Ice storage systems utilize the latent heat of fusion of water combined with heat pumps to provide seasonal heating and passive cooling.
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How do ice storage systems function for seasonal thermal energy storage?
Yes, but strictly as a low-temperature heat source for a brine-to-water heat pump, not standalone heat.
The trick is latent heat of fusion: freezing 1 m³ of water at 0°C releases 93 kWh of thermal energy without dropping below freezing point.
For a 20 MWh heating season, a typical residential tank is around 10 to 15 m³ buried in the garden. It works seasonally because:
- In autumn you pull sensible heat (cooling water from ~15°C down to 0°C).
- In the dead of winter (Jan/Feb) the heat pump freezes the water into solid ice, harvesting the latent heat while keeping the evaporator at a stable 0°C (far higher COP than -10°C ambient Spessart air).
- In summer and shoulder seasons you regenerate and melt the ice using unglazed solar thermal collectors or PV excess, which also gives you virtually free passive building cooling.
It avoids deep drilling permits (unlike 100m boreholes), but you still need electrical power to run the heat pump compressor across that 0°C to 35°C lift.