The rugged construction of the WB25 series provides for a long-life even under harsh operating conditions such as those found in off-highway vehicles and construction equipment.

A sensor manufacturer has expanded its product line of tape-extension position sensors, POSITAPE with the introduction of the WB25 series. The family was developed for applications that require the use of cable pulleys due space limitations. The measurement ranges of the WB25 series are 12m, 15m, 20m and 25m all in compact housings.

The flexible measurement tape is constructed out of a high-tech stainless steel material that is 10-mm wide with only a 0.08-mm thickness. Due to its very smooth surface, the risk of icing is reduced. An integral tape dust wiper automatically cleans the tape each time that it is being retracted into the housing.

The WB25 series has a standard IP64 enclosure rating with an option for an IP67 rating and is available with the typical analog outputs: 0.5 to 10V, 0.5 to 4.5 and 4 to 20 mA. For the digital output versions, CANopen, CAN SAE J1939 and SSI protocols are available. The linearity of WB25 series sensor is ±0.05% of full scale.

The angular sensing element consists of a magnetic encoder which translates the linear motion into an electrical signal. This highly reliable magnetic encoder is very shock and vibration resistant which allows it to function in demanding environmental conditions. The space saving stainless tape design provides a small housing foot print with long measurement ranges.

ASM Sensors Inc.

www.asmsensors.com

Windpower Engineering & Development

By:  Christian Fritz, Senior Product Manager for Advance Machine Control at National Instruments, www.Ni.com
Dale Berg Staff, Wind Energy Technologies Department at Sandia National Laboratories, www.sandia.gov

Static blades such as these are a compromise of aerodynamic charactersitics. Dynamic blades with movable surfaces will let turbines generate more power.

With a power generation capacity of more than 215 GW worldwide, wind clearly tops the renewable energy scoreboard. It grew by almost 18.5 GW in the first six months of 2011. However, this continued growth alone is not enough to meet goals discussed at the World Climate Council, or defined in the Blueprint for a Secure Energy Future. Meeting these goals will require additional investment and innovation. Duke Energy CEO James E. Rodgers, a member of the Copenhagen Climate Council, agrees. “It is a myth that we have the technologies to do the job. We don’t. New technologies are crucial, as is further development of existing technology.”

There are two key areas of innovation: Power distribution and power generation. The infrastructure for power distribution must be upgraded and converted into a smart network that can handle more distributed-power generation. It must also adjust for generators that don’t provide consistent wind energy injection without failing at energy consumption peaks.

As for power generation, the industry has progressed in making renewable-energy resources more competitive. Many challenges, however, need overcoming to lower the cost of energy (COE) and further increase its acceptance. Just focusing on wind-power generation, by far the largest source of clean energy, it is evident that further industry growth will be difficult.

Consider Germany. The nation focused on renewable energy early and has recently decided to completely move away from nuclear power. Today, wind energy accounts for about 7% of German energy generation. To meet increasing demand and compensate for the nuclear-power plants that will cease production by 2020, the nation aims to up that number to 25%. To do this with current technology would require building 1,000 additional wind turbines per year. But with an area smaller than California and less than 2% of it suitable for wind-power generation, Germany needs higher-efficiency turbines to meet its ambitious goals.

Bigger is better

Development of worldwide installed wind-power generation capacity through June 2011 Source: German Wind Association (BWE .e.V.)

One prevailing wind-turbine technology trend throughout the past couple of decades has been increasing the rotor size. This facilitates the harnessing of generally higher winds available at greater heights and increases nominal power ratings. Studies on a 1.5-MW turbine show that increasing blade length by 10% results in 10 to 15% more energy capture and a 5 to 9% decrease in COE.

Today’s standard turbine provides 3 MW of power, but the recent E126 turbine from OEM Enercon provides 7.5 MW. Its 200-m height and almost 60-m blades support a nameplate of more than twice that of the current standard. The next power class of turbines is already on the horizon. For example, leveraging innovative lightweight materials and superconductors, American Superconductor Corp. is working on a 10-MW turbine aimed at large offshore wind projects to further lower the COE and attract more investors.

