Multi criteria dynamic design optimization of a distributed energy system

摘要

Combined heat and power plants(CHP)are highly efficient,but their operation strongly depends on the heat demand and thus,among other parameters,on the ambient temperature.Due to the continuously increasing and highly fluctuating power production of renewable energy sources in Germany,the flexibility of CHP plants should be increased.Heat-storage vessels enable the temporal uncoupling of heat demand and power generation,whereas a district-heating network allows for centralized heat production.In this way,not only can the specific investment costs of a CHP unit be kept low due to the effect of scale economy,but also a higher share of heat production can be generated by the CHP units.The aim of this paper is to analyze the competing components heat storage and district-heating network considering economic and ecological aspects.Therefore a mixed integer linear program(MILP)of a distributed energy system is formulated with a weighted multi-criteria objective function including profit and operational CO2 emissions.The time horizon of the model,and thus for the input parameters heat demand,ambient temperature and day-ahead electricity prices of the energy exchange,is one year with a temporal resolution of four hours per time interval.The computed designs as well as the operation of the energy system are compared under varying weightings and different technology scenarios.We also conduct a sensitivity analysis of the investment costs associated with heat storages and of the piping costs for the district-heating network.The general results favor the construction of heat-storage devices over a district-heating network.This applies to both environmental impact and cost of energy supply and can be well explained by the decoupling of heat demand and electricity production,which is shown in a correlation analysis.