you have the heating switched on throughout the year.
A solution that might work well for you though is a combination of wind turbine and solar panels, using an electric heater as a 'dump load' for when your batteries are full, thereby providing a small amount of heat in the house when you are not around. I've written an article on solar vs wind (you can find it under the SOLAR NEWS AND ARTICLES section on the web site) which will give you a basic grounding in that.
Without knowing a lot more about your project and your energy consumption, it is not easy to give you a real indication of what it is going to cost you. There is an online project analysis tool that will work out some estimated figures for you based on your location and energy consumption on this site - visit the ONLINE CALCULATORS section and follow the links to the PROJECT ANALYSIS TOOL.
I have a basic photovoltaic question. If a solar panel is exposed to the sun, but the solar panel is not part of a circuit (not hooked up to anything), where do the electrons caused to move within the solar panel go? Do the electrons go into the atmosphere, or do they somehow remain in the panels? Please elaborate.
Charles, May 22, 2010
The energy turns to heat.
Hello!
I find this site very interesting, however I have an issue with the solar angle calculator. It lists cities for every province and territory except Alberta. Since I live in Alberta, I find this inconvenient to say the least. Any idea as to why it is this way and will it be corrected in the future?
Thank you for answering my question and this very interesting site.
Joe
Joe, May 23, 2010
You've found a bug in the system. Oops! My sincerest apologies. We're working on a fix now and it should be working by the end of today.
Hi Micheal,
I just finished reading your book, it was an excellent introduction to Solar power (especially all the information on sizing of the systems energy requirements), Thanks.
I apologize its a long mail
I have three questions though;
1. In certain equatorial parts of the world, a fan (ceiling, table or standing) are an absolute necessity, and they would normally run at least 12 hours a day. If I am careful I could choose a model which only consumes say 75Watts, in 12 hours this will require 900 WH of energy! If I use an 80W polycrystaline panel, and the minimum daily insolation throughout the year is about 4 (Port Harcourt in Nigeria), this means that each solar panel can fetch about 4 x 80 = 320 WH of energy daily, should come down to 85% of this if battery and inverter inefficiencies are considered, so I get about 320 X 0.85 = 272 WH of energy per panel per day. This implies that I would need about 3 solar panels to support each fan! What would you normally do when you have to support ceiling/table fans please?
2. From the insolation app on your website, the lowest daily insolation for the Port Hatcourt in Nigeria is approximately 4hrs. There sure seems to be longer hours of sunlight than this, there sre probably lots of rainy days during these period. In your experience how accurate would you consider the daily insolation information?
3. Have you every heard of "HQRP solar panels"? Their monocrystaline solar panels appear to offer more power per cost of panel. But I suspect they are probably cheaper because they might be inferior to Kyocera and Sharp. Do you know how they stack up to the top brands please?
Chizim Eleyi-Okpara, May 24, 2010
Thanks for the questions and for the comments about the book.There are such things as solar extractor fans that are designed to extract hot air from a room. These use very small motors using only 3-4 watts per hour. I've asked a couple of my contacts about proper room fans that can be run on solar panels - no responses yet, but I'll keep looking and let you know if I find anything.
With regards to the insolation figures, they've been provided by NASA based on satellite observations. They take solar insolation readings from the surface of the earth every three hours and the data is based on a 22 year period between 1980 and 2002, taking into account average weather and solar angles at different times of the year. NASA say the figures are accurate to within +/- 20% on any one single day, but provide this average figure over a period of an entire month.
The figures don't say how many hours of sunlight you will get in a day, but the total irradiance of the sun over a period of the day - in other words, you may get ten hours of sunshine, but in terms of irradiance it is the equivalent of four hours of noon-day sun.
HQRP is a brand of solar panels that I have come across, but never used. Here in the UK they are not particularly cheap. Looking at the specifications, they look similar to a lot of panels built in China. So long as the warranty is as good as they claim (25 years) they would strike me as a good budget choice.
