Five and a half options for tidal power
Kitesurfers, twitchers, anglers, employees of the Port of Bristol, citizens of the West and Wales. Listen up because this affects all of you. There's a public consultation going on right now to discuss the options for tidal power generation in the Severn Estuary. science.TV was at an event on the 7th of March at the University of the West of England in which a shortlist of options was presented and discussed.
The shortlist:
- 1. Cardiff Weston Barrage: A barrage crossing the Severn estuary from Brean Down, near Weston super Mare to Lavernock Point, near Cardiff. Its estimated capacity is over 8.6 gigawatts (GW). (B3 in diagram below)
- 2. Shoots Barrage: Further upstream of the Cardiff Weston scheme. Capacity of 1.05 GW, similar to a large fossil fuel plant. (B4)
- 3. Beachley Barrage: The smallest barrage on the proposed shortlist, just above the Wye River. It could generate 625 MW. (B5)
- 4. Bridgwater Bay Lagoon: Lagoons are radical new proposals which impound a section of the estuary without damming it. This plan is sited on the English shore between east of Hinkley Point and Weston super Mare. It could generate 1.36 GW. (L3d)
- 5. Fleming Lagoon: An impoundment on the Welsh shore of the estuary between Newport and the Severn road crossings. It too could generate 1.36 GW. (L2)
- 5 and a half: Embryonic schemes including tidal reefs and tidal fences.
Diagram showing the original longlist of proposals:
Each of these options presents a complex set of benefits and problems. The environmental impact is particularly hard to predict but one thing for certain is that it's not possible to take energy out of a high-energy system like the Severn without transforming it forever. The appeal of tidal power is, of course, its predictability. The downsides are the environmental impacts and the cost.
The most expensive scheme (once you've factored in optimism bias) has a capital cost of £35bn. Once built, the electricity created by the schemes is relatively expensive too, ranging from 10.4 to 22.7 pence per kWh. I just looked at my last electricity bill for comparison and I am paying 10.6 pence. This means that even when the schemes are complete, they will have to be subsidised by taxation and no doubt some more quantitative easing. (I think that one thing we'll certainly need in the future is a new euphemism for "unprofitable".)
However, this consultation is not about whether or not we should pursue a tidal scheme - that consultation is likely to happen in 2010 and it's more complex than my flippant summary suggests - it's about which of the mooted schemes gives the best overall return when all factors are considered.
Artist's impression of proposed new tidal technology, the tidal fence:
The average projected service life for the tidal schemes is 120 years, so if you care about any of the above, please furnish yourself with the facts and get involved. I am assured that this is not an exercise in "policy-based evidence making" and that it's not too late to influence the outcome.
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