Tidal power is getting closer to commercial viability, as shown by a comprehensive lifecycle assessment of a megawatt-scale array in the United Kingdom.
The MeyGen tidal energy project, located in the Inner Sound of Scotland’s Pentland Firth, is slated to be the world’s largest tidal energy plant. Phase 1A of the project is a 6MW demonstration tidal stream energy array comprised of four 1.5MW tidal turbines.
Three turbines were manufactured by Andritz Hydro Hammerfest, and one more by SIMEC Atlantis Energy. All the turbines are upstream, three-bladed, horizontal-axis machines, fully submerged and mounted on gravity-base foundations resting on the seabed. Each turbine is connected to shore by its own cable to a single onshore converter/grid connection station. The onshore station includes power converters for each turbine and the connection to the local electricity distribution network.
Phase 1A of the project is partly funded through a £10 million grant from the Department for Business Energy and Industrial Strategy, with a requirement that lessons learnt from the project were collated and shared.
Over the project’s 24-month operational period, the array has successfully exported 21 gigawatt hours to the grid to date, with an average turbine availability of 95 percent.
Several key lessons learnt over the project’s operational period were summarised in a document published by Black & Veatch, which has been made free to access will help the process by further de-risking the development of future tidal energy projects.
“The assessment offers valuable lessons for everyone involved in developing tidal-stream energy as a viable source of power,” said Tim Baker, Black & Veatch marine energy director. “At each point in the asset’s lifecycle the report identifies where efficiencies, cost savings, economies of scale and improvements can be achieved. Crucially, the assessment also shares safer ways of working in the potentially high-risk marine environment.”
Aside from planning and siting issues, the report stated that the majority of early stage issues that required interventions were as a result of faults in standard components, rather than novel components specific to the tidal industry. This is a major step towards commercial viability and lower maintenance costs. The report also stated that capital expenditure costs were around £51.3 million, with operating expenses at £1.4 million per year.
For further development of the MeyGen project, there is a further 80MW of consented capacity in Phase 1, and an overall total of 392MW of further development capacity (beyond Phase 1A) in the MeyGen project. Phase 2 will increase the installed capacity to a total of 252MW, the extent of the currently secured grid connection capacity. Phase 3 will then require an additional expanded grid connection to build the project out to the full site capacity of 398MW. The project will eventually consist of 250 turbines, generating enough energy to power 175,000 homes.
Tidal energy can theoretically supply more than 150 terawatt hours globally. Several tidal power projects like Rance in France and Sihwa Lake in South Korea already produce 240MW and 254MW respectively. The predictable nature of tidal energy can help balance load and demand alongside other forms of renewables such as wind and solar power.