There is less and less to choose between the cheaper panels and the top brand panels now. Quite often the cheaper panels are built on the same production lines as the top brand panels, but are rebranded and downgraded to a lower watt rating if there are a higher number of defects found at the end of the manufacturing process: so you might find a 200 watt big brand panel might only produce 195 watts at the end of the production line test and therefore sold as a 190 watt panel from a 'non-brand' company.
Hello. Iam a nigeria and wish to have solar irradiance(sun-hour) of some major Nigerian cities to assist me in designing solar electricity systems. how do i get your solar electricity handbook?
MUSA NUHU MADAKI, June 6, 2010
I will ensure Nigeria is added to our list of countries this week. You can buy the Solar Electricity Handbook from most bookshops, although you will probably have to order it in specifically.If you ask for ISBN 978-1-907670-00-8 and give the full name of the book (SOLAR ELECTRICITY HANDBOOK - 2010 EDITION), any bookshop should be able to order it for you.
Alternatively, you can buy it online from The Book Depository, an English bookshop who will deliver it free of charge to Nigeria.
Dear Boxwell,
Your book and the website attracted my attention because I wish to do a solar project in the PHILIPPINES.
However, when I look at the online calculators, I noticed that Philippines or any other South East Asian countries are not in the list. Is there any reason for this?
I'm already convinced of the usefulness of your book but I am quite surprised not to be able to use the online calculators.
Looking forward to hearing from you.
Jonathan Mendoza
Jonathan Mendoza, June 7, 2010
Hi,
You are doing a good job here and please keep it up.
I was wondering why Calabar, a city in Cross River State in Nigeria is not included in the calculation table you have prepared.
Could you do something about that please.
In the same vein, Africa is not captured in the your solar project analysis table.
Finally, could you advise if I am building a house that has a power consumption of about 23kw could be powered by solar and at what cost?
Alph UK June 2010
Alph Takon, June 9, 2010
Thank you for the comments about the web site.I will ensure that we update the Nigerian data on our system this week. We will be doing some updates to the Solar Project Analysis table in around two weeks time and Africa will be included on the next release.
I want to run solar fans to cool my horses stall.How can I do it?
patti, June 19, 2010
You can actually buy solar extractor fans as complete kits. Have a quick look on Google for 'solar attic fan' or 'solar extractor fan' and you'll easily find them. The question is, what do you actually want to achieve?Do you want a fan cooling system to blow cool air at the horses, or do you want a system to extract hot air from the top of the stall which will pull in cooler air into the bottom of the stall? Do you want a system that can run at any time - including the night, or are you just something for the daytime?
A daytime system, or an extractor system, is the easiest - simply buy a solar panel and a 12v fan - you don't need a battery because the system will be self regulating. When the sun is shining, the fans run fast, when its a dull day, the fan won't run at all.
Alternatively, if you want a system that can continue to provide air movement into the evening and night, you'll need a battery and a solar controller that switches off when the battery charge gets too low. Then you can have a system that will continue to run into the evening and when the battery gets too low, the fans then automatically switch off - by which time, with any luck, the ambient temperature is cool enough for your horses anyway.
Hi,
I purchased the book through Amazon but it has not arrive yet fro 1 month now. so I decided to read the preview and utilize some resources to familiarize myself with Solar PV. When I used the Solar Angle calculator, the Philippines is not included. Are there plans to include that in the future? Or is this included in the book?
Thank you.
Lucky Hormigos, June 25, 2010
The Philippines is not yet included, but I will speak to our programmer and arrange for it to be added to the list of countries to include in the next week or so.Sorry to hear that it has taken so long for your book to arrive from Amazon - they usually keep my book in stock for very prompt delivery. If you still have not got the book, you may wish to cancel your order and reorder from http://www.bookdepository.co.uk as they will offer free delivery and usually dispatch within 1-2 working days.
