Solar-powered cooling solution for off-grid applications

Phaesun and German startup Solar Cooling Engineering have jointly developed the SelfChill cold room, a solar-powered cooling solution for off-grid applications.

“The technology is based on high-quality energy-efficient core components, but can be used in a modular way,” Germany-based solar Phaesun said in a statement. “Different systems can be configured and built using the same core components and other construction materials [available locally] such as piping, insulation, and pumps: from small refrigerators to large milk cooling tanks and cooling containers.”

The companies have installed 25 cooling systems in six African countries. A SelfChill system with a 20 m³ volume was installed in a basil and mint farm in the Kenyan village of Thika in 2021. Farmers store the crops in the cold room at a temperature of 4 C until the produce is picked up for sale.

“The SelfChill cooling units consist of DC-powered vapor compression heat pumps that generate the cold,” Geraldine Quelle, project manager at Phaesun, told pv magazine, adding that the heat pumps have a COP of 2 and are powered by a 2.8 kW solar array. “The cold is then stored in a water bath (thermal storage), and moved via a water-air heat exchanger.”

The system took part in the Off-Grid Cold Chain Challenge by the Global Leap Initiative, where the technical performance of 12 cold rooms installed in the tropics and subtropics was field-tested over a period of six months. It reportedly showed the best and most reliable performance in the competition and was named “Top Winner of the Global Leap Award.”

“The cold room in Thika has been in continuous use for 18 months and is bringing enormous benefits to the local farmers,” Phaesun engineer Florian Martini said. “Previously, they had large post-harvest losses because onward transport of the herbs was often delayed, and parts of the harvest spoiled. Now they store the harvest in the cold room for up to four days before collection.”

The Global Leap Initiative, sponsored among others by the World Bank and the IKEA Foundation, aims to encourage market transformation toward the best, most-efficient off-grid energy service technologies through its Awards programs.