Generation innovation for wind turbines

Part two: We continue our focus on cost reduction in wind energy, and ask some major innovators in the sector where we are heading for in the major markets.

Wind turbines just keep getting bigger and bigger: this image shows the size of a blade for Vestas' newly-announced V164-7 MW turbine.
Wind turbines just keep getting bigger and bigger: this image shows the size of a blade for Vestas' newly-announced V164-7 MW turbine.
Gamesa has launched a new 4.5 MW low wind site model (G136-4.5 MW Class III) with a 66.5 metre segmented, modular blade design, unique on the market), which makes it as easy to transport and assemble as a 2.0-MW turbine, and also simplifies maintenance.
Gamesa has launched a new 4.5 MW low wind site model (G136-4.5 MW Class III) with a 66.5 metre segmented, modular blade design, unique on the market), which makes it as easy to transport and assemble as a 2.0-MW turbine, and also simplifies maintenance.
REpower Systems has introduced a wind turbine of the 3MW class with a hub height of 143 metres. With a 114 meter rotor diameter, the new variant of the 3.XM series turbine is aimed at low-wind locations (image shows a 3.4M104 turbine at Project Clauen).
REpower Systems has introduced a wind turbine of the 3MW class with a hub height of 143 metres. With a 114 meter rotor diameter, the new variant of the 3.XM series turbine is aimed at low-wind locations (image shows a 3.4M104 turbine at Project Clauen).
US President Obama visited Siemens' rotor blade plant in Iowa in 2010.
US President Obama visited Siemens' rotor blade plant in Iowa in 2010.

According to the Global Wind Energy Council (GWEC), the global wind market is expected to grow again in 2011, with an expected 40 GW of new wind power capacity to be added.

The organisation predicts that by 2015, global installed wind power capacity will more than double to 450 GW - from 194.4 GW at the end of 2010.

Demand is expected to be especially strong in the European and Chinese markets. It remains to be seen how developments in the U.S. will affect the market as we go forward. The U.S. still suffers from the ‘stop-start’ policy support that has lead to uneven growth over the years, and the current political situation remains turbulent.

What can we expect in terms of technology development from some of the larger organisations - those whose development can be seen as something of a barometer for where the industry is heading?

Larger power ratings – trend to continue

Perhaps top of the list with the companies we spoke to was the strategy to increase the capacity of individual turbines:

“The machines are getting bigger,” begins Dr. Hartmut Brösamle, ceo of wpd AG, a developer and operator of wind farms - managing assets of roughly 500 MW in projects worldwide.

The company has just begun construction of two wind farms in Poland (Slupca and Czy ewo wind farms), using 4.8 MW, Enercon E82/E53 and 6 MW, Gamesa G90 turbines, respectively, at the sites. Both are to be connected to the grid in summer.

With a focus on varying sized projects, wpd is well placed to have a good feel for some of the new turbine technology coming on stream: “The average rated power today is between 2.3 and 3 MW,” Brösamle continues.

“We are very close to the market-price of fossil energy production, and we are able to generate power in significant dimensions. All turbine manufacturers have developed turbines with higher hub heights and longer blades…and we expect that this will continue, though there will be a limit in size for onshore turbines”.

There have been a number of new announcements in recent weeks from the turbine manufacturers themselves that back up this observation. German wind turbine manufacturer REpower Systems for example has introduced a wind turbine of the 3 MW class, with a hub height of 143 metres. With a 114 metre(m) rotor diameter, the new variant of the 3.XM series turbine is aimed at low-wind locations.

GE, also, is introducing taller wind turbine towers for its onshore wind turbine product line, bringing hub heights to 130 m. The taller towers will initially be offered for GE's 2.5 MW series, including the 2.75-103 wind turbine.

wpd's Brösamle also points to modifications in blade-design, which he says can translate to 10%-12% in better output: “In future, innovations can also be expected in materials, which will have an impact on production and manufacturing, as well as for transport and installation (and the operation-phase).”