Hi Michael... Firstly, your book has provided me with the most answers in the simplest of languages for a complete novice like myself. I now have so much more confidence that previously and am well on the way to coming up with a final design for my isolated house in Portugal.
I think I have decided on a 48v system, using a 3750w/5000w peak inverter. What would be the minimum quantity and spec of batteries and panels to get this system working, at first with low loads planning on expansion as time goes on? I'm guessing that I will need 4 batteries and 4 panels, maybe min 60w a piece?
Many thanks, Kevin.
Kevin North, June 27, 2010
Thank you for your message and for your comments about the book. They are much appreciated. Apologies for the delay in responding as I have been away.The number of batteries and panels you require really does depend on your overall load on the system. If you are planning to expand your system in the future, I'd recommend that you over-specify the batteries now so that you don't have to extend your battery pack in the future when you get more panels. Mixing old and new batteries later on down the line does reduce performance.
You've got quite a big inverter there, so you're going to be pulling a drain of around 100 amps peak on a 48 volt system, so I would suggest that you want a minimum of a 200 amp-hour battery pack as a minimum: even a 200 amp-hour battery system will only give you around 2 hours worth of power at peak usage, so you may want to consider more.
My personal recommendation would be 6v Trojan deep cycle batteries for that sort of application as they can easily withstand that sort of load for extended periods of time.
A 240 watt solar array made of four 60 watt panels generate between 400 watts-hours per day in the depth of winter and 1.8kWh per day in the height of summer. If anything, that seems a little low, although of course that does depend on your actual usage is.
Greetings Michael,
I recently purchased your book to assist me in learning and setting up a small solar electric system at our remote cabin the Adirondack mountains for NY State. My system has meager need and will only be running some lights and maybe a radio. I have used your solar analysis calculator (very nice I may add) to calculate our battery needs at 90 Ah. I wound up purchasing a 110 Ah AGM battery just as a precaution. I will be charging the battery with an inexpensive 45 watt solar array (Chicago Electric). My question is this, can I store my battery and charge controller in a (slightly modified) cooler instead of purchasing a commercial battery enclosure? I have read that the enclosure should be weather proof and insulated to protect the battery from temperature extremes. If you think this would work should the cooler be ventilated even though I am using a AGM battery?
I would like you opinion on this idea.
Best Regards,
Christopher Cooper
Christopher Cooper, June 29, 2010
Dear ChristopherWhat a great project! A cooler box would make a great battery box, but yes, you will need to add some ventilation holes into it.
If I was to conduct some maintenance on some solar PV panels and wanted to record the improvements in efficiency how could I calculate the result? I have a Solar Power meter (W/m^2) and can review the watts on the internal house meter. I was thinking if I could record the irradiance value and the internal electric meter (watts) before and after the maintenance (Cleaning) I could show the improvements. If it was a cloudy/sunny day and therefore the irradiance changed frequently just reading off the internal electric meter before and after would not be a fair result. So how could I factor in the reading from my Solar power meter (W/m^2) to achieve a fair result in efficiency?
Rich C, July 4, 2010
I'd recommend a few different approaches in order to get an accurate picture. Firstly, I'd measure the average watts-hours over the previous few days before cleaning and then again afterwards - as hopefully this would counter any minor differences in weather conditions.I would also use a handheld watt meter to measure the difference immediately before and after cleaning.
You should get a fair indication of the difference using these two different techniques. From my experience, grubby solar panels have a 10-15% impact on efficiency, so it is definitely worth keeping them clean!
Hi,i have seen your review of a 12v 12watt panel on maplin's website, i was wondering if you could give me an idea of how much this would charge my 110amp leisure battery assuming good light. I am not particulally well knowledgeable on watts,amps etc.The method i use to give me an indication of the state of the battery is just by using a voltmeter ie... 13v = fully charged and 12v = discharged.
So how long would it take to raise the voltage by 0.1 for example using this panel ?
