Hello Mike,
Yes, it doesn't look like big springs are able to be used
for storing much. I was hoping they could be wound up during high wind or
hot sun times for overnight use. Michel sent me the following which about
nails the idea but I wonder if they just mean a straight helical spring as
opposed to the spiral mainspring type - would there be a difference in the
theory?
<<http://en.wikipedia.org/wiki/Energy_density
Excerpts from their main table:
Storage type MJ/kg MJ/L
EEStor (claimed) 1.2 5.7
battery, Lithium ion 0.46-0.72 0.83-0.9
Flywheel 0.36-0.5
battery (NiMH), High Power 0.250 0.493
battery (NiCd)[5] 0.14 1.08
battery, Lead acid[5] 0.14 0.36
Spring 0.0003 0.0006
Springs therefore don't seem to be a practical energy storage solution (mass
per stored kWh is about 1000 times more than that of other types)>>
Nick Palmer
On the side of the Planet - and the people - because they're worth it
