Navigant Research Blog

High Focus on Low Wind Turbines

— October 5, 2015

Wind turbines with taller towers and larger rotors designed for efficient power generation in areas of low-speed wind have taken over the industry over the past few years with no sign of slowing. At this year’s HUSUM Wind 2015 wind conference and exhibition in Germany, four new low wind speed models were unveiled to the market by four top wind turbine original equipment manufacturers (OEMs). These turbines are targeted toward the Northern European wind market where low wind speeds and space constraints favor these designs, but they are growing more popular. The system specs show the industry is continuing to innovate and push the boundaries for onshore wind turbines.

Denmark’s Vestas unveiled the largest rotor variant of its 3 MW platform—its new V136-3.45 designed for low wind International Electrotechnical Commission (IEC) class IIIA sites. Following now-typical naming conventions in the industry, the 136 denotes rotor diameter in meters, and the 3.45 represents the turbine’s rated megawatt capacity. The 66.7 m blades are Vestas’ largest yet for onshore turbines, and are the latest in a series of blades released in recent years that follow the company’s switch to structural shell designs after decades of using a central spar design. As with long blades from other vendors, preimpregnated carbon fiber plays a key role in achieving strength and length with manageable weight. The blades also have a slim design that is augmented with aerofoils, vortex generators, and serrated trailing edges (which appears to be a newly revoked patent previously owned by Siemens).

Also notable is the use of the Vestas’ large diameter steel tower (LDST), a tower design that is detailed in Navigant Research’s Supply Chain Assessment 2014 – Wind Energy report. Put simply, the tower design vertically splits the largest bottom tower section into three shell sections that are bolted together at the wind plant site. This allows for a wide enough base (6.5 m) to support hub heights of 132 m and 149 m.

Germany’s Senvion also unveiled a new IEC IIIA low wind turbine, the 3.4M140, which features a 140 m rotor using 68 m carbon-infused blades and hub heights of 110 m and 130 m. This is an uprated design from the company’s current 3.2 MW, 122 m rotor offering. Notably, the doubly fed induction generation drivetrain moves to full power conversion on the new model from partial conversion on the existing 3.2 MW units. Senvion achieves its tall hub heights using a hybrid approach that combines lower sections of prestressed concrete with standard tubular upper sections. Navigant Research has detailed recent hybrid tower designs, which are the most common approach used to reach high hub heights.

Uprating the drivetrain is German company Nordex’s approach to its new low wind turbine, the N131-3.3MW. This turbine retains the existing 131 m rotor and carbon-infused 65.5 m blades used on the company’s current N131-3.0 offering, but uprates the power output with changes in gearbox torque, generator, and power converter (retaining DFIG with partial conversion). The N131-3.3MW is also designed for remarkably tall hub heights of 134 m and 164 m by use of hybrid concrete and steel towers.

European OEMs weren’t the only players showcasing new low wind offerings at HUSUM. U.S.-based General Electric (GE)—which has grown minor market share in Germany—unveiled a 3.2 MW turbine with a 130 m rotor turbine designed for IEC IIIA wind speeds. GE’s largest offering presently in the low wind category is its 2.75-120 model, so this is a notable uptick that brings the company closer in line with its European competitors. Hub heights for the 3.2 MW turbine will range from 85 m to 155 m, with the higher-end options employing GE’s unique space frame design, which features a bolted lattice tower covered in fabric.


Wind Industry Poised to Benefit from Intellectual Property Court Ruling

— August 5, 2015

Intellectual property (IP) is a double-edged sword in every industry. The marketplace rewards companies with the best innovations. In aggregate, these technology advances accelerate competitiveness and improve the offerings to the marketplace. However, companies pay princely sums and engage small armies of attorneys and experts to vigorously pursue and defend IP advantages over their peers. These battles churn out winners and losers on a regular basis and can often stifle the broader progress of an industry.

The wind power industry has had its fair share of IP battles. One of the latest fights is over so-called de-rated operation. Late July saw a U.K. court rule in favor of Siemens over ENERCON. ENERCON has been defending its IP over its Storm Control solution, which is its name for de-rated operation.

