Design And Optimization Of A Small Solar Distributed Energy Supply System In Off-grid Regions

With the continuous development of the global economy, a series ofproblems such as the increasingly tight energy supply and the increasinglyserious environmental pollution follow one after another, so improving energyutilization rate and reducing pollutant emissions have become a commonconcern all over the world. The distributed energy supply system is widelyconsidered to be the preferred method to effectively solve the problem of energyand environment by the countries all over the world, because of its advantagesof high energy utilization rate and low emissions. At present, for the study ofdistributed energy supply system，domestic and foreign scholars are mainlyfocused on parallel grid systems with natural gas as the main energy. Most ofthe systems are used in developed cities which can supply natural gas adequately.For some remote areas such as plateau, border and islands, the existence of badclimate, traffic inconvenience and lack of coal and water resources makes itdifficult to provide power for the local users through the power transmission, ahydropower station or a thermal power station. It can only rely on dieselgenerators to provide power for residents. Therefore, the reseach on new energysupply system and the utilization of local clean and renewable energy are ofgreat importance to provide power and improve the living conditions of localresidents in remote areas.With the unique advantages of widespread existence, reserves infinity andthe cleanness of exploitation and utilization, solar energy has become the mostnoticeable clean renewable energy. At the same time, because of itsdisadvantages of dispersity, intermittent and randomicity, other sources of energy must be added. The combination of solar energy and traditionaldistributed energy supply system, on the one hand can reduce the consumptionof fossil energy, on the other hand can make up for the solar energy itselfdisadvantage of discontinuity and instability. Based on the above background,by using solar energy as the main energy and diesel oil as auxiliary energy, asmall solar distributed energy supply system that combined solar energyutilization technology with traditional distributed energy supply system isdesigned and optimized for the remote areas far from the power grid in thispaper.Firstly, based on the DeST building energy simulation software and thehour energy load apportionment ratio method of the Japanese CCHP designhandbook, the annual hourly cold, heat, electriccal and domestic hot water loadare simulated for a frontier sentry in Mohe, Dunhuang and the South China Seaislands.Secondly, according to the different load characteristics of the targetbuilding in three regions, three kinds of small solar distributed energy supplysystem are designed. The structure and working process of the system isanalyzed. At the same time, the thermodynamic, economic and pollutionemission models of the key devices are established.Thirdly, for year-round operation cycle, the optimization model isestablished, which takes the maximum comprehensive benefits of economy,energy and environment as the objective function. Based on different values ofeconomic, energy saving and emissions reduction weight factors，three kinds ofweighting scheme of each system are obtained. The optimal configuration andthe best operating strategy of each scheme are obtained through the optimizationcalculation of each weighting scheme of the three regions.Fourthly, the influence of per-unit cost of solar energy utilization devicesand local energy price on performance of the small solar distributed energysupply system is analyzed. The results show that: With lower costs of solarcollectors and photovoltaic panels and higher diesel price, comprehensivebenefits of the small solar distributed energy supply system is better. Finally, from the aspects of energy saving, emissions reduction andeconomy, optimization results of each scheme for different regions are evaluated.The results show that compared with the traditional supply system, the smallsolar distributed energy supply system has great advantages on providing energyfor residents in remote areas far away from the power grid. When the small solardistributed energy supply system is applied in Dunhuang, the energy,environmental and economic efficiency is better.The results of this study can provide a reference for the design andapplication of solar distributed energy systems in remote areas far away from thepower grid.