A computer program determines parameters that maximize system performance

Solar-powered adsorption cooling systems (SACS) have gained traction as a renewable energy technology that could provide clean energy for air conditioning and refrigeration while significantly reducing the load on the power grid. But these systems lack energy efficiency.

In the Journal of Renewable and Sustainable Energy, by AIP Publishing, researchers at Anna University in India have developed an optimization tool to design, evaluate and optimize the performance of different types of SACS under various operating scenarios. The tool was created using the Visual Basic programming language which is easy to learn and enables rapid application development.

“Our user-friendly optimizer is a multifunctional tool capable of designing and analyzing a complete solar-powered adsorption refrigeration system,” said co-author Edwin Mohan. “Our tool is able to evaluate different combinations of operational parameters to determine which parameters maximize system performance.”

The SACS, which converts solar energy into heat, consists of a sorption bed, a condenser, a liquid storage tank, an expander and an evaporator. At night, water or another refrigerant is vaporized through the evaporator.

During the day, heat obtained from the sun causes vapor to travel through the condenser, where it is liquefied to release latent heat. The liquid eventually returns to the evaporator to repeat the process.

One of the most important elements of SACS is the pairing of materials used in the adsorption process in which atoms or molecules of a substance (the adsorbate) adhere to the surface of a porous material (the adsorbent), such as activated carbon and zeolite, to maximize surface area to volume ratio.

In their study, the researchers used their computer tool to test two adsorbent/adsorbate pairs: activated carbon and methanol, and zeolite and water. The experiments were conducted for four days in a prototype SACS with a cooling capacity of 0.25 kilowatts. They found that the activated carbon-methanol combination achieved a higher coefficient of performance, but the zeolite-water adsorption system could operate at higher temperatures.

The optimization tool predicted the appropriate material mass concentration ratios. The method calculated the cooling load, predicted the maximum performance and performed the analysis of the overall performance of the cooling system.

Although the study focused on residential cooling systems, the researchers said their optimization tool could be extended to larger-capacity systems.

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Materials provided by American Institute of Physics. Note: Content may be edited for style and length.

Gordon K. Morehouse