Hope all that made some kind of sense !! many thanks
Steve Holcroft, July 5, 2010
The particular panel you are referring to is great for maintaining a battery charge on this size of battery, but not big enough to charge it up from flat. I use two of these particular panels to charge up an 75 amp-hour battery on a caravan, and this will charge the battery from flat to full in around 7 days during the summer months. Because I rarely use more than half the battery's charge, that works out to a recharge in between 3-4 days in the summer and a week during the spring and autumn - which is perfect for the sort of use I use the caravan for.So one panel isn't really enough for a 110 amp-hour leisure battery unless you're only using a small amount of the battery's capacity. I'd recommend two or three, or preferably go for a higher wattage crystalline panel which will be a similar size to the bulky Maplin amorphous panel.
I have installed 1.5 Kw solar PV plant in my office in India.I want to know how long (hours)I can use the la loads i.e. FAN (75 W)x 5; CFL :18W x 15; Fridge
Sumit Roy, July 9, 2010
You don't say where abouts in India you are from, but from the sound of what you've got, it sounds like you have a big enough system to achieve what you need: your system should generate between 6kWh-9kWh of energy per day.Your fans are using 0.375kWh for every hour they are running. Your lighting is using 0.270kWh for every hour that is running. You don't say what sort of fridge you have, but it is likely to be in the region of 0.060-0.100kWh for every hour that it is running, unless you have a special low-energy solar fridge in which case it is likely to be around 0.010kWh per hour.
So you have enough power to run your fridge 24 hours a day, plus run your lighting and fans when you need them.
Hi Michael,
I am here in Brisbane, Queensland, Australia - over the last few years the cost of power has sky-rocketed with the current State Government the sole cause. I could go on at lenght but that is not the reason for my email.
Anyway, I have been researching how I can utilitse the use of solar power to supplement or if possible replace our grid feed for our house and pool usage. From the snippets on the web I have seen of your book, I was wondering if there are any issues i.e. relating to conversions to what we use here in Australia?
Thanks.
Ivor, July 10, 2010
There is no particular issue in using solar power in Australia, and the amount of sunlight you get there makes using solar all around the year a practical solution.You can start small and grow your system as you like: a very popular solution is the grid-fallback system, so your home runs on solar power when you have power available and when you've run out, the system switches straight back to the grid.
I have a simple question and I would appreciate your honesty. I want to know how much money I would save if I built a system like this as oppose to buying the one you see in this link.
http://www.mrsolar.com/page/MSOS/PROD/rv/MSRV-160
I have time to learn and do the project but if the saving is enough I will just purchase one. Money is tight right now and I do won an RV that needs this much solar power to charge by my large batteries that I now charge at home with an electric chord to my house outlet.
Thanks,
Tony
Tony, July 11, 2010
It is difficult to advise precisely without knowing your exact energy requirements and where in North America you're based.However, the specification of that Mr. Solar kit look good, it should provide enough power for most people's needs and it is a reasonable price.
If I were you, I'd just buy the kit! Yes, you could save some money if you read my book and work out all the figures for yourself, but probably not enough to make the extra time worth while.
Recently spoke with a manufacturer that suggested using 185W monocrystalline modules on a 2-axis tracker rather that 280w polycrystalline modules. What is the reason for this? Is the difference in power generation so noticeable? Furthermore, if given the option, would it be best to choose monocrystalline over polycrystalline in any type of installation (tracker or fixed mount)?
Ramses Torres, July 14, 2010
The benefit of a tracker is that the panels track the movement of the sun across the sky. It depends on where you live, but a good two-axis tracker can effectively increase the power generation by around one third during the summer, and a little bit more than that in the winter.However, all that is offset by the cost of the tracker. If the tracker costs more than around $300 (and most of the ones I've seen cost a lot more than that) then often the benefits of the tracker is outweighed by the extra cost - you may as well just buy extra solar panels.
