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Tag Archives: tidal

Renewables in Russia – not much interest

By Dave Elliott

Russia’s renewable energy potential is vast. A 2003 IEA report said that, overall, renewables with economic potential corresponded to about 30% of the country’s then total primary energy supply, while the technically viable potential was estimated to be more than 5 times greater than its energy needs. Only about 20% of the hydro resource has been tapped so far, and the target for new renewables is very  low. (more…)

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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: http://www.gov.uk/government/news/ensuring-value-for-money-and-maintaining-investment-in-renewable-energy
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. www.decc.gov.uk/en/content/cms/meeting_energy/renewable_ener/re_roadmap/re_roadmap.aspx
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. www.gov.uk/government/consultations/transition-from-the-renewables-obligation-to-contracts-for-difference

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. https://www.gov.uk/government/news/over-200-million-boost-for-renewables 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. https://www.gov.uk/government/news/britains-energy-security-strategy-now-fully-in-place

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! Carboncommentary.com 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. www.carboncommentary.com/2014/04/

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’. www.heraldscotland.com/politics/wider-political-news/minister-sought-to-dissuade-msp-from-role-in-eu-inquiry-inquiry.23914772
Clearly the independence referendum is going to be a lively affair!

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Green electricity in the USA

By Dave Elliott

The share of renewables is growing in the United States, up from its current 13%, although the US does not have a nationwide renewable electricity target. However 30 individual states and the District of Columbia do, adding up to a cumulative target of about 18% by 2025. (more…)

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Green energy in China

By Dave Elliott

China is pushing ahead with renewables on a very large scale, with renewables and other non-fossil fuel options expected to provide around 15 % of its total energy needs by 2020: the nuclear programme is a small part of that, aiming to get to 4% of electricity by 2020. Renewables already supply 17%.

Wind power is the big new thing. There is 62 GW of capacity installed so far- way ahead of every other country. And that’s just the start. The Chinese Wind Power Development Roadmap 2050 stipulates that China will have 200 GW installed wind capacity by 2020, 400 GW by 2030, and 1,000 GW by 2050.

However, it is trying to refocus what has so far been something of a uncontrolled boom, with, for example, insufficient attention having been paid to proving the necessary grid links. The result has been that, although China had over 42 GW of wind capacity installed by the start of 2011, only an estimated 31 GW was grid-linked. Many of these projects, most of which were in remote areas in the North West, poorly served by grid links, were often unable to dispatch their full potential output to users, most of whom are in the major urban areas on the coast. This issue is now being addressed- the 12th Five-Year Plan period (2011 – 15), includes significant investment in grid infrastructure.

(more…)

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The Severn Barrage: a lost cause?

By Dave Elliott

One time Welsh Secretary of State Peter Hain recently resigned from the Shadow Cabinet to devote more time to promoting the idea of a Tidal barrage on the Severn estuary. He said that it could potentially be ‘the biggest single source of renewable energy in Europe and one of the biggest in the world.’

It would certainly be a large project. The version proposed by the Severn Tidal Power Group in the early/mid 2000’s would have 8.6 giga watts (GW) of turbine generating capacity mounted in a barrage stretching 11 miles or so across the Severn from Lavernock Point in Wales to Bream Down in Somerset and costing over £30 billion. It could generate around 4.6 % of the UK’s electricity. However, it is not clear how much of this could actually be used. The barrage would trap a head of water at high tide and generate power from it on the ebb for a few hours twice each day. But, the tide cycles shift each day and also vary in height over the lunar cycle, so that at times the barrage would deliver full power when there was no demand for it, but at others, when demand was high, it would produce no power at all. Who needs 8.6 GW in the middle of a summer’s night? It is conceivable that at some point in the future we will have a hydrogen economy, so that large slabs of energy like this could be stored, but for the moment the big barrage just looks too big and inflexible.