Most long blades are possible through efficient structural design and optimal material use, which produces the necessary structural capability for 60-m blades.

Challenges of larger turbines

Engineers and scientists face diverse difficulties. Future designs for even larger machines will continue to push design limits. For instance, blade-length limitations induced by the penalty of weight can only be pushed so far through new materials and optimized mechanical structures. In addition, the higher altitudes these longer blades reach provide the benefit of higher wind speeds, but they must also handle higher gusts. Therefore, these larger wind turbines must operate under turbulent and unpredictable environmental conditions. This results in loads that quickly vary and are spaced along the blade due to the impact of gusts. The resulting oscillating (or fatigue) loads are the design drivers for the blades and core components of the drive train. This means massive research and innovation for more sophisticated load-control techniques.

Active aerodynamic load control

One promising approach is the addition of active aerodynamic load control (AALC) devices. These are distributed along each blade to provide feedback load control. This technology is often referred to as a ‘smart structure’ or ‘smart rotor control’ and includes trailing-edge flaps or deformable trailing edge geometries with associated sensors and an embedded control system. AALC are receiving significant attention because of the direct lift control capability of such devices and recent advances in smart material actuators. Their short response time and relatively small size compared with the blade length of AALC seems independent of the existing blade-pitch control and could be a good supplement to it.

One of the leading research institutes in this technology is Sandia National Laboratories. Sandia conducts applied research to increase the viability of wind technology by improving wind-turbine performance and reliability and reducing the cost of energy. Sandia specializes in all aspects of wind-turbine blade design, manufacturing, and system reliability. By partnering with universities and the industry, Sandia works to advance the state of knowledge in the areas of materials, structurally efficient airfoil designs, active-flow aerodynamic control, and sensors. Lab researchers are investigating integrated blade designs where airfoil choice, blade platform, materials, manufacturing process and embedded controls are all considered in a system perspective. By collaborating with operators, developers and manufacturers, Sandia evaluates reliability problems and develops tools and methods to anticipate and investigate future reliability issues.

Smart sensor networks and instrumentation

For the instrumentation of the smart blades, Sandia adopted National Instruments CompactRIO controls that combine an open embedded architecture with small size, extreme ruggedness, and hot-swappable industrial grade I/O modules. Its computation power comes from a field programmable gate array (FPGA).

Over the last few years, Sandia has been instrumental in validating the value of AALC. The Lab has performed extensive simulations with a focus on estimating a damage reduction on rotor and gearbox, and on the technology’s COE benefits. As a next step, scientists and engineers are validating the simulation results with real-world data and implementing a prototype of a smart rotor to learn more about the potential and technical challenges of using AALC. For this purpose, the Sandia team operates a small test turbine equipped with a set of 9-m blades with chord flaps that cover about two meters on the outer area of the blade span. Besides validating simulation results and getting a better understanding of how to model smart rotors, the research project’s goal is to evaluate different sensor systems to provide input and feedback signals for the AALC controller. The sensors must be durable enough to withstand the harsh environments into which they will be deployed. For the instrumentation of the smart blades, Sandia adopted controls that combine an open embedded architecture with small size, extreme ruggedness, hot-swappable industrial grade I/O modules, and compute power from a field programmable gate array.

For the initial prototype, Sandia modified an existing blade design to incorporate a three part servomotor-actuated flaps, an array of accelerometer, fiber-optic strain, metal-foil strain, and fiber-optic temperature sensors, as well as pressure taps and Pitot tubes.

A wind turbine is a highly coupled dynamic structure because of its slender geometry and flexibility. Consequently, Sandia had to develop a sensor-optimization strategy and state estimators to maximize the performance of the controls observer and minimize the number of required sensors. The technology in these sensor optimizations includes a modal filter for stochastic monitoring, a patented static blade-deflection estimator based on centripetal acceleration, and order analysis for the deterministic monitoring of structural response.

