Research On Analysis And Optimization Of Distributed Energy System

It is a common situation in the distributed energy system that unmatched capacity of system components is determined, improper operation strategies are selected, and the natural gas is chosen as the only fuel, which are great obstacles of the further development of distributed energy system. This thesis focuses on the problems mentioned above and mainly includes optimization in DES design, selection of operation strategies and studies on the novel DES with renewable energy sources. Two hotel and office buildings are objects of this study and DES is comprehensively explored and analyzed from three aspects including energetic, economic and environmental characteristics.(1) The simulation of the hourly cooling, heating and power loadsThe hourly cooling, heating and power loads of the hotel and office buildings are simulated by the software DeST, based on the design standard for energy efficiency of public buildings in China. Furthermore, the change rules of building loads and ratios of heat to electricity of all months and representative days are analyzed and summarized, which are the same with the hourly change rules during the whole year. The change rules of cooling, heating, and power loads of buildings are always neglected in other papers and theses. The simulation conducted in this thesis overcomes these shortcomings and makes the load data more accurate, which is of great importance to determine the capacity of the devices.(2) Study of one novel operation strategy based on FHL strategyThe models of following the electric load (FEL) strategy and following the thermal load (FTL) strategy are proposed. One comprehensive evaluation model of three different strategies are construted based on primary energy saving ratio, annual cost saving ratio and carbon dioxide emission reduce. The essential differences between FEL, FTL and following the hybrid load (FHL) are analyzed. What’s more, the key problems in FHL strategy are proposed and formulas derivation and comparison are conducted to point out essence of the problem. Based on the aforesaid analysis and FHL strategy, one novel operation strategy called improved FHL (IFHL) is presented in this thesis. Comparative analysis of energy consumption and supply in FHL and IFHL strategies are carried out which proves that IFHL strategy is one optimal operating strategy. IFHL strategy can dramatically improve the integrated performance of DES applied to the Beijing hotel building whenever the ratio of heating and power is high and low.(3) The intelligent optimization model of distributed energy systemOne intelligent optimization model of DES is constructed based on the maximum rectangle method and genetic algorithm. The maximum rectangle method is used to determine the range of variables and the purpose of using genetic algorithm is to find out one optimal solution. It is a common phenomenon that the ranges of parameters used in the genetic algorithm are not the appropriate values. Moreover, When the capacity of power generation is determined by the maximum rectangle method, some key factors, such as the system structure and equipment investment are neglected. Considering the disadvantages mentioned above, the intelligent optimization model of DES in this thesis can overcomes previous model’s shortcoming. The rationality, accuracy and effectiveness of the proposed model are proved by case study of the Beijing office building. In addition, the special optimization about the ratio of electric cooling to total cool load are employed in this thesis, which makes the integrated performance of DES more satisfactory.(4) Optimization and analysis of distributed energy system combined with solar energyIt is obvious that the traditional DES depends mainly on natural gas, which leads to so many disadvantages and cannot earn DES a bright future. One novel distributed energy system combined with solar energy (DESSE) is designed with usage of the optimization model described above and the optimal capacity of power generation, the ratio of electric cooling to total cool load, the ratio of solar power generation area to total area are determined. Afterwards, the sensitivity of the performance of DESSE to device characteristics and market factors is studied. Another important comparison between DESS and DES is made from three aspects, namely, energy consumption, cost and carbon dioxide emission. It turns out that DESSE can save more fuels, have fewer carbon dioxide emissions and enjoy better integrated performance.(5) The influence of heat storage tank on DESSEA heat storage tank is installed in DESSE put forward in previous section and its influence on the DESSE is studied. After the optimal value of relevant parameters are determined, comparative analysis of DESSE with and without heat storage tank is conducted from different time perspective. The conclusions are that installing a heat storage tank with proper capacity can improve the system operation in energy saving, cost saving and carbon dioxide reducing aspects, and especially can overcomes the disadvantage of bad economic nature caused by great investments of DESSE. Moreover, it turns out that the heat storage mainly works at night in cool seasons, stores and releases heat in hot seasons. In transition seasons the heat storage tank works all day and has the greatest effects on the operation.