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Renew your energy: February 2010 Archives

Tides come in

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The use of tidal energy for generating electricity is moving ahead rapidly around the world, and the potential for expansion is significant, with the emphasis being on tidal current turbines, although some tidal barrages are also being developed or planned – for example, various barrage and lagoon scheme are still under consideration for the Severn estuary. A decision on which to go for should emerge later this year.

The global potential is quite large. Trade network Tidal Today's second annual 'Tidal Summit', held in London last November, heard from a speaker from the Fraunhofer Institute for Wind Energy and Energy System Technology (IWES) who relayed some estimates of tidal energy potentials: China: 50 TWh p.a; Ireland: 10 TWh; UK: 31 TWh; France: 10 TWh; Norway: 3 TWh; US: 115 TWh. The big ones, in terms of capacity, included Canada: >40 GW and South Korea: 1000 GW.

In terms of tidal turbine development and deployment, the UK still leads the pack, with Marine Current Turbines' 1.2 MW Seagen in Strangford Narrows to be followed soon by a 10MW tidal farm off Anglesey – MCT has just got £4.8 m from Siemens, EDF Energy, HighTide and others for the next stage. Meanwhile, the European Marine Energy Centre (EMEC) on Orkney is providing key test facilities for UK devices and systems from overseas. It has the world's only grid linked tidal test facilities – five open sea births, with 11 kv, 5 MW subsea cables. And, as the Crown Estate noted at the Summit, Scotland has 25% of the available European tidal potential – Pentland Firth and Orkney Waters contain six of the top-10 UK tidal sites. Crown Estates seem to have been taking their time assessing these, but are about to announce site licenses for selected projects. So prospects for the future look good.

One of the leaders of the new projects is Open Hydro's novel 'open centre' rim generator turbine, which was tested at EMEC. There are plans for deployment off Alderney and in the bay of Fundy. Next up, Atlantis Resources Corp, the international marine energy company, is to test its AK-1000 tidal turbine at EMEC this summer. Tidal Today reported that the AK-1000 has been designed specifically for harsh marine environments. It features what are claimed to be the world's most efficient blades – 18 meters rotor diameter – and has minimal moving parts. It should be capable of generating 1 MW of power in a 2.6 m/s tidal current. The company says that it will award contracts associated with the deployment supporting over 100 UK jobs. The AK-1000 will be its second grid-linked turbine. Its Nereus turbine in San Remo, Australia, first deployed in 2006, still continues to generate power for the grid.

The US is also active in the field. The summit heard updates on Verdant powers seven turbine projects in New York's East River, and there are several other North American projects, including the Canadian 'Clean Current' ducted rotor, which is now being developed in conjunction with Alstom. At the summit it was reported that 'in September 2006, clean current installed a 3.5 m diameter, 65 kW demonstration unit at race rocks, BC, Canada,' and that 'performance met or exceeded expectations'. On-going testing is now being carried out, with a view to installation in the Bay of Fundy.

There's also a lot happening in South Korea – who seem likely to become the world leader. Developer Voith Hydro noted that tidal range (barrage) projects in planning/execution included Shiwa: 254 MW; Garorim Bay 520 MW; Incheon Bay: 1320 MW, and that the Korean Ministry of Knowledge Economy estimates tidal current potential at 470 MW. Voith are installing 100 MW of its 500–1000 kW propeller type turbine at Jindo, Jeollanamdo Province and there's also a project involving the UK's Lunar Energy ducted-rotor system.

But not everyone was quite so positive. RWE npower told the summit that costs and financing were still issues. There was an 'immature market so commercial costs are not yet apparent' and 'utilities won't loss lead demo projects for uncertain future market – demo projects must promise stand alone economic returns'. There were also 'inadequate support mechanisms'. And there was a 'massive offshore wind potential', whereas tidal 'has a fair way to go'. Consultants Douglas Westwood evidently felt similarly: they told the summit that it cost about '£60 m to take a device through to commercialization' and felt that the 'forecast of 41 MW installed capacity by 2013 may be missed', and that without proper support, tidal might only provide '1% of UK power generation capacity by 2030'.

