Ice Storage Technology - Storing Thermal Energy Dynamically

The latent heat principle

When water freezes, the temperature of the ice remains constant at 0°C until all water in the environment has frozen. During the freezing process, energy is stored in the ice as latent heat. When changing the state of aggregation, 80 times more energy can therefore be stored in the ice than would be possible in liquid water. When the ice melts, this energy becomes available again. The principle of ice energy storage is based on this physical property.

Ice energy storage transformation

Today's ice storage systems are modern variants of a millennia-old technology that has harnessed the energetic process of latent heat. Whereas in the past it was mainly a matter of storing ice for cooling foodstuffs such as beer or milk and their manufacturing processes in summer, today ice storage facilities are needed with short, daily charging cycles.

Therefore, ice energy stores are now usually filled at night at reduced electricity costs and the stored cooling power is used during the day to cool offices or industrial processes. The pre-produced cooling requires significantly less energy than direct cooling at the time of cooling demand. In addition, shifting the cooling processes to the night enables a more favourable working coefficient of the refrigeration technology due to the reduced outside temperature.

Features of ice storage technology

  • Silent operation
  • High energy density
  • Favourable working coefficient of the refrigeration technology
  • Almost maintenance-free
  • No danger to nature and the environment

New requirement, different technology

In combination with heat pumps, ice storage tanks serve as heat sources whose temperature is "pumped up" to the required heating water level by the heat pump. This is also referred to as ice storage heating. The work of the heat pump causes the water in the storage tank to freeze into ice. In summer, this ice can also be used to cool the rooms. In this application, the storage tank may have a long charging time and a long discharging time. These "seasonal" ice storage tanks can therefore also be built with simple pipe systems.

If the thermal ice storage is to cover the peak cooling demand during the day or the entire cooling demand during the day, then a fast-reacting storage is required. It must absorb the entire energy during the few night hours and dynamically release it again during the day when cooling is required. These ice energy storage units are daytime oscillating storage units. The sp.ICE was developed especially for this requirement of dynamic and efficient cooling.

Ice energy storage design - stationary or transportable

Existing containers, basins or sinks can be converted into ice storage units by installing heat exchanger surfaces.

In the case of temporary use and requirements for modularity and scalability of the cooling capacity, or if a short construction period is specified, a transportable thermal ice storage unit in a container is the ideal solution.

Ice energy storage and economic efficiency

The thermal ice storage provides a cap on peak cooling demand. At times of day when the existing cooling technology is not fully utilised, the storage is charged. The stored energy is fed back into the system when required. In this way, the refrigeration technology can be aligned with the average demand and dimensioned more economically. In existing systems, the subsequent integration of an ice store can save the investment in larger chillers if the cooling demand increases or additional users are added.

The operation of an ice energy store becomes particularly attractive when there are large differences between day and night electricity tariffs. By charging at favourable night-time electricity rates and saving energy during the day, electrical operating costs can be significantly reduced.

In addition, the ice storage system can be used as a thermal energy storage system in order to store excess electricity capacity from the sun or wind in the form of "cold", which is used later, and feed it into the cooling network at the time of need. In this application, thermal ice storage also contributes to smoothing the load on the electricity grid.