Assessing the performance of geothermal pavement constructed using demolition wastes by experimental and CFD simulation techniques

Abstract

This paper studies the possibility of harnessing renewable thermal energy from road pavement constructed using construction and demolition (C&D) materials in Australia. This research study aims to evaluate the efficiency and heat gain capacity of geothermal pavement system with constant inlet water temperature and closed-loop approach. An experimental model was developed using copper pipe and C&D materials as pavement structure and the tests were conducted during summer-time in Melbourne, Australia. Numerical computational fluid dynamic (CFD) simulation was used to study the capacity of simulation in modeling heat transfer and the temperature field in the geothermal pavement. The results showed that the geothermal pavement system with constant inlet water temperature can gain almost 450 (kJ/m2) of thermal energy while subsequently decreasing the surface temperature of the pavement, hence increasing the service life of the geothermal pavement. The pipe burial depth of 40 mm to 60 mm was found to lead to the best efficiency of the geothermal pavement. The thermal efficiency of the geothermal pavement could increase and reach 25% during the day for a geothermal pavement system with constant inlet water temperature. Thermal conductivity and surface albedo would also increase the thermal efficiency of the system. Results showed that increasing thermal conductivity from 1 (W/m.K) to 3.5 (W/m.K) led to an increase in thermal efficiency from 20% to 34%. Also, increasing surface albedo magnitude equal to 0.1 would decrease efficiency by approximately 5%. The experimental results of the closed-loop geothermal pavement system demonstrated that the maximum hourly heat gain capacity of the system was 1000 (kJ/m2), which is twice higher than this value for a system with a constant inlet water temperature. The thermal efficiency of geothermal pavement system increased to its peak value equal to 30% throughout the day.