International study detects consciousness in unresponsive patients

Study co-led by Mass General Brigham found that one in four patients with severe brain injury who appeared unresponsive responded to instructions covertly. Understanding this phenomenon can help guide decisions about life-sustaining treatment.

Mass General Brigham

New research co-led by experts at Mass General Brigham found that brain scans can detect consciousness in some patients with brain injury who are unresponsive.

In the study, 241 participants with severe brain injury who do not respond when given a simple instruction were assessed with functional MRI (fMRI), electroencephalography (EEG), or both tests. During these tests, participants heard instructions, such as “imagine opening and closing your hand” followed, 15-30 seconds later by “stop imagining opening and closing your hand.” The fMRI and EEG brain responses showed that 60 (25 percent) of participants repeatedly followed this instruction covertly over minutes. According to the authors of the study, published August 15 in the New England Journal of Medicine, patients who demonstrate this phenomenon, called cognitive motor dissociation, understand language, remember instructions and can sustain attention, even though they appear unresponsive. For these patients, cognitive (i.e., thinking) abilities exceed, and are therefore dissociated from, motor abilities.  

“Some patients with severe brain injury do not appear to be processing their external world. However, when they are assessed with advanced techniques such as task-based fMRI and EEG, we can detect brain activity that suggests otherwise,” said lead study author Yelena Bodien, PhD, an investigator for the Spaulding-Harvard Traumatic Brain Injury Model Systems and Massachusetts General Hospital’s Center for Neurotechnology and Neurorecovery. “These results bring up critical ethical, clinical, and scientific questions – such as how can we harness that unseen cognitive capacity to establish a system of communication and promote further recovery?”

Following a significant brain injury, individuals may have a disorder of consciousness, which can include coma, a vegetative state or minimally conscious state. Since the first study demonstrating cognitive motor dissociation in individuals with disorders of consciousness was published nearly two decades ago, centers around the world have found that this condition occurs in approximately 15 to 20 percent of unresponsive patients. However, the current study suggests it could be present in 25 percent of patients, or even more. Cognitive motor dissociation was most common in participants assessed with fMRI and EEG, suggesting that multiple tests, using different approaches, may be required to ensure consciousness is not missed.

This study included participant data from six different sites spanning the United States, United Kingdom, and Europe collected over approximately 15 years. Each site developed and rigorously tested their methods for detecting cognitive motor dissociation to minimize the possibility that a positive result was obtained spuriously. Some sites recruited participants from the intensive care unit just days after they sustained a severe brain injury, often from a trauma such as a car accident, a stroke or cardiac arrest. Other sites included participants who were months to years after their injury or illness and were living in nursing facilities or at home.

In addition to studying the 241 participants who did not respond to simple instructions, the research included 112 participants who did respond to simple instructions at the bedside. This latter group would be expected to perform well on the fMRI and EEG tests, but, in 62 percent of those participants, researchers did not detect brain responses suggesting they were covertly following instructions. The authors note that this finding may reflect the complexity of the fMRI and EEG tasks and underscores the high-level of thinking skills required to perform them. 

Just knowing that somebody is cognitively aware and more capable than is immediately apparent, can alter their clinical care substantially. “Families have told us that once a positive test result revealing cognitive motor dissociation is shared with the patients’ clinical team, it can change the way that the team interacts with their loved one,” Bodien said. “Suddenly, the team is paying more attention to subtle behavioral signs that could be under volitional control, or speaking to the patient, or playing music in the room. On the other hand, failing to detect cognitive motor dissociation can have serious consequences, including premature withdrawal of life support, missed signs of awareness, and lack of access to intensive rehabilitation.”

“We find that this kind of sharp dissociation of retained cognitive capabilities and no behavioral evidence of them is not uncommon. I think we now have an ethical obligation to engage with these patients, to try to help them connect to the world,” said senior study author Nicholas Schiff, MD, the Jerold B. Katz Professor of Neurology and Neuroscience in the Feil Family Brain and Mind Research Institute at Weill Cornell Medicine and administrative lead of the consortium. “What we need here is what we in our consortium have been trying to get started for twenty years: a sustained effort to benefit patients who have disorders of consciousness with systematic medical research, technology development, and better clinical infrastructure.