“In future, innovations can also be expected in materials, which will have an impact on production and manufacturing, as well as for transport and installation (and the operation-phase).”
- Dr Hartmut Brösamle, wpd AG

Gamesa for example has also just launched a new 4.5 MW low wind site model (G136-4.5 MW Class III) with a 66.5 metre segmented, modular blade design, unique on the market), which makes it as easy to transport and assemble as a 2.0-MW turbine, and also simplifies maintenance. It shares the same design standards as the G128-4.5 MW Class IIA, says the company.

Superconductors in the mix

One of the many companies that has leveraged its technology successfully to provide key wind USPs, is American Superconductor (AMSC), which provides a variety of licenses and customised designs for onshore and offshore turbines through its Windtec subsidiary (a dozen wind turbine manufacturers today are using the company's suite of conventional wind turbines, with power ratings up to 6 MW).

AMSC also supplies advanced electrical control systems for the turbines its customers produce, and can count as its clients a number of high profile manufacturers in China and Korea - including Dongfang turbine company.

So where does AMSC see the future technology battleground?

“The development of higher power rated wind turbines, and particularly technologies that enable power density – or wind turbines to produce ‘more power per tower’ - will be necessary to capture the full potential of both on and offshore wind,” begins Jason Fredette.

“One technology that we are excited about these days is permanent magnet generators (PMGs). These systems have very compelling advantages over asynchronous copper generators”. AMSC recently acquired The Switch in Finland, which, according to Fredette, “has one of the industry's best PMG systems”.

He also believes that superconductor wind turbine generators will be a dominating technology, particularly for offshore wind, and could lead to some huge machines, such as AMSC's 10 MW SeaTitan – currently under development - using superconductor direct drive generators.

“Until now, among the greatest challenges to developing larger wind turbines for both onshore and offshore use have been the practical size and weight limitations of the wind turbine generator. The power density of superconductors will maximise the ‘power-per-tower’ capability of multi-megawatt turbines, while overcoming these barriers – as well as reducing overall project costs. A 10 MW SeaTitan wind turbine would be similar in weight and size to a conventional 5 MW system”, Fredette claims.

The superconductor generator achieves this by using high temperature superconductor wire, which conducts more than 100 times the electrical current (amperage) of copper wire of the same dimensions. Fredette says he expects AMSC to select its first SeaTitan wind turbine licensee in “the months ahead”, and will then “work with this customer to establish a full supply chain for this wind turbine, including a manufacturer for the SeaTitan generator”.

Direct Drive vs. Gears

One of the questions destined to elicit a “roll of the eyes” from turbine manufacturers is the relative merits of direct drive vs. gearboxes. Up until recently, it appeared that Direct Drive was winning the propaganda battle, until Vestas announced its new V164 machine, the first in the company's history specifically designed for offshore wind.

“The power density of superconductor direct drive generators will maximise the ‘power-per-tower’ capability of multi-megawatt turbines.”
- Jason Fredette, AMSC

One of the biggest surprises to many was that Vestas had bucked the direct drive hype to go for a geared solution. According to Finn Strøm Madsen, President of Vestas Technology R&D, two parallel R&D development tracks were running during the design process, one focusing on direct drive and one on a geared solution:

“It soon became clear that if we wanted to meet the customers' expectations about lowest possible cost of energy and high business case certainty, we needed a perfect combination of innovation and proven technology and so the choice could only be to go for a medium-speed drive-train solution. Offshore wind customers do not want new and untested solutions. They want reliability and business case certainty – and that is what the V164-7.0 MW gives them.”

Some would argue that geared turbines are inherently less reliable, but according to Vestas that isn't simply to do with a gearbox, and in fact many turbine failures have been down to other things like electrical systems. And then there are the difficulties present in sourcing rare-earth metals needed for direct drive systems.

Vestas has a broad range of products, which are regularly optimised to ensure the best possible output and return from wind power plants, according to the company's ceo Ditlev Engel. The V112-3.0 MW, and a special offshore edition of the same turbine, was released for sale in 2010 for example.

