Bob Sciamanda already mentioned this, but I'll add a bit more.
One of the highlights of a summer I spent doing work at Pacific Northwest
Labs (Richland, WA) was taking a weekend trip to Grand Coulee Dam. During
low electricity demand, some of the "generators" can be used as motors to
pump water about 280 feet above Lake Roosevelt. This water can then be used
for irrigation, or it can also be allowed to flow back into Lake Roosevelt
through the "pumps" which now act as generators. This can then be used to
provide electricity during peak demand. My understanding is this is routine
operation for the dam... some pumped water goes toward irrigation and some
pumped water returns to the lake to provide peak-demand electricity.
Therefore, the idea of "lifting weights" for energy storage is not only
possible, it is currently being done. However, as Laurent Hodges points
out, it is not very practical on an individual homeowner basis.
Michael D. Edmiston, Ph.D. Phone/voice-mail: 419-358-3270
Professor of Chemistry & Physics FAX: 419-358-3323
Chairman, Science Department E-Mail edmiston@bluffton.edu
Bluffton College
280 West College Avenue
Bluffton, OH 45817