Increasing power system flexibility through utilizing VRE curtailment and power-to-heat strategy

When increasing the share of variable renewable energies (VRE) such as wind or solar power, power curtailment may become necessary to balance the power system. In general, curtailment may be needed because of transmission congestion or lack of transmission capacity with a high share of VRE. Here we explore the effects of wind power curtailment utilization in Finland. The study examines the effect of curtailment on two levels: on a city level for Helsinki (Finland’s capital), and on a national level (whole Finland). For each level, a specific optimisation-based model has been developed. The city-level model employs 10-minute time steps, while the national model uses 1-hour time steps. Both models aim to minimise system costs, and the main constraints of the models are the characteristics of power plants and balancing methods, in addition to securing the energy demand and supply balancing. The city-level results reveal the optimal transient operation of power plants and their CO2 emissions, while the national-level results demonstrate the effects of wind curtailment on the whole energy system and its composition. The curtailment has been defined through 3 different scenarios, estimating the wind curtailment based on fixed percentages of the wind generation peaks, the wind generation profile, and a fixed percentage of the power demand profile. The fixed percentage of the wind power generation results in most curtailment, whereas the wind peak-shaving results in least curtailment. To increase the wind power penetration, the option of power-to-heat utilizing the curtailed wind power was applied on both levels. Increasing the amount of wind and curtailment and implementing power-to-heat conversion may not automatically lead to positive effects, but may need additional measures such as higher CO2 emission pricing and more effective heat generation (heat pumps) to get the full benefits.