As the wind sector grapples with questions surrounding the continuation of federal programs and incentives, the industry should also focus on accelerating technological development and deployment. Doing so would continue driving down the cost of wind energy and, therefore, lead to further growth.
The past two decades have seen an increase in wind turbine power output sizes and ratings, as well as significant progress in the refinement and reliability of the equipment. The sub-megawatt-rated turbine sizes of the early 1990s gave way to 1-MW-class ratings by the mid-to-late 1990s. More recently, turbine ratings have grown to multi-megawatt sizes. Blades have gotten longer, meaning rotor diameters are larger, easily exceeding the wingspans of large aircraft, such as the Boeing 747 and Airbus A380. Towers have gotten higher, with heights now exceeding the length of a football field, meaning more than 30 stories high.
The electrical side of power generation is also more advanced now. Induction generator system architectures have given way to a variety of doubly fed induction generators, permanent magnet generators and synchronous architectures. Turbine control systems have become more complex, and power output quality has improved dramatically. Grid-fault and low/no-voltage transient ride-through systems now rival – and, on occasion, outperform – conventional power generation ride-through capabilities.
Onboard sensors are measuring and recording more and more data – gigabytes per day per turbine – to enable control systems to provide better onboard telemetry and improved uptime performance.
What used to be the weaker aspects of wind turbines, such as reliability concerns, has largely been mitigated through innovations borne from technical investigation and subsequent design improvements. Today, reports of gearbox, generator and bearing failures are the exception rather than the rule. Additionally, damage from lightning strikes to blades and other structural areas of a turbine, as well as insulated gate bipolar transistor failures in power converter systems, have been diminished significantly. Technology has pushed modern wind turbines to a marked trend of improvement in reliability and availability performance.
As turbine power output ratings continue growing larger, so, too, will the turbine’s physical attributes. So, what does the future hold for wind turbine technology development?
Blades. Many original equipment manufacturers (OEMs) are introducing longer blades on existing turbine platforms – meaning that rather than completely redesigning the turbine’s load-bearing components, some companies have finessed the design by bolting on larger blades and refining the operating algorithms. Rotor blade lengths – and, therefore, rotor diameters – have increased as much as 35% over the past several years. The resulting improvements have translated to higher capacity factors, higher megawatt-hour production and an increased revenue stream for the turbine owner, thereby improving the competitiveness of wind power compared to other competing forms of power generation.
In addition to innovative advanced dynamic blade design configurations, increasingly sophisticated advanced control systems will become more prevalent to better manage the otherwise-increased loads resulting from the longer blades and, thus, largely avoid significant and costly changes in other areas of otherwise-unchanged turbines.
Major turbine OEMs and several blade OEMs are also working to develop sturdier, lighter and more durable blade designs with an increasing scrutiny on multi-piece and monocoque – or structural skin – blade structures. Using low-mass and high-performance materials will help achieve higher capacity factors, which ultimately will yield favorable economics. Efforts continue to focus on lowering costs while improving performance, on both a capital cost per megawatt rating and cost per megawatt-hour basis.
Towers. Until recently, the push for higher towers has been less bullish, due primarily to the incremental cost of materials required for higher towers and the foundations to support them. Simply put, a higher tower does not necessarily yield a benefit at every wind site – unless site wind shear conditions are present. Therefore, the benefit is site-specific.
Like the movement to larger rotors, the rationale for higher towers is increased energy capture. Expectation of higher energy capture is driven by the expectation that mounting a rotor higher in the air exposes the rotor to higher wind velocities than at lower distances from the ground.
A cost/benefit analysis for any given site can provide guidance as to whether a higher tower is cost-effective. Nonetheless, efforts continue to develop more cost-effective tower solutions that yield much higher towers than the current 80-meter norm.
Tower heights in excess of 140 meters are now being contemplated by several turbine OEMs, such as Vestas, GE and Siemens, as well as by tower fabricators, such as Max Boegl. These tower configurations incorporate design innovations, such as advanced lattice designs, advanced concrete designs and hybrid steel/concrete.
For example, GE is fielding a recently acquired lattice tower design that provides for 100-meter and taller towers at a more economical cost, without the maintenance issues traditionally associated with lattice tower designs.
Other manufacturers have been developing and fielding their own approaches to advanced towers. It remains to be seen whether these will be accepted into the mainstream; nonetheless, economics and transportability issues are pushing the industry in this direction.
With respect to the future, look for higher towers for deployment in those projects wherein the cost/benefit analysis yields a favorable conclusion for the added expenditure.
Performance optimization. In the quest for more efficient, reliable and dependable turbine operation, including greater productivity via greater megawatt-hour generation on both new and existing equipment, OEMs and others are trying to mine the mountain of data generated by each turbine via onboard sensors. The number of sensors has increased dramatically in recent years, with turbine control systems and SCADA systems monitoring and potentially reporting the data per established protocols.
