Testing the Performance of a Solar Energy Collector
Preponderance of demands shows the objective need to evaluate generation of solar energy by using simple laboratory method to fabricate a parabolic trough for use as solar energy collector. Designing a parabolic energy collector require the connection of parabolic ribs to a torque. The foundation for the parabolic collector is made up of a preformed aluminum which is sized and bolted to the rib. The containing mirror is replaceable, partly made of acrylic aluminized material and protected by a reflective plastic material.
The solar tracking is provided by using gear box motor synchronized by chain drive as proposed by the combined Minneapolis-Honeywell Project. Using a theoretical model to calculate performance at variable operating system, we can evaluate the efficiency of the solar energy collector produced. An example of a model computation using cylindrical trough collector, usual calorimetric measurement with flowing fluid is substituted for aluminum metal.
For a cloudy day where radiation loss occurs for a small temperature change, we use the linear approximation to calculate thermal balance and the equation above becomes (fig 1). Fig 1. fig 2 The thermal balance is calculated from the nonlinear approximation when there is a constant solar angle and constant isolation on a standard clear day especially between 10am and 2pm (see fig. 2). Following several computations and assumptions, test results indicate that a constant temperature of about 400oC can be easily isolated from parabolic trough collector.
The simplicity of the procedure requires mounting a black chrome, 3. 8cm aluminum rod in the choice of vacuum environment as so wish Advanced Reflector Materials for Solar Concentrator With an objective to design reflector materials with prolonged efficiency of specular reflectance, US National Renewable Energy Laboratory did combine with private organizations. The objective equally comprises ensuring durability and provision of cost effectiveness reflector materials in relation to the present produce.
The overall success of mounting a good solar thermal powered system is dependent on both advanced optical materials used and the huge concentrator cost in procuring heliostat (for example). Over the usual glass mirror used as reflector, the use of advanced optical materials such as stretch membrane design. An example of stretch membrane design such as silvered-polymer reflector is advocated. Silvered-polymer reflector balances the need for flexibility, light-weightiness, and reduced cost over weighty, fragile and expense glass mirror. It is of high performance and durability.
Since the need is to balance concentrator costs with glass mirror advantages of high specular reflectance, durability, long lifetimes and moderate degradation rate of reflectivity function, solar manufacturing industries suggested new goals to pursue reflective mirror with reduced cost and lifetime of over 10 years under outdoor use. In the pursuit of these goals, two factors to evaluate before end product manufacturing includes the solution to high cost problem of preventing degradation of solar reflector materials and the criticality of method applied in predicting the outdoor lifetime.
Program of outdoor testing and continuous monitoring of meteorological data are measures established by NREL to achieve these solutions. The Program Structure; activities Basically aimed towards achieving the desired advanced optical materials, there is need to harness resources from all stakeholders in solar technology in the production and promote the following activities; concept investigation, outdoor testing, manufacturing investigation and commercial testing.
Concept investigation activity requires identification new materials and laboratory performance check for projected life. Industries are involved in the overall process of investigation to share understanding of practical use of materials. This activity is crowned by production of template materials to evaluate projected optical and mechanical properties, and testing the degrading reflection function over time. According to the paper, coating metallic materials with mirror-like substrates such as polyethylene terephthalate film is promising.
Several samples of organic and inorganic substrates have being put to test by NREL; tin oxide coated on silver and polyurethane coated on silver reflector materials are tested among others and were found remarkably good. In collaboration with other organizations NREL also investigate forms of reflecting materials’ designed with different findings; Directly Deposited Reflector Material, Silvered TeflonTM Reflector Material, Polymer Multilayer Reflector Material, All Polymeric Reflector Material, and Adhesively Bonded Reflector Material.
Outdoor Testing entails an organized monitoring and checking of intended materials to predict outdoor service lifetime when put to use. This activity provides reduced investment risk for intended manufacturers and promotes the use of optically durable mirror. It testing is also done with concern on geographical demonstration of functional variation of lifetime when exposed. Manufacturability investigation determines specific method of manufacturing the chosen reflector and whether the quality of the produce certify laboratory standard for the material.
Commercial Testing, done with involvement of concentrator suppliers, ensures that products simulate required environmental deployment. Achieving the stated satisfaction of an advanced reflector materials with high reflectance capacity is not impossible but there is a need to develop a faster approach to service-life prediction since it is impossible for market supply of this existing materials to wait for 10 years minimum duration for the program structure; there is a need for accelerated lifetime testing. The Parabolic Trough Power Plants Andasol 1 to 3
In Europe, solar energy and thermal plant is increasingly becoming a major focus as substitute for the fossil resources because it is cheaply available in surplus of the total earth need. Some countries like Germany have demonstrated its advantageous use over electricity in the generation of about 250 megawatt to produce it. Considering the fact that oil and gas resources are only finite on earth and their effect of industrial pollution (green house effect), it is important to source out for a more efficient solar-thermal plant that can provide electricity even round the clock.
Concerning the market forecast for solar energy, though not without the initial assistance of States to lift starting financial asset, a renounced institution (German Aerospace Center, DLR) points out that by 2025, renewable solar power will be cheaper than fossil fuels. Adding that, solar capacity will hugely amount “combined wind photovoltaic, biomass, and geothermal power stations. Solar-thermal power plants can produce up to double the amount of energy when equipped with thermal storage”. Spain has successfully pioneered the market in the last few years.
The use of parabolic trough converts sun rays to huge amount of solar energy for large scale production of comparable magnitude outweighing other sources. It has a structural arrangement containing solar field that fuel conventional steam turbines. The solar collectors (silver coated mirror) absorb the rays and produce 80-fold concentration of the absorbed light energy. This is then transmitted through a high precision optic device that transfer heat to non-labile oil, circulating through heat exchanger and continuation of steam cycle power plant produces the electricity.
Andasol 1 Power Plants (APP), developed by Solar Millennium AG in Southern Spain (1998), uses this process in energy generation in range of 50MW to 250MW, the world largest solar power plant. APP merit the advantage of low energy amortization and smaller specific surface area for amount of energy produced. The location is best suited for availability of resources and distant from residential buildings. It has a thermal storage tank, containing ingredient of molten salt mixture, to allow scheduled electricity production.
The overall tank arrangement allows continuous supply of high voltage grid in accordance with Spanish energy law. In summary, the use of parabolic trough power plant in Andasol 1 Plant in the generation of energy so far has demonstrated good template for the rest of the world to contest. Andasol 2 and 3 have capacity of 2000MW output voltage. An upcoming development is in the construction of parabolic trough for hybrid power generation; combining natural gas and solar energy to produce electricity for maximum energy yield and conservation of fossils.
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