Optimization and Performance Comparison of Heat Pump Supplemental Heating Systems in a Heat Supply Station

Due to urban expansion and limited heat sources, the heating capacity of heat supply stations is inadequate to meet the growing heat demand. In current heat supply stations, heat from the primary heat network is generally conveyed to the secondary heat network solely via plate heat exchangers, resulting in the return water temperature of the primary heat network being as high as 50 °C, with a substantial amount of recoverable waste heat resources. In this paper, a case study of a heat supply station with insufficient heating capacity in Beijing is conducted to propose supplemental heating systems using vapor-compression heat pumps and absorption heat pumps to further extract waste heat from the primary heat network. Through the TRNSYS platform, simulation models for both systems were developed. Then, based on the bilevel optimization method, the design scheme and operational strategy were co-optimized with the objective of minimizing the lifecycle cost. The performance of the two systems was compared from the perspectives of energy consumption, economy, additional footprint, and regional applicability. The results indicate that the energy consumption of the vapor-compression heat pump supplemental heating system (VCSHS) is 0.85% higher than that of the absorption heat pump supplemental heating system (ASHS), with supplementary heat of 3500 kW. The initial cost of the VCSHS is approximately 1 million CNY lower than that of the ASHS, while the operational costs of both systems are nearly identical, making the VCSHS more cost-effective overall. Additionally, the footprint of new equipment in the VCSHS is nearly 30% smaller than that in the ASHS. Compared with cold regions, it is more economical to adopt ASHSs in severe cold regions due to their lower heat price.