Guinness
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| posted on 9/9/07 at 08:23 AM |
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Solar Power?
My father in law has just bought an old cottage which is "off the grid"!
The generator looks like its seen better days, and I'm going to have a look at repairing it next week.
But we were thinking of wiring it up to run on 12v electrics / solar power with a battery back up. Anyone know how to go about it?
At the moment we have got 2 x 900amp 12v batteries. They look like they came off a truck or something. I guess it's a bit more complex than
just wiring them up to a solar panel and then to the lights inside the cottage?
Any help gratefully received!
Cheers
Mike
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smart51
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| posted on 9/9/07 at 08:45 AM |
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Solar panels produce a CD voltage that is proprtional to both the brightness of the sunlight and the load on them. They float at around 17V. You
need a regulator to "waste" the excess voltage so that you only present 14V to the lead acid batteries for charge.
12V lights are not usually all that good. You can get inverters that run off car batteries and create 240V AC.
In direct sun light, we get around 1kW of light per square meter pointing directly at the sun. The best solar panels are 15% efficient, so 150W per
square meter. Less if the panel doesn't point directly at the sun, which it won't most of the day. you lose upto 3/14 in the regulator
then 2/12 in the battery, or more, then 30% in the inverter. 50W usable power per square meter. You're going to need a lot of square meters to
run a house. for example, 2 square meters of panel will power a 100W bulb for 1 hour for every hour of direct sunlight you get.
Solar electricity like this is good for runing the background drain of your house only. Things like your alarm clock, central heating timer, video on
standby, microwave clock etc.
The best use of solar power is solar hot water. The panels are many times more efficient than electricity. They even work a bit in cloudy weather as
they absorb IR and UV as well. Even this is only a top up to other power sources. With solar hot water, some days you need no gas or electric, some
days only part of what you'd otherwise consume.
You need that generator.
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caber
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| posted on 9/9/07 at 08:53 AM |
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Big problem will be getting enough from Photo Voltaic cells to provide enough power to sustain a house. Have a look at small wind turbines, check out
what you can buy for yachts.
I would get the generator working and get it to charge the batteries. Look at the stuff you can reasonably power from them, for instance get a 12V
fridge as supplied for caravans. Lighting is no problem just carefully count the power you are using.
Obviously heating is out of the question but you may want to look at pumping water depending on the reliability of the supply and it's effective
head. You should aim to keep one day's supply stored in or near the cottage, that at least gives you a chance to fix anything that has gone
wrong with the water supply, or make alternative arrangements if the supply has dried up for any reason, also best get this checked for contamination
by agrochemicals and sheep or human poo!
As for the cottage do whatever you can by way of Loft or roof insulation, wall insulation and the floor, also make sure the damp proof course is
effective. Buy a good wood burning stove, a chain saw and a log splitter. Ideally a land Rover and trailer as well then go looking for recently
fallen hardwood trees. You will probably burn 2-3 tons a year with a good stove and well insulated cottage.
Good luck and have fun with it.
Caber
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StevieB
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| posted on 9/9/07 at 08:53 AM |
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Probably worth looking at fitting a windmill too - given the british weather and long nights in the winter, it'd be nice to have the backup of a
different power source.
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BenB
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| posted on 9/9/07 at 10:53 AM |
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Yup. Sounds very sensible advise so far. My experience with solarpanels is that they rarely provide much electricity unless the sun's really
bright and even then you need quite a few square metres to make a usable amount of electricty....
Wind turbines are a better option.
And I'd recommend an inverter- 12v fluroscent tubes are rubbish! When I didn't have electricity in my garage I fitted 8*8W 12v tubes
running of a freshly topped up battery. 64W of fluroscent light- but it was still dingy and gloomy in there.....
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JoelP
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| posted on 9/9/07 at 11:43 AM |
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why does no one use old alternators to make wind turbines? Are they not efficient enough? I cant help but think that if it was a good idea it would be
more popular! 
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Bob C
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| posted on 9/9/07 at 05:53 PM |
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solar panels are seriously expensive - 125W panel costs ~£500.
And you don't get 125W from it - ever, even peak. Note also that the ESH (equivalent sunshine hours) for manchester in winter is less than 1. So
if you want a continuous 20W, you need 500 watts of panels - 2 grand!!!
The little wind turbines you can buy are pants too - to get any useful power they have to be MASSIVE.
cheers
Bob
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violentblue
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| posted on 12/9/07 at 08:39 PM |
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if its in a breezy (but not to windy) area, than wind power would be ideal.
a few pics of my other projects
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