Offshore wind development is taking off around the world. The wind projects, however, pose logistic challenges that call for solutions from new ideas. For example, the UK has opened new areas for offshore wind development. However, these locations are farther from shore and in rougher water than ever before, which makes transporting crews and equipment difficult.

To help solve this problem, Carbon Trust (www.carbontrust.co.uk) held a contest for innovative transportation vessel designs for offshore wind. The non-profit company provides support to help business and the public cut carbon emissions and save energy. The 2011 Offshore Wind Accelerator Access Competition aimed to identify and develop new access systems to improve turbine availability and worker safety. Over 450 submissions from around the world included designs for vessels, transfer systems, and launch and recovery systems. Somehow, Carbon Trust narrowed that number to 13 designs, which received financial and technical support. Here are four of the finalists:

Windpower Engineering & Development

Along with his Vice Chairman and son, Willy Lowndes IV, the company has accomplished notable firsts in product development, from the first precast-concrete manhole in South Carolina to modular prison cells. Innovations now extend to the wind industry with the patent-pending Atlas CTB precast concrete tower system.

Lowndes III still chairs weekly product development reviews with Willy, a graduate of Georgia Tech, and a diverse group of experts within the Tindall organization that is focused on the next generation of wind towers. Tindall holds a variety of product and manufacturing patents that support the company mission to deliver “Better Building Through Technology.”

The distinctive design of the Atlas CTB wind-tower base provides wind-farm developers with increased hub height, while reducing foundation costs by 50% or more and delivering double digit increases in power production. The Atlas design supports a wide range of OEM turbines from 1.6 to 3.0 MW with hub height flexibility based on site-specific wind characteristics.

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To enjoy engineering, it also helps to come from a like-minded family of tinkerers. “My first experience with renewable energy came from my brothers who built a parabolic solar collector for fun,” he says. It was a breakthrough experience for him because it exposed him to the idea of harnessing the power of natural forces.

In addition to his brothers, Catalán says engineering inspiration comes from his father. “He could fix anything and he proposed innovative solutions to most problems,” says Catalán. For example, he says, when the clock in the village church tower stopped working, the town could not find repairman. Catalán’s father volunteered to give the repair a try and succeeded in getting the mechanism working.

“Most of my career at Gamesa has been devoted to leading our 2-MW platform projects designing, developing, validating, and certifying most of the variants,” he says. “We are always looking at ways to advance the platform that will better serve the needs of customers. For example, we’ve added new rotor sizes, airfoils, and wind classes for specific grid codes. Driving platform evolution is important for Gamesa because this family of turbines is fundamental to our product portfolio.”

The G11X 5.0MW is a new platform for the company and the first offshore wind turbine to be designed in the U.S, so Catalán says it’s an exciting challenge. He explains that extensive testing is a key driver for design enhancement. The major components and subsystems of the G11X-5.0 MW have gone through more than 240,000 hours of testing and validation including applying a counter-yaw system to evaluate how effectively it behaves under extreme conditions.

Most members of Catalan’s North American offshore engineering team are housed in Gamesa’s North American Offshore Wind Technology Center in Chesapeake, Va, which opened in early 2011. “Plans for the offshore industry in the U.S. are moving ahead, so we want to be ready to supply the first wind farms to be installed here,” he adds.

talled here,” he adds.

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The agreement is set for three years with an option to extend for two additional years and provides the foundation for a long-term relationship among Iberdrola, GE and Tamoin. GE will act as the technology partner in the consortium to provide high availability and reliability for the installed GE wind turbine fleet by supplying parts, specialized labor and technological support, while Tamoin will supply skilled labor.

The scope of the agreement includes planned and unplanned maintenance for the GE wind turbines at the following Iberdrola wind farms: Cuesta Colorada, Cerro Calderón, Cerro Palo, Muela 1, Maza, Calleja, Isabela and Sierra Quemada y Gavilanes.

“Our goal, in collaboration with our partner Tamoin, is to provide Iberdrola with the highest level of service to help optimize operations while maximizing production,” said Ramon Paramio, Europe wind services leader at GE’s renewable energy business.

The GE-Tamoin consortium has been working with Iberdrola for the past two years under an existing services agreement at Iberdrola wind farms in Germany and Poland. In addition, GE has provided equipment and services to Iberdrola for a wide range of energy projects over recent years, including the thermal, aeroderivative and renewable energy sectors.

