Thermodynamic analysis of pavement roads underground heat harvesting through water pipelines for effective management of urban heat island effect integrated to space cooling applications

Abstract

Urban heat island effect drastically affects the climate by approximately increasing the surroundings temperature by 2°C, thus, rises the energy demand for space cooling. As roads/asphalt pavements makes 20–30% of urban areas that are fully exposed to solar radiations, this unused energy can be utilized by laying down a network of underground cross-linked polyethylene (PEX) pipes full of heat transfer fluids. In this research, the cold-water from a reservoir is pumped to various pipeline configurations to gain effective heat from the pavements/roads. This water circulation absorbs the heat, increasing the temperature (10–25°C) of cold water, also decreasing the pavement temperature by about 15°C. Furthermore, a solar collector is attached to increase temperature of circulated water to be used by low-grade temperature applications. Here, double effect absorption cooling (DEAC) and ejector cooling systems have been analysed thermodynamically for efficient space cooling application. The overall energy and exergy efficiency of DEAC integrated system is calculated to be 40.79% and 5.08%, respectively. The rate of cooling obtained by the evaporator is 6.75 kW, when rate of heat supplied is 4.3 kW. For the ejector cooling integrated system, the overall energy and exergy efficiencies are recorded as 15.27% and 3.38%, respectively. The rate of effective cooling through ejector cooling system is 2.7 kW.

Keywords

• Absorption cooling
• Asphalt pavements
• Ejector cooling
• Solar energy
• Underground heat harvesting
• Urban heat island effect