Fortunately, in February the UK government finally got its support system working and has allocated £22 m from its new Marine Renewable Proving Fund (MRPF), to six projects, two wave systems (Osprey and Pelamis) and four tidal current projects – using new turbines from Atlantis, Voith, MCT and Hammerfest Strom UK.

The MRPF is managed by the Carbon Trust, which notes that all of the devices receiving MRPF funding will be deployed in UK waters, and will stimulate supply chain opportunities associated with construction and deployment of these technologies, with over 75% of the funding released through the MRPF going to the UK supply chain.

The MRPF aims to accelerate the development of marine energy devices to the stage when they can qualify for the Government's existing, but so far unused, £42 m Marine Renewables Deployment Fund (MRDF) support scheme and, ultimately, be deployed on a commercial scale, with support from the Renewables Obligation. MCT's Seagen has in fact managed to jumped straight to that, after several years of grant aided and independent development, and is now getting 2 ROCs/MWh for its 1.2 MW unit in Strangford Narrows. The new MRPF money means that it, and the other developers, can now get moving on new projects.

In addition to those already mentioned, there is quite a range of projects at the starting gate, or at least under development, with some novel UK designs emerging. Scottish projects are well represented, with for example the Scotrnewables' floating device and TidalStream Ltd.'s unique tidal turbine platform design – Triton. But Wales is also in the race, with Swanturbines' Cygnet, developed at Swansea University, and Tidal Energy DeltaStream device, which is to be put through trials at Ramsey Sound, near St Davids.

Humberside is also figuring strongly. For example, following tests on models at the University of Hull, a full-scale prototype of Neptune's ducted vertical-axis turbine 'Proteus' device is being tested in the Humber Estuary at Hull. Pulse Tidal's hydrofoil device is also under test in the Humber. Its 100 kW test rig currently feeds power to a chemicals company on the banks of the river. Tidal Today reported that it is to receive a grant of €8 m from the EU's technology research and development fund (Framework Programme 7) to enable the company to begin work immediately on developing its first fully commercial tidal energy generator – a 1 MW unit, to be commissioned in 2012.

Not all of the many new tidal current devices emerging will succeed or get sufficient funding to prove themselves. But there is a mood of pioneering enthusiasm, with developers like Pulse Tidal's chief executive Bob Smith, being very positive about the future: 'We have developed an economic way to recover predictable, renewable energy from the tides and are entering a young market predicted to be worth at least £6 bn annually in electricity sales'. He added: 'The Pulse system is expected to match the cost of offshore wind after only 100 MW has been installed. In the future tidal energy is set to surpass wind as the most economic and predictable source of offshore power.'

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What happens in China, in terms energy use, is widely seen as a key to whether serious global climate impacts can be avoided or limited. China is relying heavily on coal but is also turning increasingly to non-fossil energy sources. Its nuclear programme often gets the headlines but in 2008 China had as much wind capacity in place as it had nuclear capacity – 8.9 GW. Of course, the relatively low load factor for wind (under 20%) meant that nuclear produced more energy – 68 TWh as against 13 TWh for wind. Moreover, new nuclear plants are planned, including fast neutron reactors to be supplied by Russia. In all, plans announced in recent years call for nuclear stations to supply 4% of China's power needs by 2020, up from about 2% now, although of course its energy use is expanding rapidly, so that is more than a doubling in capacity. But wind has now more than doubled – installed capacity reached 25 GW in 2009, and a 2020 wind target of 150 GW has been mentioned. China's wind programme is also moving offshore: it recently installed its first 3 MW 90-metre diameter "Sinovel" offshore turbine, the first unit of a 100 MW Shanghai Donghai Bridge demonstration project.

