Applications of parabolic solar collectors, nanofluids and phase change materials to reduce pollutant emissions

Abstract

Different green technologies have been investigated in our research group in the last two decades to produce clean energy and more efficient thermal systems with the purpose to reduce the emissions of pollutants. Simulations, experiments and thermal analysis have been performed to develop and improve the efficiency of Parabolic Trough Collectors (PTC). In this type of collectors, solar radiation reflected in a parabolic surface is concentrated to heat a fluid that circulates in an absorber receiver. One of the strategies to enhance the heat transfer of the PTCs is the application of nanofluids as a working fluid. These nanofluids are produced by dispersing nanoparticles in a fluid base with the purpose to increase their thermal properties. Nanofluids with nanoparticles of Al2O3, TiO2 and graphene dispersed in water and oil have been developed and characterized by our group. These nanofluids have been experimentally tested in a PTC for real operating conditions. We have also developed a hybrid PTC with photovoltaic cells in the receiver with the objective to generate simultaneously thermal and electrical energy. The technical and economic feasibility of a plant of hybrid PTCs to satisfy part of the demand of heat and electrical energy of the industry and the building sector have been investigated for different applications, climates and economic scenarios. In order to reduce the energy consumption of the buildings, the application of phase change materials (PCM) in components of the envelope, such as the roof and the walls, has been studied. The purpose of these PCMs is to reduce the heat gains of the buildings and delay the maximum peak loads because the thermal energy that is transfer through the envelope of the building is used to melt the material of the PCM. Experimental and simulations results performed in different types of buildings and climates are discussed. Finally, it is presented a computational platform (http://www.tecsb.com) developed by our group that use satellite information of solar radiation and available roof surface of a metropolitan area to predict the solar potential for generation of electrical and thermal energy with different solar collectors technology and to estimate the reduction of energy consumption in the building due to the application of different passive technologies such as PCM, reflective paintings and insulator materials. The program has the capability to provide an estimation of the reduction of CO2 emissions due to the use of these renewable and green technologies instead of technologies that burn fossil fuels.