Session: 02-02: Advances in Green Energy Modeling and Innovative Technologies

Paper Number: 126975

126975 - Experimental Investigation of the Thermal Performance of a Prototype Direct-Expansion Solar-Assisted Heat Pump System in a Cold Climate 

Abstract: 

Space/water heating constitutes a considerable portion of total energy consumption in countries with cold climatic conditions. In several cities in Canada, natural gas is the primary source of thermal energy for domestic applications, which significantly contributes to greenhouse gas emissions. Electrification of heating can be an alternative to natural gas-based heating to minimize emissions from buildings. Heat pumps can efficiently supply thermal energy for buildings when powered by electricity. Direct-expansion solar-assisted heat pumps (DX-SAHP) take advantage of solar energy to enhance the efficiency of conventional air-source heat pumps in frigid climates. However, their performance in cold climates is not well understood. In this study, a prototype DX-SAHP is developed to experimentally characterize performance under realistic operating conditions. The system mainly consists of a 2.3 m² solar collector with a serpentine heat exchanger as an evaporator, a scroll compressor with a rated power input of 0.8 hp, an expansion valve, a coaxial coil heat exchanger, and a 178 L water storage tank. A set of experiments was conducted under realistic ambient conditions to assess the system’s thermal performance. The system achieved an average COP of 3.1 on a sunny day in winter to raise the water tank temperature from 16.1 ^oC to 50.3 ^oC in 4.5 hours.  Conversely, the minimum average COP of 3.0 was recorded on an overcast summer day, while the DX-SAHP achieved the highest average COP of 3.44 on a sunny summer day. The highest instantaneous COP during the operation was 4.33. However, the system was unable to operate continuously during overcast winter days, due to inadequate available thermal energy. The experimental results indicate the need to replace the solar collector/evaporator, as the high values of the degree of superheat at the compressor intake are attributed to the inefficient heat transfer from the absorber plate to the refrigerant. Moreover, increasing the heat transfer performance with forced convection is being considered in the new version of the system.

Presenting Author: Aggrey Mwesigye University of Calgary

Presenting Author Biography: I am Bardia Abbasi, currently pursuing my Master of Science degree at the University of Calgary in the sustainable thermal energy systems lab. I hold a Bachelor of Science degree obtained from Mechanical Engineering Department of Sharif University of Technology in 2022.
My academic journey has encompassed a comprehensive exploration of both experimental and numerical research, providing me with a well-rounded understanding of sustainable energy solutions. I am deeply passionate about the intricacies of modeling and optimizing renewable energy systems, with a specific focus on the innovative domain of heat pumps.
My academic pursuits are dedicated to advancing the understanding and application of renewable energy technologies with the goal of contributing to a more environmentally conscious and sustainable future. I am committed to exploring the potential of efficient and eco-friendly energy systems in addressing contemporary energy and environmental challenges.

Authors:

Bardia Abbasi University of Calgary
Simon Li University of Calgary
Aggrey Mwesigye University of Calgary