Certainly renewable energy, along with clean coal (i.e. with carbon capture) seems to be seen as a key way ahead. Chen Mingde, vice-chair of the National Development and Reform Commission, in comments quoted by the China Daily newspaper last year, claimed that "nuclear power cannot save us because the world's supply of uranium and other radioactive minerals needed to generate nuclear power are very limited". He saw the expansion of China's nuclear power capacity a "transitional replacement" of the country's heavy reliance on coal and oil, with the future for China being in more efficient use of fossil fuels and expanded use of renewable energy sources like wind, solar, and hydro.

China's current target is to get 15% of its energy (not just electricity) from renewables by 2020, although this is likely to be raised to 20%. In addition to wind, it's pushing ahead with solar as well as hydro and biomass. China's hydro capacity is expected to nearly double to 300 GW by 2020. And a recent REEEP study suggested that 30% of China's rural energy demand could be met through bioenergy. China already has 65 GW of installed solar thermal power, and the potential for expansion is significant (e.g. for large scale, concentrating solar power units in desert areas, feeding power by HVDC links to the cities). A 1GW prototype plant is planned.

PV solar is also set to expand rapidly. China is already the largest producer of solar cells globally and, although until recently most of them were exported (around 1 GW in 2007), the emphasis has now changed, so that the current national target of having 3 GW of capacity in place by 2020 could be exceeded by perhaps a factor of three. Looking further ahead, work in also underway on tidal and wave energy projects.

Some major integrated projects are also emerging. For example, Reuters reports that China is currently developing a demonstration zone in Hangjin Banner, with a planned 11,950 MW renewable-energy park, which, when completed, should have 6,950 MW of wind generation, 3,900 MW of photovoltaics, 720 MW of concentrating solar power, 310 MW of biomass plants and 70 MW of hydro/storage.

Some innovative new grid links are also being established, designed to deal with the problem that much of the renewable electricity resource is remote from mostly coastal centres of population. The new extended grid system could also help with balancing the variable output from some renewables. Modern Power Systems reports that Siemens Energy and China Southern Power Grid has started commissioning part of a High Voltage Direct Current (HVDC) transmission line, with a capacity of 5000 MW, covering a distance of more than 1400 km. It's claimed to be the first HVDC link in the world operating at a transmission voltage of 800 kV. Commissioning of the second phase, and startup of the full system, is scheduled soon.

The Yunnan–Guangdong interconnector will transmit power generated by several hydro power plants in central China to the rapidly growing industrial region in the Pearl River delta in Guangdong Province with its megacities Guangzhou and Shenzhen. This system can, it us claimed, reduce the annual CO2 emissions that would otherwise have been produced by fossil-fuelled power plant by over 30 megatonnes. In addition Modern Power Systems reports that there is the 800 kV Xiangjiaba–Shanghai link, on which ABB has been working with the State Grid Corporation of China (SGCC). It will be capable of transmitting 6400 MW of power from the Xiangjiaba hydropower plant, located in the southwest of China, to Shanghai – a distance of over 2000 km. It is claimed that transmission losses on the line will be less than 7%.

China is now the world's largest carbon dioxide emitter and its energy demand is still rising rapidly, despite the global economic recession. However, in the run up to the COP 15 climate negotiations in Copenhagen last December, while not willing to commit to reductions in net emissions, China said it would cut its energy intensity (emissions/GNP) dramatically – by 40–45% by 2020. That's not the same as reducing net emissions of course, but it would be a start. And if that is acted on, renewables would clearly play a major part.

China's role at COP 15 has been much debated – essentially it seemed to want to protect its continued growth, and avoid imposed emission targets targets – much like the US. But, like the US, it also seems keen to be a leader in the move to green energy technology – perhaps becoming the "green workshop of the world" feeding the expanding markets for renewable energy systems around the world. In addition to exporting solar PV cells, it was even planning to build wind turbines for and in the US – although a US senator's objections may have scotched that.

