          R. DAGHIGH, A.IBRAHIM, G.L.JIN, M.H. RUSLAN, SOHIF MAT, ZULKIFLI MOHD NOPIAH, AZAMI ZAHARIM, K. SOPIAN Solar Energy Research Instiute, Universiti Kebangsaan Malaysia 43600 Bangi, Selangor, MALAYSIA Ronak_d@eng.ukm.my, zmn@eng.ukm.my , azami.zaharim@gmail.com , ksopian@eng.ukm.my   A system with PVT collectors generates electricity which can utilize it directly, store it in batteries and send it to electrical grid. This system produces thermal energy that can be employed for process heat, hot shower and tap water, solar cooling and desalination. Building integrated photovoltaic thermal systems (BIPV/T) is a new concept that received much more attention. This work shows the results of performance simulation study of a:Si and c:Si photovoltaic/thermal (PVT) solar collector in tropical climate such as Malaysia. The results show that at solar radiation between 700:900 W/m 2 , ambient temperature between 23: 34°C and fluid flow rate of 0.03 kg/s, the highest thermal and electrical efficiency of the PV/T (a:Si) was 72% and 5%, respectively, the highest thermal efficiency of (c:Si) was 51% and cell efficiency was 11.6%.   Photovoltaic thermal (PVT), Electricity, Thermal efficiency, Solar Energy, Water Heating, a:Si.   The advent of the energy crisis in the early 1970s led to the concept of hybrid PV/T systems became much more favorable research area. The hybrid photovoltaic/thermal (PV/T) systems refer to the integration of a PV and a conventional solar thermal collector in a single piece of equipment [1] which can be used effectively for the conversion of the absorbed solar radiation into electricity and heat, therefore increasing their total energy output [2]. The first research of water based PV/T systems were reported in the middle of 1970s to early 1980s where the performance of integration of photovoltaic and thermal system for hot water production based on Hottel:Whillier model [3] had been analyzed and it was observed that the system is economic and feasible [4]. The main concept of photovoltaic thermal collector using water or air as the working fluid was proposed by Kern and Russell in 1978 [5]. Florschuetz performed the theoretical analysis of a PV/T collector through an improved Hottel–Whillier model [6]. A comparative experimental study in (PV/T) collectors with liquid and air as the heat removal fluid (working fluid) was made by Hendrie and Raghuraman (1980) [7]. The heat transfer at the air gap behind the photovoltaic panels was studied by Moshfegh and Sandberg [8]. Later, a commercial polycrystalline PV module was used for making a PV/T collector as compared to a conventional solar water heater and to demonstrate the idea of an integrated photovoltaic and thermal solar system (IPVTS). The primary:energy saving efficiency of this IPVTS exceeded 0.60. This was higher than for a pure solar hot water heater or a pure PV system. The characteristic daily efficiency reached 0.38 which was about 76% of the value for a conventional solar hot water heater using glazed collectors [9]. Research of hybrid PV/T solar systems for domestic hot water and electricity production continued and in recent years, one combined system was designed [10]. In this work, both passive (thermosyphonic) and active systems were considered. The results of this study showed that a substantial amount of thermal and electrical energy was produced especially when both hot water and electricity was required, particularly in applications where low temperature water like hot water production for domestic use, was required. A PV/T water heating system with natural circulation was proposed [11,12], the whole PV/T assembly was placed in a flat:box Al:alloy frame and the water heating system comprises of one collector, one water tank, the valves and pipes. The results of experimental works revealed that by RECENT ADVANCES in APPLIED MATHEMATICS ISSN: 1790-2769 534 ISBN: 978-960-474-150-2