Evaluation of the Optimum Hybrid Power to Heat Configuration for a Gas Turbine Based Industrial Combined Heat and Power Plant

Combined heat and power (CHP) is a very efficient way to generate both power and heat. However due to the increase in renewable power, the position of CHP in the energy system shifts: 1) the benefits of low effective CO2 emissions and low primary fuel consumption decrease and 2) the income from the generated power will show stronger fluctuations and will generally decrease. Most CHP plants have shifted from base load operation to flexible operation on the power market to cope with these challenges. But due to the requirement for stable heat supply, flexible operation is more challenging than for a CCGT plant. Significant flexibilization of CHP plants can be achieved by the integration with power to heat (P2H): the heat supply requirement enables the opportunity to create value out of low electricity prices during periods of excess renewable power generation using hybrid CHP-P2H-operation while during hours with high electricity prices and relatively low renewable power generation the CHP plant can run economically in its original configuration. In this paper a study is executed on the implementation of P2H in an industrial CHP plant for four different configurations, varying from a ‘simple’ external electrical boiler to a full integration using air preheating and flue gas heating. The added flexibility and reduction of fuel consumption of these configurations have been calculated. The economic analysis identified the imbalance market as the most attractive option for a hybrid CHP-P2H installation. The maximum income is generated by the CHP-P2H configuration that combines an inlet air preheater with electrical duct firing. P2H appears to be a technical feasible option to make existing CHP installations fit for operation on a power market with an increasing share of renewable power.