“The V112-3.0 MW, together with the V100-1.8 MW, has a larger rotor diameter than general and has been developed to ensure maximum output and return at low and medium winds, which account for about 75 per cent of the world's wind resources”.

Although the company's new V164 turbine is an evolution of the V112, there are a number of highlights. Notable among these is the 164 metre diameter blades, and a swept rotor area of over 21,000 m2. Reports also claim that 80% would be made from recycled material.

Away from developing new turbines per se, Vestas is focusing on a number of other key areas that address well-documented problems. “Large numbers of wind farm sites are being blocked on the grounds that turbine blades interfere with radar from air traffic control and air defence systems,” continues Engel. “But with the help of stealth, used mainly in warplanes, Vestas came up with a way to make its turbines and blades almost invisible to radar. Blades incorporate two layers of glass cloth printed with special link that is embedded in the structure as part of the normal manufacturing process. The radar passes through the first layer, but bounces off the second and so is trapped between the two”.

In addition, Vestas is also developing de-icing technology: “The icing of blades is a serious issue for wind turbines, particularly as the best wind sites are those with low temperatures,” Engel says. “Icing of the blades poses problems for safety as well as the efficiency of power generation, causing loss of production, reduction of power, overloading due to delayed stall and increased fatigue of components”.

Recently, Siemens launched its second gearless wind turbine type, and EWEC 2011 award winner Henrik Stiesdal, the company's chief technology officer, believes that direct drive wind turbines will play a major role in wind power moving forward:

“The core feature of the Siemens SWT-2.3-113 turbine – designed for low to moderate wind speeds - is an innovative drive concept with a compact permanent magnet generator. Like the SWT-3.0-101, the 3-MW direct drive wind turbine type launched by Siemens in April 2010, the SWT-2.3-113 features only half of the parts required for a conventional geared wind turbine and a significantly smaller number of moving parts, making it especially light weight. And because gearless technology is low-maintenance, it maximises our customers' returns”.

Alongside the SWT-2.3-113, Siemens has introduced the Quantum Blade, a new generation of rotor blades: “The new blade is lighter than previous models but retains the superior strength of earlier generations”, continues Stiesdal. “The new B55 Quantum Blade used for the new wind turbine is 55 metres long and features a redesigned tip and root section. The root section uses Siemens ‘flatback’ profiles to minimise root leakage and provide greater lift.

“The blade tip has also been redesigned to minimise loads and reduce noise levels. With a noise level of only 105 decibels (dB) the SWT-2.3-113 is one of the quietest wind turbines on the market”.

Stiesdal adds that the company plans to release a 6 MW direct drive prototype “later this year”, which will be “one of the largest permanent magnet machines ever built”. He also anticipates that “advances in aerodynamics and blade manufacturing will continue.”

Cost reduction

Of course, a key aim of all the technologies discussed above – is to reduce the cost of wind energy and increase its competitiveness with fossil fuels and other low carbon forms of energy such as nuclear. So how close are we to this goal?

“Currently we are not far away from market prices,” believes wpd's Dr. Hartmut Brösamle: “If we had real market prices, and a functioning system of CO2-certificates, wind energy would already be one of the cheapest energy sources,” he says. “Today we already see big competition between the manufacturers. New market actors are entering the market with new products”.

AMSC's Fredette agrees: “Overall, project costs for both on-and offshore wind farms are already declining and that trend will continue. Key to achieving those cost reductions particularly for offshore, however, will require Megawatt ratings for wind turbines to continue to rise. It will also require the use of technologies capable of increasing the power density or ‘power-per-tower’ output capability. Advanced wind turbine blade technologies designed to increase the efficiency and performance of multi-Megawatt wind turbines, such as developed by UK-based Blade Dynamics Ltd., will also reduce costs” (AMSC acquired a 25% ownership position in Blade Dynamics Ltd. in August 2010).

