Just reaching out to the locostbuilders collective knowledge to see if anyone has any experience on this subject.

I have about 20w of equipment I want to run, all 12v stuff. It is going to be located where there is no mains power available, so solar seems the obvious answer. However, I need it to run 24/7 so I need some kind of battery system that charges up during the day and supplies power overnight.

Does anyone know...

1. Whether these Chinese solar panels available on eBay and the like live up to the spec that they claim?

2. If I buy a 40w one for example, is it the case that it will only produce 40w on the brightest of summer days? What can I expect as an average?

3. How many times should I overrate the panel power vs the load? ie is 40w enough to operate a 10w load 24/7?

Any experience or hands-on knowledge gratefully received!

Chris

Chris

I have a full 4kW set of panels on my house, on their best performance which is during May thro' August on a really good day they will make between 15 & 20kWh of power, so saying the sun is high in the sky for say 7 or 8 hours they are at best producing around 60% of their potential output (in fairness my house is not facing in the best direction & the panels are partially shaded for some of the day, so if you had your panel in perfect conditions you could do better than I am). However, the problem comes at this time of year, during Dec & Jan, on a really poor day they might make no more than 300Wh of power! (I'm ignoring snowy days when they do nothing) so if you said the sun is high in the sky for say 4 hours during Dec & Jan then the potential output is 16kWh, so 300Wh is about 2% of the output!

Hence on winter days with poor weather a 100W panel, might be making as little as 2W - not a fat lot of use for powering anything.

I think you have a couple of choices, buy a couple of sizeable leisure batteries, 100Ah or so & charge 1 whilst using the other, just keep swapping them each time you go there or use an even bigger battery & get a sizeable solar panel & back it up with a small wind turbine - between the 2 you should be able to keep the battery topped up - not a cheap way of getting power tho'. At least in the short term one of the baby 850W generators you can pickup for around £60 -£70 might be a better bet.

Cheapest way of getting powerful solar panels is to buy ones with broken glass - doesn't usually affect their output significantly, you can buy them for peanuts & just make sure you protect them from the elements - either glue fresh glass over the top or put them under some sort of frame.

Good luck!

Russ

Thanks Russ

Out of interest, how old is your installation? It sounds like you have had it for a while?

Either way, I guess you have confirmed what I suspected in that a panel only produces it's maximum output for a few hours a year and that I will have to hugely overrate the panel in order to guarantee a 24/7 supply.

I will do some more investigation! As you say, a wind generator might be a good way to go either as an alternative or to supplement the solar. However my concern is that by the time I do all of this it might be cheaper to dig in a cable to the barn and come up with some kind of arrangement to buy power from the farmer!

Chris

My installation went in Nov 2011, got it under the last of the stupidly good deal that the government was doing, it cost me £10k to install, but has already returned me around £1200, plus saved me about £200 on last years electric bill (might have been a bit more than that) so for me it has been brilliant, but of course it all only really works due to the sceme being incredibly incentivised & of course it has no storage capacity at all you either use it or it goes straight back into the grid.

If you're funding it yourself it makes a lot less sense. If you are at all close to an available power source, I'd say it would be cheaper to hire a digger for a day & dig a cable in, put a meter in at your useage point & agree to pay the farmer 1p a unit more than he pays, or 10% or whatever seems like a reasonable amount. Or carry a battery to & fro as I suggested originally. Certainly putting any sort of installation in which can store sufficient power when you're not using it & will be reliable throughout the year is certainly going to come to a few bob!

[Edited on 4/3/13 by russbost]

Without the subsidised FIT rates solar power rarely makes any sense in the UK as a sole provider day to day, and without the FIT rates (which IIRC are not guaranteed to continue, despite what many installers will tell you!) solar is too expensive to consider unless you live in an area with significant sunshine hours (not just daylight hours).

You'll lose a good chunk of the capacity due to aging too.

If you want I could have a chat to a chap I know who did small installations for 24/7 operating equipment all over the world.

Thanks for that Russ, been thinking about solar electric recently as my house ideal but you put me right off them tbh don't seem to be remotely woth it output wise

Cheers