Second Generation Solar Direct-Drive Refrigerators

The overall aim of the project is to develop and test the next generation of direct solar-powered coolers for storing vaccine and other temperature sensitive products such as fish and meat in areas without power supply. The next generation solar DD technology will use the energy from the PV panels more efficiently, enabling use of smaller panels with less transport and installation costs. The product will be cheaper to produce and will be even more competitive than current models when compared to alternatives, including gas-powered absorption and refrigerators powered by gasoline-powered generators. The temperature distribution will be better than the current generation of vaccine refrigerators, which means there will be better security against vaccine freezing. Moreover, the new generation will include an optional monitoring system that is able to provide warnings (via SMS) when preset temperature limits are exceeded or other malfunction is detected. Service can thus be carried out before WHO accepted temperature limits have been exceeded. This can reduce spoiling of expensive vaccine. This part of the project will be conducted in collaboration with UNICEF in a way to fulfill their wishes as expressed at an international meeting held in Copenhagen in October 2016. The monitoring system will also have other features such as automatic self-check at start up and notification of correct function after installation.

Refrigerators for food and beverages will typically need bigger compressors than vaccine coolers, because the food and drinks need to be cooled down after loading. The project will therefore look at possible ways to find compressor solutions with increased cooling capacity compared to the models found today. The project partners are planning for the following specification targets for the new compressor:

- More than 20% increased cooling capacity (suitable for cabinets up to about 200 l)

- Higher cooling efficiency (more than 20%)

- Wider dynamic range 1:3 (Now it is 1:1.75)

- For natural refrigerant R600a or R290

- Voltage adapted to most common PV module market (72 cells)

- Improved power electronics for MPP tracking and soft start