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.

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 followingthe the here described approach, high-tech components (as the cooling units and electronics) can be exported, while the assembling of the insulation-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.

[[File:Example System 1 - Overview.JPG|thumb|left|370px|Example System 1 for ice production|alt=Example System 1 - Overview.JPG]] [[File:Example System 1 - Cooling units.JPG|thumb|right|370px|Cooling units of the system|alt=Example System 1 - Cooling units.JPG]]

[[File:Example System 1 - Open cover.JPG|thumb|right|370px|Inside view of system|alt=Example System 1 - Open cover.JPG]] [[File:Example System 1 - Fans.JPG|thumb|left|370px|Fans in the system for better heat transfer|alt=Example System 1 - Fans.JPG]]

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.

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.

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 (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

Additional information

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