That is not always the case, because you also have to have space for mounting the panels and so on.
Traditionally, mono-crystalline panels have been more efficient than poly-crystalline panels, which effectively means the mono-crystalline panels are slightly smaller than the equivalent rating poly-crystalline panels. However, that is often not the case any more and many solar panel manufacturers now claim their poly-crystalline panels are just as good as monos.
Interestingly, most of the new generation of solar panels now being developed are all either amorphous or poly-crystalline panels, capturing a much wider spectrum of light. I suspect the days of the mono-crystalline panel are numbered.
Hi Michael!
Very cool tool you have to calculate solar radiation. I was wondering what the equations you used to calculate the solar radiation and whether you would be willing to share with me the code! I'm a grad student and i'm new to modeling - i'm trying to model the amount of solar radiation in the photosynthetically active radiation band (or just a given wavelength) as a function of cloud cover and azimuthal angle but i'm running around in circles trying to calculate this.
Thanks a lot!!! Awesome inspiring work!!
Heather
Heather, July 15, 2010
Thanks for your message. Unfortunately I am not at liberty to share the code for my solar calculators as this belongs to the publishing company and has been created at quite some significant expense. However, you could do a lot worse than to visit the NASA solar site to get your hands on the raw data and to find out the calculations that they use.Have a quick google for 'NASA SOLAR TOOLS' and you should find what you are looking for quickly enough.
Hi, I have a roof line that faces 249 deg SW. The pitch of the roof is 35 deg. If I angle the solar panels aiming towared true south would I have to also increase the angle towared true south also? The location would be in the Southern New Jersey Area. Thank you Jerry
Jerry Duffy, July 21, 2010
The 'perfect' angle for solar panels changes throughout the year and working out the optimum for you depends on when you want to optimize the panels - do you want to generate as much power as possible during the winter, or do you want to maximize your generation capacity in the summer.35 degrees is actually pretty good for New Jersey for all-round power generation, giving you good generation capabilities throughout the Spring, Summer and early Fall. If you wanted to optimize late Fall, Winter and early Spring, you may want to increase your angle by around 8 degrees, but quite frankly, unless you want to squeeze every last watt out of your panels, you're pretty good on what you've got.
My caravan is kept in a barn. What maximum distance between the panel and the battery could a solar panel cope with? What size panel and who from?
r wilkins, July 22, 2010
I guess you're looking at a 12v system. Go for the best quality solar interconnection cables you can and aim for a maximum distance of around 30 feet/10 metres.As for the size of panel, that really depends on how much power you actually use. In my caravan, we used around 40 watt-hours per day on lighting, 100 watt-hours per day on a portable TV and 50 watt-hours per day on the water pump - a total of just under 200 watt-hours.
We only needed to provide this power for six months a year so we needed a 50 watt panel to cover our usage.
However, your requirements will be different to mine. Go and look at the 'Online Calculators' on the www.SolarElectricityHandbook.com and use the Project Analysis tool to find out exactly what you need.
Hi Michael
I'm an electrician just getting into solar. I am currently looking at a stand alone system for greenhouse/shed. the simplest plan is 3x 12v caravan style lights powered from a 110Ah leisure battery. however, I would also like to provide a price for a system using an inverter to create 240ac so that an anti frost heater (about 500W) could be installed. I have calculated that the batery will give me about 20 hours running time. what I am not sure of is how long the battery will take to recharge itself. I am looking at a small panel of 10W or so, do you think this will provide sufficient recharge? I would estimate 3-4 hours use of the lights and up to 12 hours use of heater (in winter when of course insolation is at its lowest!!)
According to my calc on a 10w panel in dec itwould take several days to recharge, meaning in a cold spell the heater will ceaseto function after a couple of days.
would appreciate your views
Andy
Andy Thompson, July 24, 2010
Hi AndyHeating is really not a good idea with solar electricity. Electric heating uses an awful lot of electricity.