The illustration identifies the type and location of sensors used along each AALC turbine blade.

In addition to finding the best locations and comparing the quality of the sensor information as input for the control system, Sandia focused on ruggedness and reliability, knowing that electrostatic discharge (ESD) is a field-test hazard that contributes to sensor failure. Lightning is a well-known example of ESD but the sensor system must deal with other physical phenomena. One is the tribo-electric effect which leads to a static build-up of charge due to the contact and separation of dissimilar materials. Another large charge comes from air passing over turbine blades. These can vary significantly along the blade, leading to discharges from one portion of the blade to another, or to the ground. To acquire all this sensor information and correlate it precisely via GPS timing, Sandia developed a rugged and reliable, hub mounted data acquisition system using NI CompactRIO hardware that wirelessly transmits information to a control center. There, data is merged with information from additional sources.

Leveraging this scientific instrumentation system, Sandia will start collecting real-world data from the working wind turbine. This data will allow performing system identification and modeling. For this purpose, the Lab will first perform open-loop tests. The collected information will help confirm and calibrate previously designed models within a simulation environment. These calibrated models will then serve as a foundation for the development of a Reduced Order Model that will be used for the Multi-Input Multi-Output design, implementation, and validation of a controller for a smart rotor. While this is the primary reason for developing the instrumentation and data-acquisition system, the improvements and lessons learned from this development may be immensely valuable to the wind-turbine industry in general. The embedded monitoring system also provides unique techniques for monitoring rotor performance and structural health. This technology could easily be adopted to estimate current loads and the state of damage. In this way, Sandia will be able to predict the future life of the rotor based on damage-growth models.

This innovation will encourage improved turbine performance and optimal turbine operation and maintenance. Ultimately it will make wind energy more cost-competitive and offshore wind-energy applications economically viable. WPE

Windpower Engineering & Development

Recent improvements to the equipment include Sodar 2.0, a modular platform offering, fine-tuned data filtering tools.

Triton is a sonar-based wind sensor for measuring speed and direction at hub height and higher. Equipment users at a recent AWEA Wind Resource and Project Energy Assessment workshop learned about remote sensing research and the latest product developments — and gave feedback to developer Second Wind on the ways they are using the sensors in development and operation of wind farms. Second Wind CEO Larry Letteney discussed Triton deployments, especially in challenging climates and hard-to-reach locations. Despite the use of Tritons in more and more extreme situations, fleet reliability is increasing, up to 97.67% in 2011. He also highlighted the community of experts that has sprung up worldwide to help the wind industry do everything from installing and servicing the equipment to analyzing its wind data.

The sodar-based sensors in short-term measurements, such as validating the shear projections from a long-term wind project or doing greenfield prospecting, has led the developer to expand its rental program and work with partners in the UK and Chile to offer rentals. The rental option lets users deploy the equipment rapidly and use it for short studies without incurring ownership costs.

A few significant improvements to the equipment include Sodar 2.0, a modular platform offering, fine-tuned data filtering tools. It enhances data quality and its usability. The firmware comes with the standard SkyServe support package. It has completed field testing over several months and is available to all equipment users.

The first module filters out environmental background noise, such as crickets. In the past, a consultant would typically ignore data that appeared corrupted by noise. Sodar 2.0 can filter an individual “chirps”. If there are enough “good” chirps in a ten-minute interval, the ten-minute average is retained. This makes a significant increase in the recoof quality data in noisy situations.

Second Wind
secondwind.com

Windpower Engineering & Development

The 2000 series SoDARs measure vertical and horizontal wind speed, and wind direction with 10-m resolution up to 700m.

