Low temperature deicing of road infrastructure using renewable energy

Abstract: Winter road maintenance is costly but it is inevitable since it is necessary to keep roads accessible and safe during winter. Current winter road maintenance methods use annually 600 000 tons of salt, in the Nordic countries. The salt ends up in the environment along the roads and results in environmental challenges. This thesis proposes an alternative, winter road maintenance concept for critical parts of the road infrastructure. The proposed concept consists of a hydronic heated pavement (HHP), utilised as pavement solar collector (PSC), which is connected to a borehole thermal energy storage (BTES). The combination of an HHP and a BTES means that the solar radiation will be harvested in the summer time and the stored energy will be used for winter road maintenance. This system can be installed at critical parts of a road infrastructure. In existing hydronic pavements district heating or other high temperature energy sources are currently used, however, high temperature energy sources limit the implementation of HHP systems. Research on using low temperature energy sources can result in a reduction of primary energy need and makes implementation of HHP systems more feasible. The purpose of this thesis is to investigate the feasibility of implementing hydronic heated pavements using renewable energy, in the Scandinavian countries. This manuscript presents the experimental and numerical results from a field station of BTES connected HHP system. The field station was constructed during 2017 and experiments on harvesting were conducted during the summer of 2018. The anti-icing and de-icing function of the HHP system were studied during the winter of 2018/2019. The results revealed that the solar efficiency of the HHP system reach as high as 42 % and 245 kWh/m2 of solar heat was harvested during the summer of 2018. This is a comparably high value for a pavement solar collector. The harvested energy were higher than the supplied heat (132 kWh/m2) during the following winter. However, the cold climate at the field station required supplementary heating since the BTES did not have the capacity to supply the required supply temperature of 7 degC to the HHP. The numerical simulations has reveald that by using a dew-point regulation and weather forecasting the energy consumption can be reduced by 62 % compared to a simple air temperature regulation. Based on the experimental and numerical results it can be concluded that it is feasible to design HHP systems to use low temperature (<10 degC) sources and at the same time achieve a substantial improvement of the surface conditions in a Scandinavian climate.