One limitation of the study was that the testing was not standardized; each of the study sites tested patients in their own way, creating variability within the data. In addition, many participants were enrolled because family members heard about the study and reached out to researchers. This recruitment approach limits the researchers’ ability to determine the global prevalence of cognitive motor dissociation. There are no professional guidelines that stipulate how cognitive motor dissociation should be assessed and most centers are unable to provide this testing; clinical translation will need to be a focal point for future research. 

“To continue our progress in this field, we need to validate our tools and to develop approaches for systematically and pragmatically assessing unresponsive patients so that the testing is more accessible”, said Bodien. “The Emerging Consciousness Program at Mass General Hospital offers these evaluations clinically, however elsewhere, a patient may have to enroll in a research study to get tested. We know that cognitive motor dissociation is not uncommon, but resources and infrastructure are required to optimize detection of this condition and provide adequate support to patients and their families.”

The researchers added that the findings may spur research of specific interventions to foster effective communication, including brain-computer interfaces.

A separate team of Mass General Brigham researchers are investigating brain-computer interfaces (BCIs) as a potential intervention that may one day have applications to many types of patients unable to effectively communicate. Another study published in the same August 15th issue of New England Journal of Medicine from co-author Leigh Hochberg, MD, PhD of Mass General Hospital's Department of Neurology and Center for Neurotechnology and Neurorecovery, reported that a man with ALS and severely impaired speech used an investigational BCI implant to convert his attempted speech into text on a screen. Read more about that study, and about the BrainGate clinical trials for which Hochberg serves as principal investigator. 

Authorship: In addition to first author Bodien, Mass General Brigham co-authors at the time of the study include Camille Chatelle PhD; Phoebe K Lawrence BS; Anogue Meydan BS; William R Sanders BS; Brian L Edlow MD; and Joseph T Giacino PhD. Other co-authors include senior and corresponding Schiff; Judith Allanson, FRCP, PhD; Paolo Cardone MS; Arthur Bonhomme MD; Jerina Carmona MPH; Srivas Chennu PhD; Mary Conte PhD; Stanislas Dehaene PhD; Paola Finoia PhD; Gregory Heinonen BS; Jennifer Hersh BME;  Evelyn Kamau MSc; Victoria C. Lupson; Benjamin Rohaut MD PhD; Jacobo D Sitt MD PhD; Andrea Soddu PhD; Mélanie Valente BS; Angela Velazquez MD; Henning U Voss PhD; Athina Vrosgou MSc; Jan Claassen MD; Joseph J Fins MD; Olivia Gosseries PhD; Steven Laureys MD PhD; David Menon MD; Lionel Naccache MD PhD;  Adrian M Owen PhD; John Pickard MChir; Emmanuel A Stamatakis PhD; Aurore Thibaut PhD; Jonathan D Victor MD PhD; and Emilia Bagiella PhD.

Funding: The study was funded by the James S. McDonnell Foundation. Bodien is supported by grants from the National Institute on Disability, Independent Living, and Rehabilitation Research: H133A120085; 90DPTB0011; and 90DPTB0027.

Disclosures: Disclosure forms are available with full text of this article at NEJM.org

Paper cited: Bodien, YG et al. “Cognitive Motor Dissociation in Disorders of Consciousness.” New England Journal of Medicine. DOI: 10.1056/NEJMoa2400645

 

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About Mass General Brigham

Mass General Brigham is an integrated academic health care system, uniting great minds to solve the hardest problems in medicine for our communities and the world. Mass General Brigham connects a full continuum of care across a system of academic medical centers, community and specialty hospitals, a health insurance plan, physician networks, community health centers, home care, and long-term care services. Mass General Brigham is a nonprofit organization committed to patient care, research, teaching, and service to the community. In addition, Mass General Brigham is one of the nation’s leading biomedical research organizations with several Harvard Medical School teaching hospitals. For more information, please visit massgeneralbrigham.org.

