The developers of the wave technology of the Horizon 2020 VALID project are discussing the progress made so far in designing a hybrid platform for testing ocean energy technologies.
Efficiency, reliability, cost competitiveness, a more streamlined path to commercialization – these are the goals of three European wave energy developers, whose devices form the core of Horizon 2020 VALID project, which is developing a hybrid platform for testing ocean energy technologies.
Hybrid testing is common practice in many industries, especially in the automotive world. It significantly reduces marketing time while enforcing stricter performance and reliability requirements, ultimately creating a better product in less time and less money.
Through VALID (Verified Testing leading to improved wave energy design) and its consortium of European partners, this method is being adapted for wave energy for the first time. In the middle of the project, the initial framework for accelerated testing was created and now the focus is shifting to technology developers.
We spoke with representatives from each user case – CorPower Ocean Technical Project Manager Ross Harden, IDOM Advanced Design and Analysis Team Patxi Etxaniz and Wavepiston A / S Chief Technical Officer Steen Grønkjær Thomsen – to find out their attitude towards the implementation of hybrid testing methods for energy waves.
What is your device?
CorPower: The Wave Energy Converter CPO (WEC) is a point absorber with a rising buoy on the surface, absorbing energy from the ocean waves, which is connected to the seabed by means of a stretched mooring line. New “phase control” technology causes compact devices to oscillate in resonance with incoming waves, greatly enhancing motion and power capture.
IDOM: The device that IDOM is developing, MARMOK, is a buoy that captures wave energy with oscillating water column technology. The buoy is a vertical cylinder open at the bottom so that there is a water column inside. The relative movement of the buoy and the water column creates a variable volume air chamber that is turbocharged to extract electricity.
Wave piston: Wavepiston WEC qualifies as an offshore surface attenuator. The concept is based on capturing the horizontal component of the surge energy using a number of horizontal moving energy collectors attached to a common string located just below the water surface.
What are you testing within VALID?
IDOM: Our experience, both during the three winters at sea with MARMOK-A-5 and in previous tests at Mutriku, has shown us that one of the most critical elements of our technology is the turbogenerator, which is subject to much greater fluctuations. than in conventional applications.
wave piston: The Wavepiston PTO system is based on hydraulic cylinders that send raw seawater under pressure to a ground turbine. The seals of these cylinders are heavily loaded both due to the aggressive environment and due to the fact that the cylinders operate at approximately 60 bar. Understanding and reducing the wear and tear of these seals is the key to Wavepiston’s success.
CorPower: CorPower focuses on dynamic sealing systems. These are critical components in our system and by understanding them better, we can improve not only the reliability and survival of our device, but also its energy efficiency.
How do you apply the hybrid testing methodology?
Wave piston: Our team has created the first version of a numerical model that simulates the movement and pressure variations in hydraulic cylinders. We also designed a physical platform for testing hydraulic cylinders at realistic speeds and pressures. Upon completion, this will be installed with a hydraulic cylinder, which will be moved according to numerical estimates. The platform will send performance data, including pressure, leakage volume and friction, to the hybrid model.
CorPower: We are currently focusing on upgrading and commissioning our custom installation for dynamic sealing testing. With this device, we can test different seal designs through accelerated testing to help establish the life of our sealing systems and better understand the range of failure modes. This test installation is the part for physical testing of the hybrid setup, and our Wave-2-Wire model is the simulated part.
IDOM: Optimizing the size of the generator in order to maximize performance and reliability is one of the critical elements in the design of our device. The methodology of the VALID project will allow us to conduct accelerated tests to better understand the behavior of the generator in these conditions and its degradation.
What are the challenges and successes so far?
CorPower: One of the main challenges is tackling the effects of scaling. In the automotive industry, the components are usually relatively small, so hybrid tests are always performed on full-scale components. In the ocean energy sector, the components are much larger. For example, our ocean rods are approximately 9 m long and 0.35 m in diameter. We are looking for ways to reduce testing, while ensuring that it is representative of full-scale components.
IDOM: Performing these tests under real conditions of a device at sea is extremely complex and expensive. The ability to perform these tests on a test bench, on a scale and in a shorter time, will allow us to get to know the process of decomposition of the generator with a detail unattainable in real conditions.
wave piston: Our main challenges include the lack of computational speed, as true hybrid testing requires a real-time model of the entire system running in the background, and the submission of motion data to the test platform, constantly taking into account the values measured in real time. the test platform. We have completed the Wave-2-Wire model, which means a model in which the actuators are driven by numerical calculations, but we are not yet ready to receive feedback from the experimental setup.
What do you hope to achieve through VALID?
IDOM: The knowledge we will gain from the VALID project will allow us to optimize the use of the generator, making it more efficient and at the same time more reliable.
wave piston: The ultimate goals of this project are an improved Wave-2-Wire model, high-quality test results of our pump set design (useful for both certification and design improvements) and a hybrid test platform that can be further developed for to cover other parts of Wavepiston’s Wave Energy Solution.
CorPower: We want to better understand our dynamic sealing systems, as well as establish the basis of the methodology for hybrid testing of ocean energy devices. Ultimately, the VALID project will contribute to a better understanding of our system, lower operating and maintenance costs, which will further reduce the equalized energy costs we can offer for wave energy.
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