Tidal ‘old lady’ still powers third of Guernsey island

Operating for over 50 years, the Rance tidal power plant – located in the estuary of the Rance River in France – has in 2017 supplied close to third of total energy consumed by the island of Guernsey’s residents.

The Rance Tidal Power Station (Photo: EDF)

Built in 1966 as the world’s first tidal power station, the Rance Tidal Power Station operates by using the barrage to build up a reservoir to create a difference in the height levels of  water, in order to release it twice a day through 24 turbines.

The incoming and outgoing flows spin the turbines of the power plant, operated by EDF (Électricité de France), to generate a maximum of 240MW.

The Rance plant operates by exploiting flows in both directions (Photo: EDF)

Through an agreement with EDF, the sole commercial electricity supplier on Guernsey island – Guernsey Electricity – has been using the clean electricity produced by the Rance tidal plant delivered to the island through a 60MW subsea cable.

According to the utility, the electricity delivered via the cable has in 2017 met 86% of the island’s electricity demand – with 53% coming from nuclear sources, and 33% from the tidal barrage on river Rance.

The remaining electricity was generated on island, Guernsey Electricity said, revealing also that it is currently looking into adding a second cable to link the island directly to France.

For 45 years, the Rance tidal plant was the largest power station of its kind in the world by installed capacity, before South Korean Sihwa Lake Tidal Power Station surpassed it in 2011 by adding 14MW more to reach impressive 254MW.

La Rance infographic/in French (Image: EDF)

Taking six years to complete construction, the Rance tidal barrage spans 750 meters long, with the power plant portion of the dam of taking up a little over 330 meters. Its tidal basin measures almost 23 square kilometers.

The annual electricity generation of the power station amounts to 540GWh – the equivalent to the consumption of the city with the population of over 200,000 people.

The Rance tidal power plant has last year placed France at the top of tidal energy generating countries, with 500GWh of electricity produced from its tidal resources in 2016, according to the International Energy Agency’s (IEA) 2017 renewable energy statistics.