SelfChill
Introduction
Reliable cold chains are essential for reducing food losses, improving food safety, increasing farmers’ incomes, and ensuring access to temperature-sensitive products such as milk, fish, fruits, vegetables and vaccines. However, conventional refrigeration systems are often difficult to operate in regions with unreliable or no electricity supply due to their dependence on batteries or diesel generators.
SelfChill is a modular solar cooling technology specifically developed for off-grid and weak-grid applications. The system combines photovoltaic (PV) power with thermal energy storage instead of relying primarily on electrical battery storage. This significantly reduces system costs, maintenance requirements and environmental impacts while enabling reliable refrigeration under fluctuating solar conditions.
Background
In many developing countries, a significant share of food losses occurs after harvest because products cannot be cooled immediately. Rural communities often lack reliable electricity infrastructure, making conventional refrigeration technically and economically challenging.
Solar-powered refrigeration has become an attractive alternative. Nevertheless, many PV cooling systems depend on large battery banks that increase investment costs and require regular replacement. SelfChill addresses this challenge by storing cooling energy directly as ice instead of storing electrical energy.
Technology Principle
The SelfChill concept is based on three key components:
- Solar photovoltaic generator
- High-efficiency DC refrigeration units (SelfChill Cooling Units)
- Thermal ice storage
During periods of solar irradiation, electricity generated by the PV modules directly powers highly efficient DC compressors (SelfChill Cooling Units). Instead of only cooling the storage chamber, surplus cooling capacity is used to freeze a thermal storage medium (typically water or brine).
The stored ice acts as a “cold battery”. During the night or cloudy weather, the ice slowly melts while maintaining the required storage temperature without electrical battery support.
This approach shifts energy storage from expensive electrochemical batteries to low-cost thermal storage.
The whole system is DC powered thus electronics remain simple. Due to the ice storage and the natural refrigerant, SelfChill systems are most economically friendly.
Modular Design
One characteristic feature of the SelfChill technology is its modular architecture.
Instead of using one large refrigeration machine, several identical SelfChill Solar Cooling Units can be combined depending on the required cooling capacity.
Benefits of the modular concept include:
- easy scaling of cooling capacity
- implified transport
- easier maintenance
- redundancy if one unit requires servicing
- local assembly possibilities
The modular design also facilitates adaptation to different agricultural value chains and climatic conditions.
Applications
SelfChill technology has been developed for various productive-use applications, including:
Solar Cold Rooms
Cold rooms for fruits, vegetables and other perishable agricultural products.
Typical users include:
- farmer cooperatives
- traders
- ollection centres
- agricultural processors
Milk Cooling
Milk collection centres often operate in remote areas without reliable electricity.
SelfChill enables immediate cooling after milking, helping to:
- reduce bacterial growth
- improve milk quality
- increase market value
- reduce spoilage
Fish Cooling and Ice Production
Fishing communities frequently experience high post-harvest losses because fish cannot be cooled immediately after landing.
SelfChill systems can provide:
- ice production
- support for local fish value chains
Other Applications
The technology can also be adapted for temperature-sensitive medical products where reliable cooling is essential or for household needs.
Advantages
Compared with conventional solar refrigeration systems, SelfChill offers several advantages:
- Reduced battery requirements
- Lower lifecycle costs
- Improved reliability
- High energy efficiency
- Modular expansion
- Easy transport
- Reduced maintenance
- Suitable for off-grid operation
- Use of natural refrigerants
- Very low environmental impact
Business Models
Different ownership and service models are possible depending on local conditions.
Examples include:
- Direct ownership by farmers or cooperatives
- Cooling-as-a-Service (CaaS)
- Lease-to-own financing
- Community-operated cold storage
- Private cold-chain entrepreneurs
Selecting an appropriate business model is often as important as selecting the technology itself.
Limitations
Although SelfChill reduces battery dependency considerably, it is not suitable for every application.
Potential limitations include:
- careful system sizing is necessary
- trained technicians remain important for installation and servicing
- target temperature depends on the cooling medium. For most systems water is used for the thermal storage thus target temperatures in cold rooms is 10°C, which is suitable for most vegetables and fruits.
- for lower temperatures system adaptions (other cooling medium) are needed.
Field Experience
SelfChill systems have been demonstrated in several countries in Sub-Saharan Africa in applications including agricultural cold rooms, milk cooling and fish cooling. Field experience indicates that thermal energy storage can significantly improve system reliability while reducing operating costs compared to battery-based solutions.
In addition to the technology itself, successful projects emphasize user training, local technical capacity building, business model development and continuous monitoring to ensure long-term sustainability.
Awards and International Recognition
The innovative approach of the SelfChill technology has received international recognition from leading organisations in the fields of clean energy, sustainable cooling and renewable energy innovation.
Among the most notable recognitions are:
- Global LEAP Award – SelfChill was recognised by CLASP in the Global LEAP Awards, an international initiative promoting high-performance, energy-efficient off-grid appliances for developing markets as most efficient solar cooling technology.
- The smarter E AWARD – SelfChill received recognition through The smarter E AWARD, one of the renewable energy sector's most prestigious international awards, highlighting innovation, sustainability and market relevance, as winner 2025 in the category “outstanding projects”.
- pv magazine Award – SelfChill was honoured with the pv magazine Award for its innovative contribution to solar-powered refrigeration and productive use of renewable energy in 2023.
Future Developments
Current development activities focus on:
- integration into productive-use energy systems
- local manufacturing and assembly
- circular economy approaches and component recyclability
Future systems may also integrate smart energy management and hybrid renewable energy sources.
References
International Renewable Energy Agency (IRENA): Renewable Energy for Productive Uses.
Food and Agriculture Organization (FAO): Cold Chain Development for Agriculture.
energypedia: Solar Cooling.
CLASP: Global Leap Awards.
The Smarter E: The Smarter E Awards 2025.
SelfChill website: How it works (technical documentation).
Phaesun GmbH: SelfChill Technology (technical documentation).
