Integrating solar into existing power systems

I am currently looking into the feasibility of all forms of renewables as a supplement to existing power supplies. I have had a number of amorphous PV panels on test for six months with a quite small load. Any thoughts on how to integrate a small scale system for lighting(using LED lamps) would be appreciated ! Simon.

Hi Simon,

When you mention 'existing power supplies' do you mean mains electricity or a battery powered system? The two are fundamentally different. To integrate solar panels into a battery system is trivial - simply connect the panels into the system via a regulator.

For mains supplies, integrating is harder. You can get inverters to convert the DC electricity from the panels into 240VAC to connect to the national grid, but they are not cheap, and it's not DIY wiring! For a small scale system of less than a few hundred watts it's not worth the effort and the cost. Besides, LED lights are usually low voltage DC types, so converting from DC to AC and back again is a bit pointless.

An alternative is to run the lights from a switch that can be set to either 1) a battery bank that is charged by solar panels or 2) a mains-powered 12V power supply. Most of the time you can run the lights off your batteries, but when they begin to get low, simply switch over to the mains supply. It wouldn't be terribly hard to create a circuit to do it automatically when the voltage began to drop.

A friend of mine runs the lighting in his kitchen from such a setup, and it has worked very well for him.

Solar panels for Antarctic expedition

I am starting to make enquiries about solar power for a proposed antactic expedition in 2009/10. I would be after lightweight panels that could be put over tents or the sledges to charge sat phones etc.

Please let me know if there is anything you can offer that may be suitable.

Yours, Chris

Hi Chris,

 

Unisolar used to make some excellent flexible panels that were ideal for strapping to tents and sledges, and performed very well. Unfortunately they are out of production at the moment, but if they come back into production in the next few months (as I understand Unisolar are planning) they would be the best ones to go for.

 

There is a similar flexible solar panel from Powerfilm, although a friend who used one in the Antarctic last year was a little disappointed with the output.

 

I would however recommend the Spectra solar panels as a good solution. Although not flexible, they are very slim, have grommet holes in the corner so are easily lashed to sledges and tents, and are very lightweight (and good value). We sell 5W, 10W, and 20W models - see http://midsummerenergy.co.uk/buy_solar_panels/spectra_marine_solar_panels.html for details.

 

Best wishes for the expedition anyway!  As it happens I'm off to Antarctica myself for a couple of months shortly - it's a fantastic place to spend some time!

Solar power for narrowboat

hi
What would you recomend as a wind and solar system for our narrowboat? It will be for liveaboard, battery bank is 600amp, running lights and 12v fridge, 12v tv, dvd, and usual waterpump/shower emptying pump.
regards
bob

Hi Bob,

If you are running a fridge you need a fair area of solar panels to make a difference, even in the summer. I would recommend a minimum of 2 panels of around 60 watts or so. By far the neatest solutions are the adhesive backed 'peel and stick' Unisolar panels. You should probably go for the kit option which includes the most appropriate regulator - click on 'solar panel kits' in the shop menu.

The advantage of the adhesive-backed panels is that they are very low-profile and simple to install. However, because they are flat on the roof they won't be quite as efficient as a framed panel which can be tilted towards the sun. The Unisolar ES62 panels are a very good value alternative if you want to go for framed panels.

Wind power is useful in the winter when you get less from solar. Be aware though that the output from a wind turbine does depend very markedly on your location - if you are surrounded by trees or buildings the amount of power can be a bit disappointing! However, they can give very useful power in locations which are more exposed. Again, as you are running a fridge, which is quite power hungry, you would be looking at the larger of the models we supply, the Rutland 913. You would also need the HRS913 regulator to connect it into your batteries.

Tristar regulator and battery monitors

We have just installed 7 x170w 34v solar panels and we need a regulator. Would the Tristar TS 60 be too big?  Also we have two other regulators for other panels - is there a monitor into which we can feed all the solar info to give us one lot of information on charging, battery status in % or amp hrs?
Sally

Hi Sally,
I'm slightly confused - 34V is an unusual voltage for a battery-powered system! Big panels such as those are usually used for grid-connected systems, where you produce 240V AC (domestic electricity). In those cases you wouldn't use a regulator such as the Tristar; instead you would use an inverter.
If you have a battery system, it would usually work at 12 or 24V DC. If it's a 12V system, your panels are really producing too high a voltage. But, if what you have quoted is the maximum voltage (usually given as 'Vmax'), they are about right for a 24V system. You have a total power of 1190 W (7 x 170), which at 24V is still a bit under 60 Amps. So yes, if you are running a 24V system, the Tristar 60 would be perfect.
You can get battery monitors to give you the state of charge of your batteries. For 12V systems the NASA BM-1 is very good (http://www.nasamarine.com/). I think Steca make a similar instrument for 24V systems - if that is of interest I can get you more details. At the moment we don't stock them, but we may be able to get one in.

