COST OF ELECTRICITY GENERATION FROM TIDAL BARRAGE POWER PLANTS
A tidal barrage power plant will generally be a highly capital-intensive project and the cost of electricity during the period associated with repayment of any loan associated with the project will be higher than for a similarly sized hydro- power plant, because the tidal power plant cannot operate continuously but only during certain periods of the tidal cycle.
While the high initial capital outlay is likely to provide a disincentive for many project developers, the longevity of a tidal barrage power plant means that once the loan has been repaid the plant will enjoy a long life providing low-cost electricity. The tidal power plant at La Rance, France, has been operating for over 40 years and is likely to continue for another 40 years while the electricity produced by the plant is cheaper than French nuclear power.
The most recently constructed tidal power plant is the Sihwa plant in South Korea. This 260 MW project is estimated to have cost $250 m, or just under $1000/kW. However, the power plant was installed into an existing barrage so the costs for this scheme cannot be considered typical.
One of the most intensely studied barrage projects is that on the Severn River in the United Kingdom. The latest study was carried out by the U.K. govern- ment and published in 2010.1 This study examined a number of possible schemes across the river, concluding that the largest, with an installed capacity of 8640 MW, would have a cost between £23.2 bn and £34.3 bn or £2690–3970/ kW. This figure was disputed by a consortium that claimed the barrage could be built for £17–£18 bn, a unit cost of around £2000/kW. The lifetime of the plant was estimated in the U.K. government report to be 120 years. While the initial cost of a barrage will be large, it can be partially mitigated if the structure can also provide a road or rail crossing. In the case of the Severn barrage, where no transport crossing was proposed, the U.K. government suggested that the cost of electricity from the plant would be more expensive than offshore wind or nuclear power.
Another proposed large tidal barrage project is at Incheon, South Korea. This 1320 MW scheme has an estimated cost of $3.4 bn, or $2580/kW. Work on the project is currently scheduled to start in 2014 with completion in 2019.
Tidal lagoons have been claimed to be cheaper to build than barrages but opinions differ. An independent review of a proposed 60 MW tidal lagoon project in the same region as the proposed Severn barrage in the United Kingdom put the cost of this project in 2006 at £234 m, or £3900/kW. This was significantly higher than the cost proposed by the company that had developed the scheme of £82 m or £1370/kW.
The preceding costs are higher than typical costs for hydropower plants of a similar size. Even so they could be economically viable. In most cases, how- ever, such projects will only be built if they can serve additional uses and so attract public sector investment to help support the financing.