Do It Yourself - Solar Cooling Units

Background

The University of Hohenheim has been carrying out research on solar cooling for the last 5 years. A smart solar ice-maker has been developed and applied for milk cooling. Up to now, 18 Systems have been successfully assessed together with local partners in Tunisia, Kenya and Colombia showing its technical feasibility. Since 2017, the economic feasibility is under study in cooperation with partners of the private sector and in synergy to several on-going public initiatives. The project is financed by the GIZ programme Powering Agriculture - Sustainable Energy for Food.

Description

The developed Do It Yourself - Solar Cooling Unit is a promising solution to promote refrigeration equipment for food value-chains. Under provision of technical support, local companies and entrepreneurs can design and produce small and medium scale solar cooling systems. This allows to reduce the final price of the technology, while creating specialized jobs locally. By following the approach described here, high-tech components (such as the cooling units and electronic controls) can be imported, while the manufacturing of the insulated box can be carried out locally. This way, entrepreneurs have the possibility to adapt the technology to the local market and offer distribution and maintenance under their own product brand.

Example Cooling Systems (for local assembly)

Example System 1: Smart ice-maker for ice-based milk/fish cooling

This system is based on the Hohenheim smart ice-maker (modified STECA refrigerator PF166-H) but suitable for local production. It uses two cooling units and applies force convection for a daily production of around 25 kg ice per day. Batteries are optional but preferred in this system in order to increase the daily ice production. The system can store up to 50 kg ice, which can be used for different purposes, e.g. for milk cooling or fish cooling.

Example System 1 for ice production

Cooling units in the back the system

Inside view of system

Fans in the system for better heat transfer

Example System 2: Battery-free refrigerator for milk and vegetables

This refrigerator uses a single cooling unit which integrates ice-storage. Therefore, the refrigerator operates at a temperature range between 4-8°C all over the day while the compressor only works during sun radiation hours.

Battery-free refrigerator for milk and vegetables

Refrigerator with open door

Ice packs in the back of the fridge

Example System 3: Ice-storage system for cold rooms or chilled water

This scalable system operates with one cooling unit which produces ice in a water bath (Ice storage). The system provides with water at around 4°C to a heat exchanger with a fan which then produces cold air for cooling rooms. An alternative application for the chilled water is the cooling of milk by introducing milk-cans in a chilled water bath.

Ice-storage system for cold rooms or chilled water

System with open cover

Ice within the storage tank

Features and Interoperability

Following main features are implemented in every single solar cooling unit:

• Cooling units specially design for a plug and play local assembly
• Battery free compatible
• Usage of climate-friendly natural refrigerants (R600a)
• PAYGO compatibility (currently Angaza)
• Remote monitoring

Every single control unit can be programed by the final manufacturer in dependence of the application. Design tools for the sizing of PV panels according to location and application are available.

Transport

Transport of cooling units to target countries:

8 Cooling units on one EUR Pallet

8 Cooling units (ready for Plug&Play) can be transported in one EUR Pallet:

• Dimensions(L x B x H):1400 x 800 x 1200 mm
• Aprox. 90kg total weight

A saving of around 75% of transport cost is expected in comparison of importing solar refrigerators/systems.
Size per solar cooling unit: 250x600x630mm (LxBxH) 11Kg

Workshop Material

Please find the following files from the Solar Cooling Workshop in Nairobi (March 2019):

• Solar Cooling Design Tool (Excel file)
• Solar cooling example systems – construction manual

Additional information

Workshop - Do It Yourself - Solar Cooling Units in Mali (September 2019)

Workshop - Do It Yourself - Solar Cooling Units in Kenya (March 2019)

PA Project - Promotion of solar refrigeration for agricultural value-chains