A critical review on large-scale research prototypes and actual projects of hydronic asphalt pavement systems

In recent years, harvesting solar energy as a renewable and sustainable energy source has been studied extensively across engineering fields. Having reviewed more than 50 large-scale projects of Hydronic Asphalt Pavement (HAP), this paper offers a series of findings: the range of construction cost of asphalt collector varies between 25 and 151 (sic)/m(2) and 1.760-3.000 (sic)/m(2) for the heat exchanger and the total cost. The energy harvest capacity of asphalt solar collector systems (0,6-0,8 GJ/m(2)/year) and the required amount of heat for snow melting projects (100-900 W/m(2)) vary significantly in different projects. Using grid supports for easier pipe placement and protection of pipes against heavy loads during and after construction is recommended. Pavement solar collector systems reduced carbon dioxide emissions by 8-100% in different projects by changing their source of energy from fossil fuels to renewable and sustainable sources. Moreover, in order to further evaluate the sustainability of the HAP systems, a detailed life cycle assessment is required, including all available data related to the energy performance, pavement service life, material end-of-life recycling, etc. Finally, the paper identifies the knowledge gaps requiring further research especially in the area of energy output of the HAP systems, pavement service life and life cycle assessment. (C) 2021 Elsevier Ltd. All rights reserved.