Grate-fired cogeneration power plants are typically used for the incineration of solid waste and biomass. They are characterized by slow dynamics and low operational flexibility. Increasing their flexibility could enable participation in balancing markets and improve revenues under volatile electricity prices. We assess the operational flexibility of grate-fired plants using a validated dynamic model of a typical grate-fired CHP plant and simulate the effects of flexibility-improving measures that were originally developed for coal-fired plants. The results show that changing the live steam pressure setpoint can provide peak power increases of up to 12% with average ramp rates exceeding 18%/min, while changes in superheater or live steam temperature provide peak power increases of 1%–2%. Similar effects are achieved with condensate throttling. Exploiting the thermal inertia of a connected district heating network allows power increases above 5% (up to 16% at high heat load) and the largest electric energy shifting potential, exceeding 1.8 MWh. Turbine bypassing enables power reductions of more than 13% within seconds, however, this comes at the cost of a reduced cycle efficiecy. The results demonstrate that the short-term operational flexibility of grate-fired plants can be substantially improved through steam-cycle and heat-network–based measures without modifying the combustion system. • Significant short-term flexibility without combustion system modification is possible. • DH networks provide the largest energy storage and sustained flexibility potential. • Flexibility gains differ from those at coal-fired plants because of plant layout. • Validated dynamic model of a typical grate-fired waste incineration plant.
Lips et al. (Sun,) studied this question.