Solar Thermal Refrigeration System

Designed and Prototyped by a collaborationg between SAAP & UD's ETHOS Students

Learn more about University of Dayton ETHOS program

Check out Solar Alternatives & Associate Programs (SAAP)

Learn more about Solar Thermal Refrigeration. Note: I didn't contribute to this article, but it is one of the best summaries of the tech out there!



In India, as in many parts of the world, the electrical grid is not consistently operational. Specifically for hospitals, and even more specifically for refrigerators in hospitals, this can cause issues. A solar thermal refrigeration system, or an Adsorption System, is a completely non-electric refrigeration system to remove a refrigerators dependency on the grid.

I collaborated with the engineers at Solar Alternatives & Associate Programs (SAAP), a small organization in Patna, India, to work on the system. For many years, students at the University of Dayton had been collaborating with SAAP via ETHOS, a UD program that fosters this type of collaboration. Our team worked throughout my senior year developing analytical models for the heat cycle and brainstorming design solutions to some of the challenges previous teams had encountered. Our team then traveled to India for the summer after I graduated to re-build the prototype and preform tests against our models.

Solar thermal refrigeration systems have a rocky past, its an old idea with only a few successful prototypes, all built in labs. It is like any other refrigeration system, except it operates at a vacuum. It uses ethanol as the heat transfer medium which is evaporated from inside an ice chamber when the system’s pressure drops at night. The ethanol vapor is absorbed by activated carbon inside a large solar array. In the morning, the solar array heats up which releases the ethanol as vapor again, which condenses and drips back into the ice chamber.

It was a great, but extremely challenging project – ripe with technical problems. We did not accomplish nearly what we set out to accomplish, but we did make some strong headway in making the prototype air tight, a major problem in India using local resources. We traveled with the installation team which would install solar PVs, hot water arrays, and battery systems in rural schools, hospitals, and religious monasteries – this taught me a lot about my place in the world and was a good excuse to break a sweat.

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