Is your 500 watts an hourly or a daily figure? Either way, it is a lot for a small system to generate. You don't say where you are based, but if you are based somewhere in the UK, and 500 watts is a daily figure, you'd need around 600 watts of solar panels to generate that amount of energy in the middle of winter.
There are some other ways to achieve a similar effect. Here is a link to a really good article on solar heating in a greenhouse using a heatsink: http://www.reuk.co.uk/Solar-Greenhouse-Heat-Sink.htm
Solar panels are rated at STC values which makes sense to achieve a standard for comparison purposes but where irradiance levels are well above 1000 w /metre squared they surely produce a higher output. While the voltage remains sensibly the same I have measured higher currents than the specified Imp so what are the limits - does the pn junction become saturated? So can a 180w module produce more than the rated value?
Peter Vowles, July 25, 2010
Many solar panels can generate a higher output than their rating in optimum conditions, but in a real world environment they are unlikely to do so.Solar panels produce less energy when they are hot. When irradiance levels are above 1000w/metre, the high temperatures are reducing the efficiency of the solar panels.
So what you gain in one hand... you lose in the other. Sorry!
I think your solar angle calculator on this page http://solarelectricityhandbook.com/solar-angle-calculator.html is labeled incorrectly.
I think those angles should be labeled "Figures shown in degrees from HORIZONTAL"
NOT "Figures shown in degrees from vertical"
Bruce Schena, July 28, 2010
The figures can be read in two ways. The way I meant it to be read is the angle of the SOLAR PANEL is from the vertical.However, it is also true that the figure is the angle of the SUN from the horizontal.
So I guess I need to put a clearer description on the panel to avoid this confusion in the future. I shall speak to my webmaster.
Thanks for the comment.
Hello.
Thank you for writing a book about this subject.
It makes the subject a lot more accessible!
I just started reading the book, and I wanted to find out what the solar irradiance figures are for the Netherlands, but they are not mentioned in the country list.
Do you know where I could find them?
Thank you!
:-)
Anna, July 31, 2010
Thank you for your comments about the book. I'm not entirely sure how we managed to miss The Netherlands from the list of countries. I will see what we can do about that.In the meantime, you can find out the information based on your latitude and longitude from NASA figures here: http://eosweb.larc.nasa.gov/cgi-bin/sse/sse.cgi?na+s02#s02
Hi Michael,
Having recently purchasd your publication, which I have found extremely helpful, I need clarity regarding the placement of the batteries.
I intend having 3 deep cell batteries, 6 cells each and 165 amps. I would like to place these into my roof.
I am aware of the hydrogen hazard and hence why the question. The roof is pitched and the floor area is 10 x 16 meters, the apex of the roof is 2.1 m high. There is a small amount of air flow through, but no extraction system as such. Is this acceptable or not?
Many thanks,
kind regards,
Judi
Judi Robinson, August 1, 2010
There will be a small amount of airflow in the roof space to make siting bateries there suitable. However, it is difficult to give accurate advice without seeing your site.Roof spaces can often get very hot and this can be a problem for batteries in general, and especially as they vent more at higher temperatures. I would be tempted to fit a small extractor just to be safe.
You can buy a solar powered extractor fan that is designed to be installed into roof spaces which does not require much power.
having a solar panel put on my motor home to keep my batteries topped up,been offered a crystalline and mono crystalline panel,which in your opinion would be the best .
alan johnson, August 2, 2010
There is not a lot of difference to be honest. The physical size of the mono crystalline panel may be slightly smaller but otherwise there will be no real difference in operation.
Do you by any chance have an digital copy of your book that I can load onto my computer for a quick reading reference? I think Amazon may have a digital book, but it is designed for "digital readers" rather than for a straight working computer. We're buying the printed version, but could really use its digital equivalent.
And, you have a great website!