GE
www.ge.com 

Windpower Engineering & Development

Streamlines over complex terrain show recirculations in some regions, places to avoid when positioning turbines, and areas that might go undiscovered if using only linear modeling.

The emergence of software and science can turn even complex terrain into productive wind farms.

As potential sites with simple, flat terrain are developed, more wind projects are built in or near forests and complex terrain. These sites—associated with harsh flow conditions—are likely to affect wind-turbine performance. Complex terrain can, for example, induce large amounts of turbulence and high loads on wind turbine blades. As a result, there are increasing concerns about under-performing wind farms with higher than expected maintenance costs, performance drops, and warranty claims. Tools and methods for designing efficient wind farms in complex terrain are available, but there is little awareness of wind software within the industry.

Complex flow
The wind industry defines complex flow as that which affects wind-turbine production or safety. Several parameters, such as wind shear, turbulence intensity, and inflow angle, are useful to quantify flow complexity.

Wind shear characterizes the variation of horizontal wind speed with height. In flat, non-complex terrain wind speed increases with height following a logarithmic or power-law profile. Forests and slopes can significantly perturb such a profile. As wind blows over a forest, it loses momentum as trees resist the wind. Above the canopy, wind shear is typically high with a reduced distance for the wind to reach high speeds aloft. Downwind of forests, areas of recirculation can be generated at tree level, implying high wind shear aloft. Wind shear depends on topographic features as well. As wind blows over a hill, wind shear typically decreases with an increasing altitude, and increases downwind of the hill.

Temperature can also significantly affect wind shear. Heating at the ground induces flow motion and diverts wind shear from a smooth log-law profile. In some instances this can result in negative wind shear, that is, decreasing wind speed with height. High or low values of wind shear usually imply increased fatigue loading, reduced power output, and reduced availability. If not properly assessed, high shear can lead to underperformance due to not meeting a turbine’s power curve, higher than expected shut-downs, or even failure.

Turbulence intensity is a measure of wind-speed variation in space and time. Turbulence is generated by trees: the energy of flow converts into motion of leaves and branches within the canopy, which in response perturbs the flow at canopy level. Turbulence is also absorbed by trees. One effect of a canopy is to dissipate larger eddies into smaller ones. These perturbations are generated at canopy level, and transported up and down by the mean flow. This is the reason tree-generated turbulence can be felt kilometers downwind of forests at hub height.
Topography and temperature also affect turbulence intensity. Turbulence is typically low at hill tops and higher downwind, where the flow is more perturbed.
Diurnal and seasonal variations of turbulence can be significant. In some cases, turbulence intensity can double in 12 hours. The effects of high turbulence on wind turbines are similar to the ones previously mentioned for wind shear, expect increased fatigue loading, reduced power output, and reduced availability.

Inflow angles
In flat terrain, wind typically reaches turbines perpendicular to the rotor. When the wind blows up a steep slope, it follows the slope close to the ground, typically reaching the rotor perpendicularly and not at an angle. This is the inflow angle. The IEC 61400-11 recommends that values of an inflow angle are within ±8°, which is often not the case when turbines are planned for the vicinity of steep slopes. Values of wind shear outside of the ±8° limits usually imply increased fatigue loading and reduced power output. The application of the IEC standard can lead to sector management, e.g. turbine curtailment or in extreme cases turbine shutdown and, therefore, reduced wind energy yield.

When the wind blows over a hill that is steep enough, a recirculation can be generated downwind of this hill. Trees on the hill increase the chances of recirculation for a given slope. While recirculations combine high inflow angles, turbulence, and wind shear, they are a definite no-go.

The flow over a smooth, uniform hill shows how wind shear changes on the approach and downwind side.

Handling complex flow
Steep slopes, forestry, and thermal effects can therefore lead to turbine underproduction and failure. However, wind software can predict these phenomena and mitigate their impact on wind energy yield.

Assessing complex flow
A first step assesses the terrain complexity. Although the use of RIX (Ruggedness Index) values can help assess complex terrain, it is not always readily available to investors or developers and does not take in to account the effect of land cover on flow complexity. In response, Natural Power has developed a complexity assessment applet that is freely available on the company’s website. To provide an estimation of flow complexity, the applet simply requires turbine locations, which can be uploaded as Google Earth place marks, and a simple estimation of forest coverage in the area of interest. The applet then computes a complexity index, taking into account topographic features and approximate land cover. It provides visual results in a summary report that summarizes findings, recommendations, and the next development steps. On-site measurements can also provide an indication of flow complexity. High values of turbulence or wind shear can, for instance, indicate complex flow at a specific location. The amplitude of daily or monthly variations should be accounted for and can indicate the presence of thermal effects.

