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August 3

Heat capacity, sand battery, check calculation

Could someone please check my work? Sand has a specific heat capacity of around 800 kJ/kg·K. I calculate that if you put 10 000 kWh (10 MWh) into 900 kg (0.6 cubic metres) of it, you raise its temperature by 50 °C. This video is talking about a massive ~40 cubic metre sand battery but it's capacity is only ~10 MWh? Either I'm wrong or the video is wrong, right? https://www.youtube.com/watch?v=KVqHYNE2QwE&t=377s 80.46.251.32 (talk) 01:05, 3 August 2024 (UTC)[reply]

According to the article Thermal energy storage, there is a prototype 8 MWh sand battery, built in Finland in 2022. The source given on this system says it is a "steel container, which is 4 m wide and 7 m high, [and it] is filled with 100 tonnes of builder’s sand", and is heated to 500 °C. There is a picture of the silo. So it seems that your calculation must be wrong. Abductive (reasoning) 06:09, 3 August 2024 (UTC)[reply]

The specific heat capacity of quartz sand is more like 800 J/kg·K, lower by a factor of 1000. The specific heat capacity is temperature-dependent. At 500 °C it is substantially higher, about 1230 J/kg·K.^[1] --Lambiam 10:47, 3 August 2024 (UTC)[reply]