Solurban - Solar Energy Utilisation Potential of an Urban Site

Solurban Project, Solar Utilisation Potential of Urban Sites

Raphaël Compagnon, Marylène Montavon, Darren Robinson, Jean-Louis Scartezzini

Besides providing a more efficient energy use, a large scale application of solar energy technologies in the urban context will be required in the upcoming decades to achieve a drastic reduction of greenhouse gas emissions in the biosphere. Three different urban sites, representative of three of the largest Swiss cities (Basel, Geneva and Lausanne), were examined in order to assess their respective solar potential. Spatial distributions of solar irradiation and daylight fluxes over the overall building facades and roofs were calculated using ray-tracing simulation techniques to determine the appropriate placement of different solar technologies (passive and active solar, photovoltaic and daylighting). Several performance indicators were used to assess the solar utilisation potential of these urban sites (e.g. statistics of sky view factors and daylight factors). A comparison of the results observed for the three urban sites is presented in this paper. It has been observed in the three cases that the building surface areas appropriate to solar technologies are very significant.

2005

Assessment of Solar Thermal Power Technologies

James Spelling

In the present climate of growing awareness about the dangers of global climate change, the development of new renewable energy technologies is primordial in the efforts to reduce emissions of carbon dioxide and other greenhouse gases. Rapid increases in the price of oil and worries about the stability and security of the extraction of fossil fuels have lead to renewed interest in the development of local energy sources, thereby reducing dependence on foreign fuel sources. Amid the plethora of option available, one of the more promising solutions is the increased use of solar power. Two main contrasting technologies exist for the conversion of the Sun’s energy into useful work, namely photovoltaic cells and solar thermal systems. The development of photovoltaic power has shown massive growth in recent years despite high costs, due mainly to the modular nature of the cells which allow their installation by private citizens, coupled with a number of government incentives. Development of solar thermal power generation has however been reasonably limited until recently, with the only continually operated commercial plants being the Luz SEGS I-IX plants at Kramer Junction in the United Sates. Solar thermal power generation shows great potential for supplying the base electricity needs of numerous countries in the sun-belt regions, stretching from the tropics to the Mediterranean. This has lead to a recent renewal in the development of such systems, notably with the construction of the PS10 central receiver plant in Spain. The Spanish government plans to bring the total solar generation capacity to a total of 300 MW by 2013. In other countries around the world, interest is growing in solar thermal power, with increased government and private spending fuelling research and innovation. Most solar thermal conversion technologies are still at the experimental stage, and no single technology has yet to impose its dominance. Different countries and research groups hold different solutions dear, but if solar thermal power is to become a fully mature electricity generating technology, the best of these diverse solutions must be combined in order to achieve optimal performance of the power plants.

2008

Energy-Efficient Sol-Gel Process for Production of Nanocomposite Absorber Coatings for Tubular Solar Thermal Collectors

Yannik Antonetti, Marina Garcia Gonzalez, Thomas Gascou, Martin Joly, Martin Python, Andreas Schueler

The energy efficiency of production processes for components of solar energy systems is an important issue. Other factors which are important for the production of products such as black selective solar coatings include production speed, cycle time and homogeneity of the coating, as well as the minimization of the quantity of the needed chemical precursors. In this paper a new energy efficient production process is presented for production of optically selective coatings for solar thermal absorbers. The latter should ideally behave as a black body, absorbing a maximum of the incoming solar radiation, while minimizing energy losses by infrared radiation, acting as an infrared mirror. The used method to produce such coatings is sol-gel dip-coating. The optical and morphological properties of the Cu-Co-Mn-Si-O based triple layer have been characterized by spectrophotometry, electron microscopy and time of flight secondary electron microscopy. After optimization of the multilayer design, a solar absorptance of 0.95 and a thermal emissivity of 0.12 at 100°C have been achieved. The intermediate Cu-Co-Mn-Si-O layer was analyzed by high resolution transmission electron microscopy. The likewise obtained images show an agglomeration of crystalline grains with 10-20nm in diameter. Therefore, we can consider that the Cu-Co-Mn-Si-O phase is nanocrystalline. In order to roughly estimate the corrosion resistance of the coating in an acidic environment, a simple corrosion test in harsh conditions was designed. With respect to a commercially available durable black chrome coating, this test of corrosion resistance confirmed the durability of the novel sol-gel coating in an acidic environment. Moreover, the excellent stability at elevated temperatures in ambient air makes the coating an interesting candidate for solar applications involving concentrated solar radiation, such as the generation of solar electricity (concentrated solar power), industrial process heating and solar cooling. For that reason, prototype coatings consisting of stacks of three individual layers were deposited on 2 meter long stainless steel tubes.