Dispatchability Potential of Geothermal Power Plants in São Miguel Island, Azores

Abstract

In São Miguel Island, Azores, Portugal, up to 42% of the electricity demand is provided by the operation of the Pico Vermelho and Ribeira Grande ORC geothermal power plants. The available resources are abundant and could support an expansion. However, this will depend on the ability of geothermal to operate in flexible mode to follow the grid demand when it is required. Currently, the average annual base load of São Miguel is around 34 MW, with 20 MW given by geothermal, 10 MW supplied by the thermal plant, operating at its minimum required technical limits to ensure the power system stability, and the remaining 4 MW given by hydro and wind, where wind power is mostly being curtailed at off-peak hours. In the coming years, there are plans to expand the Pico Vermelho plant (+5 MW) and to meet the Ribeira Grande plant nominal capacity (+3 MW). The addition of 8 MW means that some of the geothermal capacity might not be fully loaded at off-peak hours. In this paper, the operational implications of integrating more 8 MW of geothermal to the power generation system of São Miguel are discussed, and the possibility of turning the geothermal plants to flexible and dispatchable units, that can timely ramp up and down, are analyzed.