Al Schacher

Numerical Modeling and Ocean Testing of a Direct-Drive Wave Energy Device Utilizing a Permanent Magnet Linear Generator for Power Take-Off

For the past several years an inter-disciplinary research group at Oregon State University (OSU), working in conjunction with Columbia Power Technologies (CPT) has been researching innovative direct-drive wave energy systems. These systems simplify the conversion of wave energy into electricity by eliminating intermediate energy conversion processes. In support of this research OSU and CPT have developed a hybrid numerical/physical modeling approach utilizing a large scale linear test bed (LTB), and a commercial coupled analysis tool. This paper will present an overview of this modeling approach and its application to the design of a 10kW prototype wave energy conversion system that was tested in the open ocean in the fall of 2008. The data gathered during ocean testing was used to calibrate the numerical model of the device and predict the energy capture potential of the system.Copyright

Numerical and Experimental Analysis of a Novel Wave Energy Converter

A novel point absorber wave energy converter (WEC) is being developed by Columbia Power Technologies, LLC (CPT). Numerical and physical experiments have been performed by Columbia Power, Garrad Hassan and Partners (GH) and Oregon State University (OSU). Three hydrodynamic modeling tools including WAMIT, GH WaveFarmer, and OrcaFlex are used to evaluate the performance of the WEC. GH WaveFarmer is a specialized numerical code being developed specifically for the wave energy industry. Performance and mooring estimates at full scale were initially evaluated and optimized, which were then followed by the development of a 1/33rd scale physical model to obtain comparable datasets, aiming to validate the predictions and reduce the uncertainty associated with other numerical model results. The tests of the 1/33rd scale model of the CPT WEC were recently carried out at the multi-directional wave basin of the O.H. Hinsdale Wave Research Laboratory (HWRL), in conjunction with the Northwest National Marine Renewable Energy Center (NNMREC) at OSU. This paper presents details of the modeling program and progress to date. Emphasis is given to the coupling of WAMIT with GH WaveFarmer for performance estimates and the coupling of WAMIT with the OrcaFlex model for mooring load estimates. An overview of the novel 3-body WEC, including operation and mooring system, is also presented. The 1/33rd scale model functionality is described including an overview of the experimental setup at the basin. Comparisons between the numerical and experimental results are shown for both regular and irregular waves and for several wave headings and dominant directions using a number of spreading functions. The paper concludes with an overview of the next steps for the modeling program and future experimental test plans.Copyright

High Resolution Wave Tank Testing of Scaled Wave Energy Devices

In many industries, such as the wave energy industry, the importance of accurate physical model testing in the development process to full scale devices cannot be overemphasized. This paper presents a new, high-precision wave tank testing system and process designed and implemented by Columbia Power Technologies (CPT) and Oregon State University (OSU). The system’s high level of functionality was demonstrated during characterization of CPT’s wave energy converter (WEC) and is now established at OSU’s O.H. Hinsdale Wave Research Laboratory (HWRL), in collaboration with the Northwest National Marine Renewable Energy Center (NNMREC) headquartered at OSU. The critical instrumentation, optical motion tracking system, data acquisition and related components developed for wave tank testing are fully characterized herein, and the paper concludes with example testing of a scaled wave energy device including experimental results.Copyright

Development of a Novel 1:7 Scale Wave Energy Converter

This paper presents a novel 1:7 scale point absorber wave energy converter (WEC), developed by Columbia Power Technologies (COLUMBIA POWER). Four hydrodynamic modeling tools were employed in the scaled development and the optimization process of the WEC, including WAMIT, Garrad Hassan’s GH WaveFarmer, OrcaFlex and ANSYS AQWA. The numerical analysis development is discussed, and the performance and mooring estimates at 1:7 scale and full scale are evaluated and optimized. The paper includes the development of the 1:7 scale physical model and the associated WEC field testing in Puget Sound, WA.Copyright

Numerical Analysis and Scaled High Resolution Tank Testing of a Novel Wave Energy Converter

This paper presents a novel point absorber wave energy converter (WEC), developed by Columbia Power Technologies (COLUMBIA POWER), in addition to the related numerical analysis and scaled wave tank testing. Three hydrodynamic modeling tools are employed to evaluate the performance of the WEC, including WAMIT, GL Garrad Hassans GH WaveDyn, and OrcaFlex. GH WaveDyn is a specialized numerical code being developed specifically for the wave energy industry. Performance and mooring estimates at full scale are evaluated and optimized, followed by the development of a 1:33 scale physical model. The physical tests of the 1:33 scale model WEC were conducted at the multidirectional wave basin of Oregon State Universitys O.H. Hinsdale Wave Research Laboratory, in conjunction with the Northwest National Marine Renewable Energy Center (NNMREC). This paper concludes with an overview of the next steps for the modeling program and future experimental test plans.

