> Pumped hydro. Yes, I did some beer-matt calculations on this. I believe it is 10J to raise 1kg by 1m. So to raise 2000lt of water (2000kg) by 10m it would ne

> Pumped hydro. Yes, I did some beer-matt calculations on this. I believe it is 10J to raise 1kg by 1m. So to raise 2000lt of water (2000kg) by 10m it would need 10J * 2000 * 10 = 200,000J. Call it 0.5MJ to take possible losses into account. A kWh is 3.6MJ. Which basically means I would get 0.14kWh storage as a reward for building a 10m high tower which can support 2 tonnes. When my batteries can store 10kWh (in theory), it just doesn't seem to make sense to me. Of course if I had a lake on the top of a hill that could be a different matter. It would also be a different matter if I didn't need 10m head (1bar). Sprinklers do require pressure though. > Or... Just don't water the grass? A good point. There are two reasons I do this: 1) I'm from the UK, green grass feels homely to me, 2) forest fires are an actual part of life here, and stopping the area around one's house being flamable is important. Paving, gravelling, tarmacking, and watering are all ways to deal with this.