Quote:
Originally Posted by HardDrive
I am aware that there have been efforts to create cars that use some sort of flywheel system to store energy. But what about systems for use in homes or business?
I have to assume that there would be a great deal of loss due to mechanical inefficiency in the process of storing energy from a power source (wind, solar, etc).
I guess what I had in mind would be some sort of large weight that gets raised using solar power, then is used to drive a generator at night to power lights and such. I suppose one could also pump water, compress air, etc....
I'm just ranting here, but I know there are some folks with the engineering chops here that could illuminate the subject. Do tell.
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The only thing that is done that is somewhat cost effective is pump hydro. You buy cheap power at night from plants that cannot easily reduce load (Nuclear and Coal fired big plants), and pump water into an upper resevoir. During the day, you make power during peak. The price difference between night time base and day-time peak is significant.
But lets do a small one for your house! So, lets pump some water and see how this works.
Energy is m*g*h, assuming the water is still before and after. If you use 3000 kWh per month, then you are using 100 kWh per day.
Assuming you have a water tank ~30 feet off the ground, how big does the tank need to be to support your 50 kWh (night time) usage?
h = 10 meter height (close enough!)
g = 9.81 m/s^2
m = kg
water is 1 liter per kg
50 kWh = 180 000 000 joules (kg * m^2 / s^2)
e = m*g*h
m = e/(g*h)
180,000,000/(9.81*10)=1,834,862 kg of water = 1,834,862 liters of water
or about 416,552 gallons
With efficiency issues, call it 1/2 million gallons for your house. The OBVIOUS solution is to increase the height. The pump-hydro I visited 20+ years ago had I think 1500 feet between the upper and lower ponds. If you had that, you could cut the tank to something like 10000 gallons. However, your piping and pump system would need to be able to handle upwards of 750 psi!