Power System of the Azores

The Azores archipelago is an autonomous region of Portugal, consisting in a group of 9 volcanic islands spread across more than 600 km in the North Atlantic Ocean, located at around 1400 km west of the Portuguese coast. It has a total population of about 240 thousand inhabitants, with the main economic activities involving dairy farming, agriculture, livestock and tourism. In terms of its electric system, the Azores is composed of nine small and isolated systems, with no interconnections between them or the mainland.

Introduction to the Power Company Utility EDA – Electricidade dos Açores, S.A.

The power utility company EDA was founded in 1981, with the goal of establishing the public service of production, transmission and distribution of electricity in all the islands of the Azorean Archipelago. Nevertheless, the electrification of the Azores began in 1899 with the construction of a hydro power plant aiming to provide public lightning to the municipality of Vila Franca do Campo, in São Miguel Island, the largest of the archipelago. Back in 1988, the Azores were also in the spotlight for having the second wind farm to start operation in Portugal. It was in the island of Santa Maria and consisted of 8 wind turbines of 30 kW each.

EDA is currently responsible for the activities of thermal production, transmission, distribution and commercialization of electricity in all the archipelago. Besides acting as TSO and DSO, EDA is also the global systems manager (dispatch operations). The company is 50,1% owned by the Autonomous Region of the Azores with the remaining shares belonging to two other major shareholders and a residual of 0,2% belonging to small shareholders and emigrants. EDA is the mother company of a business group consisting of 3 other companies: EDA Renováveis (production of electricity based in RES), GlobalEDA (information and telecommunication systems) and SEGMA (electromechanical construction and maintenance).


The vision of “greener” electric systems in the Azores

Nowadays, the Azores have already reached interesting numbers in what concerns RES share in electricity production (above 35% in 2021 and 2022). However, the goal is to go well beyond these numbers and to reach values above 70% in the near future. Guideline documents have been developed in the region to establish the pathways for ambitious goals towards the decarbonization of the islands’ economy, namely, the “Azorean Strategy for Energy 2030” and the “Roadmap to Carbon Neutrality in the Azores 2050”.

In order to contribute for these challenging intents, an ambitious investment plan concerning RES production has been outlined, consisting in the diversification of resources, new power plants, remodelling/expansion of existing plants near the end of its life cycle and, the installation of BESS systems in all the islands to assist in the integration of larger amounts of renewable energy.

Previously mentioned investments include: new PV power plants in almost every islands; the remodelling and expansion of existing wind farms with more installed power and newer and technologically more advanced wind turbines; the expansion of the geothermal production capacity; and, the installation of BESS systems which will be of the outmost importance in order to maintain the systems stable and thus, allow the replacement of thermal production (diesel/HFO) with renewable production, most of which with variable availability and intermittent nature.


9 Disperse Islands, 9 Isolated Power Systems

The Azores archipelago consists of 9 electric systems, all isolated. The two largest islands (São Miguel and Terceira) represent close to 80% of the annual energy demand (year 2022). Then, the islands of Pico and Faial combined represent around 12%, which leaves less than 10% for the remaining 5 smaller islands (São Jorge, Santa Maria, Graciosa Flores and Corvo).

The largest peak demands in the region are also in São Miguel (76 MW) and Terceira (33 MW). All the remaining islands have peak loads inferior to 9 MW (Faial), with the island of Corvo, the smallest of the archipelago, having the lowest peak demand (only 330 kW).

There is one thermal power plant in each of the 9 islands. The 4 largest islands (São Miguel, Terceira, Pico and Faial) have thermal production based in heavy fuel oil, while the remaining 5 smaller islands use diesel. The largest thermal installed capacities are in São Miguel (98 MW) and Terceira (68 MW). All the other islands have thermal installed capacities inferior to 20 MW. Corvo island has the smallest thermal power plant in the region (close to 1 MW).

The most important renewable resource in the region is geothermal, responsible for supplying approximately 21% of the total regional demand in year 2022, despite being explored only in São Miguel and Terceira islands. There are 3 geothermal plants in the Azores, two of which are in São Miguel (10+12 MW) and the smallest (4 MW) is in Terceira.

The most common and abundant renewable resource is wind, which was responsible for 8,3% of the overall regional electricity demand in 2022. There are wind farms in all the islands except for the smallest island, Corvo. Nevertheless, actions for the installation of a wind farm in this island are underway. The two largest wind farms in the region are in São Miguel and Terceira (both with 9 MW of installed power). The remaining islands have smaller and older wind farms, close to the end of useful life and will be, for this reason, replaced and expanded with larger and state-of-the-art wind turbines. The exceptions are the islands of Corvo, as previously mentioned, and Graciosa which has a wind farm of 4,5 MW, part of a hybrid system (BESS, wind and PV) installed on that island by a private entity.

