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Swansea tidal power: not so cheap or green

Image: Nizam Sagar

Tidal power is one of the great untapped sources of renewable energy.  This is why a proposal to construct a tidal lagoon in Swansea Bay has attracted so much positive publicity.  If successful, the project would merely be the first part of a much larger system of tidal power at seven sites around the UK.

After a review by Charles Hendry urged the UK government to back the project, the go-ahead was anticipated this summer.  However, according to Jim Pickard at the Financial Times:

“Ministers are planning to reject a £1.3bn project to build a tidal power lagoon in Swansea Bay as early as next week…

“The company hoped that it would be the first of a series of new lagoons around the country, with the potential to export the technology overseas.  But ministers have balked at the level of subsidy that TLP has demanded from British taxpayers, which is much higher than alternative low-carbon schemes.”

Concerns about the project have been rumbling for several years, with satirical magazine Private Eye running occasional stories concerning conflicts of interest over the cost of the materials needed to build the project.  However, matters seem to have come to a head at a Parliamentary Committee hearing last month as the full cost of the scheme became apparent.  As Jillian Ambrose at the Telegraph reports:

“Mark Sharrock, the boss of Tidal Lagoon Power, told a committee of MPs that he would need a deal offering financial support of £89.50 for every mega-watt of electricity produced to build the groundbreaking 320MW project.

“But under questioning he admitted that this could only be achieved with extra financial help from the Welsh Government, and a contract almost double the length than what is typically offered to developers of new nuclear or renewable energy projects.

“On a like-for-like basis the Swansea Tidal project would need a contract price of £150/MWh. The sum is well above the eye-watering price of the Hinkley Point C nuclear power project which will cost bill payers £92.50 for every megawatt produced over 35 years.

“It is also almost triple the price of the newest offshore wind power projects which will be built for £57.50/MWh.”

Coming on the back of the UK government decision to cancel the electrification of the railway between Cardiff and Swansea, the decision to oppose the Swansea Bay tidal power project will no doubt be seen as a further slight to the people of Wales.  It will also be used by greens as further evidence of the government’s lack of concern for the environment or for meeting its own carbon reduction targets.  However, on this occasion, the government’s decision is probably correct.  As Pickard notes:

“One senior government figure, asked what the chances were of the project getting the go-ahead, said there was not a ‘cat’s chance in hell’.  Another Whitehall figure said that a negative decision was taken a fortnight ago but ministers had been discussing ways to mitigate the political impact by offering support for other new low-carbon energy projects in Wales.”

In and of itself, the Swansea Bay project is simply too small and too expensive to make any kind of sense.  That is, in commercial terms it fails simply because the UK public will not be able to afford to pay for it if – as was proposed – the cost was added to business and household energy bills.  With a maximum output of 320MW – roughly the same as the Gwynt-yr-Mor offshore wind farm off the coast of North Wales – the Swansea project produces a tenth of the power of the Hinkley Point C nuclear plant for twice the price.  And even if you object to nuclear power, a much larger wind farm in the Severn Estuary or the Bristol Channel could generate twice the power for half the price.

Even the one supposed benefit of tidal power – predictability – may be of little benefit.  Swansea Bay had been intended to provide proof of concept for a network of much larger tidal power plants around the coast of the UK at:

  • Llandudno
  • Heysham
  • Workington
  • Immingham
  • Newhaven
  • Hinkley

Each of these tidal power plants would be in the 1GW to 1.5GW range.  The theory behind this was that since the timing of the high tide varies around the coast of the UK, the intermittent output from any one tidal plant would be ironed out by the others; thus providing steady baseload electricity.  The trouble is, as Roger Andrews at Energy Matters points out:

“There are no two sites where the difference is three hours or even within an hour of three hours. The differences cluster around zero and six hours, meaning that combining output from any two sites or group of sites will tend to accentuate rather than smooth out the intermittent power delivery…

“With a more judicious selection of lagoon sites it would of course be possible to combine output from the sites into something that does resemble baseload generation. But it can’t be done with the sites Tidal Lagoon Power plc has selected. The fact that Tidal Lagoon Power plc haven’t acknowledged this can only charitably be called an oversight.”

Worse still, because of the change in tide height between spring and neap tides, whatever combination of tidal power locations is used, large scale storage is still required:

“As discussed above we can’t smooth out these spring-neap fluctuations by combining output from different sites. We can do it only by storing the power for re-use. So how much storage do we need? To smooth out Swansea Bay generation to the point where it provides constant baseload power we would need about 7.5GWh for the tide range squared case and about 11.7GWh for the tide range cubed case (note that we need only consider the larger peak in the second half of the month). In short, we would need another Dinorwig -sized (9.1GWh) pumped hydro facility. And constructing another Dinorwig for a project that generates only 495 GWh/year is clearly not viable.”

Things do not get any better when the storage requirements of all of the proposed tidal power plants are considered.  According to Andrews:

“It comes out to approximately 500GWh, over fifteen times current UK pumped hydro capacity, or if you like five million 100kWh utility-sized Tesla storage batteries. And even with this much storage tide power supplies only about 8% of total UK electricity demand.”

Whichever was you split it, unless the cost of tidal power can be dramatically reduced, other low carbon electricity schemes will always be more cost/materials/energy-effective.  That is, if the intention is to build massive new storage capacity, then the latest generation of wind turbines erected off the South Wales coast and facing directly into the Gulf Stream will always come out on top.  And if you don’t want to build all of the extra storage but you still want to cease using fossil fuels, then, I’m afraid that nuclear is your only option…

This brings us to the final problem with the Swansea Bay tidal power project; its pretention to being a green technology.  In order to build even the demonstration project in Swansea requires us quite literally to move mountains.  Two mountains to be precise; the one that will provide us with the rocks required to construct that 9.5km long 20m high wall to enclose the tidal lagoon, and the one that will have to be hollowed out to provide the pumped storage to balance the load.  None of that heavy lifting is going to be done using electric vehicles.  Rather, heavy, diesel-powered machinery is going to be used to dig out the rock.  That rock will then be loaded onto very heavy diesel-guzzling trucks that will move it to the nearest port, where it will be loaded onto bunker fuel-powered ships.  Then there are the staggering volumes of concrete and steel (that are manufactured using coal) that are required for the construction itself.  So yes, it is “green” in comparison to, say, building a replacement for the 1.5GW coal plant just up the coast at Aberthaw.  But compared to a modest offshore wind farm with the same power output, the tidal lagoon is an environmental disaster.

If there is an argument to be had with the UK government here, it is not that they have ditched a project that had little hope of success, but they have yet to commit to investing the £1.3bn (minimum) price tag in the deployment of more cost/resource/energy-effective low-carbon electricity technologies in Wales… and, no, the nuclear plant at Wylfa doesn’t count.

As you made it to the end…

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