Design and techno-economic impact assessment of a hybrid solar-assisted heat pump for water heating: a case of Central University of Technology, Free State student residence

Abstract

This research emphasizes the important benefits of retrofitting an outdated and inefficient electric boiler with solar collectors and an Air Source Heat Pump (ASHP) unit making it a Hybrid Solar-Assisted Air Source Heat Pump (HSAASHP) water heating system in a university residence. The study showed that the HSAASHP water heater system offers major reductions in energy consumption and operational expenses, making it both economically feasible and energy efficient. The proposed HSAASHP water heating system greatly reduced electricity expenditures by reducing energy usage from 151 128.9 kWh to 41 036.8 kWh annually. Over the seasons, the Energy Factor (EF) of the HSAASHP water heater ranged from 3 to 5.2, with summer exhibiting the highest efficiency. The techno-economic analysis further verified the HSAASHP water heater viability with a payback period (PBP) of 2.19 years, a break-even point on the third year, an annualized return on investment (AROI) of 14.39% at the end of its 15-year operation, an investment gain of R2 624 547.17 (139 101 USD) and a profit margin of 87%. Its estimated total net present value (NPV) was R3 027 461.79 (160 455.5 USD), demonstrating its long-term economic advantages. To predict an Energy Factor (EF) of the HSAASHP water heater, a multi-nonlinear regression (MNLR) model was developed. The MNLR model’s r2 value of 0.9641 illustrated that it was highly accurate, meaning 96% of the difference in the target variable of the model was elaborated by the model. The model further validated its reliability by confirming a good correlation between the expected and measured EF values This research tackles the urgent demand for economical and energy-efficient water heating systems in South African university residences. It offers an affordable method to lower energy use, enhance stability in the economy, and support environmental preservation. The favourable results of this research at the CUT Mannheim ladies’ residence suggest that other university residences should effectuate similar retrofitting of water heating systems. The viable approach of this study, by merging economic viability and technological innovation, minimizes the electrical dependency in higher education sectors, which is in line with South Africa's larger objectives of sustainability and energy efficiency.