The contribution of heat storage to the profitable operation of combined heat and power plants in liberalized electricity markets

Combined heat and power (CHP) plants are characterized by high fuel efficiency and are therefore usually the thermal power producing units of choice within a district heating network. The operation of CHP units is typically controlled by the current heat demand and thus delimits the range of electricity production. Heat storage devices are a promising alternative to uncouple the heat load of the district heating network from the commitment of the units and to allow for price-oriented electricity production.In this paper we present numerical results for the combined optimization of the operation of nineteen existing power plant units and the design of six proposed heat accumulators which supply the district heating network of Berlin. A mixed-integer programming problem (MIP) is formulated in GAMS and solved with CPLEX. This paper focuses on the potential for increasing profitability through the addition of heat accumulators in the energy system described above, on the optimal storage capacities for different price scenarios (variation of fuel costs, prices for carbon dioxide emission certificates, and electricity price time series) as well as on the adjustment of the operation of the power plants due to heat storage.

► Case study: A real, large scale district heating network including all CHP plants.
► Approach: The MIP model is effective for the design optimization of heat storages.
► Temporal resolution: 4 h time intervals and a time horizon of one year.
► Numerical experience: Strengths and limitations of this MIP approach are presented.
► Conclusion: Heat storages increase the profitability of the CHP plant park of Berlin.