Your Questions About Solar Energy Generators For Home

Donald asks…

Is there a way that a wind mill can generate enough electricity to turn the lights on in a house?

I am writing an essay for school and it has to be on everyday life and how you can use alternative fossil fuels to do the same things. So if they are other things you can think of that i can use (wind energy, solar energy, hydroelectric energy, etc), to put in my essay that would be extremely helpful. Thanks!

admin answers:

A good way to discuss it would be to think about using Alternative energy to supplement fossil fuel energy. Aside from hydropower, alternative energy is not consistent enough to be used on a small scale to power a home (like if clouds cover your solar panels, you’re screwed).

If you used all kinds of alternative energy and then supplemented with a generator, then you’d have a really good, and consistent source of energy.

Mandy asks…

how car batterie to for solar system of 5kw and how much roughly cost?

i am planing to have independent solar system at home 5 kwh capacity , how many car size batteries do i need for this system.
with thanks for the answer.

admin answers:

Batteries are only 50% efficient at charging and lose 1% per day. If you can, use net metering and just sell your excess power to the utilities and buy the power you need back from them. How many batteries you need depends on your energy usage ( a figure of 5 kwh is meaningless without the period of time that is over ) and how long you want to run without solar power. Most people design just for diurnal use and fill in with a generator for back up power in an off grid home. But it is possible to consult the weather office and determine how many days in a row you can expect to be without productive sunshine and how many days you can expect to be able to recharge your batteries over. Note that the average North American home uses 950 kwh per month.

You also have to take into account that most systems are designed for just the bulk charge to 80% capacity.

If you are saying that you use 5 kwh evenly over a day and you can expect 8 hours of useful sunshine then considering the 50% charging efficiency of lead acid batteries you would be looking at storing 5 kwh * ( 2 * 16 / 24 ) = 6.7 kwh. A typical car battery is 12 V at 65 AH so it would hold 780 WH, at 80% capacity that would mean you would need 10.73 batteries and you would need 2,504 watts to provide for the 1/3 of the 5 kwh that you use when the Sun is out plus the recharging of the batteries, that would be about 25 of those 100 watt two foot by four foot solar panels which sell for about $250 so with a charge controller you would be talking about a $13,000 system. However, this assumes you have DC appliances. If you toss in an inverter, those can be as bad as 65% efficient so you would have to increase everything by about 54%.

Of course, power usage isn’t even though the day so you should characterize your power use better plus 5 kwh per day amounts to 150 kwh per month which is only 1/6th of typical usage so it may be an unrealistic value.

I would strongly advise that you characterize your power use carefully, consider net metering as that would mean you only have the inverter inefficiency to worry about and not the battery inefficiency. If you must go off the grid, consider DC appliances to remove the inverter inefficiency and consider an absorption refrigerator which could run off a propane tank buried in the yard as food storage can not risk possible daily outages, plus you can run a gas stove top off the propane. Gas ovens are a problem as many have glow plugs which consume 300 watts constantly but if you can find one with piezoelectric lighters or one of the old outlawed ones with a pilot light then a gas powered oven becomes possible. You can also run your backup generator off the propane.

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