DESIGN TOOL FOR THE THERMAL ENERGY POTENTIAL OF ASPHALT PAVEMENTS Marcel Loomans 1 , Henk Oversloot 1 , Arian de Bondt 2 , Rob Jansen 2 and Hans van Rij 3 1 TNO Building and Construction Research, Delft, The Netherlands 2 Ooms Avenhorn Holding B.V., Scharwoude, The Netherlands 3 TipSpit, Vlaardingen, The Netherlands ABSTRACT This paper describes the development of a design tool for the calculation of the thermal energy potential of a so-called asphalt collector. Two types of numerical models have been developed and validated against experimental results from a full-scale test-site. The validation showed to be a tedious procedure due to the complexity of the full-scale testing of this type of systems. Nevertheless, the models are found to be applicable for performing design studies with. Example results presented in the paper indicate that the thermal energy potential of an asphalt collector is lower than that of a normal solar hot water system. The quality of the energy is also less. However, further advantages of the use of an asphalt collector are found in the reduced maintenance of the road and the avoidance of slippery roads in winter time. The latter is also an example of the heat exchanger capabilities of the asphalt collector. INTRODUCTION Asphalt pavements have gained attention in recent years as an interesting new renewable energy source. As asphalt pavements can heat up to 70 degrees Celsius during solar irradiation, a comparison with solar hot water systems seems obvious. Given the enormous area of asphalt pavement that is available the thermal energy potential therefore appears infinite. This heat can be applied in several ways. Generally the energy will have to be stored over seasons. For example in an aquifer. Over the last years, several designs have been developed to extract heat from an asphalt pavement. Most available solutions apply a heat exchanger design by incorporating tubes in the asphalt pavement. This type of asphalt pavement in the Netherlands now is known as ´asphalt collector´. Besides the energy potential, the advantage of the use of an asphalt collector is also found in the maintenance of a road. In summer time the maximum temperature of the asphalt pavement can be damped so that the chance of formation of ruts is reduced. In winter time, it is possible to avoid slippery roads by damping the minimum pavement temperature. Though these additional advantages of the use of an asphalt collector are obvious, interest in such a collector is mainly focussed on the energy potential and the application of this energy in the built environment. In terms of cost-effectiveness, this aspect of the application of the asphalt collector is most important. To clarify the application of the asphalt collector in the built environment Figure 1 presents an example of the use of the asphalt collector as part of a larger energy system. In this figure the demand side is presented by the building, the energy supply is presented by the asphalt pavement. Through the use of an aquifer, the difference in timing between supply and demand is covered to a large extent. Figure 1 shows that the presented set-up is also able to adhere to the other advantages of an asphalt collector. Figure 1. Example of the application of an asphalt collector in a larger system in summer condition and winter condition. The first question however is what the thermal energy potential of an asphalt collector will be and what parameters are critical in this respect. The second question relates to the efficiency of the collector in the total energy system as shown in Figure 1. In the project described in this paper focus was put on the Eighth International IBPSA Conference Eindhoven, Netherlands August 11-14, 2003 - 737 - - 745 -