Preliminary study of an energy harvesting system for road pavements made with marginal aggregate

The progressive reduction of available energy resources and the continuous increase in demand are providing strong incentives for the use of renewable energies. Asphalt solar collectors are efficient energy harvesting systems for roads, able to extract thermal energy from pavements and convert the heat collected by their surfaces. Indeed, the possible reuse of waste materials in road construction, converted into valuable resources, has a strategic importance and could surely enhance the environmental sustainability of road pavement applications. This paper presents a preliminary experimental study aimed at evaluating the feasibility of a pipe-based energy harvesting system, which allows fluid circulation on a coil embedded in asphalt concrete manufactured with marginal aggregates. For this purpose, two-layer dense-graded asphalt slabs (AC8) were prepared in the laboratory, using different aggregate types (limestone and steel slag). A steel coil positioned at the interface was utilized to establish water circulation below the wearing course. The collected thermal energy was measured varying the water flow characteristics; the system was monitored through thermographic analysis while being subjected to a selected radiative power. Main results indicated that water flow rate was crucial in determining the temperature mitigation effect on asphalt concrete surfaces and the efficiency of the energy harvesting system. Some concerns about the operative approach were evinced (mainly related to the scale of the test); however, steel slag inclusion did not seem to compromise nor enhance the thermal conductivity of mixtures.