Becuase if I did this, i'd want to do it with new materials. ( its going to have to last for a while ). I'm also wanting to do somethign thats repeatable, and doing that with 2nd hand materials that may or may not be avaialble is problematic.
Also the form factor and all those other thigns just dont' lend them selves to the problem well.
I have variable priced power.. ( we buy power on Spot Market ) which menas on average i pay about 20-25% less than people who are paying on fixed rate contracts. I can get pricing indication 15 minutes before the next 1/2 hour charing period of what the price point is going to be.
I need to do some deeper analysis of our usage, and price peaks etc, and work out what the optimal investment in the technology is, in terms of how much to buy to futher reduce the peaks. Putting solar on will optimize this further.