Complex terrain is often characterized by large variations in wind flow over short distances. Therefore, in such terrain, a measurement mast located at the center of the site is usually not representative of all turbine locations. Wind flow uncertainty can be minimized by increasing the number of masts, but this approach quickly becomes expensive.

Portable wind sensors, such as lidars or sodars, can assess flow conditions at several locations. However, wind speeds measured by these devices can be biased in case of complex flow. In such instances, computer modeling can convert lidar or sodar measurements to cup-anemometer equivalents.

Unless measurements are scheduled at every planned turbine location, computer modeling the flow is ultimately required to map it over the area of interest.

Performing relevant simulations. If complex flow is not expected on site, linear modeling (WAsP-like) of the flow is usually relevant. As the name suggests, linear models solve linearised, i.e. simplified, versions of the Navier-Stokes equations, which makes them quick and easy to use. Linear models do a good job predicting wind speed over a site provided the terrain is not too complex.

As terrain complexity increases, the assumptions embedded within linear models break down. It is advised to solve the full 3D Navier-Stokes equations for an accurate picture of the flow. CFD (Computational Fluid Dynamics) codes do this.
CFD models have several advantages over linear versions:

• They embed more physics, including a turbulence model, which allows predicting its intensity at each point of the flow field.

• They usually include an advanced canopy model, which means forests are actually modeled as 3D bodies that extract momentum from the flow, absorbing and generating turbulence. This allows a more accurate description of the flow field in the vicinity of forests than simply using a value of roughness at the ground, such as with linear models.

• They are 3D which, among other things, implies they allow modeling of inflow angles and mapping areas of recirculation.

The colored map shows the turbulence intensities over a potential wind farm site.

Thermal effects are believed to influence the flow-field. Some recent CFD codes, such as the VENTOS/M code currently in testing, can couple with mesoscale models that are used over larger distances than CFD models cover, and consider thermally-driven flow. The output of these larger models can feed CFD models, provided they simulate thermally-driven flows. Such codes generate a time-series of the flow at any location of interest. This is similar to what measurement masts could measure there, and include diurnal and seasonal variations of flow variables, such as wind shear, turbulence intensity, wind speed, and inflow angle.

These advanced models, however, have drawbacks. First, they imply the use of numerous parameters to which modeled results can be sensitive. This is not necessarily the case for linear models. On top of appropriate input data, these models require proper calibration using measured data before they become representative of reality. This implies a dedicated user with knowledge and experience of measurements and a specific code. Secondly, they require the handling and analysis of numerous variables, which implies a critical mind-set and a good knowledge of fluid mechanics. Thirdly, they imply costly computations, which are more easily run on computer clusters and entail time and investment.

CFD outcomes
Once CFD computations have been successfully carried out, results must be translated into useful recommendations. At each planned turbine location, key variables to assess include values of turbulence, wind shear, inflow angle, and wind speed. The value can be compared to standard limits for choosing an appropriate turbine and locations.

The reasons for improper values (topography, forestry) can often be identified, which allow implementations and appropriate mitigation measures where possible. Managing tree height can often adjust wind shear within acceptable bounds. For more representative assessments, the impact of tree growth and felling on turbine suitability and wind energy yield can be computed throughout the entire wind-farm lifetime. If topography is the culprit, wind-sector management or turbine layout redesign are usually more appropriate, although topographic management has been seen on specific sites such as quarries. Wind software also allows generating maps showing areas where turbine operation is not recommended, and then coupled with wind speed maps to optimize turbine layouts.

It is preferable to make this information available at the first stages of a wind project because it results in more efficient wind farms, where production is maximized and machine fatigue is minimized. Unfortunately, CFD computations are frequently performed after building a wind farm and detecting underperformance. CFD is then used to better understand the reasons for underperformance, and mitigation actions are mainly limited to wind sector management, forest management, and turbine relocation.