One of the biggest surprises to many is that Vestas has bucked the direct drive hype to go for a geared solution [on its new V164 turbine].

“We see significant potential for future cost reduction, both in relation to wind turbine technology, and in relation to infrastructure and installation costs,” concludes Siemens' Henrik Stiesdal. ”On the turbine technology side we expect to bring down the cost of energy significantly in the upcoming decade. We will achieve this through innovation i.e. with our new direct drive turbines, through industrialisation i.e. by implementing lean production methods, and through the internationalisation of our supply chain network. We are also working closely with customers to bring the infrastructure and installation costs down. We estimate that the largest cost reductions will be achieved in this area”.

US wind lacks long term policy

Based on: US Wind Lacks Long-Term Policy in Renewable Energy Focus U.S., January/February 2011, by Kari Williamson

Moving away from Europe and Asia, the U.S. lack of long-term policies for wind power appears to be the biggest obstacle to the nation's wind market, if we are to believe some of the top wind turbine manufacturers active in the U.S.

The American wind power market saw 5115 MW installed in 2010 – barely half of 2009 – but has started 2011 with over 5.6 GW under construction. Total US wind capacity now stands at over 40 GW, according to the American Wind Energy Association (AWEA).

But with China now having overtaken the U.S., and with important policy decisions currently being fought over, where does that leave wind's development in the country?

GE, the largest player on the U.S. wind market with around 50% market share, has kept its dominant position throughout the financial crisis. GE believes, however, that support mechanisms must be put firmly in place. Melissa Rocker at the GE U.S. Wind Communications team says: “There remains a need for strong US Federal policy that supports the deployment of renewable energy technologies, like China and Europe have, for the US to maintain its leadership…”

REpower USA's managing director, Steve Dayney believes there will be growth in U.S. wind until 2012, but that: “Beyond 2012, the future is uncertain, and will remain so until the future of Federal tax and energy policies is clarified.”

Juan Gutierrez, head of strategy and business development for Siemens' Wind Power Americas business, adds:

“2013 will be a challenging year if there are no Government incentives put in place, such as an extension of the production tax credit (PTC). Without a PTC in the U.S., we can expect a market half the size of the current one.”

For offshore wind, Vestas Offshore predicts little development until around 2015. Vestas Offshore general sales manager, North America, Scott Keating, says: “Other than possibly Cape Wind (which has some political and other hurdles to get over yet) we do not see construction beginning on any utility-scale offshore wind farms in the next two years. We are optimistic, however, that a small handful of utility-scale projects will move forward significantly, and that we might see more encouraging news on the environmental permitting, siting and financing front that will support a strong growth in the development pipeline of projects.”

Political support

A recurring worry is a lack of certainty around policy at a Federal level, and a patchwork of support and regulations at state level, risking a boom-bust market with no long-term stability. As Dayney puts it: “At the Federal level, the short-term duration of tax credits available for renewable energy generation does not create the sufficient long-term certainty many manufacturers require when assessing whether to make large capital investments in a given market…differing state-level requirements create inefficiencies and challenges for multi-state utilities.”

Nordex USA's president and ceo Ralf Sigrist, however, believes utilities must also take some responsibility in creating favourable market conditions: “What is lacking is a long-term strategy of utilities to support wind projects by offering long-term power purchase agreements for, or even themselves investing into, wind projects, in order to take advantage of the opportunity to hedge future electricity prices against the volatility of fossil fuels.”

To support the utilities, Sigrist believes the Federal Government has to come into play with, for example, a Federal Renewable Electricity Standard (RES), a Feed-In tariff, or even a public utility commissions requirement of “firm prices under power purchase agreements for up to 20 years, not only for renewable energy, but also for conventional energy generation.”

Gutierrez at Siemens also believes there are more ways to support the market: “This can be achieved through incentives, such as the cash grant and the PTC, or through penalties, such as costs of emissions, or alternative compliance payments (when there are certain requirements for renewable energy production per state).

