Nick Palmer wrote:
Anyone have any idea if big clockwork "mainsprings" could be used at a domestic level to store energy - and how to calculate available storage capacity?
They probably could not be used. Large mechanical clock towers all used falling weights instead of mainsprings. The biggest spring driving device in common use that I know of was the wind-up phonograph.
The only mechanical energy storage device now under development that I know of is the flywheel. Modern, high-speed versions of this that operate in a vacuum can store remarkable amount of energy. They would be safe.
For large scale energy storage, pumped water systems are used in places such as Switzerland, which have loads of vertical geography. With a huge vertical gradient they are fairly efficient and don't take much space. You fill up a lake at night with extra power and use hydroelectric power at peak hours during the day.
There has been some talk of electrolysis energy storage. That is, breaking water into H2 and O2 off peak, and using fuel cells at peak hours. My guess is that it would be inefficient, except when it is also used as a method of transporting energy as H2 in pipelines. I do not know if anything practical has been developed. There are actual pumped water storage systems in use.
U.S. farmers in the Great Plains and other flat areas used to routinely use wind-powered water pumps to fill cisterns. I visited farms when I was a kid where these were still in use. That is how they had flush toilets and hoses in the barn and garden. Nowadays I suppose they use electric pumps. I wonder if a large scale version of this could not be used for local, small-scale hydroelectricity. In other words, use a smallish modern 100 kW nameplate wind turbine to mechanically lift water, and then use the water to drive a ~20 kW hydroelectric generator. You would get power on demand with backup storage for when the wind does not blow. Plus you would get pressurized water from a water tower.
- Jed
