Triton Stories

How to Measure the Invisible: Quantifying Electromagnetic Fields  
Researching Electromagnetic Fields with Molly Grear  

Magnetic fields are everywhere. The Earth’s magnetic field occurs naturally and is key to making the planet habitable. Electromagnetic fields (EMF) are invisible forces, often caused by the movement of electricity through cables, that allow humans to transmit power and information over long distances. With our increasing dependence on telecommunications and electricity, EMFs are around us more than ever. They are an unavoidable part of developing new technologies, including in the marine renewable energy (MRE) industry where EMFs are generated by electrical transmission through undersea cables and power generation from the MRE devices themselves. Some marine animals, like sharks, rays, sea turtles, and fish, utilize the Earth’s naturally occurring magnetic fields for things like communication and navigation. Anthropogenic EMF sources—those that are created by humans—may interfere with marine animals’ sensory functions. While most humans cannot detect the presence of EMFs when they walk into a space full of cables, some marine animals may be affected. Researchers are working hard to understand the field strength and spatial patterns associated with MRE to determine how EMF might be impacting the marine environment.  

EMF is one of several environmental stressors the U.S. Department of Energy Water Power Technologies Office's Triton Initiative is studying. The Triton Field Trials (TFiT) is a Triton project dedicated to creating recommendations for the use of environmental monitoring methods and instrumentation used to study  the impact of MRE devices on the environment. TFiT studies four stressors, or aspects of an MRE system with the potential to stress or harm the marine environment. These stressors include, changes in habitat, collision risk, underwater noise, and EMF.  

 The interactions between marine animals and EMF are still not well understood. In a laboratory setting, certain studies have shown marine animals, such as sharks and rays, will change their behavior around a fixed EMF source. Yet, researchers don’t understand the fundamental biology of how animals sense these fields and what levels affect them. It is known that some crustaceans, fish, marine mammals, and turtles use the Earth’s magnetic field for orientation and navigation. Additionally, elasmobranchs, such as sharks and skates, may use electric field disturbances to locate prey or mates. Regulators want to ensure MRE devices  aren’t interfering with these important signals. This leaves researchers responsible for understanding the strength of EMFs and how they transmit in various locations, and regulators responsible for determining a safety threshold for technologically-produced EMFs. Ocean engineer and budding marine biologist, Molly Grear, and her team of researchers have been tasked to determine the best methods and instruments for measuring these invisible fields.  

Grear held several jobs before she found her passion in ocean engineering at the Pacific Northwest National Laboratory (PNNL) Marine and Coastal Research Laboratory  (MCRL). Grear always thought she wanted to be a traditional environmental engineer, which landed her a job with the U.S. Forest Service in Southeast Alaska. While she valued this role, her experience spent doing environmental remediation and trail inspections made her realize how much she craved the creativity and ingenuity of research, leading her to PNNL. She first joined PNNL as a post-bachelor’s research associate in 2012, researching the environmental effects of MRE with the Coastal Modeling group. In this position, she found her passion for renewable energy and fostered a desire to creatively answer challenging questions that would help make it more viable. This work inspired her to receive a PhD in Civil and Environmental Engineering at the University of Washington. Since then, Grear has spanned the worlds of marine biology and ocean engineering, oscillating between policy-focused work and academia. She has worked for Washington Sea Grant, National Science Foundation, Seattle University, and has completed a postdoc at PNNL. She rejoined PNNL in 2020 as an engineer for the Triton Initiative. Her training in biology and ocean engineering allows her to translate between disciplines, making her well equipped to lead TFiT’s EMF task.  

 EMF is such an important topic to study because all MRE devices, no matter the type, need to transport the electricity they generate back to shore. Grear’s team is helping to strengthen the pool of knowledge around this topic by improving EMF detection technologies, expanding datasets, and modeling how EMF changes across sites and scenarios. Researchers need to develop methods to understand EMF concentrations within cable networks and how the fields propagate.  

As EMF task lead, Grear plans for field tests and keeps the EMF team on task and organized. She also likes to keep the big picture in view. Grear’s background in policy helps her think about the team’s research holistically. She often considers how research might help inform the questions of other stakeholders in the industry.  With the end-users' needs in mind, Grear knows that the end goal is to provide environmental monitoring recommendations that developers, regulators, and other stakeholders can implement. According to Grear, “sometimes the policy questions, like how to judge whether or not a technology is harming its environment, are more difficult than the engineering ones.” This motivates her to develop methods that make detecting EMFs simple and cost-effective. Thus far, Grear and her team have modified low-cost sensors to try to improve their accuracy, but compared to the more expensive, commercial sensors, they are not yet up to par. While reliability and efficacy are of utmost importance, the team is currently seeking ways to decrease costs without compromising the quality and sensitivity of the sensors. One way they are tackling this is by running series of data analyses on existing instruments and determining ways to improve less-expensive models, reducing the barrier to testing. 

To add to the complexity of TFiT’s research, there is a catch-22 for environmental monitoring around MRE applications. In order to permit the deployment of MRE devices in the water, there needs to be an understanding of the impacts that devices might have on the environment, but to fully understand those environmental impacts, environmental monitoring needs to be done while devices are deployed. The U.S. is home to several test sites, but opportunities to conduct field research at these sites are limited. The TFiT team has Sequim Bay, a tidal field site in MCRL’s front yard. Triton engineer, Nolann Williams, designed a point source generator that could mimic the expected magnetic field of an MRE device to use in Sequim Bay tests. This allowed for field testing of EMF sensors in Sequim Bay without the presence of an actual wave or tidal energy device. The team has now been able to conduct EMF field tests in Sequim Bay. Now, Grear wonders how EMF signals are affected by different currents and wave dynamics. The next step for the team is to expand testing to a more energetic wave environment to understand EMF in a location with these different oceanic and physical variables. 

Grear claims that sometimes the biggest challenge of her research involves simply detecting EMF sources. There are many natural and baseline anthropogenic sources of magnetic fields in the environment, including thunderstorms, sunlight, and power lines. Because of this, it can be difficult to isolate an EMF source and strength to a specific location. During field testing in Sequim Bay, the team addressed this challenge head-on. In 2017, the Triton team was collaborating on a project to test a highly sensitive EMF detection platform in Sequim Bay. During the field deployment, an unknown local EMF source was discovered that interfered with the instrument’s ability to detect target signals. Years later, Grear and the team of engineers on TFiT's EMF task were able to identify the unexpected sources of EMF in Sequim Bay, which has allowed them to isolate the field emitted from the cable. This revelation has resulted in an awareness of the local EMF sources and how they may impact future environmental monitoring tests. Grear states “You need to know what's there so you can understand the noise present. The most important recommendation determined so far is  to understand the baseline to distinguish EMF coming from the cables.”  

To date, the team has focused on field deployments of EMF detection sensors and has put a lot of effort into data analysis and technical development (see more on technical development here). This work keeps Grear motivated because she gets to tangibly help progress an industry she believes in. She will continue to push the boundaries of innovation as she discovers ways to creatively improve EMF research and advance environmental monitoring for MRE.

Story written by Cailene Gunn.

The remaining TFiT stressors will be featured over the next few months—stay tuned for more discussions on how the Triton team is researching MRE stressors to help remove the barriers to deploying devices.


A crab hanging out near a cable being tested for EMF in Sequim Bay.
A crab hanging out near an underwater cable in Sequim Bay. 


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