The battery stores 8 MWh of thermal energy when full. When energy demand rises, the battery discharges about 200 kW of power through the heat-exchange pipes: that's enough to provide heating and hot water for about 100 homes and a public swimming pool in Kankaanpää, supplementing power from the grid. The battery is charged overnight when the electricity prices are lower.
Eronen says that with currently available technology the process of converting heat back into electricity only has an efficiency rate of 30%. But he doesn't view that as a major issue.
The article elaborates:
There are of course limitations, experts note. "A sand battery stores five to 10 times less energy [per unit volume] than traditional chemical batteries," says Dan Gladwin from the department of electronic and electrical engineering at the University of Sheffield in the UK.
The Polar Night Energy team acknowledges this but argues that a sand battery is a far more cost-effective solution. The team has calculated that their battery is eight to 10 times cheaper than a lithium battery which stores the same amount of energy. To generate 8 MWh of energy using the Kankaanpää sand battery costs about $200,000 (£174,000), says Eronen. A lithium-ion battery storing 8 MWh of energy would cost at least $1,600,000 (£1,391,000), he says.
Gladwin says the sand battery is great for heating houses in countries with a cold climate, but warns that the efficiency drops off when it is used to return power to the electricity grid. ... "To make it more widely useable, they'd need to develop a way of converting the battery's heat back to electricity with 75-80% efficiency. That would make it a game changer," he says.
Eronen says that with currently available technology the process of converting heat back into electricity only has an efficiency rate of 30%. But he doesn't view that as a major issue. "In a cold country like Finland we're dumping 70% of the heat that remains after conversion on the district heating networks that needs a supply of heat almost all the time," he says.
Something that works adequately in Kankaanpää, Finland, might not be something that works adequately in Palm Springs, California.
200 kW is about 270 horsepower. Is that really enough "to provide heating and hot water for about 100 homes and a public swimming pool ..."?
https://www.bing.com/search?q=horsepower+to+kilowatts
They weigh less than 100 tons, and they aren't 23 feet tall.
How much would a sodium-based thermal storage system cost for the same power output?
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