 

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Journal

New England Journal of Medicine

DOI

10.1056/NEJMoa2400645 

Method of Research

Observational study

Subject of Research

People

Article Title

Cognitive Motor Dissociation in Disorders of Consciousness

Article Publication Date

15-Aug-2024

COI Statement

Disclosure forms are available with full text of this article at NEJM.org

 

New brain-computer interface allows man with ALS to ‘speak’ again

Technology developed by UC Davis Health restores interpersonal communication

University of California - Davis Health

 

image: 

Casey Harrell with his personal assistant Emma Alaimo and UC Davis neuroscientist Sergey Stavisky

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Credit: UC Regents

A new brain-computer interface (BCI) developed at UC Davis Health translates brain signals into speech with up to 97% accuracy — the most accurate system of its kind.

The researchers implanted sensors in the brain of a man with severely impaired speech due to amyotrophic lateral sclerosis (ALS). The man was able to communicate his intended speech within minutes of activating the system.

A study about this work was published today in the New England Journal of Medicine.

ALS, also known as Lou Gehrig's disease, affects the nerve cells that control movement throughout the body. The disease leads to a gradual loss of the ability to stand, walk and use one’s hands. It can also cause a person to lose control of the muscles used to speak, leading to a loss of understandable speech.

The new technology is being developed to restore communication for people who can’t speak due to paralysis or neurological conditions like ALS. It can interpret brain signals when the user tries to speak and turns them into text that is ‘spoken’ aloud by the computer.

“Our BCI technology helped a man with paralysis to communicate with friends, families and caregivers,” said UC Davis neurosurgeon David Brandman. “Our paper demonstrates the most accurate speech neuroprosthesis (device) ever reported.”

Brandman is the co-principal investigator and co-senior author of this study. He is an assistant professor in the UC Davis Department of Neurological Surgery and co-director of the UC Davis Neuroprosthetics Lab.

The new BCI breaks the communication barrier

When someone tries to speak, the new BCI device transforms their brain activity into text on a computer screen. The computer can then read the text out loud.

To develop the system, the team enrolled Casey Harrell, a 45-year-old man with ALS, in the BrainGate clinical trial. At the time of his enrollment, Harrell had weakness in his arms and legs (tetraparesis). His speech was very hard to understand (dysarthria) and required others to help interpret for him.

In July 2023, Brandman implanted the investigational BCI device. He placed four microelectrode arrays into the left precentral gyrus, a brain region responsible for coordinating speech. The arrays are designed to record the brain activity from 256 cortical electrodes.

“We’re really detecting their attempt to move their muscles and talk,” explained neuroscientist Sergey Stavisky. Stavisky is an assistant professor in the Department of Neurological Surgery. He is the co-director of the UC Davis Neuroprosthetics Lab and co-principal investigator of the study. “We are recording from the part of the brain that’s trying to send these commands to the muscles. And we are basically listening into that, and we’re translating those patterns of brain activity into a phoneme — like a syllable or the unit of speech — and then the words they’re trying to say.”

Faster training, better results

Despite recent advances in BCI technology, efforts to enable communication have been slow and prone to errors. This is because the machine-learning programs that interpreted brain signals required a large amount of time and data to perform.

“Previous speech BCI systems had frequent word errors. This made it difficult for the user to be understood consistently and was a barrier to communication,” Brandman explained. “Our objective was to develop a system that empowered someone to be understood whenever they wanted to speak.”

Harrell used the system in both prompted and spontaneous conversational settings. In both cases, speech decoding happened in real time, with continuous system updates to keep it working accurately.

The decoded words were shown on a screen. Amazingly, they were read aloud in a voice that sounded like Harrell’s before he had ALS. The voice was composed using software trained with existing audio samples of his pre-ALS voice.

At the first speech data training session, the system took 30 minutes to achieve 99.6% word accuracy with a 50-word vocabulary.

“The first time we tried the system, he cried with joy as the words he was trying to say correctly appeared on-screen. We all did,” Stavisky said.

In the second session, the size of the potential vocabulary increased to 125,000 words. With just an additional 1.4 hours of training data, the BCI achieved a 90.2% word accuracy with this greatly expanded vocabulary. After continued data collection, the BCI has maintained 97.5% accuracy.

