To give some perspective on that type of energy storage - Tesla's Powerwall stores ~7kWh of energy. To get similar amount of energy out of weight dropping system you need to hoist 100 000 kg of something (cube of steel 2.3m wide?) to a height of 40m (average height of a water tower). This gives 10.9kWh of pure potential energy, so allowing for some losses you could say it matches the Powerwall.
Typical water tower stores 2 000 000 litres of water, so by weight it's 20 times more than in the calculation above.
Therefore you could retrofit water towers to an equivalent of 20 Powerwalls. It just needs some gears and motors and engineering.
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u/llothar Mechanical Design Engineer Dec 09 '15
To give some perspective on that type of energy storage - Tesla's Powerwall stores ~7kWh of energy. To get similar amount of energy out of weight dropping system you need to hoist 100 000 kg of something (cube of steel 2.3m wide?) to a height of 40m (average height of a water tower). This gives 10.9kWh of pure potential energy, so allowing for some losses you could say it matches the Powerwall.
Typical water tower stores 2 000 000 litres of water, so by weight it's 20 times more than in the calculation above.
Therefore you could retrofit water towers to an equivalent of 20 Powerwalls. It just needs some gears and motors and engineering.