Such information on site conditions is nevertheless valuable to turbine manufacturers and investors who require reliable assessment of site conditions for making appropriate decisions and for the most safe and efficient wind farms possible. WPE

By: Claude Abiven/Senior Technical Manager/Natural Power/www.naturalpower.com

Windpower Engineering & Development

Texas Wind 2012 will feature more than 30 hours of information exchange through keynotes, breakout sessions, and networking events in the heart of downtown San Antonio. Seminars and expo will take place at the historic Sheraton Gunter Hotel in the midst of the Riverwalk, the Alamo, and all that the Nation’s seventh largest city has to offer.

Seminar topics will include wind policy outlook and intensive strategies, initiatives to increase wind project profitability, wind transmission expansion, wind supply chain manufacturing and transportation, homeland security issues and solutions, retail and wholesale market opportunities, regional project case studies, public outreach, workforce development, university and college programs, Wind Law 2012 continuing legal education about wind policy, and Texas wind energy in the media.

Registration, exhibitor, and sponsorship information and online sign-up are available at www.TexasWind.info. Early registration rates are in effect through June.

Windpower Engineering & Development

GE turbines like this 1.6-MW unit are finding more work in Canada.

Advanced technology wind turbines have been selected to power nine new wind projects in Ontario, Canada, adding about 650 MW of clean energy to the province’s electricity grid. When the projects are fully built out by 2015, GE wind turbines will be delivering about 1,200 MW of wind energy in the province.

“Ontario is a hot wind market for GE right now,” says Simon Olivier, general manager sales, Renewable Energy for GE Canada. “The Green Energy Act has created a positive investment environment and helped fuel the growth of renewable energy in Canada. In seven years GE has have grown from our first 100-MW Erie Shores Wind farm project to supplying over a thousand megawatts of clean energy to residents and businesses across Ontario by 2015.”

To date, the company has announced more than $150 million of investments in Ontario, creating three global centers of excellence: Peterborough Motors; Grid IQ Innovation Centre in Markham; and Pathology Innovation Centre of Excellence in Toronto. GE also is working with a number of Ontario-based businesses providing products and services supporting wind farm projects and stimulating new local job creation in multiple regions of Ontario.

Ontario continues to lead Canada in installed wind energy capacity, accounting for about one-third of the nation’s wind energy development, according to the Canadian Wind Energy Association (CanWEA). Overall, Canada has increased its wind power capacity nearly tenfold in the last six years, as provincial governments seek ways to meet rising energy demand, reduce environmental impact of electricity generation and stimulate rural and industrial economic development. CanWEA expects that wind energy’s rapid growth in Canada will continue, with production tripling over the next five years.

In 2009, GE Canada signed a memorandum of understanding with the Ontario government to undertake long term investments including investments in research and development and advanced manufacturing in order to enhance economic development in the province.

GE Energy
www.ge-energy.com

Windpower Engineering & Development

Tthe Nordex turbine is similar to those that will go up in Poland.

Turbine manufacturer Nordex has obtained a follow-up order in Poland or the delivery and installation of turbines for a wind farm for the Polish subsidiary of E.ON Climate & Renewables. Until 2013, the manufacturer will be delivering a total of 22 large N90/2500 turbines for the projects “Wysoka I and II”. Installation will take place in two phases: the first of with three turbines will be set up in the course of this year, with 19 more added in 2013.

The wind farm is 100 km to the south of Szczecin, near to the main Nordex production facility in Rostock. The turbines will later be serviced by a local company belonging to the Polish subsidiary, which Nordex established in 2008.

The new project is now the third E.ON-wind farm to which Nordex delivers turbines. It is also the largest individual Polish project for Nordex to date. Including the “Wysoka” wind farm, the manufacturer will have delivered turbines with a total capacity of around 200 MW in Poland.

“This is the third time E.ON has selected our 2.5 MW series, marking a continuation of the successful partnership with Nordex in the Polish market,” says Lars Bondo Krogsgaard, CCO Sales at Nordex SE.

E.ON Climate & Renewables
www.eoncrna.com

Windpower Engineering & Development

First Wind owns and operates two other wind energy projects in Hawaii, and a this writing, is building another project on Maui.

