Adaptation and Sizing of Solar Water Heaters in Desert Areas: for Residential and Hotels.

摘要

Use of flat plate collectors is significantly limited in desert areas, which presents the contrast of low temperatures in winter close to 0°C, and high temperatures in summer above 40°C. Mexicali, Baja California has a good availability of solar radiation, 5.72kWh/m~2/day, but it has a semidesert climate. Suppliers of these technologies do not include these zones as target markets, and therefore the performance of these systems in extreme climates is not very known, and so do regard the problems for the installation and design drawbacks. The present work shows the technical-economic evaluation about the performance of flat plate collectors for water heating, an outlook of economic and environmental benefits, considering its potential to be use in residential and hotel sectors in Mexicali, Baja California. The analysis was performed with data from a field monitored system during one year, to observe and record information of relevant variables for the performance of solar heater, such as ambient temperature, wind speed and solar radiation, which were obtained from weather stations located in Calexico, California, USA, and Comision Nacional del Agua in Mexicali, Mexico. Also, temperatures in the collector's fluid and in the storage tank were measured and recorded at 5 minutes intervals using a data acquisition system. This information allowed to predict the system's performance for a greater capacity throughout a year, relating the most relevant system variables. The solar heater showed a good performance in winter, keeping an average of 40°C in the storage tank and in summer a minimum temperature of 60°C and maximum up to 85°C. From the above, an economic analysis was generated considering the current market potential in residential and hotel sectors in Mexicali, which translates into savings of 33%, at least in conventional energy consumption and estimated payback in four years for the Hotel's case. Energy savings for residential case is about 80% and the investment return is approximately 5 years, because in desert areas the greater demand of hot water occurs in winter. In conclusion, solar water heater performance is adequate for residential and hotel applications in desert areas and its hot water production is enough for remunerable use of solar collectors under specific and well defined scenarios.