Energy and Exergy Evaluation of the Integrated Waste Energy Recovery System (IWERS) and the Solar-Powered Integrated Waste Energy Recovery System (SPIWERS) in Various Climates

Abstract

The integrated waste energy recovery system (IWERS) is a thermal system that recovers waste heat from steam generated in bakery ovens to produce hot water. This reduces energy and water consumption in shopping centers. This article analyzes the technical improvement of incorporating renewable solar thermal energy into the system. It introduces the new solar-powered IWERS (SPIWERS) for the first time. The exergetic efficiency of IWERS and SPIWERS was measured over 1 year in real supermarkets located in different climatic zones to determine their performance variables. This paper presents precise data for future improvements in the energy efficiency of waste heat recovery systems, making it an innovative contribution to the field. The exergetic efficiency of IWERS was found to be lower in subtropical climates, but no significant variation was observed in other climates studied. Additionally, the exergetic efficiency of IWERS components decreases with ambient temperature, particularly in warm months. Regarding SPIWERS, the highest exergetic efficiency values were obtained in oceanic climates. IWERS employs electric boilers, whereas SPIWERS system utilizes solar collectors. Although IWERS exhibited superior overall exergy efficiency, particularly in cold climates, SPIWERS distinguished itself with a reduced environmental impact, wholly supplanting electric power with solar thermal energy and a swift economic return on investment within a period of less than 4 years, a duration that is half that of IWERS. A detailed examination of the individual components of each system will facilitate the identification of potential avenues for enhancement, ensuring the system’s capacity for adaptation to specific climatic conditions and seasonal variations. Thus, the exergy efficiency of the DWH tank in IWERS remains constant across all climatic zones and throughout the year. This exergy efficiency is approximately 65%. In contrast, a notable variation is observed in the case of SPIWERS, which is more pronounced in more favorable weather conditions. On the other hand, the exergy efficiency of electric water boilers is greater in colder climates and times of the year, with a range of 30%–40%. Additionally, the exergy efficiency of the solar collector is greater in months and areas with cool ambient temperatures, optimal solar radiation, and moderate fluid temperatures within the collector, with a range of 5%–11%.