News Atlas reports on an industrial-scale sand battery that is replacing a woodchip-fired power plant in Pornainen, Finland, with clean heat and energy:
It’s set to reduce carbon emissions from the local heating network by as much as 70%, and is the largest one of its kind in the world.
Developed by Finnish Firm Polar Night Energy – which also built the world’s first commercial sand battery a few years ago – this battery is about 42 ft (13 m) tall and 50 ft (15 m) wide. It serves as a storage medium for up to 100 MWh, with a round trip efficiency of 90%. That makes it about 10 times larger than the first-ever sand battery, and capable of storing enough heat for the whole town to use for a week.
This Thermal Energy Storage (TES) reservoir is a critical tool for places like Finland, which intermittently generate vast quantities of wind and solar electricity, but also face variations in energy demand and supply. The sand battery charges up when electricity is cheaply available and can hold a charge for months at a time, helping balance the energy grid during periods of high demand.
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Here’s how it works: Excess electricity from renewable sources is used to heat the sand contained in a large insulated silo through a closed-loop air pipe system, to temperatures of up to 1,112 ºF (600 ºC). The sand gets hot and stays hot for a long time, acting as a battery.
Later, cool air is blown through the battery’s pipes, absorbing heat from the sand as it moves through the system. This heated air – which can reach temperatures of 752 ºF (400 ºC) – can then convert water into steam for industrial processes, or it can heat water for district heating using a device called a heat exchanger.
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This battery has actually been in operation since June, and the company says it’s already exceeded its efficiency targets in the early days of optimizing its functions. Many of Pornainen’s buildings, including its town hall, are currently heated by the new TES.