Second Law Analysis of Solar Powered Heat Recovery Panels in Buildings

Energy saving and its efficient utilization is of prime interest in today’s world due to the limited energy resources and growing significance of environmental issues. Despite the intensive efforts to narrow the gap between conventional energy sources (wood, coal, gas, oil, etc.) and renewables, renewable energy resources currently supply only about 14% of total world energy demand. In this regard, energy management and optimization are considered compulsory as much as the clean energy generation. Recent works indicate that the buildings play a significant role on global energy consumption. They are responsible for about 40% of global energy demand. Among the different building types, domestic buildings have the largest share with 63% and most of energy is utilized for heating, ventilation and air conditioning (HVAC) systems in those buildings. Energy consumption levels of buildings can be notably reduced through waste heat recovery in HVAC systems. Heat recovery term basically corresponds to an air-to-air heat or energy recovery system which works between two streams at different temperatures. In other words, it is defined as heating the incoming air via the recovered waste heat and hence, decreasing the heating loads. In recent years, several attempts have been made to analyse heat recovery systems (HRSs) both theoretically and experimentally. However, a detailed thermodynamic analysis of HRSs has not been presented so far. Therefore in this study, second law analysis of HRSs has been presented. The data required for the analyses has been obtained from our previous theoretical work. Unlike the energy analysis, exergy analysis enables to take into account the qualitative effects affecting the system performance. Exergy output and exergy efficiency of HRSs have been determined for different types of units. Some recommendations have also been made to enhance current efficiency range of HRSs.