August 2021

52 n RENEWABLE ENERGY July/August 2021 www.drivesncontrols.com A sea change in wave energy harvesting A round the world, there are many projects underway designed to harness the massive amounts of energy contained in ocean waves to generate megawatt-scale power outputs. But a US company called Columbia Power Technologies is carving out a more specialised niche by focusing on wavepower technologies that can produce kilowatt-scale outputs to power remote items such as offshore data communications networks, underwater vehicles, subsea equipment and sensors used to collect environmental data. Founded in 2005, Oregon-based C-Power initially got into this area of technology through a project for the US Government’s Defense Advanced Research Projects Agency (Darpa) called Wave Energy Buoy Systems (Webs). Through this project, C- Power discovered an potentially lucrative opportunity to develop localised power generation for smaller loads that were previously powered using expensive, cumbersome, non-rechargeable onboard batteries or subsea electric tethers fed from a ship or diesel generator. C-Power developed an AOPS (autonomous offshore power systems) platform that captures wave energy and converts it into usable power for a wide range of applications including offshore oil and gas exploration and production, carbon sequestration, oceanographic research, aquaculture and defence. The latest AOPS platform, known as the SeaRay, is designed to generate 10W to 1MW from ocean waves with a high power- to-weight ratio. It has been developed under a $3.2m r&d programme sponsored by the US Department of Energy (DoE). The device has a small footprint which enhances mobility and commercial viability, making it easy to deliver and set up, and potentially saving tens of thousands of dollars in daily operating costs. The SeaRay’s design makes autonomous, remote data communications possible by transmitting what happens in the ocean to the cloud in real time. Previously, marine data-gathering systems have been limited in the breadth and frequency of data collection. Using cellular networks and satellite communications to pass data in real time between the cloud and the wavepower device, allows more data to be collected and delivered more often. Hawaii trials The SeaRay is currently undergoing sea trials in partnership with the DoE and the US Navy, to test and validate its technical and economic capabilities. The trials are taking place at the Navy’s Wave Energy Testing Site on the island of Oahu, Hawaii. The test rig consists of a surface wave energy converter, a cable that combines mooring, data communications and power transmission functions, and a seafloor base with 100kWh of energy storage for operating payloads. The SeaRay will support several different payloads during the trial. A challenge when designing the SeaRay was to match the complex energy properties of the ocean waves with demanding power conversion requirements. This included a wide 30:1 input range, reflecting the unpredictable nature of the waves. The system had to be capable of converting power and charging energy storage devices with high efficiency. It also needed to accept external control signals to match the precise power conversion needs in real time. “The ability to convert a very nasty power profile into a cost-effective, practical solution, and then condition that power and turn it into usable energy for a wide range of mobile and static payloads, is really on the leading edge,” says C-Power CEO, Reenst Lesemann. “There’s nobody else that’s been able to do that yet.” “We really needed wide-range DC-DC – something that we could control and regulate as we’re converting pulsed ocean wave power into a semi-stable DC bus,” While other developers pursue megawatt-scale wavepower systems, one US company is focusing on kilowatt-scale devices to power remote offshore loads and communications networks. To do this cost-effectively, it needed an efficient power conversion technology. C-Power’s SeaRay wave energy device is designed to power small remote loads in the kilowatt power range