Analysis Of Distributed Energy Systems Based On The Energy Network Theory

Energy saving is an eternal topic, there is a lot of research in terms of energy saving at home and abroad. The current hot research is the comprehensive utilization of energy, The CCHP system and the thermoelectric system of thermal power plant are applied to the actual. But there is a lack of theoretical guidance for the comprehensive utilization of energy. The fundamental theory of energy networks in different energy forms is established following an in-depth analysis of the nature of energy for comprehensive energy utilization.The definition of an energy network is given, in which energy transmits along the wires(pipes), and a number of wires(pipes) connect with each other to form a network. Energy subnets in different energy forms are interconnected by energy converters, energy converters are those elements which can convert one form of energy to another form of energy or which can transfer one form of energy to another department. such as pumps and heat exchangers. The generalized transfer equations of energy in wires(pipes) are proposed based on the generalized balance equation of energy in space, and the energy and exergy variation laws in the transfer processes are investigated. The actual transfer processes of several kinds of common energy are then analyzed with the method proposed and the results are proved by conventional analysis.To establish the equations of energy networks, according to the characteristic of network and the intensive property, the Kirchhoff’s Law in electric networks is extended to energy networks, which is called the Generalized Kirchhoff’s Law. According to the Generalized Kirchhoff’s Law, the network equations which can describe the characteristic of energy network are founded. Then the generalized equivalent energy transfer equations with lumped parameters are derived in terms of the characteristic equations of energy transfer in wires(pipes). The generalized equivalent equations are applied to several kinds of common energy, and the results are proved by conventional analysis. The equations are finally unified into a complete energy network equation set and its solvability is further discussed.A simplified example for energy network composed of an electric network and a fluid network validates the models and methods proposed, and the numerical results show that the energy network has different losses of energy and exergy when it provides different ratio of heat for a constant user heat demand by the electric network and the fluid network respectively, and the energy loss is not directly proportional to exergy loss. and then the optimal ratio value ought to be sought out for energy efficiency.