Quote:
Originally Posted by ksa8907
Why not just punp water into a tower then use a hydro-generator to get on demand electricity?
Not very portable but far less complex.
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Time to do the math. An energy storage system big enough to seriously interest a utility should store 1 GW for 10 hours, or 10 GWH.
10 GWH = 10,000 MWH = 10,000,000 KWH.
1 KWH = 1.34 hp-hr.
1 hp-hr = 33,000 ft-lbs/min X 60 min/hr = 1,980,000 ft-lbs.
1 KWH = 1.34 X 1,980,000 = 2,654,000 ft-lbs.
10 GWH = 10,000,000 X 2,654,000 = 2.65E13 ft-lbs.
Assume two storage ponds, the high one 1000 feet above the low one.
2.65E13 ft-lbs / 1000 ft = 2.65E10 lbs of water.
2.65E10 lbs / 62.4 lbs/ft3 = 4.25E8 cubic feet of water.
4.25E8 cubic feet / 43,560 square feet per acre = 9750 acre-feet of water.
If each pond is 20 feet deep, the surface area will be 9750 / 20 = 490 acres.
If the high storage is only 100 feet above the low storage, you need 10 times as much water. That's why there are so few pumped storage systems. You need to cut the top off a mountain to hold enough water, and that does not come cheap.