The 2000 series SoDARs are intended as high-altitude sensors. These use three parabolic dishes in three separate enclosures. The 2000 series can operate in lower power consumption mode, pulsing each antenna at different time intervals. Or, they can be configured to sample all three beams simultaneously, increasing the number of complete samples during the averaging intervals. This unit captures data in real-time. The 2000 products measure vertical and horizontal wind speed, and wind direction with 10-m resolution up to 700m. The digital facsimile offers a look at the atmospheric structure exposing inversions and other critical information. The equipment can work remotely or in a network.

Atmospheric Systems Corp.
www.minisodar.com

Windpower Engineering & Development

The DT Series Large Aperture Current Transducers combines a hall effect sensor and signal conditioner into a single package for use in dc-current applications up to 1,200 amps.

The DT Series Large Aperture Current Transducers combines a hall effect sensor and signal conditioner into a single package for use in dc-current applications up to 1,200 amps. Factory calibrated ranges simplify operation and eliminate zero and span pots. Industry standard 4 to 20 mA, 0 to 5 Vdc or 0 to 10 Vdc outputs are magnetically isolated from the input to provide maximum safety, and eliminate insertion losses. Internal power regulation delivers reliable operation and helps keep installation costs low, even in applications with unregulated power. A DIN-rail mount enclosure makes installation easy.

“DT series current transducers provide design and process engineers with a rich source of equipment information,” says Philip Gregory, President, NK Technologies. “The devices are said to be economical and reliable tools for monitoring equipment status, detecting process variations and allow taking corrective action before a failure occurs, and ensuring personnel safety.”

The ability to monitor circuit up to 1,200A makes the large aperture current transducers well suited for applications that include:

• Monitoring load and charging currents, and verifying operation, of battery banks
• Measuring traction power or auxiliary loads in transportation applications
• Monitoring dc powered motors in cranes, saws, sorters, and positioning equipment
• Measuring produced or consumed current, and detecting mechanical problems before a failure, in wind and solar applications.

Test and evaluation units are available to OEMs at no cost. The Engineering Resources section of NK Technologies website provides numerous application notes, and technology white paper on current sensing technology.

NK TECHNOLOGIES
http://www.nktechnologies.com

Windpower Engineering & Development

SKF wind turbine sensor.

Expect to find sensors in more places in part because they are getting cheaper and MEMS manufacturing techniques are making them smaller. In addition, more powerful, less expensive sensors will allow their use in more places than previously possible. Smart sensors will allow making controlbased decisions at nodes, such as turning on devices, flipping circuit breakers, or sending trend data.

Sensors come in all sizes. A laser-based wind sensor, for instance, sits in a pod and mounts to the top of a nacelle to detect wind directions 200 to 300 m ahead of the turbine.

Such sensors can signal adjustments to yaw misalignment. When a turbine runs below rated power, a 10° yaw misalignment reduces power output by about 5%. Sensors (strain gages and controls) that provide data on mass and aerodynamic imbalances allow early action to maximize power generation and avoid damage. Sensors can also tell of damage affecting the structural or aerodynamic performance of a blade, allowing early remedial action.

By identifying small degradations in performance, sensors and software in recent controls can schedule preventive maintenance and even component replacement during scheduled downtime.

Particle sensors look for debris in oil to control contamination. Most use lasers to shine a beam into an oil path to analyze the reflected light by particles. Some have algorithms that discount bubbles in the oil. A few features on one particle sensor includes monitoring contamination trends, and early warning LEDs or digital-display indicators that tell of low, medium, or high contamination levels.

Leak detectors on seals are a recent development. Onboard electronics provide some analysis and can send results to a computer or telephone. This allows remotely monitoring a seal and scheduling an exchange when necessary in a normal maintenance interval. DIN 3760 standards describe function and lifespan for such seals. The sensor-seal combination is available in many different dimensions.

Windpower Engineering & Development

The ZephIR 300 provides remote resource measurements of wind speed and direction from 10 to 200m above ground.