There are also in the region several hydro plants (12 in total). However, due to the absence of large water courses, all of these installations are of river run type and with very small installed capacities (a few hundred kWs). The 2 largest hydro plants are in São Miguel and Flores, both of which with 1,6 MW. The hydro plant in Flores is of great importance for the island given the island’s very small dimension. It is the only hydro plant in the Azores with a reservoir, despite being small, with capacity to supply the hydro turbines for only few straight hours. For example, in 2021, this power plant was responsible for more than 52% of the island’s electricity consumption. Other smaller hydro plants exist in São Miguel (6), Terceira (3) and Faial (1).

Other renewables present in the region include PV, mostly from micro production or self-consumption, given that there are still only 3 utility scale PV plants, one in Santa Maria (600 kW), other in Graciosa (1 MW), and a smaller one in Corvo Island (150kW). Despite currently having little expression, PV is becoming a major investment in terms of self-consumption, in response to the recent increase in electricity prices, and a strong bet at utility scale to cope with the goals of decarbonisation.

Also, it is worth mentioning as endogenous resources, a small biogas plant (1 MW) in São Miguel and a waste-to-energy facility in Terceira Island (2,6 MW).

Find more information about the energy production of the Azores on the EDA page:


Electric Grids

In what concerns electric grids, there are several voltage levels in the Azores. High Voltage (HV) only exists in São Miguel on the transmission network of 60 kV. Medium Voltage (MV) is available in 3 voltage levels: 30 kV is used for distribution overhead lines in São Miguel and for transmission networks in Terceira and Pico; 10 kV is used in the distribution underground feeders in São Miguel and in the entire grid of Santa Maria; and finally, 15 kV is used for transmission grids in Flores and Faial and for distribution grids in all the islands, except Santa Maria and São Miguel. As for Low Voltage distribution grids, they are operated with the voltage level of 0,4 kV in the entire region.

More detailed information about all the islands electric systems in the Azores Archipelago can be found on EDA’s website, in an annual Characterization Report.


BESS Systems and good renewable experiences

Given the small dimension and isolated character of all the 9 Azorean electric systems, the integration of large amounts of RES inverter-based production is a major issue and a major barrier towards the goals of decarbonization. For this reason, EDA has promoted the development of grid studies which resulted in the plans to install BESS systems in all the islands, except for Graciosa which already had a system of the same type due to the innovative project that led to the installation of a hybrid system on that island.

EDA has already finished the installation of a BESS system in Terceira (15 MW / 10,5 MWh) and is about to complete the commissioning of an even larger system in São Miguel (20 MW / 20 MWh). The smaller islands will follow. These battery systems will contribute for a larger integration of renewable energy, given that they will provide static reserve to replace the spinning reserve of rotating thermal generators, and will also contribute to voltage and frequency regulation, thus assisting in maintaining the systems stable. Furthermore, the associated energy management systems (EMS) will assist in the overall management of the regional electric systems by increasing their automation and controllability.

This path chosen by EDA with the BESS systems is not unrelated with the very positive experience which resulted from the installation of a hybrid system in Graciosa Island. The project, implemented by a private investor in close collaboration with EDA, has proved the enormous contribution that a BESS system can have in an electric small and isolated system. Graciosa has gone from a situation with the diesel plant operating 24/7 and a RES share below 10%, into a situation with an annual RES share around 60-65% and periods of several days with the diesel plant completely off and the island loads being supplied only by wind and solar energy. Also, in what refers to the voltage and frequency regulation, the hybrid system has shown to be an upgrade, with a much narrower variation range of the frequency, even when compared to the situation of 100% diesel engine operation. The quality of service in the island, both in terms of voltage waveform quality and continuity of service, has been improved.

Another positive renewable experience in the Azores is the one that refers to Flores Island. This island, because of its small size, the abundance of water and the existence of an important hydro plant of 1,6 MW (given the dimension of the system), has remarkable values of RES share (50-60%). Not only that, but it is possible to operate the system in a 100% renewable mode (hydro and wind) for periods of several consecutive hours, usually 6-8 hours during valley periods (night). This is feasible due to the presence of a small flywheel (500 kW) that helps the hydro plant to cope with load and wind variations, thus contributing to maintain the system stable.