(more…)

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Tidal assessment

I have reported in previous blogs on some of dozens of tidal current devices of various types and scale under development in the UK and elsewhere. Some of the projects are now well established, having been fully tested at sea, and some have been deployed at full scale- notably Marine Current Turbines 1.2MW SeaGen. However, most are still at relatively early stages of development, with the claims about potential energy outputs and generation capacities being still being unproven, and some are just speculative design concepts and proposals.

When looking at novel proposals care clearly has to be taken to assess the credibility of the claims being made. For example, generation capacities are sometimes claimed which could only be achieved, given the size of the device, at very high water speeds: the energy output is proportional to the square of the turbine radius (which defines the swept area), and the cube of the water speed. At the Tidal Today.com Tidal Summit last year Peter Fraenkel from MCT showed a chart comparing some existing devices on the basis of swept area. Not surprisingly, MCT devices, being well developed at full scale, came out on top, but some of the other rankings were interesting.

While SeaGen obviously won overall, amongst what might be considered to be the other, albeit less developed, front runners, the double rotor Atlantis AK1000 came out best, followed by Tidal Generations device, while Open Hydro didn’t do well. The now abandoned Stingray oscillating hydrofoil did quite well, as did its, in effect, follow up, the double hydrofoil, Pulse Tidal see-saw design . Hammerfest Strom’s turbine did even better. But then the chart didn’t cover any of the ducted turbine designs, or Voith’s new turbine, rated at 1MW, or the new multi-turbine Hydra Morild II) which is rated at 1.5 MW, which has just been installed for testing off Norway. That will have the largest rated capacity so far.

Projected capacity or claimed energy outputs are of course only part of the issue. What really matters is whether the devices are viable in engineering and economic terms. On the former all we have to go on is their success to date- and perhaps inevitably in some cases there have been problems. For example, the Atlantis AK1000 suffered blade failure and is having to be re-installed at EMEC on the Orkneys, and Open Hydro’s test device, installed in the Bay of Fundy, lost all its blades.

You’d expect problems during development- that’s how technology improves- but some device concepts may be more fundamentally limited. For example, in the new NATTA DVD on Tidal Energy, Peter Fraenkel argues that propeller type devices will always be best, as the wind and indeed hydro industry have clearly shown, and he was fairly dismissive of other approaches. Pulse tidal has claimed that its hydroplane will be better in shallow water, since its swept area is larger than a propeller of similar scale. But then it will only extract energy efficiently in the middle of its up/down traverses, much less at the end of each cycle, so the output may be lower. There could also be problems with multi-turbine designs due to wake interaction between the rotors and rotor efficiency losses with ducted designs.

Clearly there is still some way to go before all the engineering issues have been resolved (by testing at sea) so that we can have a more solid basis for cost comparisons. But MCT is doing very well, and the tidal field is certainly an exciting one – bursting with innovative ideas. Let’s hope for some more successes.

In addition to operational and economic issues, if tidal current devices are to be used on a wide scale then a key issue will be their environmental impacts. Most studies of tidal current turbines so far have suggested that impacts will be low. Even large arrays will not impede flows significantly and the rotor blades will turn slowly, slower than wind turbines, and much slower than the turbines in tidal barrages and lagoons or hydro plants, and so should not present a hazard to marine life- fish will be unaffected. Certainly experience with MCT’s SeaGen has not indicated any problems. For example, no seal deaths have been attributed to the turbines since their installation in 2008. A sonar system has been used to detect the approach of any marine mammals, and shut the turbines down. However all structures put in the sea will have some impact, and this needs to be, and already is, carefully assessed when considering possible locations.

There can also be interactions between tidal projects if they are located near each other. The Energy Technologies Institute (ETI) developing a model of the UK’s tidal energy resources to improve understanding of these interactions. The Tidal Modelling Project will investigate the interaction between tidal energy extraction systems located at different positions around the UK, and how energy extraction at one site might affect the energy available and nature of the tidal energy resources at other sites.

