The deposition of dust on photovoltaic modules is of importance as parameter for economic analysis and life cycle assessments to evaluate this kind of technology for generation of electricity. Even though during the last two decades several photovoltaic plants were implemented, only a few studies about this issue were performed. This work tries to estimate the annual loss of generated energy caused by dust deposition on PV modules based on an experimental setup of a grid connected PV plant, monitoring of solar irradiation, onsite determination of dust deposition rate, and processing climatic data to obtain information about the frequency of rainfall occurrence. In Mexico City, air pollution with suspended particulate matter with diameter below 10 μm (PM 10) is almost permanently over 50 μg m -3 . This contamination contributed to an average dust deposition rate of 65 g m -2 d -1 on horizontal surfaces. Dust accumulation during rainless periods of more than 60 days can reduce production of PV systems up to 15%. With the capacity of natural cleaning by rainfalls, annual loss of production is estimated to be 3.6%.
This paper describes the design of an ultrahigh solar concentration device (C> 10 4 ) and shows the technical feasibility of using solar energy in processes requiring high temperatures with relatively simple devices. The concentration is effected in two stages, using in the first stage a paraboloidal reflective disc of 1.40 m. of diameter, whose focal region is located at CPC-3D without truncating. The ideal concentration achieved was 93 567 suns. A thermal-optical analysis was performed to estimate the actual concentration considering radiant energy losses in both concentration stages and the concentration was estimated to be 30 000 suns. Among the potential applications of this device is the production of hydrogen [1], power generation [2], production of alloys and special materials, destruction of hazardous industrial waste and the use of high energy lasers.
This study compares the energy efficiency of two processes covering the thermal energy demand of a swimming pool: a combined heat and power (CHP) unit on the one hand, and a heat pump with internal combustion engine on the other hand. The thermal energy demand of the swimming pool was 1438 kWh per day (78% heating the pool and 22% providing hot water for showers), owing to temperate climate in the city of Toluca in central Mexico; a mean annual temperature of 13.5 °C (10.5 °C in January and 15.7 °C in June) offers a large potential of renewable thermal energy stored in the atmosphere. Its utilization in heat pumps driven by thermal combustion engines can provide energy below 60 °C; this temperature level provides hot water for showers while a lower temperature level of about 40°C heats up the pool water and swimming hall. Depending on outdoor temperature, which defines the load for the units, the efficiency in terms of total primary energy consumption is better for the CHP solution (100% and 80% load) and is better for the heat pump in the case of a 57% load. The energy losses for the CHP unit on-site are equivalent to half the losses caused by extraction and distribution of natural gas under current circumstances in Mexico. The results provide a decision tool.
Parabolic trough technology is currently one of the most extended solar thermal systems for the production of electricity. This paper describes a thermo-economic study of an integrated, combined-cycle parabolic trough power plant. The parabolic trough plant is considered an economizer or a superheater of the HRSG (heat recovery steam generator). The main objective is to obtain the optimum design of the different sections of the boiler and the size of the parabolic field. The configurations analyzed are two pressure levels with and without a reheater. A Euro Trough (ET) concentrator was used in this study, the working fluid being water with direct steam generation. There will be no problem with the evaporation in the absorber, since the solar plant will be the economizer of the HRSG and an approach point greater than 3°C is considered. The methodology applied for the optimization is Genetic Algorithms. This methodology was employed in previous works developed by the authors and yielded good results. So that method is applied to the configurations analyzed but including the parabolic trough plant. As a result, a thermoeconomic optimum design of a parabolic trough plant used as the section of the HRSG is obtained. The results show that the solar field increases the power and efficiency of the combined-cycle plant during the operation and makes it less susceptible to load variations.
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