To demonstrate the viability of the technology, Rainey wants to build a much smaller version, spanning just 50 meters (160 feet) of the estuary and generating 2 megawatts.
Despite the prices of solar and wind-generated electricity falling, often making them cheaper than fossil fuels, the problem of intermittency remains. Even as it becomes cheaper and easier to store electricity, experts fret about how viable it is to power a country through a cloudy or windless week without resorting to polluting sources.
After the 70s oil shocks, the tides were investigated as a source of energy but largely abandoned as more expensive than other options. Only recently has attention returned. Like most renewable sources, tidal energy does not operate 24/7. However, the lulls as the tide turns are fairly short and can be predicted years in advance, making them easy to cover with batteries or other sources.
There are far fewer suitable sites for tidal power than wind or solar, but the Severn Estuary is one of the best. Lying between south Wales and Somerset, its shape serves as a funnel, giving it one of the highest tidal ranges (15 meters or 50 feet) in the world. Unlike most other extreme tide locations, it is close to major electricity consumers.
Ideas for harnessing these giant tides for electricity go back to the 1920s, but have been appearing with renewed frequency in response to the need for clean and reliable power sources. Questions remain, however, about both the economic viability and the environmental effects.
[H/T: The Economist]