Tom Meeker, August 3, 2010
Thank you for your comment about the website.We don't have a digital version available at present, but a digital version of the book in all the usual digital book formats (Kindle, ePUB, PDF) will be released this Autumn.
Hello Michael,
i have just ordered your book after going through this website,i found it a spot on resource.we have a requirement to power a billboard with solar pv in Ghana\West Africa
the system will power 5x400 watts halide bulbs for 8 hours and the system will be a stand alone,can i ask if deep cycle batteries can be placed (hidden)under ground to make it less conspicuous.i will really appreciate any advice on insolation, solar panel, and battery type.
many thanks
James Yasembi, August 4, 2010
Siting batteries underground can make a lot of sense as they are more insulated against extremes of temperature. The only thing you need to ensure is that they are accessible so you can check and water them regularly and that there is an extraction system in place to allow the batteries to vent properly.You can find the insolation figures for Ghana in the 'Online Calculators' on the web site. You've got quite high power requirements, so your system is not going to be a small one, but you also have excellent solar irradiance throughout the year so that will certainly help you.
I have your handbook and have read it several times, I do need some help if you would please. I need help hooking up my battery's ( total of 4 ) ( 2x12 volt & 2x 6 volt ) I will be using a 12 volt system. From left to right with the 12 volt battery's with the 12 volt + up at the top on the left side of the battery bank. First connection would be to parallel the + terminal to the + term of the second 12v battery, same for the neg side ( I have that with no problem ) my problem is connecting the last two battery's both 6 volt to have them parallel with the 12 volt battery's. Then once I get that part done I know the charge controller ( and inverter ) positive side would be connected to the + terminal at the first battery. Where would the Neg - side of the charge controller and inverter go. I know in your book you want us to connect the neg - side at the last terminal to have equal discharge from the battery's, until I know exactly how to wire the last two battery's to the first two I wont know where that is. Last question I promise, I guess its best to go ahead and install a ground rod and tie the Neg - side of the battery's to the ground rod ( Am I reading that correctly ? ) Does it matter what battery you come off of? O.K. Wew! I think that's it, and thanks again for your assistance.
Joe Groves
jgroves@broadlink.biz
joe groves, August 5, 2010
You'll have some problems with having different types of batteries in the same system, because they will charge and discharge at different rates. You will end up with an imbalanced system.My recommendation is that you have a set of identical batteries and ditch the others. Alternatively, you can set them up in two banks of batteries - one bank with all the twelve volt batteries and one bank with the two six volt batteries and switch between them. This would have the benefit of allowing your batteries to rest occasionally which will improve battery life.
So you connect your 12v batteries in parallel, connected to a battery switch, you connect your 6v batteries in series and connect them to a battery switch, and then connect the battery switch to the controller. You can buy these battery selector switches from most solar suppliers. Here is the sort of thing I have in mind: http://www.maplin.co.uk/Module.aspx?ModuleNo=264721
With regards to the ground rod, connect it to the negative terminal on the first battery in the series - i.e. between the battery and the controller.
I hope that helps!
Hiya,
I just flew from Albuquerque NM (my home) to Oregon and along the way, I read your book. First off, well done on making a potentially complex subject seem rather simple. As an electrical engineer I understand more than most so perhaps that helped. In any case, well done. Now my question. Regarding grid-tie, why isn't there a configuration that allows one to use batteries to store from the solar array and then once the batteries are fully charged, offload the additional energy from the array onto the grid? If I read correctly, the grid tie configuration means you are using the energy as it's produced and when not being used, it's directed to the grid. Nothing about storage involved. Is this due to safety concerns or the potential for the grid to drain the batteries? If so, rectifiers could easily fix this. Just curious.
