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Tag Archives: marine energy

Down on wave and tidal farms

By Dave Elliott

In my last post I looked at how solar farms were being constrained in the UK. But they are not alone. Marine renewables are also facing problems. Tragically, pioneering wave energy company Pelamis has gone into administration, after failing to secure development funding. And Siemens is to sell off Marine Current Turbines (MCT), the pioneering UK tidal company it look over in 2012, due to the slow pace of orders. Aquamarine Power, who have developed the Oyster inshore wave device, is also to “significantly downsize” its business. (more…)

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DECC Reviews Renewables

By Dave Elliott

In its 2014 review of renewable energy policy, part of its Electricity Market Reform deployment exercise, the UK Department of Energy and Climate Change outlined how it saw each key option developing:
There have certainly been some changes since its 2011 Renewable Roadmap, which selected eight technologies as likely to be key to meeting the UK’s 2020 renewables targets.
PV solar was not amongst the selected eight. But now it’s a front runner. In its new report DECC says, ‘We consider solar PV now to be an established technology in the UK,’ and with 2.7GW or more in place that’s clearly true. And they add ‘Solar is anticipated to be the first large-scale renewable technology to be able to deploy without financial support at some point in the mid-to-late 2020s’. Didn’t it do well! Despite the cuts in Feed In Tariffs. DECCs main concern now seem to be that PV, especially solar farms, will expand too fast! They note that ‘Solar PV is a technology which can be deployed quickly even at large scale’. But they are worried about the costs and eco-impacts of large ground mounted projects and would prefer Building Integrated schemes, large and small. On costs, they accept that these are falling (which is why take-up has grown) and will continue to fall (in part due to the take-up), but they say ‘because the UK is a small part of the global market, it is likely that these cost reductions will largely occur independently of what the UK does’. And they have sought to limit the cost pass-through to consumers, most notably by entirely cutting Renewables Obligation (RO) support for large projects. Otherwise they say they might reach 5GW by 2020! Nevertheless they still talk of an overall possible 10GW of PV by 2020 and perhaps even 20 GW.

Wind power did feature strongly in the 2011 DECC review, offshore especially. Now, despite being the cheapest of the main new renewables, on land-wind has fallen out of favour in some circles (e.g.due to vociferous campaigning and some local opposition), although, as DECC says, ‘current installed capacity in the UK is 7.3GW, with a further 1.5GW under construction’ and ‘there is also a large potential pipeline of UK projects with 5.4 GW having received planning consent and a further 6.5GW currently in the planning system. This means we are well on our way to reaching our ambition for 11-13GW of onshore wind by 2020’. But by contrast offshore wind is seen the biggie: ‘Offshore wind is the most scalable of the renewable technologies, and it is the renewable technology that has the most potential to make a significant contribution to decarbonisation goals, if required. There is significant long-term potential for cost reduction and it is at an early stage of deployment – DECC’s central estimate is a 25-30% reduction in central costs by 2030, which could be higher depending on the level of deployment between now and then. The UK is the market leader for offshore wind, with the biggest pipeline to 2020, and deployment in the UK is therefore a key driver of cost reduction to 2020’. DECC had earlier said up to 39GW was possible by 2030. But that depended on the market.

Wave and tidal stream also featured in DECC’s 2011 Renewable Energy Roadmap, which suggested that there could be 200-300 MW of marine capacity by 2020. That was much less than the 1-2 GW forecast in the Government’s Marine Energy Action Plan 2010, or even the 1.3GW by 2020 UK figure in the EU Renewable Energy Action Plan. And although the UK is still in the lead in this area, the new DECC Review reduces its expectations further: ‘Wave and tidal stream technologies are still at the demonstration stage and are not currently competing in the mainstream market. There are currently around c.10MW of wave and tidal stream capacity deployed in sea trial around the UK – more than the rest of the world combined. We anticipate that by 2020, wave and tidal stream could reach 100-150MW in the UK alone. This deployment could then increase quickly beyond 2020 to reach GW-levels in the late 2020s-early 2030s’.

Unlike heat pumps (still strongly backed), geothermal wasn’t in DECCs 2011 key options list, but a 2012 SKM study claimed that it could supply 20% of UK electricity from around 9.5GW of capacity. The new DECC review however relies on a 2013 Atkins report on deep geothermal power which suggested a possible best case potential of up to 3-4% of current average UK electricity demand. So it’s still seen as something of an outsider option, although worth backing.

By contrast, DECC is still very enamored of biomass, including EfW combustion, advanced gasification/pyrolysis, biomass CHP and AD from farm and other wastes. There are limits though, mainly related to land use constraints and concerns about the sustainability of importing biomass pellets for large biomass conversion plants. I’ll be looking at that in my next but one post.

The new DECC renewables review is just about electricity supplies, so it doesn’t look at solar or biomass heat (both being pushed quite hard by the Renewable Heat Incentive), or biofuels (on which progress is less spectacular). But arguably it does add up to a package might help the UK meet it 2020 15% renewable energy target. However, with the various cuts and uncertainties about the effects of the new Contracts for a Difference support system, that is not certain: DECC has just imposed a £205m p.a. cap on renewable CfD allocations up to 2020 which may constrain new offshore wind and large PV solar projects seriously. I will be looking at that in my next post. And beyond 2020 there are no renewables targets, with, under current policies, the continued expansion of renewables likely to be constrained by the commitment to nuclear and maybe shale gas CCS. But policies can change and with renewables costs falling, they may break through further and accelerate more, so there is still all to play for.

