Energy storage brings batteries to mind, but there are more familiar ways to store energy. A refrigerator or a hot water tank stores energy as cold or heat rather than as electricity. Ice thermal energy storage applies this same idea to buildings.
A recent review in Renewable and Sustainable Energy Reviews brings together evidence on ice storage technologies, building applications, solar integration and control systems. The principle is simple. A cooling system produces ice when electricity is cheaper, demand is lower or solar power is locally available. Later, when the building needs air conditioning, the ice melts and provides cooling, reducing the need to run chillers at full power.
This does not necessarily reduce total electricity use but shifts part of it in time. Cooling demand often rises in the late afternoon and evening, when buildings keep releasing heat absorbed during the day and people return home and use air conditioning and other appliances. These peaks can stress electricity grids, especially during heatwaves. According to evidence, well-designed ice storage systems commonly reduce peak cooling demand by 20 to 40 percent and operating costs by 10 to 30 percent compared with conventional direct cooling systems, although results depend on the building, climate, tariffs and control strategies.
There are several ways to store cooling as ice. Some systems form ice around coils inside a tank. Others use capsules filled with water or phase change materials. More advanced systems circulate ice slurry, a fluid with small ice crystals. These options differ in cost, complexity, space needs and how quickly they charge and discharge.
Ice storage should not be seen as a direct replacement for batteries. Batteries store electricity and can serve many uses. Ice storage stores cooling only, which makes it less versatile but well suited to buildings where air conditioning is a predictable daily peak. It can also work with rooftop solar by using midday electricity to make ice for later cooling.
The review also points to barriers. Ice does not always freeze and melt evenly, systems need good integration with existing cooling equipment, and economic viability depends on capital cost and how often the storage is used. More long-term field evidence is still needed.
Even with these limitations, ice storage shows an important idea. The energy transition will not rely only on storing electricity. In some cases, storing heat or cold may be a more practical way to make buildings and grids more flexible.
Researcher in Energy Systems at ISAAC – SUPSI