De-rated operation is the ability of a wind turbine to operate below its maximum capacity during times of high wind speed.  Traditionally, when a wind turbine reaches its threshold for maximum wind speed (around 25 meters per second), it will enter a cut-out shutdown mode to protect the turbine from damaging high winds.

The traditional process takes the electricity production offline, which can destabilize the broader power grid.  As the commercial-scale deployment of wind turbines increases, this becomes a larger concern.   To address this concern, de-rating allows a turbine to remain online, using a range of control methods from pitch control of blades to generator torque control to operate a wind turbine at below its maximum capacity.

For example, instead of a 2 MW wind turbine shutting off once it encounters its threshold cut-off wind speed parameters, it can reduce its output to 50% capacity, or 1 MW.  This ensures that the wind plant remains operational, balancing the electrical grid, and that kilowatt-hours continue to be produced instead of lost due to a full shutdown.  There are also economic inefficiencies associated with stopping and restarting wind turbines that can be avoided by running at reduced load.  This approach can also be used to continue the operation and revenue generation of a wind turbine that is experiencing high operating temperatures within the turbine drivetrain. De-rating can allow power production to continue while temperatures are reduced to acceptable levels without entirely shutting the turbine down.

ENERCON said that Siemens’ High Wind Ride Through (HWRT) infringed on ENERCON’s Storm Control system. Judge Justice Biress of the London High Court ruled the challenge invalid in favor of Siemens. Some of the technical aspects of prior art, or known technology, that bolstered Siemens’ case are well-cited at Windpower Monthly. In short, the judge accepted submitted evidence that previous technology existed–and was even obvious for de-rated operation, ramping generation down as wind speeds went up.

Making an Appeal

ENERCON says it is considering its options for appeal. In the meantime, the U.K. decision may sway how the issue is interpreted by the European Patent Office (EPO), which would have reverberations across the European market. Should the U.K. ruling stand, and the EPO meet a similar conclusion, this ruling will produce a broader benefit to the wind industry, allowing de-rated approaches from Siemens and other vendors.

ENERCON is among the most highly respected wind turbine companies, with solid performance and reputation, and it has always been on the leading edge of innovation and should be lauded for it. But if this case means more efficient and cost-effective wind technology is available for most or all wind turbine vendors, then wind plant owners, electricity consumers, and anyone with a vested interest in more clean generation are winners.


Following Election, U.K. Renewables Policy Plans Come to Light

— June 2, 2015

A couple of weeks after a surprising result in the United Kingdom’s parliamentary election, in which the Conservative Party won a majority, plans for the government’s renewable energy policies are becoming clearer. Although the Conservative Party has governed for the last 5 years, it was part of a coalition, so there is a possibility that significant policy changes will occur.

Amber Rudd Takes the Lead

On May 11, Prime Minister David Cameron appointed Amber Rudd as the United Kingdom’s new Secretary of State for Energy and Climate Change, which was well-received by the renewable energy industry. The renewable energy trade bodies in the United Kingdom (Renewable Energy Association, RenewableUK, and the Solar Trade Association) appeared to have good comments about Rudd, and Nina Skorupska, the chief executive of the Renewable Energy Association, had the following comments on Rudd’s appointment.

“Amber Rudd has been a champion of renewables and the low-carbon economy in the past year, and her appointment will do much to allay the fears some may have after the general election … ensuring we meet our targets in the most efficient way … and making sure the UK is leading the way in green jobs and cost effective renewables.”

While RenewableUK, which mainly represents the wind industry, criticized the Conservatives’ manifesto when it was launched, its chief executive, Maria McCaffery, was also pleased by the appointment of Rudd. In a note released to the press, McCaffery said:

“We welcome the positive commitments which she has made on reducing emissions, tackling climate change and protecting the environment. We are looking forward to working with her and showing how all the technologies we represent: onshore wind, offshore wind and wave & tidal energy, can help achieve these aims.”

