Abstract
This report discusses the expected energy yield and the expected costs for a road solar collector. A road solar collector is a system of pipes embedded in the, usually asphalt, pavement that utilises the heat generated in the asphalt due to insolation to heat water. This water can be stored
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and used in winter to heat house by using a heat pump. To calculate the expected energy yield, a model of the heat flows in the pavement and collector system was made in Matlab. The model calculates the yearly energy yields from a road solar collector at different depths in the three most common road types in The Netherlands paved with asphalt: a municipal road, a provincial road and a highway. While the characteristics of the first two road types are nearly the same, the highway has a much more porous wearing layer, thus lower energy yield was expected. The yearly energy yield, that is calculated by the model, from a road solar collector in a municipal road and provincial road is about 1 GJ/m2. The yield from a system in a highway is lower, about 0.8 GJ/m2. The levelized costs of energy of this heat, when connected to a heating system capable of providing space and tape water heating, is about 33 €/GJ, making it close to competitive to more conventional heating systems. The emission factor of this heat, at 29 kg CO2eq/GJ make it less polluting than most heat networks in The Netherlands. As with all models, this model relies on assumptions. Some of these assumptions are not very realistic. Therefore, sensitivity analyses have been done. One of the most important parameters of optimization is the length of the pipe. While it reduces to overall energy yield, it increase the average temperature of the stored water, increasing the efficiency of the connected heating system. Some aspects of the model leave room for improvement, such as the constant temperature assumed at the lower boundary, and computational times. Data to validate the model is currently unavailable. Heijmans is planning to build a road solar collector in a field lab, with the required measuring devices to validate the model and to improve on it.
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