Annual transient simulations and experimental investigation of a hybrid flat plate and evacuated tube collectors array in subtropical climate

Abstract

Non-concentrating solar thermal collectors are being used for various heating and cooling applications. Flat plate collectors and evacuated tube collectors are extensively being used in this regard and their hybrid configuration could be an energy efficient solution. In the current work, model-based transient simulation approach is implemented using TRNSYS to decide the optimal number of flat plate collectors. Detailed experimental analysis of standalone and hybrid configurations of flat plate collectors and evacuated tube collectors is performed under real climate conditions of Taxila, Pakistan. Experimental tests have been conducted to analyze the system performance in terms of energy and exergy efficiencies. Afterwards, annual transient simulations are performed for whole year to determine the overall performance of the hybrid system. The maximum average temperature difference per unit area for flat plate collectors, evacuated tube collectors, and hybrid collector array was found to be 0.95?C, 1.67?C, and 0.98?C, respectively. The maximum energy and exergy efficiency were found 65%, 41% for flat plate collectors, 88.36%, 60 % for evacuated tube collectors, and 62.14%,42% for hybrid collector, while 10% increase in energy efficiency of hybrid collector array is found as compared to the standalone flat plate collectors. Average 9.78% deviation is observed in experimental and model-based efficiency. Finally, annual simulations show that hybrid collector array is 16% more efficient than standalone flat plate collectors throughout the year.