A U.S. based, wind-energy company announced it has obtained $236 million in financing for its 69 MW Kawailoa Wind project on Kamehameha Schools’ Kawailoa Plantation lands on Oahu’s North Shore. A subsidiary of developer First Wind closed a $220 million non-recourse construction and term loan and $16 million in letters of credit for the Kawailoa project. Union Bank served as Administrative Agent and Joint Lead Arranger. Other Joint Lead Arrangers include Bayern LB, Rabobank and Siemens Financial Services. CIBC, and CoBank also participated in the financing.

Early construction work began on the project in December of 2011 and has progressed steadily. The project is expected to complete by end of 2012. Major construction work, including delivery and erection of turbines, is expected to begin in the summer of 2012.

Once complete, Kawailoa Wind will be the largest wind energy facility in Hawaii. The project’s thirty 2.3-MW Siemens wind turbines will have capacity to generate as much as five percent of Oahu’s annual electrical demand.

“This financing is an important milestone for the construction of Kawailoa Wind,” said Paul Gaynor, CEO of First Wind. “Hawaii has a genuine commitment to having more renewable energy on the islands, and these banks recognize that this project will be an important component toward reaching that goal. We appreciate the commitment of our financial partners, which will help First Wind deliver clean, renewable energy for the benefit of Oahu residents and businesses.”

“The Kawailoa Project will play an important role in Hawaii’s increasing energy independence and is yet another example of First Wind’s ability to develop innovative projects,” said Lance Markowitz, Senior Vice President at Union Bank.

In December 2011, the Hawaii Public Utilities Commission approved a power purchase agreement between Kawailoa Wind and the Hawaiian Electric Company (HECO), which serves more than 400,000 Hawaii customers. Hawaii state law mandates 70% clean energy for electricity and surface transportation by 2030, with 40% coming from local renewable sources. Kawailoa Wind will significantly advance the state’s progress toward these goals.

Kahuku Wind, also located on Oahu’s North Shore, is a 30 MW wind project that has the capacity to generate enough energy to the power the equivalent of 7,700 Oahu homes. The Kahuku project went online in March of 2011. Beginning commercial operations in 2006, the 30 MW Kaheawa Wind project is above Ma‘alaea. First Wind is currently building a second Maui project, Kaheawa Wind II that will consist of 14 wind turbines, capable of generating 21 MW of energy. Once Kaheawa Wind II is complete, the two Kaheawa projects will have a capacity of 51 MW.

First Wind
www.firstwind.com

Windpower Engineering & Development

“Distributed and community wind is the next frontier for Gamesa,” said David Rosenberg, Vice President of Marketing for Gamesa North America. “Combine our turbine platform with Harvest the Wind’s vast network of distributed wind developers, and the wind energy solutions we can jointly bring to communities and businesses across North America is enormous.”

Gamesa's G5X 850-kW turbines, like these, will soon be working in community wind projects.

Gamesa’s G5X-850-kW platform is a good fit for community and distributed wind energy projects. First installed in 2001, the turbine’s performance is well tested and validated, with more than 9,482 units (8,060 MW) installed around the world.

Because Gamesa says it continuously adapts its equipment to the most demanding connection grids and surroundings, the G5X-850 works well regardless of environmental conditions such as corrosive, desert dry, humid, and high or low temperatures. Environmental flexibility is vital to developers as community and distributed wind energy projects spread across the United States and occupy a variety of terrains.

Distributed and community wind projects are among fastest-growing segment in the U.S. wind industry as more cooperatives, smaller utilities, commercial businesses, small and large industrials, and communities embrace the clean-energy opportunities and utility savings.

Harvest the Wind Network is part of BTI Inc., a fourth-generation family business in southwest Kansas. BTI launched the network while rebuilding after a powerful tornado destroyed their business and community in Greensburg, Kansas, in May 2007. The small southwest Kansas town resolved to rebuild as America’s “greenest city,” and BTI Inc. was reborn, with a new addition, BTI Wind Energy LLC.

Harvest the Wind Network consists of 13 independent dealer groups in more than 200 locations. The network has installed and is servicing over 125 turbines, with more than 100 projects in progress ranging in size from 50 kW to 10 MW.

“The United States currently has a mid-scale wind turbine void that will be filled through this timely partnership,” says Haley Estes, Vice President of Harvest the Wind Network. “The two companies will provide American industries with the ability to power manufacturing plants, schools and large industrial facilities, which will create nationwide jobs and foster energy independence.”

Gamesa

www.gamesacorp.com/en/

Harvest the Wind Network

www.harvestthewindnetwork.com

Windpower Engineering & Development