UK's long-term bet: tidal technology
August 12, 2015 | By
Jaclyn Brandt
Tidal power is still very much a mystery to many, but the UK is betting on the technology as an endless source of industry -- as long as they can get it going.
The high costs of production for tidal energy have been a hindrance -- but researchers at the University of Oxford think they have found a solution. The researchers have been working on a project -- the Transverse Horizontal Axis Water Turbine (THAWT) -- that has the capacity to work underwater in shallow water -- compared to conventional turbines that are so large they must be used in water deeper than 30 meters. "Experimental tests of scale models have shown that the device is capable of producing power with an efficiency significantly greater than the Lanchester-Betz limit," the researchers explained. "This is because the device can be scaled across a channel and utilize blockage effects to extract a greater amount of energy from the flow than a more conventional horizontal axis device." The researchers developed a truss design that uses turbine blades as structural members to allow the device to be stretched laterally across a tidal channel. "Structural analyses of the device, performed using Finite Element Analysis software, has shown that the truss configuration reduces the stresses significantly in a multi-bay rotor so that very long devices are feasible," the researchers said. "The simple design and scalability of the device mean that fewer foundations, bearings seals and generators would be required for a given area of energy capture when compared to a more conventional horizontal axis turbine." Research on Tidal Basin Hydrodynamics, Turbine Local Hydrodynamics, and device structural analysis has allowed the researchers to predict and optimize results. But the research isn't staying at the university level -- it is also being used to bring a 30-megawatt (MW) tidal energy fence online by Kepler Energy. The new installation will cost around £143m and be located in Bristol Channel. "Given its tidal flows and proximity to electrical infrastructure, Kepler considers the Bristol Channel to be an ideal location for its first scheme," Kepler Energy said in a statement. "The first phase of the tidal fence scheme will be up to a 1 kilometre long. Kepler believes that its tidal fences in the future could be 10km or longer." The technology used in the fence allows it to generate renewable more reliably, and in lower velocity and more shallow waters. The truss design allows for a minimum of moving parts, with the electrical equipment and controls housed in dry columns. The design is economical because the rotor installation does not require any high cost vessels, and has a wider range for weather conditions. "As our tidal technology can operate in lower velocity tidal waters, there is greater scope for its deployment in the UK and overseas. It means that we can achieve greater economies of scale as our projects are deployed," said Peter Dixon, Chairman of Kepler Energy, in a statement. "We can happily co-exist with tidal lagoons, and the power peaks will occur at different stages of the tide, meaning that the combined output into the Grid will be more easily manageable. In addition, our levelised costs of production will be in the range £100 to £130 per megawatt-hour (MWh) for utility scale production, so costs will be cheaper than lagoons and in time we will be cheaper than offshore wind generation. Furthermore, investment risk is manageable since turbines are added incrementally to form the fence, with each one generating revenue as it is added." The new fence is expected to be in operation by 2020 or 2021. For more:
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