Of course if we have tidal projects sensibly sited at various points around the coast then there can also be positive interactions in terms of overall power availability, since high tide and , maximum tidal flow, will occur at a different times at each site.

The Tidal Energy DVD can be obtained from NATTA: www.natta-renew.org(http://www.natta-renew.org). A short taster is at www.youtube.com/watch?v=nsntWXR63Sc

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Marine Renewables – end of year report

Offshore renewables have been doing well- notably offshore wind (see my Blogs earlier this year) now nearing 1.5G off the UK coast, but also tidal current turbine systems. MCT’s 1.2MW SeaGen has been earning ROC’s in Strangford Narrows, Northern Ireland. And dozens of other tidal current devices have been under test, some at full scale (1MW and above), including Neptunes ducted vertical-axis Proteus rotor system (in the Humber), and Open Hydro’s Open Centre turbine (in the Bay of Fundy) . Meanwhile, Pulse Tidal is looking to install a 1.2MW version of its novel twin hydrofoil device off Skye in Scotland, and Hammerfest Strom UK has developed a 1MW version of its turbine which is to be deployed in Scotland. The largest unit developed so far is Hydra Tidal’s 1.5MW multi-rotor tidal device, being tested off the Norwegian coast.

Wave energy had a somewhat less good year. Although the 600kW in-shore Oyster wave flap device has proved very successful, the leading wave device, the Pelamis segmented wave-snake, three units of which had been installed of Portugal in a 2.25MW tidal farm, had technical and financial problems. In addition, the giant 2.5MW Oceanlinx project Oscillating Water Column prototype fell foul of heavy weather just off the coast of Australia at Port Kembla, and was wrecked – much like the UKs 2MW Osprey, with which it shared some features- back in the 1980’s.

Waves are clearly harder to tame than tidal flows, with even novel designs sometimes not doing so well- Tridents 80 tonne 20kW linear motor prototype sank off East Anglia back in Sept 2009. And even what you would think was a robust design, Finavera’s prototype buoy system, sank off the Oregon coast just before its 6 week test period ended.

However, lessons are being learnt, with wave developers pressing on- the Mk 2 750kW Pelamis P 2 is being deployed at EMEC in Scotland with backing from E.ON, along with Oyster 2, an enlarged 2.5MW version of Oyster wave flap, and the Wave Hub undersea power socket off North Cornwall is now open for business. Wavegen is also moving ahead with its 4MW in-shore Siadar project off the Western Isles. And, as with tidal current turbines, new ideas are emerging all the time, like the clever Wave trader device that is attached to the bottom of the tower of an offshore wind turbine, and shares its grid link to shore. And elsewhere in the world, there’s Portugal’s WEGA ‘gravitational wave energy absorber’, and in the USA, Atmoceans WEST Wave Energy/Sequestration Technology, using buoys, and Florida Tech’s ‘wing wave’ system, using a sea-bed mounted flap.

We need all we can get of both wave and tidal of course, so there is no direct competition. Earlier this year The Crown Estate allocated Scottish sites for over 1.2 GW of wave and tidal current projects on an equal basis, and the UK governments new £22m Marine Renewable Proving Fund supports each type equally, as does Scotlands new £12m funding. Nevertheless, PIRC’s Offshore Valuation claims that, contrary to earlier assessments, the practical tidal current resource (now put at 33GW) is actually larger than the wave resource (18GW), so maybe the former will dominate in the UK. www.offshorevaluation.org/

Elsewhere it may be different: wave projects are moving ahead around the world- OPT are doing well, and there is talk of a 10GW wave programme in China. But South Korea seems to be focusing on tidal, as does Canada – e.g. in the Bay of Fundy. Basically it comes down to the physical resource, and, the tidal regime in both these places, as in the UK, is large. Canada and the USA are both supporting tidal projects on the NE east coast.