With the proliferation of sensors comes a proliferation of data, which, when properly stored, cataloged and analyzed algorithmically, can provide a basis for optimizing performance. This is already done in most new cars, wherein the average new car generates about 15 gigabytes of information per hour. The same rationale is now being applied to wind turbines. The amount of data available for capture and analysis today far exceeds the gigabyte level – hence the term “big data” – and can provide a gold mine of opportunity for deep analysis and fine-tuning of the turbines in the continuing quest for improved operation and performance to an optimal level.
OEMs and others are developing and deploying such analytic and optimization tools. GE, for example, recently introduced its PowerUp performance optimization product. Firms specializing in asset management and firms specializing in operations and maintenance, as well as firms serving as owner-operators, are also digging into new ways to utilize the mountain of data generated by the wind turbines in a quest to improve operating performance, with the prime focus on net revenue optimization.
Other technological innovations. Among the most interesting turbine advances are technologies that have the potential to change the current paradigm, such as integrated drivetrain solutions, integrated power converter/inverter/controller systems, mass flow modeling and optimization focused on energy capture from various meteorological conditions. Though years away, such game-changing technologies truly demonstrate the potential of future turbine technology.
For example, Boulder Power is developing a new integrated generator technology that could revolutionize the wind power industry. The company is developing an axial gap air core permanent-magnet direct-drive generator that – the company claims – can produce the same torque with half the mass of conventional iron-core direct-drive generators. This design enables a more compact and favorable mass-to-output ratio. Potentially, the technology could achieve greater reliability and yield more power at a lower cost than comparably rated generators. Boulder claims its technology has the potential to lower the cost of energy as much as 20%.
Not to be outdone, the Delft University of Technology is developing the Electrostatic WInd Energy CONvertor (EWICON), a generator that converts wind energy into electricity without the use of moving parts. According to the university, the EWICON generator features substantially lower maintenance costs.
Technological development and refinement is the key to addressing almost every issue and objection facing the wind power industry. The following is essentially a to-do list for technology to resolve and solve:
Cost-competitiveness. Over the past several years, by way of a combination of larger rotors, more efficient generators, more reliable equipment and a comprehensive understanding of the physical phenomena yielding more sophisticated and efficient control systems, the cost of energy per kilowatt-hour from a wind turbine has continued to decline dramatically, becoming very competitive. The widely held belief is that federal incentives, such as the production tax credit, are what make wind power competitive. In reality, this is decreasingly true, as compared to historic comparisons. What got us here to a point of near parity? Two primary factors: market and technology. While the industry cannot necessarily control the market, it can absolutely control technological progress. That is the key. Some might say that natural gas has the cost advantage now. Why? Because of fracking. The reality is that fracking is a technology developed by the oil and gas industry. Similarly, technology developed by the wind industry can do the same for wind power – reduce the cost and improve competitiveness. In the end, the industry improves its vitality, technological sophistication grows, low-cost energy helps the economy grow and the average consumer benefits as well. Everyone wins.
Financeability. Ultimately, financing for a wind power project differs little from funding other types of projects. Indeed, a unique wrinkle to wind power development is a tax equity investment play, which is present in a number of wind power projects. However, the financing is market based, meaning the market looks at individual project returns and financial performance to determine whether to participate. Technology can provide the means by which acceptable returns can be achieved, without tax policy support and with reasonable risk mitigation. Technology paves the way to the money.
Policy. When there is stable policy, wind energy proliferates. We all know the inverse is also true. But proper technological development and deployment can result in wind power being competitive without incentives. Then the issue becomes not one of subsidizing wind power, but one of the country holding a critical debate toward establishing a proper energy policy aimed at the real issues – economy, environment, energy autonomy/independence and decisions based on what the country believes in, not ones served only by powerful parochial interests.
Grid management. There is a lot of debate regarding grid penetration, spinning reserve and equipment availability. Objective research and study, without the noise of partisanship, can reduce this to a technological issue, with finite problems to be resolved by specific technology-based solutions.
Environmental considerations. These include, but are not limited to, avian migratory patterns, predator avian compatibility, noise generation, shadow flicker and bat compatibility. In each case, proper technological enhancement can help resolve the issues.
So, what does all of this mean to investor-owned utilities, developers, community wind projects, and other wind turbine developers, owners and operators?
First, appropriate emphasis on technology will provide the means to meet the needs of each of the stakeholder groups. Utilities need energy and power generation solutions that are reliable and low risk, provide proper returns on investment, and easily integrate into the grid as manageable and predictable energy blocks.
Developers, on the other hand, are more focused on low-risk, financeable power generation solutions. Community wind owner-operators are looking for economically viable energy solutions that can be funded and will reliably provide energy on an ongoing basis to the community. Technological innovations and advances provide a strong level of support to achieve the unique goals of each stakeholder group. w
Industry At Large: Turbine Technology
Technology Shall Lead To True Competitiveness
By Robert C. Rugh
A reliance on wind turbine technological advancements – as opposed to tax policy – can help the industry achieve grid parity.
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