Portugal's Renewable Transition with Hydroelectric Power Plant

In the first four months of 2024, Portugal is averaging 91% of its electricity from renewables while having the lowest wholesale electricity price in Europe of €13.32/MWh. 48% of the electricity mix is hydroelectric, 30% is wind, 7% is solar, and 6% of biomass. The electricity mix of the country has changed drastically in recent years, the share of renewable up from 27% in 2005 and 54% in 2017. 

Tâmega hydroelectric complex is one of the largest energy storage facilities in Europe, and also the largest hydroelectric power plant to be developed in Europe in the last 25 years. Constructing such large facilities in Europe faces challenges such as high costs, long lead times, and opposition from residents and environmentalists due to concerns about flooding river valleys and the subsequent impact on riverine habitats for fish, birds, and plants.

The complex consists of three dams and hydroelectric power plants capable of producing 1,766 GWh per year while having a storage capacity of 40 million kWh. Connected with two wind farms, the hybrid plant utilizes a pumping system during windy periods, which uses electricity generated by the wind farms to pump water from a lower reservoir to an upper one, allowing the facility to generate power when the demand is high.

Photo credit: Iberdrola 

Electricity grids have to be balanced at all times, which means that the amount of electricity consumed has to be the same as the amount produced. The challenge with renewable energy sources like solar and wind is their variability; their output can fluctuate significantly due to weather conditions. To address this, the intermittent nature of solar and wind power often requires support from more consistent energy sources like fossil fuels or by employing energy storage technologies such as pumped storage systems. 

Hydroelectric facilities have their own environmental impacts. For rivers that host salmon, building dams may result in habitat loss and fish stranding due to flow alterations. Some methods to allow fish to pass include using fish ladders or bypass, or trapping and hauling hauling fish by truck or barge. However, concentrating fish in small areas also makes them easy targets for predation. Another environmental impact of hydroelectric comes from the generation of greenhouse gas emissions from the reservoirs. When the land is flooded, vegetation decomposes under water and generates methane, a primary resource of natural gas. As the emotion depends on factors such as location, rainfall patterns, and reservoir age and size, Québec’s largest reservoir, Caniapiscau, has a carbon footprint double that of coal power: about 2,200g CO2-equivalent per kilowatt/hour. Bluemethane is testing technology that uses gravity to capture methane in water bodies, aiming to commercialize a system that integrates smoothly within the existing infrastructure.