hot water

thermal energy storage

heat pump

thermal network

Energy Conversion and Management

• Proposed new latent heat storage integration layouts for load shift with a heat pump. • Utilized de-superheater and subcooler in heat pump to charge storage in new layouts. • Simulated dynamic load shift performance with validated storage and heat pump models. • Improved energy efficiency with new layouts against conventional one using condenser. • Assessed economic and environmental load shift effect and provided investment advice. Integrating latent heat thermal energy storage (LHTES) units into building heating systems has been increasingly investigated as a heat load management technology. A conventional LHTES integration method for heat pump based heating systems is to connect the heat pump’s condenser for charging the LHTES unit. This integrating layout however usually leads to increased electricity input to the heating system. To underline this issue and provide solutions, this paper presents three new LHTES integrating layouts where the LHTES unit is connected with the de-superheater of the main heat pump (Case 2), the condenser of a cascaded booster heat pump cycle (Case 3), or a combination of using both the de-superheater and the booster cycle (Case 4). In the context of a multi-family house in Stockholm, a quasi-steady state heating system model was developed to evaluate the new integrating layouts, which were benchmarked against the baseline heating system without storage (Case 0) and the conventional integrating layout using the main heat pump condenser (Case 1). Hourly electric power input to the heating system was modelled for calculating the performance indicators including the heating performance factor, the operational expense and justifiable capital expense, and the indirect CO 2 emissions. Two load shifting strategies were simulated for an evaluation period of Week 1, 2019: 1) charge during off-peak hours (8 pm to 6 am) and 2) charge during daytime hours (10 am to 7 pm). The simulation results of the off-peak charging strategy show that, in Cases 2–4, the heating performance factor is 22%-2...

Latent heat storage integration into heat pump based heating systems for energy-efficient load shifting