Onshore Wind on the Chopping Block

The Conservatives’ manifesto included a promise to stop incentives for onshore wind farms and to give local residents more influence in planning approval of the projects. In an interview with the Sunday Times this week, Rudd reiterated the Tories’ manifesto pledge to effectively end the development of new wind farms on U.K. land, outlining her hopes for the new measures to come into force by May 2016. While onshore wind in the United Kingdom can be competitive with fossil generation, the additional requirements to develop a project, like signing a power-purchase agreement, and survive what would be a gruesome planning application process, carry extra risks that few investors would like to face. This is expected to affect Navigant Research’s U.K. wind energy forecast, which is part of the World Wind Energy Market Update 2015 report.

Currently, there are about 7 GW of onshore wind capacity under development. While the onshore wind utility-scale installations are expected to decline, there will be room for companies willing to participate in community-scale projects. Community projects have the double advantage of a guaranteed buyer for the electricity produced while getting local support for the project by sharing the benefits of the wind farm.

A Solar Revolution Underway

While at first look this looks like a step back for the renewable industry, in reality, the winners if this policy is implemented would be all other sectors within the industry. In another interview, Rudd said she hopes to “unleash a new solar revolution” as a government cabinet minister. This seems feasible given that solar PV would become the cheapest source of renewable energy that can be deployed at scale. Other sectors will benefit as well. Some biomass projects would become competitive, and even offshore wind would benefit if the bids in the Contract for Difference (CfD) increase.


Surprises in U.K. Renewables Bidding Round

— April 15, 2015

The U.K. Department of Energy & Climate Change (DECC) has announced the results of the first competitive Contracts for Difference (CfD) allocation round. CfDs are designed to give investors the confidence and certainty they need to invest in low-carbon electricity generation. The government does this by paying the generator the difference between the cost of investing in a particular low-carbon technology, known as the strike price, and the reference price, or the average market price for electricity. Generators participate in the electricity market, including selling their power, as usual. This means that if the reference price is higher than the strike price, generators must refund the difference.

The DECC assigned 27 contracts, totaling 2.1 GW of capacity, in round one; the government estimates its total spend will be £315 billion ($470 billion in 2012 prices). Wind projects will supply 1,910 MW of capacity, of which 750 MW will be onshore and 1,160 MW will be offshore. These projects, along with the five offshore projects (3,184 MW) that were allocated CfDs in the so-called round zero, underpin Navigant Research’s forecast in our World Wind Energy Market Update 2015 report that the United Kingdom will install 10.6 GW of wind capacity in the next 5 years.


In addition to the wind capacity, round one winners include two energy-from-waste projects, with associated combined heat and power systems, that total almost 95 MW of capacity. Three additional projects that use biomass gasification technologies have a combined capacity of 62 MW. Finally—and perhaps surprisingly, given the well-known cloudy and windy British weather—five solar plants, with a total capacity of 71 MW, are also included.

The winning strike prices also brought some surprises. On the one hand, low-bidding solar projects outbid onshore wind projects—which are usually considered the cheapest source of renewable energy. The solar projects offered £50 per MWh, or roughly $0.075 per kWh—very close to the current U.K. wholesale electricity price.

On the other hand, the offshore wind winning bids offered £114.39 ($0.169/kWh) and £119.89 ($0.178/kWh). Interestingly, the Danish Energy Agency announced the winner of its 400 MW Horns Rev. 3 offshore wind farm on the same day. The winning bid was 52% lower than those in the United Kingdom were and will run for 3 fewer years.

Storm Clouds 

If these solar projects actually get built, they will put solar costs in the United Kingdom at a similar level to winning bids in regions with excellent solar resources, such as Dubai and Texas. But there are some clouds on the horizon. James Rowe, director with Hadstone Energy (the developer of one of the lowest bidding projects), put this construction in doubt in a pair of LinkedIn posts (“We Got Our CfD … Oh Dear” and “What Went Wrong with the CfD Auction for Solar?”) in which he explored the reasons why the players (including Hadstone) bid so low.

At this point, it’s difficult to measure the level of success or failure of this allocation round. The solar bids at £50 per MWh are unlikely to ever be built. If others, which bid £79.23/MWh, do come online before the end of 2017, it will be the first time that solar in a resource-poor country has outbid onshore wind in a country with good wind resources.


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