Solar Resources Analysis And Thermodynamic Properties Research Of Household Solar Hot Water System In Chongqing Hilly Rural Area

With the national urbanization process and rural ecological civilization construction,villages and towns,as a rapidly rising population,occupy an increasingly important position in the energy consumption.How to promote clean,green and efficient energy utilization under the condition of meeting the increasing living environment requirements of the villages and towns becomes a new subject.With the on-the-spot investigation and the actual measurement,this subject mainly research the solar resources and practicability of the solar hot water system in mountainous villages in Chongqing.With the energy analysis method and the exergetic analysis method to discuss the energy saving potential of solar hot water system.Through the field investigation of more than 10 villages and towns and nearly 600 rural residents in Chongqing area,commodity energy(electric,natural gas)and traditional energy(firewood)are the major source of domestic hot water.But the rustic residents’ demand of domestic hot water stands out because electric and natural gas is hard to gain in mountain village.So acceptance and utilization of renewable energy sources(solar energy)are gradually increasing.Through monitoring the solar energy resources all year round,the annual total radiation in mountainous villages is higher than that in central Chongqing,because of the higher altitude and the better air quality.The disequilibrium of monthly or daily solar radiation contribution is standout,the amount of solar radiation from May to September accounted for 60.8%.Considering radiation intensity noon(12:00-14:00)is the optimum utilization period,then the afternoon.The weather(sunshine duration)and daily range of temperature are closely related to daily radiation.The solar radiation prediction model based on the empirical coefficients is established to simulate 4 monthly radiation and compare with measured data by using the quantity of sunshine duration and daily range of temperature.Through the actual operation parameters all year round of the solar hot water system,the temperature of hot water in tank(considered as supply hot water temperature)is closely related to daily radiation.According to the fitting curve,when the daily radiation is 10MJ/㎡,the water temperature is about 55℃.According to calculation,the guarantee rate of 40℃ hot water is 50% and the guarantee rate of 60℃ hot water is 25%,the guarantee rate of 40℃ hot water in winter is 33%.Collection efficiency is range from 0.4 to 0.8 all year round.When the temperature of hot water in tank is in the range of 40-60℃,the collection efficiency is high,when the temperature of hot water in tank is higher than 60℃,the collection efficiency begins to decrease.With the energy analysis method and the exergetic analysis method to research the thermodynamic characteristics of solar hot water system.Compared with other household domestic hot water systems such as the electric water heater,gas water heater and air source heat pump hot water system,the solar hot water system has the highest primary energy ratio.The exergetic efficiency of solar hot water system is as low as the electric water heater and gas water heater,but the input exergy of solar hot water system is free,so the energy-saving effect is remarkable.