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STAR: Solar Thermal Adsorptive Refrigeration

Develop an alternative refrigeration technology that does not require electricity, and uses materials that can be produced locally.

Photo of Jun-Ki Choi
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This project would have significant impact to our society by providing an alternative refrigeration technology for the developing world that does not require electricity and uses environmentally friendly materials.  Specifically this technology is designed to keep vaccines cool in locations with unreliable electrical power. 

Explain your idea

Attached figure show the evaporator, condenser, and adsorption bed of the STAR prototype in Patna, India. This STAR was designed to reach evaporative temperatures between 2°C and 8°C using only solar thermal heat, and not using electricity. Activated carbon-ethanol was selected as the adsorption pair because it is non-toxic and is readily available in rural India and other developing nations. While there have been some minor successes with the system in India, a working prototype was not created because it cannot maintain a sufficiently high vacuum. Therefore, the project group has built a small bench-scale prototype which consists of a vacuum chamber, a freezer compartment, and an adsorption bed of activated carbon, connected by tubing and valves that allow the vacuum chamber and adsorption bed to be isolated from one another. The prototype operates in two modes. In the cooling mode, liquid ethanol in the vacuum chamber evaporates, and the ethanol vapors flow to the adsorption bed, where they adsorb onto the surface of the activated carbon. The heat to generate the ethanol vapors is drawn from the freezer compartment through the walls of the vacuum tube, leading to evaporative cooling. The cooling mode can continue until the activated carbon is saturated with ethanol. In the regeneration mode, valves connecting the adsorption bed and the vacuum chamber are closed and the adsorption bed is heated, causing the ethanol to desorb and the partial pressure of ethanol vapor in the adsorption bed to increase. When the valve connecting the adsorption bed and vacuum chamber is opened, the ethanol vapors flow, cooling as they move through the line, and condense in the vacuum chamber, setting the stage for a second cooling stage. This prototype has been repeatedly used to obtain temperatures between 2⁰C and 8⁰C on the external wall of the vacuum tube, and full cycle of cooling and regeneration has been run. So far, we have successfully built a prototype that demonstrates adsorptive refrigeration with ethanol and activated carbon as the adsorption pair.

Who Benefits?

STAR project would enable public health clinics in underdeveloped countries to store vaccines locally without the threat of them spoiling because of power cuts, and without costly, polluting backup electricity sources like diesel generators, which can only be obtained by the very wealthy. Frequent power cuts in these areas have resulted in a cultural preference for non-electric technologies, and STAR has the potential to be more culturally acceptable than other refrigerator designs. Developing this STAR also serves the community in underdeveloped countries by engaging the local “people” while constructing the refrigerator. When the local population participates in designing and constructing the adsorption refrigerator, they become the educators on a revolutionary form of refrigeration. When people are served by the planet in an innovative way, sustainable, economic "prosperity" has the potential to follow.

How is your idea unique?

Solar thermal adsorptive refrigeration (STAR) is a fundamentally different approach to cooling. No electricity is required to operate a STAR refrigerator, and the key components of a STAR system – ethanol and activated carbon – are environmentally benign and can be produced from renewable, widely available resources. In our previous work, we demonstrated the key step in adsorptive refrigeration – that evaporative cooling at sub-ambient temperatures can be achieved by using the adsorption of low-pressure ethanol vapors onto activated carbon. We will develop a sustainable electricity-free refrigeration system can be used to chill vaccines in medical clinics in the underdeveloped countries where conventional sources of electricity are unreliable or not available and solar PV cells are often appropriated for other uses.

Tell us more about you

Dr. Amy Ciric, a chemical engineer, has expertise in chemical process synthesis and optimization, reactive distillation, waste minimization, and mixed-integer nonlinear programming. She teaches courses in biofuels, thermodynamics, separations, and process design. Dr Ciric will mentor students in the STAR project, providing hands-on expertise on evaporative cooling and physical adsorption. Dr. Ciric received her B.S degree from the Carnegie Mellon University and Ph.D from the Princeton University Dr. Jun-Ki Choi, a mechanical engineer, is an Assistant Professor in the Department of Mechanical Engineering at the University of Dayton. He is working as an Assistant Director in the Industrial Assessment Center (IAC). UD-IAC received the Center of Excellence award by the U.S. Department of Energy in 2015. Dr. Choi has expertise in life cycle assessment, sustainable design and manufacturing, end-of-life management, macro-economic analysis for energy and environmental policy. He received his M.S and Ph.D from the University of Michigan and the Purdue University respectively. Dr. Malcolm Daniels, an electrical engineer, obtained his B.Sc. and Ph.D. degrees in Electrical and Electronic Engineering from the University of Strathclyde, Scotland. He teaches an array of courses in electrical engineering in the broad areas of signal and system analysis, control systems, electrical machines and power systems. He serves as the Director of The ETHOS Center in the School of Engineering and in that capacity teaches courses in the Design of Appropriate Technology and manages an international immersion program for engineering students. His primary research activities focus on control issues associated with the integration of renewable resources into the electric grid.

Expertise in sector

  • 3-5 years

Organization Filing Status

  • No, but we are a formal initiative through a university.

3 comments

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Photo of Kate Rushton
Team

HI Jun-Ki!

Interesting project!

Which University are you a part of it? How long have you been working on the project?

How many hours of 'equivalent storage life' do you have from the solar thermal units? How long can they keep the 'refrigerators' cool for? (I hope that makes sense, it has been a while since I have done anything with solar thermal).

What testing have you done on the prototype? What are the next steps?

I can see how you are touching planet but would you elaborate more on how you bridge planet and prosperity?

Photo of Kate Rushton
Team

How does your project compare to this one - http://www.africanreview.com/manufacturing/industry/dulas-delivers-solar-fridges-to-yemen-sierra-leone-and-nigeria-to-fight-illness?

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