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A concentrated solar and photovoltaic thermal cooled system for domestic use
Nteka, Nambua Elizabeth
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Electric power shortage remains one of the biggest problems in Africa. Over 600 million people on the continent lack access to electricity. Researchers and engineers around the continent are looking at solar energy as a quick and environmental friendly solution to this crisis. Solar PV panels are considered to be the best way to generate electrical power from the sun's radiation. However, the conversion efficiency is known to be between 10-15%. This is not considered to be cost effective by many people. Over 80% of incident energy is dissipated as heat. Research shows that, PV panels lose efficiency due to overheating of the cells. As a solution to the above, this research work presents a design that overcomes a big part of the downsides of using photovoltaic panels. A concentrated solar photovoltaic thermal cooled system (CSPVT) was developed. The system aimed to improve the efficiency of PV modules while also producing useful thermal energy simultaneously. The CSPVT consists of the following: a concentrating reflector, a PV panel, a water cooling system and a sun tracking mechanism. The cooling system is introduced to prevent overheating of the PV panel and to produce hot water for domestic use; the reflector is meant to increase the intensity of sunlight onto the panel so that more energy can be generated and/or collected from the system using the same PV surface; the tracking mechanism ensures that the panel and reflector surfaces are pointed to the sun at all times throughout the day. The methodology used was a design, construct and test, supplemented by both MATLAB® programming and TRNSYS simulation for validation. The performance of the CSPVT was analysed under Cape Town meteorological conditions and compared to an identical non-modified PV panel. Experimental results showed an increase of at least 60.1% on electrical yield, coming from both concentration and tracking compared to the normal fixed PV panel. TRNSYS predicted an electricity yield increase of 40% and a combined electricity and thermal efficiency of 82% from the CSPVT. The actual overall efficiency of the normal PV panel was 11% compared to a combined 62.4% (14.5% electrical and 48% thermal) from the CSPVT. The study showed that the CSPVT has a great potential in improving both the efficiency and the total energy yield of PV panels. A quick economic analysis also showed the system to be cost effective because of concurrent generation of electricity and useful thermal energy in a space that is less than half of what would have been necessary if two systems were used. As an improvement, the study recommends use of pumping in place of natural convection to control the cell temperatures better and improve the electric efficiency further.