The paper proposes a comparison of different district integration options for a distributed generation system for heating and cooling in an urban area. The system considered includes several production units located close to the users, a central unit and the district heating and cooling network which can connect all the users to each other and to a central unit, where a cogeneration system and a solar plant can be placed. Thus, each user can be regarded as isolated from the others, satisfying its energy needs by means of an autonomous production unit. Alternatively, it can be connected to the others through the district heating and cooling network. When a district heating and cooling network is included in the design option the synthesis-design and operation problems cannot be solved separately, because the energy to be produced by each production site is not known in advance, as the flows through the district heating and cooling network are not defined. This paper uses a mixed integer linear programming (MILP) methodology for the multi-objective optimization of the distributed generation energy system, considering the total annual cost for owning, operating and maintaining the whole system as the economic objective function, while the total annual CO2
emissions as the environmental objective function. The energy system is optimized for different district integration option, in order to understand how they affect the optimal solutions compared with both the environmental and economic objects.
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