In Korea, although several tidal current projects are underway, the emphasis is on tidal range projects, and tidal barrages and lagoons did figure in some UK plans, notably for the Severn estuary e.g the 8.6GW Severn Tidal Barrage, despite it being opposed by all UK environmental groups. Smaller less invasive barrages concepts have also re-emerged for the Mersey and Solway Firth, although they have also attracted opposition. Moreover, the PIRC study put the UK tidal range resource at only 14GW- not insignificant, but smaller than wave and certainly less than for tidal currents. Tidal range was also seen as the most costly option.

Looking at all the options long term, the Department of Energy and Climate Change produced a 2050 Pathway report which had wave and tidal stream capacity running neck and neck in their maximum ‘Level 4’ programme- delivering 70 TWh and 69TWh p.a by 2050 respectively, with 58GW in all installed. However, DECC made clear this it felt this was very optimistic- the most that could be realistically conceived. Their lower level 3 programme only had 29 GW of wave and tidal stream (68 TWh) and level 2, only 11.5GW (25TWh). For comparison, tidal range was put at 1.7GW (3.4TWh) at level 2, 13 GW (6TWh) at Level 3 and 20 GW (40 TWh) and Level 4, by 2050- all much lower than wave or tidal stream . Perhaps then it wasn’t surprising that when the government finally published its long await review of tidal projects for the Severn estuary, tidal range was seen as unattractive, and not to be followed up at this point. http://environmentalresearchweb.org/blog/2010/11/barrage-sinks.html
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With that out the way, we might expect more progress on tidal current projects, although we can also expect problems and technical glitches. For example, Open Hydro’s 1 MW test project in Nova Scotia, installed in 2008, has had to be extracted a year ahead of schedule, after blade failure. And just before it was due to be tested at EMEC, faults were found in the blades of the 1MW Atlantis double rotor tidal turbine system. But they evidently were replaced and space has now been allocated for a 400MW project in the inner sound area of Pentland firth, bringing the total planned wave and tidal deployment there to 1.6 MW by 2020.

There are many other new ideas emerging. One of the most intriguing is the tidal kite- being developed by Swedish company Minesto. It’s an aerofoil wing, with a rotor and generator mounted on it, which is tethered to the sea-bed but free to move under the tidal flow. However it doesn’t just stay in one place, but moves rapidly in a figure of 8 glide pattern under the influence of the tether, a rudder and the lift forces created by the tidal flow. That means the rotor turns faster than if it was simply in the tidal flow- in fact, it’s claimed, up to10 times faster. Given that, unlike other tidal devices, it doesn’t need expensive foundations or towers, it ought be to be cheaper, and less invasive, and there should be many locations where it could extract power from relatively low tidal flow- thus, in effect, expanding the potential tidal resource. A prototype is to be tested off Northern Ireland www.minesto.com

Perhaps even more exotic, one of the new concepts supported under the governments Seven Embryonic Technology Scheme, and then backed as a long term possibility in the DECC review of Severn Tidal options, is the Spectral Marine Energy Converter, SMEC, developed by VerdErg. It’s based on the venturi effect – creating a low pressure area via vanes mounted in the tidal flow, which can be used create higher flow rates in a secondary flow, to drive a turbine. This concept could be used in cross-estuary tidal fences and may offer a way to extract energy from tidal flows without having major environmental impacts. So a Severn barrage, of sorts, or a project elsewhere (e.g. on Solway Firth) may still be on the cards, although the idea can also be used at smaller scale, e.g. in shallow river locations www.verderg.com.

The above is based in part on the end of year Annual Supplement to Renew: www.natta-renew.org

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Going offshore (part 2)

The UK offshore wind, wave and tidal power resource could supply about six times current levels of electricity demand, and even if we only exploited part of it, the UK could become a net exporter of power, according to the first comprehensive assessment, The Offshore Valuation produced by an informal collaboration of government and industry organisations co-ordinated by the Public Interest Research Centre (PIRC).

Drawing on published data, it puts the total practical offshore resource at 2131 TWh p/a from 531 Gigawatts (GW) of generating capacity, 406 GW of which would be wind capacity. England had 54% of the total practical resource (286.5 GW), Scotland 39% (206 GW) and Wales 7% (39.5 GW), with wind power dominating in each region.

