VATIS Update Non-conventional Energy . Oct-Dec 2015

Revision as of 05:14, 9 February 2016 by Kalpana Shibu (Talk | contribs)



New tidal energy system

Harnessing tidal power around the UK’s coast has so far been limited by the cost of the large dams and barrages required and unpredictable results. Now, Kepler Energy, the United Kingdom, in conjunction with researchers at Oxford University, the United Kingdomm has devised a way to overcome this obstacle by creating a new type of horizontal axis turbine that can be used underwater at depths of up to 30 meters, at an economical cost. Conventional propeller-type turbines are like underwater wind turbines and the number of suitable sites for them are vastly reduced by the size of their large blades, limiting their use to waters at least 30 meters deep.

The THAWT (Transverse Horizontal Axis Water Turbine) technology, by contrast, is designed for deployment in shallower, lower velocity, tidal waters. Put simply, as the water flows past the fence a head of water is produced that increases the turbine’s efficiency. The phenomenon is called a ‘blockage’ of the turbines and gets larger in proportion to the length of the fence. “The original Darrieus turbine has blades that are parallel to the axis of rotation, and that means that the loads in the blades are carried entirely by bending of the blades. That results in very high stresses. The re-design that we’ve done changes the blades so that they form this triangulated structure, and that’s a very stiff and very strong structural form,” said Guy Houlsby at Oxford.

The design has minimal moving parts in the water, while its generator and other electrical equipment are installed in dry columns, increasing their reliability, efficiency, and shelf life. The generating units consist of two sets of blades sitting on three columns with a single generator in between. The THAWT has a series of other advantages. It’s hardy, with each rotor having a 25 year design life and the columns and electricity connectors 100 years. It could also have positive knock-on effects for Britain’s carbon fiber manufacturing industry. THAWT’s electrical output would be equal to that of a nuclear power station, without any of the risk, and because the blades move at a relatively slow speed there is no danger to fish swimming through the fence.

Tidal turbine technology certified

Certification body DNV GL, Norway, has issued a ‘statement of feasibility’ for France based Alstom’s Oceade 18 tidal turbine. Alstom has received orders to deliver four of the turbines, each with a power generation capacity of 1.4MW, at one of the world’s first tidal stream arrays in France. The firm used DNV-OSS-312 for the certification process, which involves an initial full risk assessment of the turbine, assenting to actions aiming for risk mitigation in case of failure.

DNV GL will co-ordinate with the turbine manufacturer to carry out a review and approval of the turbine design documents before proceeding with the fabrication stage. This will include evaluation of the manufacturing quality and equipment testing, as well as surveillance of the installation and commissioning of the model. Final Prototype Certification of the turbine will be issued after successful completion of the actions agreed upon in the statement of seasibility stage.

“Issuing the DNV GL statement of feasibility is an important step demonstrating that Alstom is taking a responsible approach to managing risk and putting in place the foundation for a successful project,” said Claudio Bittencourt, at DNV GL. Last year, Alstom, along with GDF SUEZ, was selected by France to supply equipment for a tidal energy pilot farm at Raz Blanchard. Expected to be operational in 2017, the sea-based project is designed to generate 5.6MW of wave energy, which is enough to meet the needs of 5,000 people.

Tidal generator on storm barrier

Tocardo Tidal Turbines, the Netherlands, has installed first 1 MW tidal array in the world on the Oosterschelde storm barrier, part of the famous Dutch Delta Works. This Delta storm barrier has been designed to prevent flooding of the low lying land in the event of a North Sea storm surge and it is normally left open until higher tides than normal are forecast. This allows the tide to flow freely in and out and the tidal generators make use of this flow and the fixed barrier to generate electricity. This new installation is the largest tidal energy project in the Netherlands as well as being the world’s largest commercial tidal installation of five turbines in an array.

Tocardo has spent 6 years developing tidal current generators and this installation represents the first full working installation of their latest developments. The Tocardo turbines come in a variety of sizes to match the operating requirements. Those installed on the storm barrier are each rated at around 200 kW and use a direct drive from the propeller to the permanent magnet generator. The twin bladed propeller is shaped to a patented design that allows it to operate efficiently in the flow from either direction and is made from composites. The blade length is varied according to the expected rate of current flow.

By installing five turbines, this pioneering installation will generate around 1.2 MW and Tocardo claims that it is simpler and easier to install five smaller turbines that one larger one of the same total capacity. The foundation system of the storm barrier was specially designed for this project in such a way that the storm barrier constantly remains fully operational. This initial installation only uses one arch of the extensive barrier leaving scope for more similar installations along its length. Special care was given to the environmental challenges around this operation as the Oosterschelde is a protected area and monitoring will therefore be an important part of the project.

Wave energy device installed in UK

Wave energy developer Polygen, the United Kingdom, has deployed a full-scale device at Cornwall. Volta is a 46-metre long, sub-100kW oscillating surge converter made using high density polyethylene. Polygen is a spin-off of Chesterfield-based polyethylene pipe and fittings manufacturer Fusion, where the device’s components have been made. Polygen is not generating electricity but testing the pressure and flow rates in the hydraulic circuits. It is considering generating power at a later stage.

“The occasional extreme wave conditions makes FabTest an ideal site for us to prove the strengths of our flexible design, whilst the frequent periods of very calm conditions allow us regular access to the device for monitoring and engineering works. We are now busy studying the already encouraging performance data and really looking forward to some winter storms coming through,” said Rob Eavis, at Polygen Volta’s mooring system has been designed by Mojo Maritime, the United Kingdom.

“We are very pleased to work on this exciting project. Volta is exactly the type of project for which FabTest was intended. It is a low cost development of wave energy technology ahead of more demanding deployment at commercial scale sites,” said Richard Argall, at Mojo Maritime. The wave energy device is the first deployed at FabTest since Fred Olsen shipped its Bolt Lifesaver wave energy converter to Hawaii in January.

PowerBuoy deployed in the United States

Ocean Power Technologies, Inc. (OPT), the United States, has announced that it successfully deployed its APB350 A1 PowerBuoy approximately 14 miles northeast of New Jersey. The APB350 A1 contains an improved Power Takeoff (PTO) system compared to the APB350 that was deployed in 2011 in connection with the U.S. Navy’s Littoral Expeditionary Autonomous PowerBuoy (“LEAP”) Program and then redeployed in 2013 in conjunction with the U.S. Department of Homeland Security.

“We believe that the APB350 represents a very appealing value proposition to provide persistent and renewable, offshore power in key markets including ocean observing, defense and security, oil and gas and offshore wind. The APB350 is designed to provide a robust and cost effective alternative to incumbent solutions that utilize battery, solar and diesel power. We continue to have interest from potential customers in the APB350, and we look forward to sharing our A1 performance data with them,” said George H. Kirby, at OPT.

The APB350 A1 features an advanced PTO design with a focus on reliability, manufacturability, cost and efficiency improvement. It utilizes OPT’s prior generation modular energy storage system (ESS) capable of supplying uninterrupted power to its payloads for up to seven days in calm sea states. Real-time performance and weather data will be collected and transmitted to OPT’s monitoring and analysis center at its corporate headquarters in Pennington, NJ.


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