Joe Prudell

Machines and Drives Comparison for Low-Power Renewable Energy and Oscillating Applications

The objective of this paper is to analyze, test, and compare machines and drives in oscillating applications. In particular, this paper is focused on low-power wave energy generator applications, such as autonomous weather and monitoring buoys with power requirements in the 100 W and less range. Due to the oscillating motion of waves, the ocean environment can require bidirectional and variable speed operation of the generator. In this research, the efficiency of a set of small brushed dc, induction, brushless dc, and synchronous reluctance drives and machines were compared in constant and oscillating operation. The presented results show that drives and machines used in low-power oscillating applications (e.g., ocean wave energy) should not expect a significant derating with respect to their nameplate rating. In addition, it is shown that the frequency of oscillation (e.g., ocean wave frequency) has little impact on efficiency.

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

A novel permanent magnet tubular linear generator for ocean wave energy

This paper presents a novel permanent magnet tubular linear generator (PMTLG) buoy system designed to convert the linear motion of the ocean waves into electrical energy. The design incorporates no working seals and a salt water airgap bearing surface integration between PMTLG buoy components. The internal generator design will be discussed, in addition to the system integration with the buoy structure and the linear test bed performance results.

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

Scaled wave energy device performance evaluation through high resolution wave tank testing

This paper presents the high-precision wave tank testing of Columbia Power Technologies (COLUMBIA POWERs) 1:15 scale wave energy device in Oregon State Universitys (OSUs) large wave flume. Wave energy converter (WEC) testing in the OSU O.H. Hinsdale Wave Research Laboratory (HWRL), in collaboration with the Northwest National Marine Renewable Energy Center (NNMREC) headquartered at OSU, includes state-of-the-art optical motion tracking and data acquisition developed to facilitate the optimization of wave energy devices to efficiently convert the motion of ocean waves into electrical energy. This paper includes the high resolution wave tank testing process, and example performance results.

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

Drives Comparison for Reciprocating and Renewable Energy Applications

The objective of this work is to compare and analyze brushed dc, induction, brushless dc, and synchronous reluctance machines and drives in reciprocating applications. In particular, this work is focused on wave energy generator applications. In contrast to wind energy, the ocean environment can require bidirectional operation of the generator. For this study, the efficiency of a set of small induction, permanent magnet synchronous, brushed dc, and synchronous reluctance drives and machines were compared side-by-side in a reciprocating application against the typical constant operation used to determine steady state efficiency. The presented results suggest that drives and machines used in ocean wave energy should not expect a large de-rating in nameplate machine or drive efficiency compared to the same drive or machine producing the same amount of power constantly. In addition, it is shown that the frequency of reciprocation (e.g., ocean wave frequency) has little impact on efficiency.

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.

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