| In recent years,due to energy and environment are the key to the sustainable development of human cities and societies,which have attracted great attention all over the world.Meanwhile,China's lighting power consumption accounts for 12%-16% of the country's gross generation all the year round,take 2013 as an example,the annual power generation is 5245.1billion k W·h,and the annual lighting power consumption reaches 629.4 billion k W·h.With the rapid development of urbanization,many places also need to provide lighting during the day to meet the normal life and production.Under this background,the solar lighting technology,which actively introduces sunlight into indoor lighting,has great potential of energy-saving.The introduction of natural light is also conducive to alleviating visual fatigue,relaxing the mood of people in the building,and effectively avoiding negative emotions.However,for the purpose of protecting the transmission optical fiber and reducing the thermal effect of the output visible light,the current solar lighting technology habitually adds an infrared filter to filter the infrared ray which accounts for about 50% of the total sunlight.This method not only greatly reduces the overall utilization efficiency of solar energy,but also increases the initial investment cost of the system.In order to solve the above problems,a solar energy lighting / heating system is designed,which using the spectral selectivity of nanofluids to separate and utilize the solar radiation energy,then the infrared energy is absorbed by the circulating nanofluids for domestic hot water,and the visible light is transmitted from the fiber bundle to the indoor lighting.Firstly,the operation principle,design principle and process of the system,the selection and preparation of nanofluids are described in detail.Based on the design data of the system,the experimental test platform of solar lighting / heating system is built,and a series of system performance exploration experiments are carried out.Under the Case 1(0.025%/0.0001% ATO/graphite mixed nanofluid,100 L/h flow rate),the light transmission efficiency is 19.5%,which is equivalent to the efficiency of the current solar lighting system,and it has a heat absorption efficiency of 25.35%.In addition,the effects of the concentration and flow rate of nanofluids on the visible light transmission efficiency and heat absorption efficiency of the system were also investigated.Then,based on Lambert-Beer's law,the mathematical model of absorption and transmission of nanofluids for the system was established;combined with the human visual sensitivity function,the calculation model of visible light transmission efficiency of the system is established;based on the radiation transmission equation,the calculation model of heat absorption efficiency of the system is established.The accuracy of the mathematical model is verified by the experimental data.Finally,according to the model,the characteristics of visible light output,the influence of external parameters on the heat absorption efficiency and the annual energy output of the system are studied in detail.The results show that the spectral characteristics of the visible light output of the system are similar to that of the natural light,and the luminous efficiency is 242 lm/W,much higher than 150 lm/W of the mainstream LED lamps;when the system is used in Harbin,the annual luminous energy output is 188.15 k W·h,and the total energy output of the domestic hot water is 248.2 k W·h.Through the calculation of comprehensive energy price,the recovery of infrared energy can reduce the unit price of solar lighting technology output energy by 44%-50%.In conclusion,the solar lighting/heating system proposed in this paper has good economic benefits and application value. |
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