Solar power in Bangladesh

Hello there, I'm interested in setting up a small kit in Bangladesh as the sun is strong and plentifull as a trial to test it's usefullness. I'm unsure what to try as a starter. Can you suggest something please for me?

Many thanks
Kind regards
Saiduz

Hi Saiduz,

Bangladesh would certainly be a good place for solar power!

It depends what you want to power from the panel. I would suggest the smallest setup that would be of much use would be a Spectra 20W solar panel, with a Morningstar Sunguard regulator; you would attach that to a 12V lead-acid battery (which I'm sure would be available locally). That wouldn't give a great deal of power, but perhaps enough to run a radio and a fluorescent light or two in the evenings. However, it would give you an idea of what could be achieved with a larger setup.

Solar panels for kayaking expedition

I need a panel capable of charging video camera batteries, mobile, and laptop for a three month solo kayaking expedition. What sort, how many, what price?? Thanks.

Sounds like a fun expedition! It would be worth you working out fairly carefully how much power you need. If you use the solar panel calculator on my site ( http://midsummerenergy.co.uk/solar_panel_information/solar_panel_calculator.html) you can enter the power each item consumes, and how many hours you need it for each day. A laptop for example might be something like 100W, but only for 1 hour a day on average.

That will give you a good idea of how big a solar panel you need. I would guess though that you might be looking at something like a 20W panel. The Spectra range are pretty good ( http://midsummerenergy.co.uk/buy_solar_panels/spectra_marine_solar_panels.html), although I would perhaps go for 2 x 10W (£92 each) rather than a 20W as they would pack away smaller. They are light and reliable though, so would make a good choice. If you find your needs aren't that great, you might be able to go down to 2 x 5W panels instead.

I can also get in some Unisolar folding panels which pack very small and are designed for expedition use. They are considerably more expensive though! See http://www.uni-solar.com/ , then follow links to 'Standard products' and then 'Portable modules'.

Whichever you go for, you would also need a battery and regulator. The Sunguard regulator (£26) is small, waterproof, and ideal for panels up to 50W. A small sealed lead acid battery will be the heaviest part of your kit.

Hope that helps.

Solar propulsion for yacht

I'm considering design and building a yacht using only solar and wind generated electricity including propulsion. Comments/advice.Thanks,Dudley

It's certainly possible. Your difficulty will be storing enough energy to make it worthwhile. A yacht can motor on a diesel tank for weeks non-stop; even on a big bank of batteries it's going to be hard to get more than a few hours at a good speed. If you are content with a small engine that is only used for manouvering into and out of a marina at the ends of a longer passage under sail, I think it could well work. But don't expect to be able to do much in the way of passage making!

Two seperate charging systems

Hello, I have a 50 watt panel and a 130 watt panel, is it possible to wire them both to the same batteries (560 ah)possibly through 2 seperate charge controllers which I have.The 50 watt system is an older system and batteries are suspect where as the 560 ah system is new and could easily take the 2 panels if they can be used together.

cheers, Steve

Yes, it's usually absolutely fine to wire two seperate solar panels to the same battery bank. You could either use two seperate solar regulators, or you could even wire both panels to one solar regulator - as long as it is rated for sufficient current. In your case, that would be 180 watts(130 + 50), divided by the battery voltage (12) - 15 Amps.

Unisolar PVL 68

I am interested in these flexible panels to put on a flat roof for a new build house. Are they still available? Can substantial numbers of them be linked together?

Yes - they are still available, and they are ideal for houses. In fact that is what they were designed for! If using them in a residential situation you would usually link them together to a grid-tie inverter, in order to connect them into the national grid system. That way you can still use grid electricity at night and in the winter when you aren't getting much return from your solar panels; and in the summer you can sell your excess electricity back to the electricity companies.

You can link any number together, as long as your inverter is rated to take the power that they produce.