Patent issues

conducted in the 1980s, is estimated to run to £15 billion. The UK government's Sustainable Development Commission (SDC) estimates that this facility could save 5.6 Mt carbon dioxide per year, in comparison to new-built gas-fired power plants. The carbon footprint of building the barrage would be paid back in 5–8 months, according to the SDC. The concept is based on proven technology, as a similar barrage at the river Rance, in Northern France, has operated successfully since 1966. Even though this would clearly be a significant measure to avoid carbon emissions, environmentalists are up in arms against the idea of a Cardiff– Weston barrage. It would ensure that large areas that are currently tidal marshland would be permanently under water, and the government admits that " some of the biodiversity would be lost. " For this reason, the Royal Society for the Protection of Birds (RSPB) has criticised the decision to include the large barrage in the shortlist. The Severn estuary, which divides England from southern Wales, has the second largest tidal range in the world, so it seems a natural target to try to harvest tidal energy there, in one of the biggest potential projects to exploit renewable energy Alternative barrage projects could be located further up the river delta, with proportionally smaller impact on the environment and building cost, but also smaller energy generation and carbon dioxide savings. Two such barrage projects are under consideration, generating 1 GW and 0.625 GW, respectively. Leaving much of the estuary open to the tides, a small barrage could be combined with a 'tidal lagoon' — a walled-off area of water that is connected only to one side of the river delta and thus doesn't block it off. Two such lagoons are on the shortlist, each estimated to generate 1.36 GW. These would still sacrifice some marshland, but would leave the majority of it intact. Because of the semicircular geometry of the wall that needs to be built around a given volume of water to harvest its flow, these lagoons may turn out to be more expensive to build than barrages of comparable energy output. Other options left off the government shortlist but favoured by some environmentalists include offshore tidal lagoons and tidal flow turbines. The environmental organisation Friends of the Earth (FoE) has presented a study comparing tidal lagoons with barrage projects. While offshore lagoons would require more building material per …