Optimal design and operation of district heating and cooling networks with CCHP systems in a residential complex

• A MILP model for the optimization of complex distributed energy systems was analyzed.
• The model can be used to identify the opportunities for the integration of photovoltaic and district heating and cooling systems.
• The objective function of the optimization model is relative to capital and operational costs.
• The optimized cogeneration which includes PV and DHC system, reduces significantly both the energy supply cost and the primary energy consumption.

The aim of the paper is to describe a mixed integer linear programming (MILP) model for determining the optimal capacity and operation of seven combined cooling, heating and power (CCHP) systems in the heating and cooling network of a residential district (Shahid Beheshti Town) located in east of Tehran. In this model, by minimizing the initial and operating costs of energy supply system, capacity of various components, and optimal operation strategy are determined using continuous variables, and binary decision variables describe the existence/absence of each considered component and its on/off operation status. A distributed energy supply system is made up of district heating and cooling networks, gas turbines as the prime mover for CHP systems, photovoltaic systems (PV) and conventional equipments also, such as boilers and absorption and compression chillers. In this configuration, the required heat is obtained from natural gas consumption by cogeneration system and auxiliary boilers. Four different scenarios were defined to assess the impact of the use of photovoltaic and CCHP systems in the energy supply system in the residential complex. The economic and environmental results obtained from the scenarios revealed saving in costs and reduction in CO2 emissions in the optimal cogeneration system compared with using boilers to produce heat and of buying electricity from the grid.