Editor's Note: This piece was originally featured on HydroWorld.com's sister website, RenewableEnergyWorld.com.
The ocean energy sector has been steadily creeping towards commercial reality year after year, with technology test deployments taking place worldwide. After all, the ocean energy market is not an easy place to do business, just building a technology prototype can cost up to $30 million. This year, however, some major project announcements indicate that the industry could be moving to the next level - much faster than anyone had previously predicted.
"People are interested in [ocean energy] and they are in [the energy] industry," said Greg Leatherman of Environment Coastal & Offshore during the opening session at Energy Ocean International. "You have Lockheed Martin in China building the biggest OTEC [ocean thermal energy conversion] facility. In Scotland, you have the biggest wave project offshore farm [Swansea Bay Tidal Lagoon] in history. You have construction beginning at Cape Wind. All happening right now, this summer."
At the Energy Ocean International Conference 2013 that took place in Providence, R.I., several technologies that made it to the coveted prototype stage were highlighted during the keynote. "These gentleman are here because the technology is more viable," said Leatherman.
Small Turbine, Big Potential
The tidal team at Schottel is on a mission to produce a turbine that uses the least amount of material with an ideal ratio of power. To achieve this goal, Schottel invested in a UK-based company called TidalStream to have the most energy produced in one installation, according to Martin Baldus, product manager of renewable energy at Schottel Tidal.
"A lot of devices have 1 megawatt (MW) of installed power. We were wondering if this was the right direction to go into," said Baldus. "Is the scale of the turbine itself important, or should we focus on more installed turbines with less mass and less cost per turbine?"
According to Baldus, if a turbine is scaled down to somewhere in the range of 50 kilowatts (kW), which is about four meters in diameter, and 20 are lined up in one installation, then there would be about 16 tons of material used per MW. Other turbine systems typically use about 100 tons. "Our approach is to simplify as much as possible," he explained.
Schottel has put the technology through a long series of testing that started with a basic turbine design in its factory. Engineers developed back-to-back configurations with simulated tidal waves where they could test all main components such as bearings, motors, etc. The team then moved on to a full-scale sea trial, where a series of turbines were mounted on a tugboat that could raise the structure in and out of the water.The turbines can be arranged according to different site resources, said Baldus, such as jetty installations in a river or channel and up to different installations offshore - a series of turbines can be merged on floating platforms connected to seabed. According to Baldus, the turbines are easy to maintain because the platform allows for swift access to them, even when in operating position. Each turbine has a separate control system, which is collected and then taken from the inverter to be fed into the grid.
The technology will now move to the UK, where Marine Energy will deploy two turbines later this year. "This will achieve more working hours for the turbine, and will be our next step to move forward with the technology," said Baldus.
Strange Shape, Practical Design
In Norway, a company that had focused on building composite materials for the fossil fuel industry came to realize that it needed to switch gears. "A few years ago, we decided we have to do something after oil when it is not around, and we'd also like to do something for the environment," said John Inge Brattekas, CTO of Flumill. "So how can we use our technology in the renewable environment?"
Brattekas and partners went on to develop Flumill, twin helical devices that use a design based on flow valves in gas distribution systems from the company's fossil fuel expertise. The device is made of glass-reinforced plastic, making it buoyant. Two 30- to 40-meter turbines are mounted to the seabed and turn in opposite directions, which stabilizes the entire system. As the current moves through the system, it turns the screws, which turn a gearless permanent magnet generator.
Because it is small in diameter, the entire system moves very slowly at about 5-10 rotations per minute (rpm), "which is good for the marine environment," said Brattekas. This also allows for many devices to be placed fairly closely, without sacrificing energy output.
Flumill deployed its 600-kW device at the European Marine Energy Centre (EMEC) test site off the coast of Eday, an Orkney Island off of Scotland. After several months of successful testing, Flumill is ready to scale up its technology. In late 2012, Flumill was awarded NOK 57.5 million (US $9.8 million) to partially fund a full-scale testing project on Rystraumen, Norway. According to a release, this will be the next step towards a fully commercial tidal park, which is to be installed in the UK in 2014 or 2015.
Paddling the Waves
Based in Boston, Mass. Resolute Marine Energy (RME) has developed a technology, called SurgeWEC, which can not only create energy from waves, but also transport seawater to a desalination plant. The 2- to 3-meter device itself is like a paddle with a buoyancy tube that is mounted to the seabed. It moves back in forth with the waves, which creates energy or can pressurize seawater, and then electricity and/or seawater moves to shore. Since the system is deployed close to shore, it can also lower energy transmission costs.
The technology has been tested at a simulation center and in the ocean where it scored 30 percent efficiencies and Resolute Marine Energy is now ready to deploy a 750-kW commercial-scale project at a Yakutat, Alaska site. It received permitting earlier this year.
"With this FERC approval we can begin the studies and the planning that are necessary to design the project and to prepare the needed application for a FERC license to operate," said RME Senior Engineer and project manager Clifford Goudey. "We need to characterize the wave resource in detail and engineer a system that will provide the most benefit to the community by alleviating its current dependence upon its diesel-powered generating plant."
These are just three technologies currently approaching commercialization, and industry advocates are excited about the possibilities. "These companies are putting in the time to make the technical investment to commercial application in the near term, no longer talking about decades down the road," said Leatherman.
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