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James Joslin

Mechanical Engineer






James Joslin joined the ocean engineering team at APL-UW in the summer of 2015 after four years in the UW Mechanical Engineering Department. His research interests include marine renewable energy, instrumentation for environmental monitoring, underwater vehicles, robotics, and hydrodynamics. James supports a wide variety of marine projects from system design and fabrication to the management of field deployments and testing.

In addition to his research, James is actively pursuing the commercialization of technologies developed at APL-UW through a University of Washington spinoff.

Department Affiliation

Ocean Engineering


B.S. Mechanical Engineering, Dartmouth College, 2005

M.S. Mechanical Engineering, Dartmouth College, 2007

Ph.D. Mechanical Engineering, University of Washington, 2015


Persistent Environmental Monitoring Near an Operational Wave Energy Converter

In the first demonstration of the technology, the WEC supplied all the power needed by the multi-sensor Adapatable Monitoring Package.

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15 Jul 2019

For over 6 months, ocean environment observations were captured by the sensor package powered only by the ocean waves at the U.S. Navy Wave Energy Test Site off Oahu, HI.

Here, offshore Hawaii, the Navy is interested to understand the risk of interactions between wave energy conversion devices and marine animals, especially humpback whales. During its deployment the acoustic, sonar, photo, and video sensors detected, characterized, and recorded marine animals (no whales) relying only on the wave power captured by and converted to electricity by the Fred. Olsen BOLT Lifesaver buoy.

Wave Energy Buoy that Self-deployes (WEBS)

The Wave Energy Buoy that Self-deploys (WEBS) converts surface wave energy to mechanical and electrical power. WEBS is an easily deployed power station that can operate anywhere in the off-shore environment. Potential applications include power sensor payloads for scientific instrumentation; power station for autonomous systems, undersea vehicles, and/or surface vessels; and communications relay.

Research collaborators are the Monterey Bay Aquarium Research Institute and Columbia Power Technologies.

13 Dec 2016


2000-present and while at APL-UW

Adaptable and distributed sensing in coastal waters: Design and performance of the μFloat system

Harrison, T.W., C. Crisp, J. Noe, J.B. Joslin, C. Riel, M. Dunbabin, J. Neasham, T.R. Mundon, and B. Polagye, "Adaptable and distributed sensing in coastal waters: Design and performance of the μFloat system," Field Rob., 3, 516-543, doi:10.55417/fr.2023016, 2023.

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1 Mar 2023

Buoyancy-controlled underwater floats have produced a wealth of in situ observational data from the open ocean. When deployed in large numbers, or "distributed arrays," floats offer a unique capacity to concurrently map 3D fields of critical environmental variables, such as currents, temperatures, and dissolved oxygen. This sensing paradigm is equally relevant in coastal waters, yet it remains underutilized due to economic and technical limitations of existing platforms. To address this gap, we developed an array of 25 μFloats that can actuate vertically in the water column by controlling their buoyancy, but are otherwise Lagrangian. Underwater positioning is achieved by acoustic localization using low-bandwidth communication with GPS-equipped surface buoys. The µFloat features a high-volume buoyancy engine that provides a 9% density change, enabling automatic ballasting and vertical control from fresh to salt water (~3% density change) with reserve capacity for external sensors.

In this paper, we present design specifications and field benchmarks for buoyancy control and acoustic localization accuracy. Results demonstrate depth-holding accuracy within ±0.2 m of target depth in quiescent flow and ±0.5 m in energetic flows. Underwater localization is accurate to within ±5 m during periods with sufficient connectivity, with degradation in performance resulting from adverse sound speed gradients and unfavorable spatial distributions of surface buoys. Support for auxiliary sensors (<10% float volume) without
additional control tuning is also demonstrated. Overall performance is discussed in the context of potential use cases and demonstrated in a first-ever array-based three-dimensional survey of tidal currents.

Effect of heave plate hydrodynamic force parameterization on a two-body wave energy converter

Rusch, C.J., J. Joslin, B.D. Maurer, and B.L. Polagye, "Effect of heave plate hydrodynamic force parameterization on a two-body wave energy converter," J. Ocean Eng. Mar. Energy, 8, 355-367, doi:10.1007/s40722-022-00236-z, 2022.

