Combined heat and power operational modes for increased product flexibility in a waste incineration plant

Abstract

The expected strong expansion of wind power may cause challenges for the electricity system in terms of grid stability, power balance, and increased electricity price volatility. This paper analyses how the new market conditions impact the operational pattern and revenue of a combined heat and power (CHP) plant. The work focuses on product flexibility that enables varied ratios between products; and thermal flexibility, to shift load in time given the differing timescales of heat and power demand. Product flexibility is given by five operational modes: conventional CHP, heat-only, CHP plus frequency response, condensing, and condensing plus frequency response. Optimization and process modeling are combined to study the plant dispatch in current and future electricity market scenarios and with thermal flexibility. The results indicate that load-shifting of heat generation together with condensing operation can increase revenue up to 4.5 M€ and plant utilization up to 100% for a 50 MWel waste-fired plant; but requires a thermal energy storage to meet hourly heat demand. The electricity price profile impacts both the revenue and operational patterns, with low-price periods favoring increased heat generation and frequency response delivery. High average electricity price and price volatility results in increased profitability of product and thermal flexibility.