PIRC point out that their scenarios “are neither predictive nor prescriptive” but calculate that, even if only 29% of the total resource was exploited, by 2050, the UK could have 169 GW of offshore capacity, supplying 610 TWh, equivalent to total electricity consumption by that time, making the UK a net electricity exporter.

Most of the supply capacity (116 GW) would be conventional sea-bed mounted offshore wind but there would also be 33 GW of floating wind turbines, further out to sea, plus 5 GW of wave, 9 GW of tidal stream and 6 GW of tidal-range projects. This would create 145,000 new jobs, provide the Treasury with £28 bn in tax receipts and reduce carbon emissions relative to 1990 levels by 30%.

Under a more ambitious scenario, utilizing 76% of the total practical resource, by 2050 there could be 406 GW of offshore capacity generating 1,610 TWh – about the same as total UK energy demand (not just the electricity demand) expected by then. That would involve an additional 212 GW of floating offshore wind capacity, while wave would rise to 14 GW, tidal stream to 21 GW and tidal range to 10 GW. The jobs total would rise to 324,000, most of these being for the floating wind turbines.

Some of the scenarios are clearly very ambitious. Even using just 13% of the total, to supply 50% of UK power would need a 34 GW mix of back-up/storage/interconnector links to balance variable supplies, and if higher percentages were used then more cross-channel interconnection would also be needed for exporting excess power – 85 GW for the 169 GW scenario and 321 GW for the 406 GW scenario.

So what would it cost? Using DECC figures, PIRC estimates that the 169 GW scenario would cost £443 bn but calculates that in 2050 it would earn £62 bn p.a in net electricity exports. The 406 GW scenario would cost £993 bn and earn £164 bn p.a. Most of the technologies cost £100–125/Mh initially but get cheaper (10% p.a “learning rates” are assumed), though wave and tidal range are more costly, at ~ £175/MWh.

Most of the technology exists or is under development, but floating offshore wind turbines are relatively novel and clearly play a major role in the more ambitious scenarios. As noted in my previous offshore wind blog entry, some floating systems are already under development but there may be limits to what can be obtained from them. The PIRC report states: “The technical limitations of current designs restrict floating wind to water depths of between 60m and 700m. There has also been some concern that it will not be possible to install floating wind beyond 100nm from the coast due to the time taken to get to and from the site.” Also “access for installation and maintenance may be limited”. Of course, the longer undersea grid links to land will cost more. Even so, the resource is huge. The PIRC puts it at 870 TWh/yr, with a further 660 TWh/yr available beyond 100 nm out. That compares to 180–240 TWh/yr for conventional fixed offshore wind, additional to current site allocations.

The resource for wave and tidal range (barrages/lagoons) is seen as much smaller, at 40 TWh/yr and 36 TWh/yr respectively but that for tidal streams is seen as more significant at 116 TWh/yr. This is larger than some previous estimates. The PIRC says: “Until recently the UK’s practical resource had been estimated to lie within the range 4–30 TWh/yr. However, academic research has since highlighted uncertainty in both the underlying methodology and the assumptions used to estimate this resource, which has had the impact of increasing this range to 4–110TWh/yr.” It notes that the “kinetic energy flux” method is widely used (e.g. by Black and Veatch) but Stephen Salter’s “bottom friction” and David MacKay’s “shallow wave” method both give a factor of 10–20 more. To navigate these uncertainties a “bottom-up” calculation was employed by the PIRC to get the technical resource and this was then reduced by 60% to provide an estimate of the practical resource. It was put at 33–200 TWh/yr, corresponding to a power density of 5 MW/k sq m and 30 MW/k sq m respectively. The average of this range – 116 TWh/yr – was used in the report.

