Exergetic and exergoeconomic analysis of an experimental ground source heat pump system coupled with a thermal storage based on Hardware in Loop

More than 30% of the world's energy consumption depends on building sector which causes 27% of total greenhouse gas emissions. More than 50% of this load is associated to space heating and cooling in buildings. The ground source heat pumps are used in building sector especially in harsh and warm climates, as a valid alternative to electric air-to-air/water heat pumps traditionally used to supply heating, cooling and domestic hot water loads. This study proposes an analysis on experimental basis of a ground source heat pump with a combithermal storage by means of real components and a Hardware in Loop test bed installed in a laboratory in Germany. The study will be conducted by using Second Law analysis of Hardware in Loop system allow to investigate different operating conditions and to identify the devices of the thermal plant that exhibit the largest exergy losses, efficiency defect and the greatest room for improvement. By considering an emulated constant thermal load equal to 5 kW for building during heating period, the ground source heat pump results the highest dissipative component of whole plant by destroying about 36% of exergy input in experimental test conditions which are a ground temperature of 6 degrees C, evaporator inlet temperature of about 0 degrees C and condenser water supply temperature of 46.8 degrees C. In this condition the heat storage exhibits an efficiency defect of 19.1% demonstrating that it is a strategic component for plant. A sensitivity analysis has been defined by varying on experimental basis the brine input to evaporator and water supply temperatures. The variation in the first parameter corresponds to a range on ground temperature from 5 to 25 degrees C while the second one allows to evaluate a range of supply temperature to storage of 35 - 60 degrees C. In addition, an exergoeconomic analysis has been conducted in order to evaluate the unit exergoeconomic product cost by showing that the exergoeconomic unit price of product for end-users depends on balancing of both electricity cost and investment cost that highly depend on ground and heat pump supply temperature condition.

Automated summary

This study analyzes a ground source heat pump with a combithermal storage using real components and a Hardware in Loop test bed. The results show that the performance of the ground source heat pump is affected by heating load, ground temperature, and heat pump supply temperature.