Some of the current states' Renewable Portfolio Standards are unclear on the definition of penalties and their compliance mechanisms.”

Again, offshore is in a slightly different position. Keating at Vestas Offshore, says: “While the recent extension of the ITC (investment tax credit) was favourable for the industry in the short-term, generally, it has had very little effect on the offshore side.

“We are extremely encouraged by the recent revamping of Federal agencies, including the creation of BOEMRE [Bureau of Ocean Energy Management, Regulation and Enforcement], which brought increased focus, led by a strong offshore wind proponent in Ken Salazar,” Keating says, but adds that “there remains, however, a great deal of work to be done on the policy side in order to create the platform for the launch of a sustainable offshore wind industry.”

Gutierrez sums up the policy situation: “‘Two faces of policy exist: One that entices developers and utilities to make attractive investments in renewable energy, and another in political mandates which are demanded, and enforceable, by law. All [the] programs are needed to keep the U.S. market in its fast-paced upswing, but a sense of urgency and long-term commitment by decision makers are the cornerstones to industry strength.”

Driving down cost

Although the three-blade horizontal wind turbine design has dominated the market for years, there is still room for innovations – to make wind turbines more efficient but also, most importantly, to bring down cost and thereby make wind an even more attractive option in the U.S. power market.

Material choice and design are high on the list of what can be done to improve future wind turbines. REpower's Dayney says, “advances in materials for electrical components, blades, and gearboxes will incrementally improve the performance of wind turbines over time.”

Nordex' Sigrist believes solving grid and transmission issues could contribute to reducing the cost of wind power in the US: “Transmission capacity is certainly key in this context, since the Midwest and the Great Plains offer a vast wind potential that is currently untapped to a great degree, because of the lack of sufficient transmission capacity. The wind speeds in these areas allow a generation cost that is the most competitive compared to all alternatives to wind.”

Sigrist also mentions the ‘power-per-tower issue’, something Siemens' Gutierrez agrees with. As transmission line expansions unlock new wind areas, more low to medium wind sites can be developed. “In order to develop profitable wind projects at these sites, it is important to continue the evolution of advanced technologies that maximise the energy production at low wind speed conditions. This would mean turbines with larger rotor diameters and higher hub heights,” Gutierrez says.

It will also be important to further develop aspects such as wind forecasting, energy storage and smart control systems in order to achieve grid stability.

Post-crisis finance

As with most renewable energy projects, the upfront costs of wind power are high, and project finance can be a challenge. But despite the dip in the economy, the wind turbine manufacturers say feedback from potential investors is positive. “We are not really seeing project financing and support as a barrier to onshore wind installations,” REpower's Dayney says. However, “there is a gap between the market price utilities are willing to pay and the price a developer requires, given all the costs that go into a project.”

The issue of Federal policy-making arises again. As Nordex' Sigrist points out: “The extension of the possibility to monetise on the investment tax credit directly through the Treasury, currently until the end of 2011, instead of involving additional tax investors, is certainly a very helpful approach. It allows a wind project to keep the tax benefits itself, without adding the costs of paying a return to tax investors, and building such tax investors into the legal framework of project financing for a wind project.”

In the offshore market, no projects have achieved construction-finance in the U.S. as of yet. Vestas Offshore's Keating says the challenges include the U.S. economic situation, combined with the uncertainties around an emerging market. “The important factors in achieving financing for offshore wind are policy certainty, business-case certainty, and long-term power purchase agreements…cost of energy and ROI are the most important factors for a customer investing in offshore.”

Siemens' Gutierrez adds: “The extension of the U.S. Treasury cash grant diminishes some of the recent concerns regarding the sufficiency of available tax equity. For the U.S. offshore market, in particular, we observe a great deal of interest, especially from institutions that have already been active in European offshore wind projects, and that have acquired experience in dealing with specific topics.”


David Hopwood is Editor of Renewable Energy Focus magazine.

Renewable Energy Focus, Volume 12, Issue 2, March-April 2011, Pages 36-41