The group behind the report, co-ordinated by the PIRC, included the UK, Scottish and Welsh governments, the ETI, the Crown Estate, E.ON, DONG, RWE Innogy, Mainstream Renewables, RES, Scottish and Southern Energy, Statoil, and Vestas. The government’s Climate Change Committee also provided some support.

Tim Helweg-Larsen, director of research at the PIRC, said: “To discover that we own a resource with the potential to return the UK to being a net power exporter, and on a sustainable basis, is genuinely exciting, and a wake-up call to those in a position to foster the further development of this industry.” But, to put the UK on a path that allows it to access its “substantial and valuable” resource, the PIRC said that Round 3 offshore wind grid connections would have to be made “super-grid compliant” to enable potential future electricity sales to Europe. The PIRC wants the government to take a leading role in the current EU super-grid negotiations, to ensure that the UK derives maximum value from its design and implementation. The domestic supply chain would also have to be developed to enable economic deployment at scale, while new financing structures would have to be created to support the scale and pace of the industrial growth required.

Peter Madigan, head of offshore renewables at trade association RenewableUK, said that “we have long been saying that the North Sea will become the Saudi Arabia of wind energy” and the results of this study “amply bear this out”.

As I discussed in my previous blog entry on this topic, environmental impacts must of course be considered. For example, offshore systems have the potential for significant effects on marine wildlife, including dolphins, porpoise, grey seals and wildfowl but a range of environmental studies have been completed or are in hand and so far no major problems seem to have emerged that cannot be limited with by sensible design, location or mitigation measures. So it does seem that the UK could be on to a winner.

Source: PIRC

For more on renewable energy developments and policy, visit www.natta-renew.org.

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Going offshore (part 1)

Offshore wind energy is booming, with for once the UK in the lead, having installed over 1000 Megawatts (MW) of offshore wind farm generation capacity. Denmark is second in the league table, with 640MW in place, followed by the Netherlands at 250MMW and Sweden at 164MW. But several other EU countries are moving ahead. Belgium, Finland and Ireland all have working offshore projects, while Germany has started up its first large offshore project – it wants 10,000 MW by 2020. France has announced 10 zones for offshore projects off its Atlantic and Mediterranean coasts – it wants to have 6,000MW in place by 2020. However the UK seems likely to stay in the lead – it aims to install up to 40,000MW by around 2020, maybe more.

That’s not to say there have not been problems. Costs have risen, in part because of the increased cost of materials like steel, which in turns reflects the increased costs of conventional energy. And there have been teething problems with some of the designs. A minor fault in the design of the transitional piece which connects the tower to the monopile foundations of the newer machines has been detected, which has resulted in movement of a few centimetres in a number of turbines. Fortunately it is not thought that there is any safety risk or threat to service or output and it’s evidently planned to deal with the as part of the usual rolling programmes of operation and maintenance, with any repairs that are necessary being carried out turbine by turbine, so that there should be no impact on the operation of the rest of the wind farm. The fault evidently does not effect earlier offshore designs.

Clearly issues like this will have to be taken into account in the design of new much larger 10MW machines now being developed. However, one of the newer designs, the 10MW SWAY floating turbine being developed in Norway, won’t face quite the same problem – it’s actually designed to tilt by 5–8 degrees in the wind.

Outside the EU, in 2009 China installed a 3MW offshore turbine, the first unit of a 100MW project. And, after nearly 10 years of sometimes heated debate, the Cape project off Nantucket Sound in New England has at last got the go ahead. It will be the USA’s first offshore wind farm – with 130 turbines. But many others are being considered, including floating versions for use in deeper water. For example, researchers at the Worcester Polytechnic Institute (WPI) have a $300,000 grant from the US National Science Foundations for a three-year on floating wind turbine platforms.

The EU is of course well advanced in this field – with for example the Norwegian Sway device mentioned above, Statoil Hydro’s Hywind and the UK’s 10MW Nova project. There is also the novel floating Poseidon wave and wind platform system being developed in Denmark – a 10MW version is now planned.