“At this point, we can decode what Casey is trying to say correctly about 97% of the time, which is better than many commercially available smartphone applications that try to interpret a person’s voice,” Brandman said. “This technology is transformative because it provides hope for people who want to speak but can’t. I hope that technology like this speech BCI will help future patients speak with their family and friends.”

The study reports on 84 data collection sessions over 32 weeks. In total, Harrell used the speech BCI in self-paced conversations for over 248 hours to communicate in person and over video chat.

“Not being able to communicate is so frustrating and demoralizing. It is like you are trapped,” Harrell said. “Something like this technology will help people back into life and society.”

“It has been immensely rewarding to see Casey regain his ability to speak with his family and friends through this technology,” said the study’s lead author, Nicholas Card. Card is a postdoctoral scholar in the UC Davis Department of Neurological Surgery.

“Casey and our other BrainGate participants are truly extraordinary. They deserve tremendous credit for joining these early clinical trials. They do this not because they’re hoping to gain any personal benefit, but to help us develop a system that will restore communication and mobility for other people with paralysis,” said co-author and BrainGate trial sponsor-investigator Leigh Hochberg. Hochberg is a neurologist and neuroscientist at Massachusetts General Hospital, Brown University and the VA Providence Healthcare System.

Brandman is the site-responsible principal investigator of the BrainGate2 clinical trial. The trial is enrolling participants. To learn more about the study, visit braingate.org or contact braingate@ucdavis.edu.

A complete list of coauthors and funders is available in the article.

Caution: Investigational device. Limited by Federal law to investigational use.

Casey Harrell trying the BCI system for the first time

Postdoctoral scholar and lead author of the study Nicholas Card getting the BCI system ready

Credit

UC Regents

Journal

New England Journal of Medicine

DOI

10.1056/NEJMoa2314132 

Article Title

An Accurate and Rapidly Calibrating Speech Neuroprosthesis?

Article Publication Date

14-Aug-2024

 

Weather and geography drive waterborne infectious disease outbreaks

Columbia University's Mailman School of Public Health

An analysis of 12 years of data collected from over 500 hospitals in 25 different U.S. states shows that weather, geographic location, and urban or rural location all appear to influence hospitalizations for waterborne infectious diseases, according to a new study by researchers at Columbia University in the open-access journal PLOS Water.

Waterborne infectious diseases caused by bacteria, parasites, and viruses still affect over 7,000,000 people annually in the United States despite drinking and recreational water regulations, and sanitation infrastructure. Waterborne pathogens transmitted via contaminated environmental or drinking water can cause severe respiratory or gastrointestinal infections, particularly among vulnerable groups. Drinking water and wastewater treatment substantially reduces the burden of disease but these systems are still vulnerable to contamination. Pathogen-specific water quality monitoring is onerous and expensive, and as a result infrequently conducted.

“Understanding the factors that give rise to these infections could eventually lead to a cost-effective early warning system so public health authorities can direct resources to protect people from contaminated drinking water,” says study author Victoria Lynch, a postdoctoral research scientist in environmental health sciences at Columbia University Mailman School of Public Health.

Lynch and Jeffrey Shaman, professor of environmental health sciences and interim dean of the Columbia Climate School, looked at hospitalizations caused by 12 specific water-borne pathogens, including bacteria like Escherichia coli, parasites like Cryptosporidium, biofilm-forming bacteria such as Pseudomonas and the pathogen causing Legionnaires’ disease—distinct from other bacterial pathogens because they naturally inhabit environmental water—and Norovirus. They used data from 516 hospitals in 25 states collected between 2000-2011, as part of the National Inpatient Sample (NIS) from the Healthcare Cost and Utilization Project (HCUP). Precipitation, soil moisture, surface runoff, and temperature data were obtained from the NASA/NOAA North American Land Data Assimilation System 2 (NLDAS-2) dataset. Drinking water data were extracted from the Safe Drinking Water Information System for each hospital's community water system.