Cheers,
jlc
James Culbertson, August 11, 2010
Thanks for the comments. With regards to grid tie systems, I've shown a standard grid tie system and a grid-fallback system in the book but you are absolutely right, it would be possible to create a system as you have suggested, incorporating battery storage so that you are always (as far as possible) using your own energy, but putting any surplus onto the grid.
kindly update me about the latest inventions in soler power
adnan mahmood, August 11, 2010
What a huge question! There is so much going on with solar power at the moment, it isn't easy to know where to start.In a nutshell, solar is improving in three areas: solar thermal, multi-layer photovoltaics and thin film solar paint.
SOLAR THERMAL
For large solar power stations, the technology is moving away from solar photovoltaics (although these still play their part) and moving towards solar thermal systems, creating very hot water and powering turbines from steam. Efficiencies are high and the benefit is that the hot water can be stored for hours, allowing the energy to be released when the power is needed.
MULTI-LAYER PHOTOVOLTAICS
Photons are light energy. Released from the sun, these bundles of energy provide us with light and heat. Photons work at different frequencies, including visible light, infra-red and ultra-violet frequencies. Currently, solar panels work on visible light, absorbing these photons and generating electricity. A lot of research is now being done on capturing some of the other light frequences: infra-red and ultra violet aren't visible to human vision, but are not absorbed by clouds in quite the same way as visible light. This means they can be more effective on cloudy days. By capturing more frequencies of light, solar panels can become more efficient. We should start seeing these panels on the market in the next couple of years.
THIN FILM SOLAR PAINT
A lot of work is being done on making amorphous panels cheaper to build. The technology here is to use multiple layers of so called 'solar paint' or 'solar ink' to paint a surface (typically glass or aluminium) to make a very low cost solar panel. Whilst these aren't as efficient as other photovoltaic panels they have the very big advantage of being much easier and cheaper to produce, thereby bringing the price of solar power generation right down. Expect to see these panels incorporated into all sorts of devices such as mobile phones, laptops, MP3 players and the alike in the next couple of years. This technology can also be used to clad new-build houses and factories and the price of it will become so cheap that it is possible that solar roofing materials will be almost as cheap as non-solar roofing materials in the next five years.
I hope that answers your question.
Dear Michael,
Thanks for a very informative and great value book. I have just bought 3 x 100watt solar panels and a 250 watt grid tie inverter off eBay. The total cost was about £700. I’m planning to install it at a holiday property near Marbella which is occupied about 20% of the time. The insolation figures on your website indicate that Marbella has an average of 4.7 kwh/m2/day. Can I simply multiply this figure by the number of watts my panels generate (300) to get the average output per day (less efficiency losses)? If so, this gives about 1.4 kwh per day, does this sound reasonable or am I missing something?
Also, what is your opinion of the small ‘plug and play’ grid tie inverters available on eBay. I paid £90 for a 250 watt grid tie made by ‘Sun’. I have tested it and it seems to work OK, it produces a pure sine wave output and has island protection.
My plan is that this small system will produce enough power to run the swimming pool pump, fridges etc when the property is unoccupied. Does this sound reasonable to you?
Any help or suggestions would be most welcome. Cheers, Paul
Paul Newton, August 17, 2010
Thanks for your comments about the book. Your project sounds very interesting. In terms of the calculation, you are correct - so long as you take into account all the losses in the system.With regards to these 'plug and play' grid tie inverters, they are not certified in any country for true grid tie connection as they do not have any of the safety cut out features of the proper systems. However, as a simple way of taking a house off-grid, or to provide 'grid-fallover' power, they can work well.
It is impossible for me to say for sure whether your system will produce enough power to run a swimming pool pump, fridges and so on without knowing the wattage of the individual pieces. However, a small swimming pool pump and a low energy fridge should be fine with that setup.
Enjoy your solar power!
This question is regarding the output of your solar irradiance calculator that provide the results in sun hours/day or kWh/m2/day. Have the DC to AC derate factors already been factored into this number?
Bob Sisco, August 22, 2010
No they have not. There are a number of derate factors that have to be worked out, depending on the type of system you have, all of which are discussed in the book.