But a report released by the US Dept of Energy in 2008, says the 28 US states that have coastlines consume about 80% of all the electricity the US produces, so maybe they’ll have an incentive to push ahead too.

As in the EU, the idea of an offshore supergrid to link up offshore wind projects has also been mooted in the US. Researchers from the University of Delaware and Stony Brook University say that linking Atlantic Coast offshore wind parks with high-voltage direct current (HVDC) cables under the ocean would substantially smooth out the fluctuations. As a fix for intermittency, they say “transmission is far more economically effective than utility-scale electric storage”.

http://www.pnas.org/content/early/2010/03/29/0909075107.full.pdf+html

Currently there are proposals for five offshore wind farms from Delaware to Massachusetts. As plans stand, each would have separate underwater transmission cables linked into the nearest state electric grid. But the report suggest a single, federal offshore Atlantic Transmission Grid would be a better bet. Co-author Brian Colle said: “A north-south transmission geometry fits nicely with the storm track that shifts northward or southward along the U.S. East Coast on a weekly or seasonal time scale. Because then at any one time a high or low pressure system is likely to be producing wind (and thus power) somewhere along the coast.”

http://solveclimate.com/

Offshore wind isn’t the only offshore option. The use of wave energy and tidal streams is also moving ahead around the world, with once again the EU, and the UK especially, in the lead. For example 1,200 MW of wave and tidal current turbine project have just be given the go ahead in Scotland. But US company Ocean Power Technologies (OPT) has been making progress winning contracts for its Power Buoy wave device including one from the Australian government.

Tidal current turbine projects are also developing around the world, for example Ireland’s Open Hydro has linked with Nova Scotia Power to deploy a 1MW tidal turbine in the Bay of Fundy. And the UK’s Marie Current Turbine Ltd is to install a 1.2MW Seagen there too. Meanwhile, South Korea is pushing ahead with a range of ambitious tidal projects, over 2,000MW in all, while businessgreen.com has reported that Israeli marine renewables company SDE Energy recently completed construction of a 1MW wave power plant in China. The $700,000 plant consists of a floating buoy attached to a breakwater. It’s been installed near the city of Dong Ping in Guangzhou province. SDE is also reportedly in the final stages of negotiations over other projects to be built near Zhanjiang City and in the province of Hainan. SDE has talked in terms of ultimately having 10GW of wave energy systems along the Chinese coastline.

It looks like offshore renewables could really become a significant new option.
The big advantage of going offshore is that there is less visual impact. The energy potential is also large – wind speed are usually higher and less variable, and for tidal flow systems, there is a lot more energy in moving water than in moving air. But there may be some environmental impacts (e.g. on fish and sea mammals), something that the device developers are very keen to avoid by careful location and a sensitive design.

However, it is argued that relatively slowly rotating free-standing tidal rotors, or wave energy buoys or platforms, should not present many hazards, while it seems that offshore wind turbine foundations can provide a substrate for a range of sea-life to exploit. As with on-land wind turbines, birds can be at risk of collision with moving wind turbine blades, but observations have suggested that sea birds avoid offshore wind turbines.

Even so, environmental and wildlife impact issues need attention, for example in terms of influencing the choice of location and layout. Overall, a precautionary approach has been adopted: developers have to submit detailed Environmental Impact Statements and there is much research on specific impacts.

http://www.cefas.co.uk/publications/files/windfarm-guidance.pdf

But most of the problems seem to be during the installation process (e.g. noise impacts when driving piles for wind-turbine foundations and disruption during cable laying). Once installed, there seem to be fewer problems, other than possibly sea-bed sediment movements, although navigation hazards have led to some debates.

http://www.offshorewindfarms.co.uk/Pages/COWRIE/

  • A new UK report co-ordinated by the Public Interest Research Group puts the total practical UK resource for offshore wind, wave and tidal power as 2131TWh p.a. (six times current UK electricity use: www.offshorevaluation.org). I’ll be looking at that in a subsequent blog.
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