In October Wavepiston started accelerated tests at the testing facility at DTU, the Technical University of Denmark. These tests are a part of the Horizon-2020 VALID project, which aims to develop hybrid testing platform for ocean energy technology in cooperation with other wave energy developers.
VALID will develop one open and integrated platform for testing of critical components and subsystems, including novel test procedures beyond current testing practices based on hybrid testing methods, combining virtual and physical tests rigs. The accelerated test means that we can speed up the number of iterations of the system and shorten the necessary testing time prior to an offshore installation which reduces the risk of failure.
What are we testing?
The Wavepiston PTO system is based on hydraulic pumps sending raw, pressurized seawater to a land-based turbine. The seals of these pumps are highly loaded due to both the aggressive environment and the fact that the rams operate at approximately 60 bars. Understanding and reducing wear on these seals is key to Wavepiston's success.
Our team has created the first version of a numerical model that simulates the movement and pressure variations in the hydraulic pumps. We have also designed a physical platform for testing hydraulic pumps at realistic speeds and pressures.
The platform will feed performance data into the numerical model, including pressure, leak volume and friction. It will significantly shorten time-to-market while also applying more rigorous demands on performance and reliability, ultimately creating a better product in less time and for less money.
What has been the biggest lesson so far?
"Actually, I am very positively surprised how smoothly the system runs," points out Martin von Bülow, Chief Specialist at Wavepiston. "When starting such a new venture, you never fully know what to expect. So far, we haven’t had any major issues, which tells us that we designed the system in the right way.
"Of course, it is a constant development and learning process," adds Troels V. Lukassen, Development Engineer at Wavepiston. "We are trying to use this time as best as possible to understand the challenges of the system, its limits and parameters for the most effective operations. We are adjusting minor aspects of the device and constantly improving the installation."
One of the experiments tests the percentage of leakage that can happen over time and with different parameters. The Wavepiston device don’t use oil on the seals. For that reason, any leakage will simply mean saltwater getting into saltwater.
"The test that we are running is crucial for developing the Wavepiston’s technology," says Martin von Bülow. "There are so many variables to the installation. If we observe and test them in a controlled environment, we will be much better prepared for putting our installation in the ocean with more unpredictable factors. During the test period, we will evaluate all elements of the device and find out when and under which conditions it work the best. It will make our technology much more effective and easier to operate in the future.
The video showing the device during the test is available on Wavepiston's YouTube channel.
VALID (Verification through Accelerated Testing Leading to Improved Wave Energy Design) aims to create a hybrid testing facility that encompasses several wave energy technologies as test cases, with the final goal of delivering a novel test rig configuration methodology for accelerating wave energy technological development.