How rapidly China can and will green itself though is less clear. Certainly China has massive renewable resources: for example the wind resource is put at around 2 TW. And a new study by Michael McElroy and colleagues at Harvard and Tsinghua University in Beijing, published in the journal Science, has claimed that, in theory, wind power could meet all of China's electricity demand by 2030.

That is very unlikely happen by then of course, but China is likely to become a major player in the green-energy revolution.

Wind power seems likely to remain the main new renewable energy source for the UK given the large offshore and on land resource and its relatively good economics. However, some lobby groups, like the Renewable Energy Foundation (REF), argue that we have placed too much emphasis on wind and should also look more seriously to other renewable options. Actually, although the British Wind Energy Association (BWEA) sees wind supplying 30% of UK electricity in the decades ahead, it may agree. The BWEA no longer focuses just on wind – it has increasingly been looking to wave and tidal power, particularly tidal current turbines. It has just changed its name, to "RenewableUK" (RUK), to reflect this.

It's not surprising that the BWEA/RUK has been keen to take wave and tidal power under its wing, as well as wind. They can all work together beneficially to help cope with the variability of each source. Wave energy is in effect stored/delayed wind energy and so is less sensitive to wind variations, while tides, though cyclic, are unrelated to wind.

A recent Redpoint scenario, produced for the BWEA, is the starting point for a study of the optimum balance between wind, wave and tidal. In particular it looks at the extent to which wave and tidal power could help reduce the grid balancing costs associated with the use of variable renewables, and also reduce the excess wind "spillage", when there was too much wind to be used on the grid. The study, The Benefits of marine technologies with a diversified renewable mix, suggests that, to get the best from the different time correlations of these sources, the optimum might be around a 70% wind and 30% wave/tidal current mix, or, if tidal range projects were included, along with tidal current systems, a 60/40 wind to wave/tidal ratio. The former ratio could reduce the need for fossil fuel backup plants by 2.15 GW, the later by 2.3 GW, and the overall carbon savings could be increased by up to 6%, with wholesale costs reduced by up to 3.3%, since there would be less spillage of wind.

All of these options are about electricity production, and are mainly on the larger scale, whereas it can be argued that smaller scale electricity generation, and also renewable heat production, are equally important in developing an optimal mix. The BWEA has taken an interest in micro wind, but otherwise it has mainly been another trade lobby, the Renewable Energy Association (REA), which has covered the microgeneration area (e.g. PV solar), along with biomass-based heat and power generation (e.g. micro CHP). One of the REA's main strengths has always been biomass/waste related energy systems, including sewage gas, landfill gas and other sources of biogas, with new community-scaled AD (Anaerobic Digestion) plants being one of the latest growth areas. Along with others, it's pushed hard for a Feed-In Tariff for micro power systems, with some success – the government is introducing a clean Energy Cashback scheme for small project in April.

A year or so ago the BWEA and REA were discussing a merger, but that came to nothing. So now, while BWEA/RUK will focus on wind, wave and tidal, the REA will be left covering the rest – and possibly, increasingly, renewable heat options. That's the focus of the proposed new Renewable Heat Initiative Feed-In Tariff that the government is planning, to start next year. It's also something that the REF has focussed on in their belief that we need a more diversified approach.

The division of areas of technological interest by the trade lobbies is not absolute (e.g. REA still has a strong interest in wave and tidal power). And while some sort of rough division may make sense institutionally, it would be a shame if the potential for a more integrated approach was reduced – there is a lot of overlap. BWEA/RUK and REA have collaborated in the past. Hopefully that will continue. After all, what seems likely to emerge is a new energy system in which a range of electricity and heat producing renewable energy based technologies, large and small, are integrated together to balance heat and power needs via heating networks and smart power grids. For example, along the lines proposed by Neil Crumpton – as I reported in an earlier post.

The issue of integration, and of choosing the right mix of renewables, will no doubt be high on the agenda being addressed by Prof. Bernard Bulkin, ex-BP and ex-AEAT, who is now the "expert chair" of DECC's new Office for Renewable Energy Deployment. DECC is currently looking at what we might expect by 2050. It will be interesting to see what emerges in its "2050 Roadmap", which should be published in conjunction with the Budget in April.

