Utilizing Solar and Geothermal Energies for Sustainable Room Cooling: A Case Study

Abstract

Most cooling applications rely on fossil fuels; however, this study developed a hybrid cooling system that utilizes solar and geothermal energy to cool a room. The solar energy system provided an electrical power of 4400 watts, while the geothermal energy harnessed the earth's subsurface coolness to chill the refrigerant. The system primarily consisted of the following components: an air-conditioned space, a modified split-type air-conditioning unit, a solar power system, a cooling water circulation system, and a measurement and control system. The study was conducted in the Aoun area of Karbala City, Iraq, which experiences a hot climate. The testing periods covered daytime and nighttime conditions. The research focused on assessing the effect of varying the cold water flow rates supplied to a modified split unit system. Four flow rates were considered: 2.5, 3, 7.5, and 18 liters per minute. The findings indicate that the optimal cooling performance was achieved at a flow rate of 18 liters per minute, where the system attained a cooling coefficient of performance (COP) of 5.26. At this flow rate, the coolant temperature remained within an effective range for space cooling. Furthermore, the system demonstrated a sustainable and environmentally friendly solution, as it operated entirely on renewable energy, powering both the cooling system and all other devices within the space while generating a 15% surplus of the supplied energy. Notably, WFRL4 exhibited a COP that was over seven times higher than that of WFRL1, underscoring its superior efficiency. At the highest flow rate, the system enabled the building to function as a Zero Energy Building (ZEB), further reinforcing its sustainability credentials. Additionally, the cooling efficiency of the system significantly surpassed that of conventional air-cooled systems, with a 54% improvement in COP. Overall, this study introduces a highly efficient and eco-friendly cooling model, offering a sustainable alternative that eliminates harmful emissions and enhances energy efficiency, making it a viable solution for future applications in energy-conscious environments.