Harvesting heat energy from asphalt pavements: development of and comparison between numerical models and experiment

International Journal of Sustainable Engineering 06/2012; 5:159-169. DOI: 10.1080/19397038.2011.574742

ABSTRACT The use of flowing water in embedded pipes to harvest heat energy from asphalt pavements and thereby reducing its temperature and the urban heat island effect has been proposed. A successful use of such an approach would require a complete understanding of the effect and the interaction of various mechanisms such as conduction, convection and radiation and factors such as solar radiation, diameter of pipe and rate of flow. A large-scale experiment was conducted to understand such effects, and numerical modelling was conducted for prediction of temperature. The experiment was modelled using finite element method, and a good match was obtained between predicted and experimentally obtained results. Effects of pipe diameter and flow rate were also analysed. This model could be used in future for selection of appropriate levels of critical variables and hence successful implementation of this concept to sustainable pavements.

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    ABSTRACT: The potential of harvesting heat energy from asphalt pavement using a piping network with fluid flowing through it needs to be evaluated before spending a significant amount of time on planning details of design and construction. The key factors involved in this evaluation include the temperature of the pavement at the depth at which the system is being considered, as well as the temperature of the fluid used for harvesting the heat energy. Costs include those required for the system such as pumps and pipes, and cost of energy required for pumping. Taking all of the factors into consideration, a macro-enabled spreadsheet has been developed that allows the user to input air temperature data as well as pipe location and cost parameters. The end results are data on flow rate versus yearly savings and payback period. From these data, a user can easily determine whether the payback period is reasonable or not and could also evaluate the effect of the different parameters on the payback period. Examples of the results of analysis for different cities in four different parts of the USA and Singapore and Chennai, India, are presented. The payback period shows a good relationship with the latitude of the location – the period increases with an increase in latitude. The public domain location from where the spreadsheet can be downloaded is provided.
    International Journal of Sustainable Engineering 06/2011; 4(2):164-171.
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    ABSTRACT: A rise in temperature of asphalt pavements contributes towards the urban heat island effect, causes problems with air quality and increases the power requirement for cooling buildings. A high temperature would also lead to the potential of rutting failure in asphalt pavements. The concept of mining heat from asphalt pavements, utilising an appropriate fluid flowing in pipes installed within the pavement, has been proposed. Theoretical considerations and results of laboratory testing and modelling simulation have been presented. The results indicate that the concept is feasible, and that the efficiency of heat mining can be improved by selecting appropriate surface layer and aggregates for pavement materials. The use of this proposed method would lead to a significant reduction in pavement and near-surface air temperature, and extension of asphalt pavement life.
    International Journal of Sustainable Engineering 09/2009; 2(3):214-228.
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    ABSTRACT: Heat islands are formed as a result of construction that replaces vegetation with absorptive surfaces. Air temperature rises as a result of formation of heat islands. One suggested method to reduce the emitted heat from asphalt pavement surfaces is to reduce the temperature of the surface by flowing a suitable fluid through the pavement. The heated fluid could then be used for different end applications. Laboratory experiments were carried out using compacted hot mix asphalt samples with quartzite and metagranodiorite aggregates. Pipes with different surface area were used to flow water through the samples, and the processes were modeled using finite element method. The results clearly show the feasibility of the proposed method, and indicate the beneficial effects of higher thermal conductivity of aggregates and larger surface area of pipes. Velocity and thermal profiles of water in the pipe inside asphalt pavement are analyzed, and the necessity of good contact between asphalt mix and fluid carrying pipe is illustrated.