Most people are surprised how quiet modern wind turbines are when they visit a wind farm. Mechanical noise is usually minimal – even right up close. And the aerodynamic blade noise is often less than the noise of wind in any trees or bushes near by. However in some locations some problems have still been reported.

An international panel of experts convened by the American and Canadian Wind Energy Associations, recently released a report based on a review of a large body of scientific literature on sound and health effects with regard to sound produced by wind turbines. After extensive review, analysis and discussion, the panel concluded that sounds or vibrations emitted from wind turbines have no adverse effect on human health – an issue that was recently given new prominence by a US report, which claimed that physiological damage could be caused by low-frequency sound from wind turbines (see my earlier blog).

The new review states:

  • There is no evidence that the audible or sub-audible sounds emitted by wind turbines have any direct adverse physiological effects.
  • The ground-borne vibrations from wind turbines are too weak to be detected by, or to affect, humans.
  • The sounds emitted by wind turbines are not unique. There is no reason to believe, based on the levels and frequencies of the sounds and the panel's experience with sound exposures in occupational settings, that the sounds from wind turbines could plausibly have direct adverse health consequences.

Even so, there are still reports that aerodynamic "swishing" sounds from wind farms are an issue at some sites at night – disturbing some people's sleep. The Telegraph quoted a nurse, Jane Davis, who says that she was forced to move from her home in Lincolnshire after eight wind turbines were built in 2006. "All I know is the amount of health problems people have suffered," which she said included sleep deprivation, tinnitus, depression and psychological stress "seem to be excessive". She added: "These things have devastated my life."

The AWEA/CWEA report does say that, although "work with low frequencies has shown that an audible low frequency sound does not normally become objectionable until it is 10 to 15 dB above hearing threshold", an exception is "when a listener has developed hostility to the noise source, so that annoyance commences at a lower level". They note that "a major cause of concern about wind turbine sound is its fluctuating nature; some may find this sound annoying, a reaction that depends primarily on personal characteristics as opposed to the intensity of the sound level" and report that a "study of more than 2000 people suggested that personality traits play a role in the perception of annoyance to environmental issues, such as sound".

However, they add, a bit abruptly perhaps, that though "some people may be annoyed at the presence of sound from wind turbines; annoyance is not a pathological entity". It's certainly true that once a noise gets annoying, however low the level (e.g. a tap dripping), it can become intolerable.

The report concludes that, though "there is no evidence that sound at the levels from wind turbines as heard in residences will cause direct physiological effects…a small number of sensitive people, however, may be stressed by the sound and suffer sleep disturbances".

That rendition may not please sufferers! Of course, you could say that road traffic and aircraft landing and taking off can lead to much more noise annoyance for a lot more people, as can city living. But should we be adding more stress? Rural areas are, after all, usually quieter, which is one of their attractions. Or, assuming it cannot be resolved by careful wind-turbine location or modified operational patterns, is that just a cost that has to be borne by a small minority, who might in any case find a conventional power plant near them significantly less attractive?

The government's view certainly seems unchanged. NewEnergyFocus reported that in January, energy minister David Kidney dismissed claims that the permitted night-time noise limit for onshore wind turbines is too high. He said that the 43 dB night-time limit in the ETSU-R-97 guidance was derived from the sleep disturbance criteria in Planning Policy Guidance 24, with an addition to allow for an open window. He said that ETSU-R-97 gave indicative noise levels thought to offer "a reasonable degree of protection to wind farm neighbours" and that there was no evidence that they needed to be reviewed. He added that residents' comfort had to be balanced with the needs of wind-farm developers and so the guidelines should not place unreasonable restrictions on wind-farm development or add unduly costs and administrative burdens on wind-farm developers or local authorities. He concluded: "We have no robust new evidence to suggest that the current guidance is not achieving its aim."

AWEA/CanWEA report