Coupled heating optimization of hybrid GCHP system with heat compensation unit

Abstract

The coupled HCUT-GCHP system (integrating the GCHP with the efficient heat compensation unit (HCUT)) can operate in heat compensation mode and coupled heating mode to effectively eliminate the soil thermal imbalance and increase the heating supply at peak heating load. The coupled heating strategy directly influences the soil heat extraction not only at the peak load but also during the whole year. The system model is built in TRNSYS to investigate the optimal strategies of the coupled HCUT-GCHP systems with different boreholes. Results show that the systems with 80% and 100% boreholes can keep soil thermal balance well at different starting temperatures of coupled heating mode. Taking the system with 60% boreholes as an example, when the starting temperature of coupled heating mode increases from 0°C to 9°C, the power consumption for heating increases by 7.32MWh/°C, while the power consumption for heat compensation decreases by 9.40MWh/°C. For the systems with 100%, 80%, 60% and 40% boreholes, the optimal starting temperatures of coupled heating modes are respectively 9°C, 9°C, 6°C and 3°C and their annual system COPs are respectively 2.66, 2.64, 2.63 and 2.48 under the optimal strategies.