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Torrey, David

Publications and source records attributed to Torrey, David.

5 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

A Hydrokinetic Energy Conversion System using Underwater LLC-type Resonant Converter

The hydrokinetic energy of river and ocean currents is a valuable renewable energy resource. Conventional systems for harvesting hydrokinetic energy usually have bulky passive components, lengthy cables connecting the underwater turbine/generator with onshore power converters, and limited control over power generation. This paper presents a new hydrokinetic energy harvesting system using an LLC-type resonant converter that is placed underwater in close proximity to the generator. By using SiC devices and the soft switching characteristic of LLC resonant converter, the converter operates in 10s of kHz, significantly reducing the passive components. In addition, the LLC converter provides flexible power regulation of the system. Furthermore, the underwater placement of the power converter takes advantage of the cooling provided by the water and simplifies the system by reducing its connecting cable length.

Dai, Hang↗
DOE OSTI2023

XCT System for Harvesting In-Current Hydrokinetic Energy from Low-Velocity Sites

The Project demonstrated the functionality of a cross cutting (XCT) type turbine in laboratory and open water testing. The fundamental design approach of locating small axial rotors near the ends of driving spars, which pull the rotors through the water at a multiple of the free-stream velocity eliminates the need (and thus the cost) for a gearbox and torque resisting structures. This configuration, however, introduces the complexity of transmitting electricity across a rotating interface. Even so, cost models indicate that depending on the anchoring and mooring system, LCOE less than $0.10/kWh should be possible in high capacity-factor sites with non-reversing currents.

13 HYDRO ENERGY↗
DOE OSTI2023

A Comparison of Generator Technologies for Offshore Wind Turbines

Leading wind turbine manufacturers are racing to build larger and more powerful offshore machines. Drivetrain configurations often use a permanent-magnet synchronous generator (PMSG), in either a direct-drive configuration or coupled to a gearbox. With increasing demand for critical rare-earth magnets, new generator technologies are emerging to ensure a stable and secure supply chain. We evaluate three different topologies of radial flux synchronous generators employing high field magnets with reduced or no rare-earth content: a direct-drive interior PMSG (DD-IPMSG), a geared drivetrain combining a medium speed gearbox with a PMSG (MS-PMSG), and a direct-drive low-temperature superconducting generator (DD-LTSG). We develop a conceptual design module for each of these technologies within a larger framework for full turbine design. This provides the fairest comparison between technologies at nominal power ratings from 15-25MW, which represent the next generation of offshore wind turbines. The analyses show that if operational expenditures (OpEx) are constant across the technologies, MS-PMSG results in the lowest LCOE with reductions of up to 7% relative to DD-IPMSG. DD-LTSG also yields lower LCOE values by 2-3% for fixed-bottom turbines and 3-5% with a floating platform. However, results are sensitive to OpEx assumptions, with a mere 10% increase causing the conclusions to shift.

direct drive↗
DOE OSTI2023

Armature segment, armature and methods for assembling them

The present disclosure relates to armature segments for an armature for an electrical machine. An armature segment may comprise a plurality of coils and an electrically insulating supporting structure providing structural support to the plurality of coils. An armature may comprise a plurality of armature segments. The present disclosure further relates to methods for assembling such armature segments and armature.

Cross, Andrew Thomas↗