If so, what about grid balancing? DECC has confirmed that it will be seeking 53GW of contracted capacity for the new ‘capacity market’ for 2018/19, to help deal with supply shortfalls due to demand peaks, variable renewable inputs and plant or grid failures. For the moment much of this will involve existing gas plants that might otherwise be closed, given the increased output from renewables, but will be needed occasionally when that output is low. However any facility that can provide grid balancing services can apply to the capacity auction process in December, including storage and demand management. Contracted capacity will get a cash incentive for being available. DECC says it will add £2p to average annual consumer bills over the period 2014-30.

So what next? Given its excellent renewable resources, clearly in principle the UK could, if it wanted to, at least match the German ambition of getting 80% of electricity from renewables by 2050. Assuming that is Scotland, which has most of the resources, is still part of the UK! noted that about 15 GW of 2020 renewables will be in Scotland or in Scottish waters. Only about 18 GW will be in England and Wales. So it said Independence would mean around 40% of total UK renewables capacity would disappear, but only 10% of UK electricity consumption.

DECC sees it differently, arguing that Scotland’s small population would not be able to sustain the cost of its large renewables capacity without the RO income from the rest of the UK – or a £189 p.a increase on Scottish consumer’s bills. But in reality wouldn’t the UK have to buy in, and continue to support, Scottish green power to meet it renewable targets? DECC also sees the nuclear issue differently, and, with the European Commission currently looking at the UK’s proposals for funding the EdF Hinkley project, Westminster has evidently warned the (anti nuclear) Scottish government that any negative representation it made to Brussels on this would be viewed as a ‘hostile act’.
Clearly the independence referendum is going to be a lively affair!

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Lunar Race

The effects of the gravitational pull of the moon on the seas, coupled to a lesser extent with that of the sun, provide a significant potential source of renewable energy. There is a race underway to tap into it.

Tidal power extraction technology comes in various shapes and forms. Barrages across estuaries, trapping high tides to create a head of water, may be the most familiar, but free-standing tidal current turbines, working on the horizontal flows rather than the vertical tidal range, are a less environmentally invasive and easier to install option. There are now reputed to be 150 or so tidal current turbine projects of various types and scales underway in the UK and elsewhere, with the most developed being MCT’s 1.2MW Seagen, now installed in Strangford Narrows in Northern Ireland.

Other UK projects include the nicely named ‘Lunar energy’ seabed-mounted ducted rotor, the ‘Pulse Tidal’ oscillating hydroplane system being tested in the Humber, and the ‘Tidal Delay’ system, which feeds power to a heat store, so that power can be generated continuously. There is also a proposal for a permeable ‘tidal fence’ across the Severn estuary, housing a series of tidal turbines, as an alternative to a solid ‘tidal range’ barrage, which would in effect dam the estuary.

There are many more tidal current projects and devices at various stages of development- there is very much a flurry of innovation going on, with tidal technology being seen as basically simpler than wave energy technology. That’s hardly surprising since, with wave energy, we are trying to tap into complex chaotic wave motions in an interface between air and water, whereas tidal flows, running smoothly below the surface, are by comparison much more linear.

Although the UK still leads in this field, challenges are emerging from overseas. For example, Singapore-based Atlantis is planning to install some of their ducted rotor units in a 30MW project in Pentland Firth in Scotland. And Irelands Open Hydro is planning to install a series of 1MW versions of its novel Open Centre turbine in France, Canada- and Alderney. In addition, Voith Siemens have developed a novel gearless 1MW propellor turbine design, which is to be used in a 100 MW array in the Wando project in South Korea. Canada and the USA are also pushing ahead with a range of systems- the US Dept of Energy has allocated its first Marine Energy Grants- $7.3m in all, to 14 projects, with more now being planned.

Cleary tidal power has gone international and there is a race to be first in what could be a very large global market. In the end what will probably decide the winners is economics There is talk of some tidal current devices getting down to 2-3p/kWh in time, so the prospects look good, while there are dark mutterings amongst some of the tidal current enthusiasts about the cost of the main rival approach in the UK- the proposed Severn Tidal Barrage, put by some at 9p/kWh.

The race is on

Although it’s often seen as the front-runner in the UK, the large Cardiff to Weston Barrage isn’t the only tidal range option. There have been proposals for even larger barrages further down the Severn estuary. Alternatively, smaller barrages on the Severn and elsewhere (e.g. the Mersey Solway Firth, Humber etc) might be less invasive, and offshore tidal lagoons even less so.

There are also various different operational options. In terms of increasing the continuity of power output, there is the option of having segmented lagoons, so that some degree of storage might be possible, and it is also possible to pump water uphill behind barrages or lagoons, using excess off-peak power from the grid. Barrage operation on the incoming tidal flow is also an option, although that means using two-way turbines, which are more complex, expensive and prone to excessive wear and breakdown.

Although pumped storage is sometimes included as an option, most new barrage designs use conventional one-way turbines. The problem then is that they will only fire off twice roughly every twenty-four hours, with large pulses of energy for a couple of hours, which may not be matched to electricity demand. So, for example, although the 8.6GW Severn Barrage might be able to generate 4.6% of UK’s electricity, only some of that could actually be used effectively in practice- unless we also spent money on major electricity storage facilities. According to the generally pro-barrage Sustainable Development Commission, by some time after 2020, when it was working, the barrage would only reduce UK emissions by about 0.92% – not very much for £20 billion, the expected construction cost.

By contrast, a network of smaller tidal turbines around the coast could deliver more continuous output, since peak tide occurs progressively later in time at each site. Tidal turbines can also be designed to swivel around to run on the flow and the ebb i.e. four times per 24 hour period. And they can be installed on a modular basis relatively quickly.

All in all, with most UK environmental groups strongly opposed to large estuary-wide barrages like that proposed for the Severn, the tidal current option looks like to one the watch. But who will win in that race is far from clear. The UK may be ahead technologically, but for example, S. Korea has plans for installing a total of around 500MW of tidal current projects.


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