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12 Jun 2022

Heave plates are one approach to generating the reaction force necessary to harvest energy from ocean waves. In a Morison equation description of the hydrodynamic force, the components of drag and added mass depend primarily on the heave plate oscillation. These terms may be parameterized in three ways: (1) as a single coefficient invariant across sea state, most accurate at the reference sea state, (2) coefficients dependent on the oscillation amplitude, but invariant in phase, that are most accurate for relatively small amplitude motions, and (3) coefficients dependent on both oscillation amplitude and phase, which are accurate for all oscillation amplitudes. We validate a MATLAB model for a two-body point absorber wave energy converter against field data and a dynamical model constructed in ProteusDS. We then use the MATLAB model to evaluate the effect of these parameterizations on estimates of heave plate motion, tension between the float and heave plate, and wave energy converter electrical power output. We find that power predictions using amplitude-dependent coefficients differ by up to 30% from models using invariant coefficients for regular waves ranging in height from 0.5 to 1.9 m. Amplitude- and phase-dependent coefficients, however, yield less than a 5% change when compared with coefficients dependent on amplitude only. This suggests that amplitude-dependent coefficients can be important for accurate wave energy converter modeling, but the added complexity of phase-dependent coefficients yields little further benefit. We show similar, though less pronounced, trends in maximum tether tension, but note that heave plate motion has only a weak dependence on coefficient fidelity. Finally, we emphasize the importance of using experimentally derived added mass over that calculated from boundary element methods, which can lead to substantial under-prediction of power output and peak tether tension.

Adaptable Monitoring Package development and deployment: Lessons learned for integrated instrumentation at marine energy sites

Polagye, B., J. Joslin, P. Murphy, E. Cotter, M. Scott, P. Gibbs, C. Bassett, and A. Stewart, "Adaptable Monitoring Package development and deployment: Lessons learned for integrated instrumentation at marine energy sites," J. Mar. Sci. Eng., 8, 553, doi:10.3390/jmse8080553, 2020.

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24 Jul 2020

Integrated instrumentation packages are an attractive option for environmental and ecological monitoring at marine energy sites, as they can support a range of sensors in a form factor compact enough for the operational constraints posed by energetic waves and currents. Here we present details of the architecture and performance for one such system — the Adaptable Monitoring Package — which supports active acoustic, passive acoustic, and optical sensing to quantify the physical environment and animal presence at marine energy sites. we describe cabled and autonomous deployments and contrast the relatively limited system capabilities in an autonomous operating mode with more expansive capabilities, including real-time data processing, afforded by shore power or in situ power harvesting from waves. Across these deployments, we describe sensor performance, outcomes for biological target classification algorithms using data from multibeam sonars and optical cameras, and the effectiveness of measures to limit biofouling and corrosion. On the basis of these experiences, we discuss the demonstrated requirements for integrated instrumentation, possible operational concepts for monitoring the environmental and ecological effects of marine energy converters using such systems, and the engineering trade-offs inherent in their development. Overall, we find that integrated instrumentation can provide powerful capabilities for observing rare events, managing the volume of data collected, and mitigating potential bias to marine animal behavior. These capabilities may be as relevant to the broader oceanographic community as they are to the emerging marine energy sector.

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In The News

Plainsight and MarineSitu Using 'Computer Vision' to Protect Sea Creatures

Forbes, Jeff Kart

Plainsight, an artificial intelligence company in the United States, has partnered with MarineSitu, a hardware and software provider and spinoff from the University of Washington. The focus is on enabling marine energy devices to coexist harmoniously with aquatic life.

28 Jan 2023

Eyes Underwater Watching Aquatic Wildlife

Environmental Monitor, Karla Lant

Recent work from researchers at the University of Washington offers a promising new way to harvest energy from waves at sea and use that energy to power an Adaptable Monitoring Package.

9 Jul 2019

Converting ocean waves into electricity poses challenges—and promise

Columns Magazine, Jon Marmor

In the glorious Pacific Ocean waters off the windward coast of O’ahu, waves crash along the Kailua coast. But it isn’t just surfers who salivate over those ocean jewels. Scientists believe the motion of the ocean could bring the promise of something even more important: clean energy.

3 Jun 2019

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Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center