Sparks

Green islands, green energy

 By Livia Formisani

How do you build a geothermal power plant on a volcano, in a natural reserve, in the middle of the Atlantic Ocean? That’s exactly what Exergy, CME, and EDA Renováveis have done in the Azores…

How do you build a geothermal power plant on a volcano, in a natural reserve, in the middle of the Atlantic Ocean? That’s exactly what Exergy, CME, and EDA Renováveis have done in the Azores.
We often tend to forget that we live on a rather thin crust, forming only 1 percent of the Earth’s volume. Underneath, temperatures in the mantle increase of 60-90 °F per mile (20-30 °C per kilometer): this heat is responsible for geysers, hot springs and lava, among other phenomena. We talk in this case of geothermal energy.
Mankind has been using this energy for centuries, for bathing, cooking and heating; more recently, also to produce electricity. Indeed, it has been estimated that the geothermal energy which can be recovered and used on the Earth’s surface would be about three times the world’s annual consumption. Unfortunately, though, to generate electricity, geothermal sites need to meet a number of conditions, not always present. Furthermore, construction of these power plants also requires high initial costs and entails risks. Once these obstacles are overcome, geothermal power plants produce cost-effective energy with much lower CO2 emissions compared to fossil fuel power plants, and with an output which is independent from weather conditions, unlike solar and wind energy. A technology which has increased the efficiency of geothermal power plants is the so-called binary cycle, employed in the recently inaugurated 4 MW geothermal power plant of Pico Alto, on Terceira Island in the Azores, located on a 2650-foot (808 meters) high volcano, 1500 kilometers away from the coast of Portugal in the Atlantic Ocean.

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Angra do Heroísmo city, Azores, Portugal (José Luis Avila Silveira, Wikimedia)

Since the Pico Alto power plant joined the network, there have already been several days in which Terceira Island’s energy needs were mainly supplied by renewable sources,” said Duarte Ponte, president of EDA Renováveis, which owns the power plant, along with two wind farms on the island. Binary cycle power plants use the heat from the underground geothermal reservoirs to heat up a fluid (in this case, cyclopenthane) with a lower boiling point than water, thus producing steam at lower temperatures than those needed in traditional geothermal power plants, which use water vapor. The steam is then driven into a turbine connected to a generator.
The great advantage of binary cycle power plants is that they work with lower water temperatures than those necessary in dry steam or flash power plants. In fact, while the latter need temperatures upwards of 347 °F (175 °C) to produce electricity, binary cycle power plants work with water temperatures as little as 185–194 °F (85-90 °C). The Pico Alto power plant, built by Italian Exergy and Portuguese CME for the local energy provider EDA Renováveis, uses Radial Outflow Turbine technology to increase conversion efficiency, which has reached the highest possible level of 4.9 MW, with an average of 4.6 MW produced to supply the 56,000 island inhabitants, according to Exergy. “Pico Alto represents for us a great example of how innovation in greentech can provide sustainable solutions to meet people’s energy needs and contribute to improving the energy economics in remote and isolated sites on the planet“ said Marco Bonvini, COO of Exergy.

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Pico Alto geothermal plant in the Azores Islands (Exergy-orc.com)

Yet, construction wasn’t easy. Winters on Terceira islands can be rough, with frequent rain, thick fog and wind. The local geothermal wells also showed irregular behavior, which required designing a tailored solution. Lastly, building a power plant in such a remote location presented a range of logistical challenges, since there are no direct commercial routes to the island.
For all these reasons, an international team of experts closely followed the developments at Pico Alto. They were coordinated by Carlos Alberto Raposo Bicudo Ponte, member of the EDA Renováveis Board of Directors, who declared: “The Pico Alto geothermal power plant inauguration is the first milestone for the commercial geothermal exploitation start up in Terceira Island, increasing the diversification of the power generation mix and boosting the contribution from renewables. The construction project was a technical and management challenge, with several contractors working at same time and, in some occasions, in harsh climate conditions. This was effectively overcome thanks to the close cooperation from all the high specialized teams, where EXERGY assumed successfully the lead role. We are very pleased with the initial production results.”
Since starting operations in August 2017, and until December 2017, the Pico Alto power plant has produced 10,890 MWh, saving the equivalent of 7,380 tons in CO2 emissions. EDA Renováveis plans to increase the total capacity of the power plant to 10 MW over the next four years, for an estimated production of 46,984 MWh in 2022, accounting for a total of 31,842 tons of CO2 saved.

READ MORE: Geothermal energy gains esteem in Iceland by Sharon Fisher

about the author
Livia Formisani