Pergamon Renewable Energy, Vol. 10, No. 4, pp. 539-558, 1997 © 1997, Elsevier Science Ltd Printed in Great Britain. All rights reserved PII : S0960-1481 (96)00039-0 0960-1481/97 $17.00 + 0.00 MODELING AND SIMULATION OF SOLAR ABSORPTION SYSTEM PERFORMANCE IN BEIRUT N. K. GHADDAR, M. SHIHAB and F. BDEIR Department of Mechanical Engineering, American University of Beirut, P.O. Box 11-236, Beirut, Lebanon (Received 11 June 1996 ; accepted 8 July 1996) Abstract--An analytical study is performed on solar energy utilization in space cooling of a small residential application using a solar lithium bromide absorption system. A simulation program for modeling and performance evaluation of the solar-operated absorption cycle is done for all possible climatic conditions of Beirut. The results have shown that for each ton of refrigeration it is required to have a minimum collector area of 23.3 m 2 with an optimal water storage tank capacity ranging from 1000 to 1500 liters for the system to operate solely on solar energy for about seven hours a day. The monthly solar fraction of total energy use in cooling is determined as a function of solar collector area and storage tank capacity. An economic assessment is performed based on current cost of conventional cooling systems. It is found that the solar cooling system is marginally competitive only when combined with domestic water heating. © 1997, Elsevier Science Ltd. All rights reserved. INTRODUCTION Active solar energy systems for space conditioning are becoming an attractive alternative for designers due to the fact that the peak solar radiation is in phase with the maximum cooling loads in buildings. One of the methods to achieve cooling by solar energy is by use of an absorption cycle [1, 2]. Absorption cooling systems essentially require a heat source and have been in standard production for several decades in gas fired applications. A water- lithium bromide absorption system operates moderately well with delivery temperatures of 65-95°C to the generator [3]. Flat-plate solar collectors can generally heat fluids up to those temperatures which stimulated a considerable amount of research and development into adaptation and use of absorption systems for solar air-conditioning [1, 4]. Commercial residential units are available from 8 to 140 kW [5]. Performance predictions of absorption solar cooling systems for small residential appli- cations have been reported by Tsilingiris [6] where a 7 kW system was modeled and optimized. The yearly solar fraction was found to be proportional to the collector area. For double glazed collectors of 50 m 2 area and 1000 1 storage tank capacity, the yearly solar fraction in Greece would reach values of up to 45% [6]. For a system to be econ- 539