solar or wind for 12v supply help

[buddstud]

Hi I'm trying to get free power to run a small 12v. pump,to deliver water from a stored rainwater source around my farmhouse to feed the toilet. As we are on a water meter I feel that the savings would be very handy. The problem is I am useless with electrics(but willing to learn), and I am trying to do it with very little money.I could buy a 1.5 amp trickle chargeing solar panel,off the Web for about £10 to top up a leisure battery,but I don't know if this would give me enough charge. The other alternative would be to use a wind generator, but they cost around £300 for the cheapest sort.I would like to build one, but I don't know where to start. can anyone give me any ideas ..........thanks ......Colin

[gug]

Hi I'm trying to get free power to run a small 12v. pump,to deliver water from a stored rainwater source around my farmhouse to feed the toilet. As we are on a water meter I feel that the savings would be very handy. The problem is I am useless with electrics(but willing to learn), and I am trying to do it with very little money.I could buy a 1.5 amp trickle chargeing solar panel,off the Web for about £10 to top up a leisure battery,but I don't know if this would give me enough charge. The other alternative would be to use a wind generator, but they cost around £300 for the cheapest sort.I would like to build one, but I don't know where to start. can anyone give me any ideas ..........thanks ......Colin

Would it be possible to rig up some kind of savonius rotor to drive the pump directly - thereby eliminating all electrickery... ?

[buddstud]

thanks for the reply,sounds interesting but what the hell is a svonious rotor.?...........Colin

[jondy]

Hi, I would forget about windmills to charge a battery for a pump if you are seeking a very low cost solution. ( savonius wind generator, see them working on 'youtube') Ideally the WC would be on the ground floor, close to the water butt. Submersible 12v caravan pumps are cheap on ebay (about £10) A 12v car battery should supply the pump for a considerable time. If a solar panel can not replace the battery useage you will need to charge up from a battery charger. The cheaper solar panels won't replace the battery useage. I would try the pump first without a solar panel and use your car battery for trials. If it works OK you can ask a solar panel supplier for his advice for a suitable solar panel. (then shop around) Keep it as simple as possible to start out.
John

[Big Al]

http://www.solarkitsdirect.co.uk/default.asp

Is a site i've just found. The thing is it has a solar calculator on it that you can work out what sort of panels you want to power certain items. Thought it might be of some use.

Mind you I do need some pointers on how solar actually works... Well I know you stick a panel out in the sun at 30 deg then hook this up to a regulator and onto a battery. I presume this then charges a battery and you use the batt power for the item.

Conversly for house electrics you have a box into the grid to export / import ???

[Karmanaut]

Well, if you charge up a battery using a charger you plug into the mains, then you'd be just as well running the pump from the mains and cut out the middle man (and energy losses).

First you need to know how much electricity the pump uses.

For example, if it was a 200 Watt pump (Volts * amps = Watts) and it was running for a total of 2 hours per day, then the pump uses 200 * 2 = 400 Watt hours per day. Or 0.4 kwh per day (kilowatt hours).

Once you know how much electricity you need, you can decide which method is best/most cost effective to supply that electricity.

For solar, you'd work out how much sun you get on average. If you had a 100W solar panel and 7 hours of sunlight a day, then that panel would produce 700 Watt hours (0.7 kwh) per day. But then what happens in winter? Would you get enough sun to charge up the battery if it's cloudy for a week? The same with a wind turbine. Also, a 100W solar panel might only give out 60W most days. Is it a DC pump? If so, you can run it from a battery. If it's an AC pump, you'd need an inverter, which would lose about 15% of the power the panel (or turbine) produces.

Now to work out the cost. How much does the Electric Company charge you per kwh? (I honestly don't know. For argument's sake say... 28p?)

So how much would that kwh cost from solar? If your 100W panel gives 0.7kwh per day, then it "earns you" 70% of that 28p every day in electricity saved. So at that rate, how many days will it take to repay what the panel cost you to buy?

You could get a hand pump, which is free to power and gives you exercise.

[Rod in Japan]

Don't give up on wind power if you have good wind. Have a look at Motorwave in Hong Kong. They make very cheap turbines in various configurations that might meet your needs perfectly. I hope to get one of their products at some stage.