In regions with limited energy infrastructure, there is a strong demand for reliable cooling solutions to reduce food losses, establish cold chains, and increase local income.

Solar powered off-grid cold rooms require low cooling capacities combined with comparatively high storage capacities. The specific requirements vary significantly depending on the application and cold room size.

Within this project, a modular cold thermal energy storage system based on latent heat storage (water ice) was developed. Compared to sensible storage systems, this approach offers a significantly higher energy density and is therefore particularly suitable for compact, energy-autonomous applications.

The development focused on a system that is:

• cost-effective
• modular and scalable (stackable design)
• indirectly cooled,

while requiring only minimal secondary heat transfer fluid and being compatible with natural, flammable refrigerants.

A key objective was ease of use:

• Installation and maintenance are possible without advanced refrigeration expertise
• Integration of an air cooler and a control unit for connection to an energy management system

An innovative aspect is the use of PET bottles for encapsulating the storage medium. This approach enables:

• significant cost reduction
• utilization of locally available materials
• contribution to recycling efforts

To support system design, a web-based application for dimensioning cold rooms and storage systems in solar cooling setups was also developed.

A prototype (thermal storage module) was successfully tested and optimized in a solar-powered test stand.

Next steps:

• Technology transfer to local manufacturers
• Implementation and validation in a pilot project

Technical data: <ThermalStorageModule_30kWh_20260323.pdf>