Evaluation and comparison of solar trigeneration systems based on photovoltaic thermal collectors for subtropical climates

Abstract

Solar trigeneration systems based on photovoltaic thermal (PVT) collectors are promising for enhancement of solar energy utilization. Single-effect LiBr-H2O absorption chillers are usually employed in these systems. Since the temperature of solar heat from PVT collectors is low, half-effect absorption chillers are potential alternatives for performance improvement. However, the coefficient of performance (COP) of half-effect absorption chillers is lower than that of single-effect machines. Therefore, the comparison of solar trigeneration systems with both types of chillers is necessary. Four different system layouts, obtained by coupling glazed and unglazed flat-plate PVT collectors with single- and half-effect absorption chillers, are modeled. Annual (8760-hour) simulations are performed to evaluate and compare the thermodynamic and economic performances of different layouts. The results show that the system layout based on glazed PVT collectors coupled with half-effect absorption chillers achieves the highest Solar COP of 0.072 and the highest solar utilization factor of 0.241. Its specific electricity saving is 158.5 kWh/(m2·year), the highest among all the layouts. Additionally, the payback period of the layout based on unglazed PVT collectors coupled with half-effect absorption chillers is 12.7 years, the lowest among all the layouts. This paper is helpful for the development and design of solar trigeneration systems based on PVT collectors in subtropical climates.