Ribeira Grande and Pico Vermelho geothermal plants
Overview
São Miguel, the largest island in the Azores archipelago, is not only renowned for its stunning landscapes but also for its innovative approach to renewable energy. At the heart of this sustainable energy revolution lies the Ribeira Grande geothermal field, a testament to São Miguel's commitment to harnessing the power of nature. Comprising the Ribeira Grande and Pico Vermelho plants, this geothermal complex has been a stalwart source of clean energy for over four decades, currently supplying 23 MW of power to the island.
The journey towards unlocking São Miguel's geothermal potential began in the 1970s, although significant progress was only realized in the 2000s, spurred by groundbreaking exploratory drilling efforts led by EDA RENOVÁVEIS. This initiative revealed an estimated output capacity of 3.5 MW, laying the foundation for São Miguel's burgeoning geothermal industry. With São Miguel's population representing over half of the archipelago's total inhabitants, the island faces considerable energy demands. However, São Miguel's energy landscape has undergone a remarkable transformation over the past three decades, with renewable energy generation surging from 5% to an impressive 37% of the total power supply in the Azores. Geothermal energy stands as a linchpin in this transition away from fossil fuels, currently meeting a substantial 42% of São Miguel's electricity needs.
CO2 savings
Geothermal is the only renewable energy source that currently has the potential to replace fossil fuels as a baseload power source in São Miguel. The Pico Vermelho plant has a steady capacity factor above 95% and availability that is consistently over 99%, making geothermal at this site a reliable baseload power source.
Given today's turbulent energy market with the invasion of Ukraine by Russia, avoiding reliance on imported fossil fuels is a priority for Portugal and each of the Azores islands. Most fossil fuels burned in the Archipelago are extracted in Nigeria and Algeria, transported to mainland Portugal, and finally shipped to each island. While Portugal only imports 5% of its energy from Russia, oil prices everywhere have raised significantly, and in order to maintain resilience in times of crisis in the energy market, it is in Portugal's best interest to shift to more renewable energy production.
Since 2007, geothermal production in São Miguel Island has replaced about 390,000 tonnes of fuel, with an estimated total worth of EUR 178 million.
Area
In São Miguel, the island's geothermal activity provides natural hot springs which the local communities around them have used for centuries for their healing properties and relaxation. Additionally, one of the island's most traditional dishes, "Cozido das Furnas'' is a stew made using a unique cooking method of being heated in the ground, and is an important symbol of São Miguel's cultural heritage. In addition to these traditional uses of geothermal activity, in more recent years geotourism and geothermal energy production have provided São Miguel with sustainable energy and local economic development.
Technical details
The geothermal project is in the Ribeira Grande geothermal field, on the north flank of Fogo Volcano, one of the three active (dormant) central volcanoes of the Island. This is a brown field, with 4 decades of exploitation experience and with a total of 23 deep drillings (1-2 km depth). The geothermal system is characterised by a 240 °C liquid-dominated reservoir, which can be tapped by relatively shallow wells (1–1.5 km depth). The resource has a fluid enthalpy of 900–1100 kJ/kg and most wells discharge up to 25-40 l/s at wellhead pressures ranging from 6 to 16 bar-g.
1994 marked the beginning of the commercial exploitation of geothermal resources in the Azores, when Phase A of the Ribeira Grande ORC (organic Rankine cycle) binary power plant came online (Figures 3 and 4). The plant was designed by ORMAT and in 1998 it was later expanded to 13 MW (Ponte, 2002). More recently, the pilot plant was dismantled and was replaced by the 10 MW Pico Vermelho ORC binary plant (Kaplan et al., 2007), also designed by ORMAT, installed at the same location (Figures 3 and 4). The Pico Vermelho plant has been online since December 2016.
History
In the Azores, the initial geothermal exploration dates from the 1970s and was carried out roughly in parallel on São Miguel and Terceira Islands. However, following the more promising results in São Miguel Island, development was initially focused there, following a stepwise strategy. The Terceira Island project was resumed in 2000, but the first power plant was only installed in 2017. The main milestones of the development and the power generation history are described below. The first milestone of geothermal power generation was in 1980, with the operation of a small 3 MW pilot plant in the Pico Vermelho area (Meidav, 1981), consisting of one back-pressure steam turbine designed by Mitsubishi. The pilot plant only generated an average net power of 0.8 MW (1980–2005), but the lessons learnt from its operation supported the next stages of project development.
The power demand on São Miguel Island showed progressive growth from 1990 to 2010. In the early 1990s, the power generation was based on the consumption of fossil fuels in thermal diesel power plants, producing 90% of the electricity needs. However, over the past 30 years, the growth in the demand was accompanied by an increase in renewables production, from 10% to 51%, and this has been directly linked to the expansions of the geothermal installed capacity (Figure 4). On São Miguel Island, the current share of renewables reaches up to 51%, with geothermal assuming the predominant role, providing 42% of the island’s electricity needs. The remainder is provided in roughly equal parts by hydro and wind.
Summary
Depth of drilling: 1-2 km depth
Geothermal power: 23 MW
CO2 emissions avoided: Since 2007, geothermal production in São Miguel Island has replaced about 390,000 tonnes of fuel, with an estimated total worth of EUR 178 million.