There were 57,335 hospitalizations for waterborne disease between 2000 and 2011 from those 516 hospitals in the United States. The biofilm-forming bacteria comprised nearly 81 percent of all hospitalizations. Hospitalization rates for enteric and biofilm-forming bacterial pathogens were significantly higher in areas that used groundwater as a drinking water source instead of surface water. They also found that precipitation, water runoff, and rural locations were positively associated with hospitalizations for some enteric bacterial and parasitic infections, particularly in the Midwestern region. Conversely, hospitalizations for biofilm-forming bacterial infections were associated with soil moisture (a proxy for flooding). Legionnaires’ disease was the only infection more common in urban areas. In general, associations between hospitalization rates and meteorological conditions, location, and drinking water source varied depending on the specific pathogens.

The authors note they weren’t able to include data on specific water quality (critical to assess the probable route of exposure for pathogens that can also be present in tainted food, like E. coli), or data from much of the Southeast (where states did not report monthly data to HCUP). Lynch and Shaman hope future work will incorporate this information and track outbreaks linked with extreme weather events to further clarify the links between hydrometeorology and waterborne diseases.

V.L. was supported by a training grant from the National Institutes of Health grant ES023770; both authors were supported by NIH grant AI163023.

J.S. and Columbia University disclose partial ownership of SK Analytics.

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Journal

PLOS Water

DOI

10.1371/journal.pwat.0000206 

Method of Research

Data/statistical analysis

Subject of Research

People

Article Title

Hydrometeorology and geography affect hospitalizations for waterborne infectious diseases in the United States: A retrospective analysis

Article Publication Date

14-Aug-2024

COI Statement

J.S. and Columbia University disclose partial ownership of SK Analytics.

Hydrometeorology and location affect hospitalizations for waterborne infectious diseases in the US

PLOS

An analysis of 12 years of data collected from over 500 hospitals in 25 different states shows that weather, geographic location, and urban or rural location all appear to influence hospitalizations for waterborne infectious diseases, according to a study published August 7, 2024 in the open-access journal PLOS Water by Victoria Lynch and Jeffrey Shaman from Columbia University.

Waterborne infectious diseases caused by bacteria, parasites, and viruses still affect over 7,000,000 people annually in the United States. Lynch and Shaman analyzed potential links between weather and hospitalizations for waterborne infectious diseases, specifically looking at whether these associations were influenced by drinking water source, location (rural/urban), and region.

The authors looked at hospitalizations caused by 12 specific water-borne pathogens, including bacteria like Escherichia coli, parasites like Cryptosporidium, biofilm-forming bacteria such as Pseudomonas and the pathogen causing Legionnaires’ disease—distinct from other bacterial pathogens because they naturally inhabit environmental water—and Norovirus. They used data from 516 hospitals in 25 states collected over 2000-2011 as part of the National Inpatient Sample (NIS) from the Healthcare Cost and Utilization Project (HCUP), along with weather and soil data from the NASA/ NOAA North American Land Data Assimilation System 2 (NLDAS-2) dataset.

There were 57,335 hospitalizations for waterborne disease between 2000 and 2011 from 516 hospitals in the United States. The biofilm-forming bacteria comprised nearly 81 percent of all hospitalizations (66 percent due to respiratory Pseudomonas infections alone.) Hospitalization rates for enteric and biofilm-forming bacterial pathogens were significantly higher in areas that used groundwater as a drinking water source instead of surface water. They also found that precipitation, water runoff, and rural locations were positively associated with hospitalizations for some enteric bacterial and parasitic infections, particularly in the Midwestern region. Specifically, parasitic hospitalizations (predominantly due to Cryptosporidium) increased 9 percent (95% CI: 4%-15%) with a 1-SD increase in precipitation. Conversely, hospitalizations for biofilm-forming bacterial infections were associated with soil moisture (a proxy for flooding). Incidences of Legionnaires’ disease specifically increased 124 percent (95% CI: 90%-157%) with a 1-SD increase in soil moisture, and were the only infection more common in urban areas. In general, associations between hospitalization rates and meteorological conditions, location, and drinking water source varied depending on the specific pathogens.

The authors note they weren’t able to include data on specific water quality (critical to assess the probable route of exposure for pathogens that can also be present in tainted food, like E. coli), or data from much of the Southeast (where states did not report monthly data to HCUP). Lynch and Shaman hope future work will be able to incorporate this information and additionally track outbreaks linked with extreme weather events to further clarify the links between hydrometeorology and waterborne diseases.  

