SIMULATION, DEVELOPMENT AND PERFORMANCE EVALUATION OF A SOLAR/GAS HYBRID POWERED ABSORPTION AIR " CONDITIONING SYSTEM

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Department of Engineering

ABSTRACT
In this study, a gas assisted solar powered absorption air – conditioning system was designed, constructed and tested under Zaria weather conditions in Nigeria. A technical and economic viability study of the system was first carried out by developing and simulating a TRNSYS model of the system to cool an office block with an average space cooling demand of 151.8kWh/m2 per annum, under Zaria weather conditions. System components were sized and optimized to give maximum coefficient of performance (COP), solar coefficient of performance (SCOP) and solar fraction (SF). Design of the optimised system components was done through a programming based design, optimisation and performance evaluation method using MATLAB. A reduced size version of the system, which includes a 4 kW absorption chiller prototype was constructed. Experimental tests were conducted on the constructed system. The experiments were carried out on a test room in the months of April and June 2017. The experimental days were classified as: hot clear sky days, fairly clear sky days, cloudy days and rainy days. Results indicated that the system is capable of operating in any of the days as classified. However, the cloudy days recorded the highest gas consumption of 0.95kg, as the system relied more on the gas boiler heating mode. The hot clear sky days recorded the least gas consumption of 0.48 kg as the system operated more on the solar power heating mode. Room temperatures were cooled to between 24oC and 27oC, from initial temperatures ranging from 29oC to 33oC. Maximum cooling power of 2.7 kW was achieved by the absorption chiller. Maximum daily average COP of 0.438 was attained. Solar fraction of 0.55 was achieved in the experimental day of April, while 0.27 was attained for June. Results from life cycle cost savings simulation showed energy savings of N2, 172,558 with 35m2 collector area for a period of 20 years. Life cycle cost savings analysis of the constructed system showed the system is economically viable in the Nigerian climate studied, with a savings of ?39,991.93 achievedwith a collector area of 1.7 m2over a 20 year period. Environmental impact assessment showed CO2 emission reduction in the range of 2.7% to 58.4%. It was concluded that the system operates satisfactorily in the Nigerian climate studied and it is economically viable. Recommendations for further improvements were made.