| Research Abstract |
As we know, our society is going into the management-age from manufacturing-age today. And it is necessary to develop a new assessment method, which uses life cycle thinking by adding a long-term social value, life cycle value, to a modem economic value. However, up to now, it is insufficient to solve the above described issue by the development of a soft technology.
On the other hand, with the improvement of the concerns on environmental protection and energy-saving, energy utilization methods with energy-saving and low CO2 emissions have got more and more attention. Under such a background, a small-scale distributed power generation system is being continuously introduced in a building or a region on-site where energy is needed. In the system introduced, though each individual equipments has one high energy utilization efficiency, when the entire energy supply system is considered, the effect of energy-saving, economy and environmental protection is not necessarily high. This is becau
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se the following factors: there is not supporting system in design stage; the decision process of an initial investment is unclear considering the life cycle value; the demand site is not considered during the equipment's running.
In this research, a model for structural and operational optimization of DER system is presented. In the model, production and consumption of electrical power and heat, storage of heat are taken into account. The problem is formulated as a mixed integer linear programming (MILP) where the objective is to minimize the overall cost of DER system, i.e. the sum of running cost, the annualized investment cost, and so on. The branch and bound (B & B)algorithm is employed to solve the MILP problem because it can save a lot of computation time by eliminating unnecessary cases among every possible combination. Furthermore, this algorithm is efficient in the computer simulation for the case involving the presence of various constraints in the performance for the components.
In addition, an illustrative example of DER is presented. We analyzed the effects of fuel price and equipment efficiency on the operation time, running cost and energy saving in Japan. The increase of electricity price and decrease of gas price will increase the attractiveness of distributed energy resource. According to the load function of the system, the energy-saving, environmental improvement will have a maximum value at its optimal operating time. Compared with heat recovery efficiency, power generation efficiency has more influence on the energy saving and CO2 reduction when the total efficiency of system is fixed.
Furthermore, an investigation was conducted of economically optimal CHP investment for a prototypical residential building. A sensitivity analysis was elaborated in order to show how the optimal solutions would vary due to changes of some key parameters. In addition, as a main component of residential CUP system, the optimal size of the storage tank was analyzed. Less
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