Wednesday, February 18, 2009
Don’t get fooled again
We need tidal power- but not this way
There are two basic approaches to harvesting tidal energy. Barrages across a tidal estuary can be used to trap high tides, with the head of water then being let out through hydro turbines. This is how the 240MW barrage on the Rance estuary in France works and it is the basis of the proposed 8.6GW Severn Tidal Barrage. By contrast, with tidal current turbines, the energy in the horizontal tidal flows is harvested - in effect they are underwater wind mills. Proponents of the latter argue that, as small free-standing structures with relatively slowly rotating blades, they should have much less environmental impact than tidal range barrages, which block off entire estuaries, and they can be installed on a piecemeal, modular basis. The same is true for wave energy systems.
Unsurprisingly the Severn Barrage is strongly opposed by most environmental group, who see it as a major ecological threat. Moreover a study produced for WWF/ RSPB et al , claimed that its electricity would cost around two times more than that from most other renewable projects.
There are also some key technical issue. A large single barrage on the Severn would only deliver power for a couple of hours twice in every (roughly) twenty four hour tidal cycle, and given that the lunar cycle shifts continually, this power output would not often be matched well to peak power demands. As a result, at least in the absence of major energy storage facilities, although it could generate 4.6 % of the UK’s electricity on average over a year, not all of it could be used. A study by the generally pro-barrage Sustainable Development Commission, concluded that, by the time it was built, the Severn Barrage would only displace about 0.92 % of UK emission from gas fired plants- not much for the estimated £15billion capital cost.
By contrast it has been argued that a distributed network of several smaller tidal barrages or lagoons and /or large numbers of tidal current projects, located at different points around the coast, would be much more efficient and flexible, since the arrival time of the tides is delayed by several hours at each point.
However there is much industry support for the large 8.6GW Severn Barrage, since it uses known (hydro) technology. Moreover, it also has strong political support. It would clearly be a very visible commitment for a government keen to be seen to be supporting renewables.
The government has launched a new study of tidal energy options for the Severn Estuary, looking at large tidal barrages across the estuary and large tidal lagoons- bounded reservoirs. One of the issues is how such schemes might be funded, with some form of public support being a possibility.
However, apart from a 1.3 GW ‘tidal fence’ concept, with tidal current turbines mounted in a non-invasive permeable causeway, tidal current turbine projects are not included in the study- and even tidal fence has been dropped from an interim shortlist. Tidal current projects are evidently seen as being best developed by private finance within the context of the Renewables Obligation, with some initial extra support via Marine Renewables Deployment Fund. But as noted in an earlier Blog, that’s not happening yet- none of the dozens of projects being developed in the UK have proved to be eligible for the funding. Meanwhile the Severn Tidal Review won’t even report finally, after further rounds of consultation, until 2010. It’s all so painfully slow…
Thursday, February 5, 2009
The UK has a large marine energy resource - wave energy and free-standing tidal current turbine projects might supply 20% of UK electricity, and possibly much more.
In 2001 the House of Commons Select Committee on Science and Technology, commented bitterly that ‘given the UK's abundant natural wave and tidal resource, it is extremely regrettable and surprising that the development of wave and tidal energy technologies has received so little support from the Government’.
Since then some funding has been made available- for example some small grants from research councils and the Carbon Trust and the governments £42m Marine Renewables Deployment Fund. However, although there are many dozens of wave and tidal current turbine projects underway around the country, none so far has been eligible for support from the MRDF- which requires them to have three months operation at commercial scale in the sea.
So what’s gone wrong? Basically it’s the familiar story- a government fixation on ‘leaving it up to the market’. As the Parliamentary Office of Science and Technology put it ‘Government policy is to avoid
‘picking winners’, instead letting the market converge on the best approaches’. So the research teams are meant to push ahead, with a few small grants, and then private sector investors and companies should deciding which projects are worthy for follow up - using the MRDF to reduce their risks, backed up by the Renewables Obligation, which will offer revenue support for commercial projects.
But we’re stalled at the start. In a review in 2007, the governments Renewable Advisory Board commented that ‘the MRDF is fundamentally a sound scheme. It, in itself, is not a failure, but the R&D process has failed to supply the technologies that the MRDF was established to support’.
It’s not for lack of enthusiasm. Indeed it is getting hard to find a UK University that does not have a wave or tidal hardware or assessment project underway. There are also many new start-up companies, some of them spun out of University groups.
The pioneers were Wavegen, with their 500kW Limpet device built into a rocky outcrop of the shore of the Isle of Islay in Scotland. And subsequently there have been some other successes- notably the SeaGen tidal current turbine, a 1.2MW version of which has been installed in Strangford Narrows in Northern Ireland, and the Pelamis ‘wave snake’ device, with a 2.3 MW project being installed in Portugal. Some ambitious projects have also been proposed. For example there are plans for an 8MW tidal farm off the west coast of the UK, using Lunar energy’s sea-bed mounted ‘ducted rotor’ system. But most of the rest are still at the prototype and testing stage.
Interestingly though, the Scottish Executive is proving to be more effective with its Marine support programme, having allocated £13m in direct granted aid to nine wave and tidal current projects. This reflects its enthusiasm for renewables generally- Scotland already gets 20% of its electricity form renewables and has the very ambitious target of getting 50% by 2020.
The UK is still in the lead technologically in both areas, but new marine technologies are emerging in other EU countries and in the US, Australia, New Zealand, and elsewhere, with S Korea having a major commitment in this area. As a result, there are concerns that the UK’s lead in wave and tidal power may be lost- already several overseas developers have proposed projects in the UK using their own technology. It would be tragic if the UK, with its long history of marine and offshore engineering excellence, and its very large marine energy potential, does not the take the challenge seriously.