ZephIR 300 wind lidar, remote sensing for U.S. wind energy market, will be available in the U.S. through Campbell Scientific. The wind sensor is said to provide accurate wind data across all stages of a wind farm project. Manufactured by Zephir Ltd. of the UK, a subsidiary of renewable energy group Natural Power, the ZephIR 300 provides remote resource measurements of wind speed and direction from 10 to 200m above ground. The lidar unit can measure 50 data points every second across a full 360-degree scan providing a high sample rate advantageous in complex and fast changing air flows. Equipment of this sort can replace met towers and with several advantages. The company says lidar has demonstrated high-quality measurements across many hundreds of installations in a range of scenarios and environments. Campbell Scientific will partner with Zephir Ltd. to act as an authorized distributor for the ZephIR 300 in North America.

Ian Locker, a manager of the ZephIR business in Natural Power welcomed the announcement: “Campbell Scientific is one of the most recognized brands in the U.S. for quality data-measurement instruments and is a natural fit for ZephIR 300. Together we will meet the clear customer requirements for a high-quality lidar in the U.S. with extensive field engineering support to exceed service expectations”.

Campbell Scientific has designed and manufactured sensors, measurement and control instrumentation, and related communications peripherals for over 35 years, specializing in versatile, programmable, stand-alone systems.

Campbell Scientific Inc.
www.campbellsci.com/zephir-lidar

Windpower Engineering & Development

This nearly 1,200-page resource details the company’s family of capacitive, inductive, weld immune, special application, NAMUR, ultrasonic, and photoelectric sensors.

Pepperl+Fuchs has introduced edition 1.0 of the company’s North American Sensor Catalog and Selection Guide. This nearly 1,200-page resource details the company’s family of capacitive, inductive, weld immune, special application, NAMUR, ultrasonic, and photoelectric sensors. It also details the company’s rotary encoders, cordsets, special function devices, and accessories. Complete product specifications, benefits, and ordering information are included. More than 60 pages of the guide are dedicated to educational resource material.

Pepperl+Fuchs
http://www.pepperl-fuchs.us/usa/en/17733.htm

Windpower Engineering & Development

A hollow-shaft version of the MCD encoder makes it easy to mount these devices on shafts up to 20-mm dia.

The Magnetocode (MCD) absolute rotary encoders feature reliability, accuracy, and adaptability. Now, a new hollow-shaft version of the MCD encoder makes it easy to mount these devices on shafts up to 20-mm dia. The recent devices are available with analog (voltage/current) or digital electrical interfaces. Analog versions are a substitute for traditional potentiometers, offering superior reliability, longevity, and accuracy than units they replace. The measurement technology is based on a rotating magnet and Hall-effect sensors. Unlike traditional potentiometers, there is no contact between these components and no loss of accuracy due to wear or surface contamination. Another advantage is a flexible range-setting feature. With this, the installer can ‘teach’ the device the limits of mechanical motion that will be experienced during operations. Once these limits have been defined – which can involve multiple rotations – the device will self-calibrate so the full range of the electrical output (e.g. 0-5 volts) exactly matches the full range of mechanical movement. This improves the overall accuracy of the control system. Buttons and LEDs on the casing of the analog-output models simplify set-up. MCD encoders are well suited for applications requiring extended multi-turn capabilities (up to 8,192 revolutions). A self-powered rotation-counter (based on Wiegand wire technology) records the number of rotations – even if these occur when there is no power supplied to the sensor.

Digital outputs for MCD encoders include serial (SSI), CANopen and DeviceNet.

MCD encoders are tough. Heavy-duty enclosures protect the measurement components from mechanical loads, shock, and vibration, dust and moisture (up to IP 69K ratings). Hollow-shaft versions have a permanently lubricated steel and brass gear-set for a long, trouble-free service life.

FRABA Inc.
www.fraba.com

Windpower Engineering & Development

Premo Group
www.grupopremo.com

WPE

Windpower Engineering & Development