Solar Refrigeration

Solar refrigeration in Nigeria

Cool it down with the heat of the sun!

In case that idea sounds a little far-fetched, solar refrigeration is ideal for off-grid regions that need to keep food and medicines cool for health reasons.  Already, camels are carrying solar-powered refrigerators for mobile health clinics in Africa.  Many third-world countries simply do not have the resources to extend grid-based electricity to remote villages.

That’s why its so exciting that solar energy is being used in Tunisia and Morocco to keep perishable foods, including as milk, wine and fruit, fresh.  Scientists from the Fraunhofer Institute for Solar Energy Systems (ISE) in Freiburg, Germany, are building on existing solar technology that powers A/C in office buildings worldwide to provide energy for refrigeration in the Mediterranean region.

There, the real-life experiment is underway using a winery in Tunisia and a dairy in Morocco.  The “MEDISCO” project (MEDiterranean food and agro Industry applications of Solar COoling technologies) use solar plants to refrigerate milk and wine, which are installed with the help of universities, energy agencies and European companies. The project funded by the European Commission is run by the Polytechnic University of Milan.

According to the website:

[the program] aims to develop, test and optimize solar thermally driven cooling concepts for the food and agro industry in the Mediterranean region. In order to prove the economical and social sustainability of the technology, two innovative concepts will be fully developed and monitored during the project realization. Universities, research organizations and companies from Egypt, France, Germany, Italy, Morocco, Spain and Tunisia participate in the project.

MEDISCO brings solar refrigeration to the Mediterranean region

Solar refrigeration is best suited in areas that have many days of sunshine, yet lack access to an electric grid and/or are subject to unreliable energy sources.  Perhaps the biggest advantage is that when the sun shines brightly and refrigeration is most needed, it can best generate power for the appliances.

Simply, solar refrigeration works as follows: concentrating collectors direct sunlight onto an absorber by use of a reflector.  The solar radiation is converted into hot water at 200 degrees F.  According to Dr. Tomas Núñez, scientist at the ISE:

“This extreme water temperature is necessary in order to drive the absorption refrigeration machine for the high external temperatures that prevail there. We do not use electricity to provide the refrigeration, we use heat. The result is the same in both cases: refrigeration in the form of cold water or — in our case — a water-glycol mixture.  We use a slightly different system for wine, with the refrigerant flowing through coiled pipes in the wine tanks.”

Just as with solar hot water systems, a water-glycol solution is collected in cold accumulators and then pumped through a heat exchanger.

The science behind solar refrigeration is one that cannot come too soon. Regions world wide need to keep perishables and medicines cool.  When grid-based electricity is not available or reliable, this is the next best thing.

Tags: fraunhofer institute, freiburg, MEDISCO, solar energy systems, solar powered refrigerators, solar refrigeration