Investigation of a vertical closed-loop geothermal system for heating an educational building

This article is related to the thermal engineering aspect of the hybrid heating unit that can be operated either by shallow geothermal heat or natural gas. The thermal investigation is related to determining the fluctuation in the energy requirement if the unit is coupled with the gas boilers. Therefore, the given system was independently driven by both sources, and the conclusion was based on the comparative merit/demerit of renewable energy over the conventional power supply. The analysis assumed the steady-state energy flow processes. The heat capacity of the source and sink was assumed to be infinitely large as compared to the working fluid. The leastangle regression algorithm was adopted to establish a mathematical relationship between thermodynamic parameters. The average COP of the closed-loop geothermal unit was estimated to be 2.07. The overall exergy efficiency of the installed geothermal facility is 3%, whereas it is 33.55% for the gas boilers operated by natural gas. A square meter of the area of the building will get 26.25 W center dot h of useful convective heat energy from an installed geothermal unit and 28.59% of the total received will be dissipated through the structure. Similarly, the system driven by natural gas provided 21.88 W center dot h of the net useful convective heat energy, while the convective loss amounted to 23.06%. The net annual energy saving of 502.99 kW center dot h was expected from the geothermal site.