Background

The Laboratory Upgrade Point Absorber (LUPA) is designed to provide the broader wave energy community with an open-source WEC that is well validated, modular, and accessible for experimental and numerical testing. Experimental testing of wave energy converters is an important step to validate and calibrate numerical models, but it is time and resource intensive. The LUPA device was designed to reduce these barriers and help accelerate innovation in wave energy technology. The LUPA acts as a platform for experimental validation of hydrodynamic models, control systems, power take off designs, and hull and heave plate geometries. This introduction details the motivation, engineering design, testing, results, and future work of the Lab Upgrade Point Absorber.

The Laboratory Upgrade Point Absorber (LUPA) is a two-body point absorber wave energy converter (WEC) specifically designed to be a research platform for fundamental and applied work on hydrodynamics, controls, system integration and optimization. The LUPA provides an extremely valuable upgrade to the current open-source WECs as it was designed with an active and controllable power-take-off (PTO) and generator. It is truly an open-source device, meaning all the data, designs, models, and materials will be available to the public. The time, capital, and knowledge needed to build a tank-scaled WEC is an often-cited barrier to advancing the wave energy industry; the LUPA reduces these barriers by providing a validated, ready-to-use WEC for researchers, industry and technology developers. LUPA was designed for deployment in the Large Wave Flume at the O.H. Hinsdale Wave Research Laboratory at Oregon State University. It is a model scale based off of the water depths at PacWave North and South test sites located off the coast of Newport, Oregon, USA. Based on Froude scaling, the scale factors for North and South sites are 20 and 25, respectively.

The concept for LUPA was developed in 2020 with the goal of creating a WEC with an active PTO. Initial designs and iterations occurred throughout 2021. Several webinars and design meetings were held in 2021 to solicit feedback from experts in the industry, national labs and federal experts to improve the design and add features recommended by future users. Numerical modeling was completed throughout 2021-2022 to inform the initial design and provide predictions of WEC movement and power produced. Dry tests on the PTO were conducted in spring 2022 to physically test the generator and sensors, and improve the user interface for the active control. The construction of LUPA was completed in the summer of 2022 and experimental testing began in September 2022 and ended in January 2023.

LUPA Engineering Design

One major goal for this infrastructure upgrade was to design and build a tank scale wave energy converter with an active power take off system. Additional goals include: • Develop an open-source WEC with a high level of accessibility for future users. • Design modular systems for future users including: three PTO configurations, easy modification of heave plate and hull geometries, modification of mooring lines, space for additional sensors, and user defined fields in the control interface. • Transform the WEC into three fundamentally different WEC concepts by changing the number of bodies and degrees of freedom. • Maintain a high level of documentation in the design process and testing procedures to share lessons learnt.

The LUPA is a two-body point absorber wave energy converter with a buoyancy driven float and a spar that acts as a reactionary body. The SolidWorks design rendering and physical device are shown in Figure 1 with labels noting the major components. The motor/generator is mounted on the float along with the sensors and power electronics. The sensors onboard LUPA and deployed in the tank are shown in Table 2.