Many energy supply systems around the world are currently undergoing a phase of transition that is mainly characterized by a continuing increase in installed renewable power generation capacities. Aiming at a better integration of these additional capacities, operators of wind farms in Germany are obliged to bindingly forecast their power production. In order to maintain the continuous stability of the electricity grid, deviations from these forecasts have to be compensated by the grid operator, who charges the wind farm operators accordingly. An alternative way to compensate for forecast errors is the utilization of flexible and dispatchable energy conversion and storage units by the wind farm operator.
Heat-driven combined heat and power (CHP) units with heat storage systems offer the potential of limited short-term load adjustments to compensate forecast errors while simultaneously fulfilling their main task of providing heat.
The main objectives of the present study are the evaluation of the main technical parameters and the economic viability of the described application.
The study utilizes a theoretical scenario incorporating a gas turbine as a CHP unit providing heat for an industrial process, a heat storage and an associated wind farm. A generic wind farm power generation forecast error model is developed, providing realistic forecast errors for the study. Detailed models of all system components are developed and integrated into a common simulation environment, allowing for simulations of the overall system operation with varying heat storage capacities. The simulation results show that the combination of a heat-driven CHP gas turbine and a heat storage system makes a significant contribution to the compensation of the wind farm power generation forecast errors. Distinct correlations between the heat storage capacity and the remaining forecast errors are identified. The net balance energy costs resulting from the remaining demand for balance energy after the partial forecast error compensation are investigated as the main parameter for the economic viability. No distinctive correlation between the heat storage capacity and the net balance energy costs can be identified. This is the result of the stochastic character of the net balance energy price.