Optimal scheduling of micro combined heat and power units: Impact of degradation costs

Abstract

Increasing uncertainty and intermittency in the energy grid require greater flexibility. Micro-combined heat and power (micro-CHP) systems enhance flexibility by generating both heat and electricity while also supporting grid stability. However, frequent cycling and varying operational conditions may accelerate component degradation, which can affect both the lifetime and economic performance of such systems. This paper presents a cost-minimizing dispatch model for micro-CHP units based on micro gas turbines, which incorporates a more detailed degradation cost model compared to existing approaches. The proposed degradation model accounts for both operational degradation, driven by turbine blade temperature and rotational speed, and degradation caused by startup and shutdown cycles, including damage during critical speed transitions. A case study of a building complex in Germany is used to test the model under different operating conditions. The results show that including degradation costs leads to dispatch schedules with 12% lower total costs over one year, and up to 50% lower costs in some weeks. The results further show that it is not economically beneficial to overload the micro-CHP unit, even for short periods of high demand, as the additional degradation would offset any potential savings in the short term.