The Government has axed the Severn Estuary Tidal Scheme following a two-year feasibility study – because the high costs didn’t make business sense. So is tidal power too uneconomic to be a real alternative energy source?
Costs had escalated to £34billion and could not be justified in the current economic climate. The proposed ten-mile barrier would have cost the same as seven nuclear power stations – although its working life of 120 years would be 3-4 times longer.
As with most renewable energies its peaks don’t tend to coincide with demand. There are two tidal cycles; a semi-diurnal cycle roughly every 24 hours – with 2 high tides giving max power; and a spring-neap cycle roughly every month where the low power days equals about a quarter the power of the high days. It would generate for about 8 hours per day.
The Aberthaw to Minehead barrage would generate 15GW peak power from the Severn’s 14-metre tidal range. But with the low-tides and only eight hours generation per day this is equivalent to 2.5GW, about 5% of the nation’s electricity (or two nuclear power stations).
Conservation groups had also been fighting the hydro-electric barrage as it would have destroyed the feeding grounds of 85,000 birds. Instead the Government backed nuclear power stations, wind turbines and CCS technology for fossil fuel stations.
But the Government has not completely rejected the scheme as the decision is not purely an economic one. The Government has to reach climate and energy goals of 15% renewable sources by 2020. And tidal power still remains part of Scotland’s energy policy on a smaller scale with a proposed £13m floating wave farm off Orkney generating 3MW.