Use of Geothermal Resources in the Azores Islands: A Contribution to the Energy Self-Sufficiency of a Remote and Isolated Region

Abstract

Geothermal power has become the most important renewable energy source in the Azores islands, consistently representing about 20% of the islands’ electrical generation in recent years. The energy policy of the region, which is aimed at maximizing the use of this clean and endogenous resource, has been very successful, as demonstrated by the production results which have supported an increase in the energy self-sufficiency of the islands. On the island of São Miguel, SOGEO - Sociedade Geotérmica dos Açores, S.A. operates two binary organic Rankine cycle (ORC) power plants – Ribeira Grande and Pico Vermelho – which have a combined capacity of 23 MW. These plants exploit the geothermal resource of the Ribeira Grande field, a 240ºC liquid-dominated reservoir. In 2010 the plants generated 173 GWh, representing 38.8% of the power production of the island and 20.4% of the power production of the Azores. New projects are being developed to increase the penetration of geothermal as an energy source. The distinctive features of geothermal power generation are confirmed in the Azores: it operates as base-load power, sometimes representing over 56% of the energy produced on São Miguel; the power plants and wellfield show very high availability and reliability (the average annual generation of the Pico Vermelho plant has been 12 to 15% greater than the contracted power capacity); and it is economically competitive in a remote location, with a generation cost, including depreciation and taxes, on the order of €0.06/kWh ($0.08/kWh), which is less than 50% of the direct cost of fossil-fuel-based generation.