WEC prototype advancement with consideration of a real-time damage accumulation algorithm

Machine maintenance and repair is not a trivial issue when it comes to renewable energy devices. It has been said that one of the most important factors in enhancing the marketability of wind energy is to cut its overall maintenance costs, which is about 10% – 20% of the overall cost of energy [1]. The average maintenance and repair costs of ocean wave energy devices are yet to be determined, but it may be higher than wind energy. The harsh ocean environment, repeated cycling of the drive train, coastal storms, environmental concerns, loss of revenue due to long periods of machine downtime, safety issues concerning technicians working on the buoy while its still in operation, and so forth, all add to the maintenance and repair costs of a WEC (Wave Energy Converter). This study proposes a unique damage accumulation prediction algorithm that enables real-time determination of bearing fatigue life.

Numerical and Experimental Modeling of Direct-Drive Wave Energy Extraction Devices

The solutions to today’s energy challenges need to be explored through alternative, renewable and clean energy sources to enable a diverse national energy resource plan. An extremely abundant and promising source of energy exists in the world’s oceans in the forms of wave, tidal, marine current, thermal (temperature gradient) and salinity. Among these forms, significant opportunities and benefits have been identified in the area of wave energy extraction. Waves have several advantages over other forms of renewable energy such as wind and solar, in that the waves are more available (seasonal, but more constant) and more predictable, thus enabling more straightforward and reliable integration into the electric utility grid. Wave energy also offers higher energy densities, enabling devices to extract more power from a smaller volume at consequent lower costs. However, many engineering challenges need to be overcome to ensure wave energy device survivability, reliability and maintainability, in addition to efficient and high quality power take-off systems. Optimizing wave energy technologies requires a multi-disciplinary team from areas such as Electrical, Chemical, Ocean, Civil and Mechanical Engineering, to enable innovative systems-level research and development. This paper presents some recent research developments on experimental and numerical modeling on direct-drive approaches and the associated devices designed to convert the motion of the ocean waves into electrical energy using point absorber wave energy converters. This research is focused on a simplification of processes, i.e., replacing systems using intermediate hydraulics or pneumatics with direct-drive approaches to allow generators to respond directly to the movement of the ocean by employing magnetic fields for contact-less mechanical energy transmission, and power electronics for efficient electrical energy extraction. The term “direct” drive describes the direct coupling of the buoy’s velocity and force to the generator without the use of hydraulic fluid or air. The wave energy buoy and spar are designed to efficiently capture ocean wave energy and transfer it to the generator. These buoys have been tested at the Oregon State University O.H. Hinsdale Wave Research Laboratory, with planned testing off the coast of Oregon. The paper will examine several direct-drive approaches, including electrical and mechanical design characteristics, describe the numerical modeling of the associated conceptual devices, prototype testing, and some ongoing research on the dynamics of buoy generator systems for design optimization.Copyright

Adaptive damping power take-off control for a three-body wave energy converter

The performance of the power take-off (PTO) system for a wave energy converter (WEC) depends largely on its control algorithm. This paper presents an adaptive damping control algorithm which improves power capture across a range of sea states. The comparison between this control algorithm and other active control approaches such as linear damping is presented. Short term wave elevation forecasting methods and wave period determination methods are also discussed as pre-requirements for this method. This research is conducted for a novel WEC, developed by Columbia Power Technologies (COLUMBIA POWER). All hydrodynamic models are validated with their 1:7 and 1:33 scale tests.

A programmable mooring controller for tank testing of scaled wave energy converters

Ocean wave energy can be a promising contributor to the renewable generation portfolio for coastal communities. Developing economically feasible wave energy converters requires thorough testing of the scaled version of these devices in test tanks. One of the challenges of scaled testing is to accurately represent and model all physical characteristics of the full scale converter. This paper presents the design, construction, and performance of a small-scale active mooring system that can be programmed to accurately emulate common mooring configurations for wave energy converters. This allows for a flexible, accurate, and cost effective system to test mooring designs and their effects on overall performance and behavior of the wave energy converters in small-scale testing. With this system mooring characteristics can be changed on the fly without the need for any hardware changes. This allows quick validation of various mooring designs without increased cost in equipment and tank time.