Sensors aid tidal turbine development.

Non-contact torque sensors from Sensor Technology are playing a key role in the development of commercial-scale in-stream tidal turbines produced by OpenHydro. The company is using these novel sensors, which are based on surface acoustic wave (SAW) technology, to accurately measure rotational speed and frictional forces in a simulator for the turbine bearings, thereby allowing it to optimise the performance and reliability of its innovative products.

OpenHydro, headquartered in Dublin (IRL), is a technology company that designs and manufactures marine turbines to generate renewable energy from tidal streams. The company's vision is to deploy farms of tidal turbines under the world's oceans, where they will dependably generate electricity with no cost to the environment. This method of producing electricity has many benefits.

Because the turbines are submerged, they are invisible and they produce no noise. And because they are submerged at a considerable depth, they present no hazard to shipping. An advantage that is possibly the most important, however, is that the tides are completely predictable, which means that the energy output of the turbines is equally predictable. There are no large seasonal variations and no dependence on the vagaries of the weather, as there are with many other renewable energy sources.

Reliably and efficiently harvesting energy from the tides, however, requires the use of novel technology and, in the case of OpenHydro, this takes the form of open-centre turbines that can be deployed directly on the seabed. Clearly, installation in such an inaccessible location makes reliability a prime consideration in the design and construction of the turbines. For this reason, OpenHydro carefully and comprehensively evaluates the performance of all of the components used in its turbines.

For the bearings, this evaluation involves the use of a simulator that allows the company's engineers to determine how frictional forces in the bearings vary with different loads and rotational speeds. Central to the operation of this simulator is the measurement of torque in a shaft from the motor that drives the bearing under test. With conventional sensors, it is hard to carry out this type of torque measurement accurately and reliably, but OpenHydro found that Sensor Technology's TorqSense RWT420 series sensor provided an ideal solution.

Like all TorqSense sensors, the RWT420 units depend for their operation on surface acoustic wave (SAW) transducers. These transducers comprise two thin metal electrodes, in the form of interlocking "fingers", on a piezoelectric substrate such as quartz.

When an RF signal of the correct frequency is applied to the transducer, surface acoustic waves are set up, and the transducer behaves as a resonant circuit.

If the substrate is deformed, however, the resonant frequency changes. When the transducer is attached to a drive shaft, the deformation of the substrate and hence the change in resonant frequency will be related to the torque applied to the shaft. In other words, the transducer operates as a frequency-dependent strain gauge.

Since the transducers operate at radio frequencies, it is easy to couple signals to them wirelessly. Hence TorqSense sensors can be used on rotating shafts, and can provide data continuously without the need for the inherently unreliable and inconvenient brushes and slip rings often found in traditional torque measurement systems.

"We chose the RWT420 because of its convenient wireless operation, and because it was easy for us to fix in line with an existing shaft in our experimental set up," said Kevin Harnett, Mechanical Engineer at OpenHydro. "In addition, this model of sensor has integral electronics and a serial output, which means that we can link it directly to a laptop computer in our test laboratory. This is a very straightforward and convenient arrangement.”

OpenHydro uses the RWT420 sensor in conjunction with Sensor Technology's TorqView software. This offers a choice of dial, digital bar and chart graph format display for torque, RPM, temperature and power. It also provides facilities for realtime plotting and for data recording, and can output stored results as files that are compatible with Matlab and Excel.

"We have found both the sensor and the software very easy to work with, and the sensor has proved itself to be well able to withstand the tough operating conditions in our laboratory. We've also received excellent technical support from Sensor Technology, which was very helpful as we have never previously worked with sensors of this type. Overall, we're very happy with product and the service we've received, and the sensor is providing invaluable data for our development work."

Proof that this development work is yielding dividends was amply provided late in 2009, when OpenHydro deployed the first commercial-scale in-stream tidal turbine in the Bay of Fundy, Canada, on behalf of its customer, Nova Scotia Power.

@sensortech #PAuto #Power @openhydro 

Investment in renewable energy

There have been two releases from ABB on investments in various countries on wind and wave energy resources.

ABB invests in wind technology company

ABB has made a strategic investment in Pentalum Technologies, an Israel-based company developing advanced wind sensing technology for control and optimisation of wind turbines and wind farms.

Pentalum is developing an innovative LIDAR (light detection and ranging) technology that remotely senses the wind vector in front of wind turbines in order to optimally align them to incoming wind flow. Pentalum’s system is also applicable to wind forecasting and site assessment, and is designed to significantly increase wind farm efficiency at a lower cost per site than existing measurement technologies.

The investment was made through ABB Technology Ventures, ABB’s venture capital arm, which invests in early and growth stage companies with technologies of strategic importance to the industry segments the company serves. Other participants in funding for Pentalum included Cedar Fund, which led the round; and Evergreen Venture Partners, both from Israel; and Draper Fischer Jurvetson from the US.

"Cost and complexity issues are hampering the widespread adoption of optimization systems for wind power,” said Girish Nadkarni, head of ABB Technology Ventures. "We have invested in Pentalum because we believe their technical approach will significantly improve profitability for developers and operators of this important renewable energy source.”

“Given ABB’s broad expertise and strong position with wind turbine manufacturers and wind farm developers and operators, they are a very strong partner for Pentalum,” said Sagie Tsadka, President and CEO of Pentalum. “Our wind sensing technology can significantly improve the performance of wind turbines and wind farms, and ABB can be instrumental in helping us deliver this benefit to the marketplace through their extensive customer base.”

ABB provides a wide range of products, integrated solutions and expertise that enable the efficient generation of wind power and its smooth integration into the grid. Customers include turbine manufacturers, engineering contractors, independent power producers and utilities.

ABB invests in renewable energy company
Technology generates clean electricity from nearshore wave energy

ABB has invested about $13 million in Aquamarine Power, a Scottish company that has developed technology to convert energy captured from waves near shore into clean, usable electricity.

ABB Technology Ventures, the company's venture capital arm, made the investment in a funding round that also included a $4.8 million investment from SSE Venture Capital, the venture capital unit of Scottish and Southern Energy and other investors.

The investment gives ABB access to another renewable energy technology, and provides an entry into the emerging marine energy market, where ABB has considerable pull-through sales potential for its power systems, power electronics and medium-voltage drives.

"Wave energy is primed to become an important part of the world's renewable energy portfolio,” said Brice Koch, head of ABB Marketing and Customer Solutions, which oversees the company’s renewable energy initiatives among other activities. "This investment reflects our belief in its technical viability, and our confidence in Aquamarine’s technology and its management team.”

Aquamarine’s Oyster wave power device consists of a hinged mechanical flap connected to the nearshore seabed that pipes high-pressure water to an onshore turbine for power generation. The system is easier to install and maintain than other wave power generation systems, and has won a number of renewable energy innovation awards.

In November 2009, the first full-scale demonstrator Oyster began producing power at the European Marine Energy Center based in the Orkney Islands, Scotland. Once commercialized, Oyster wave power devices could be deployed in farms rated at 100 megawatts or more.

“This strategic investment gives ABB an early-mover advantage in our wave energy technology, while we gain access to ABB’s technical, research and engineering expertise and global supply chain network,” said Aquamarine Power CEO, Martin McAdam.

ABB Technology Ventures invests in strategically interesting early and growth stage companies. To date, investment areas include smart grid communications, cyber security for utilities, data center power optimization and wind farm efficiency.