The authors add: "Our results show how analyses focused on specific pathogens can provide insight into distinct routes of exposure and risk factors for waterborne infectious diseases. This work can help inform weather preparedness efforts, which is particularly important as heavy rain becomes more severe and frequent in a warming climate."

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In your coverage please use this URL to provide access to the freely available article in PLOS Water: https://journals.plos.org/water/article?id=10.1371/journal.pwat.0000206

Citation: Lynch VD, Shaman J (2024) Hydrometeorology and geography affect hospitalizations for waterborne infectious diseases in the United States: A retrospective analysis. PLOS Water 3(8): e0000206. https://doi.org/10.1371/journal.pwat.0000206

Author Countries: United States

Funding: V.L. was supported by a training grant from the National Institutes of Health (NIH; grant no. T32ES023770); both authors were supported by NIH grant no. R01AI163023. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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Journal

PLOS Water

DOI

10.1371/journal.pwat.0000206 

Method of Research

Observational study

Subject of Research

People

COI Statement

J.S. and Columbia University disclose partial ownership of SK Analytics. J.S. discloses consulting for Business Network International (BNI).

 

Climate reporting standards insufficient, must be expanded, say Oxford net zero experts

We need a way to compare and reward companies that are changing the world, not just their operations.” - Kaya Axelsson

Peer-Reviewed Publication

Taylor & Francis Group

A new paper from the Smith School of Enterprise and the Environment, University of Oxford concludes that current climate standards are not sufficiently incentivising the big picture innovations necessary to deliver net zero, and must be expanded to include a company’s broader influence on climate action. The peer-reviewed research, published in Carbon Management, comes after a period of fierce public debate about climate standards and offers possible solutions for those seeking to improve both integrity and impact of corporate climate action.

Incentivising climate action and innovation in the corporate world is essential says co-author Dr Matilda Becker: “Of the 2000 largest companies, close to half still do not yet have a net zero target, while some are going further without reward. We need to incentivise companies' efforts beyond their boundaries.”

The authors discuss actions that companies can take to accelerate the global transition to net zero across three spheres of influence: product power, purchasing power and political power, and propose an additional reporting track to capture their impact in these areas. This track would demonstrate a company’s wider contribution to global net zero, and examples could include lobbying for cleaner energy systems or signalling financial support for new net zero technologies.

To date, corporate climate standards have been created primarily to guide companies in setting targets (e.g. through the Science Based Targets initiative) and to help them track their own emissions resulting from their activities (e.g. using the Greenhouse Gas Protocol). While these standards have been essential for reducing the emissions of individual companies, say the authors, they fail to incentivise broader climate action and can even discourage it.

“It is essential that companies report and reduce emissions across their value chains,” says co-author Claire Wigg, Head of Climate Performance Practice at the Exponential Roadmap Initiative. “But it is also essential that they drive – and are rewarded for driving - systemic change via the products they produce, the purchases they make and the policies they lobby for or against.”

 “The way standards are currently set up, a high-growth renewable energy company might fare poorly because of the emissions generated in making turbines and solar panels, despite the fact these products can help to reduce  emissions globally,” explains lead author Kaya Axelsson, Research Fellow and Head of Policy and Partnerships at the Smith School. “We need a way to compare and reward companies that are changing the world, not just their operations.”

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Journal

Carbon Management

DOI

10.1080/17583004.2024.2382995 

Method of Research

Commentary/editorial

Subject of Research

Not applicable

Article Title

Is Impact out of Scope? A Call for Innovation in Climate Standards to Inspire Action Across Companies’ Spheres of Influence

Article Publication Date

15-Aug-2024

 

Combining computational methods and experimental techniques to unlock floating offshore wind potential

Portland State University

 

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Zein Sadek and Natalie Frank perform experiments in the wind-wave facility at Portland State University to observe/characterize the flow behind an offshore floating wind turbine using particle image velocimetry.

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Credit: Photo by NashCo, courtesy of Portland State University

A collaboration between researchers from Johns Hopkins Whiting School of Engineering (WSE) and Portland State University (PSU) aims to help unlock the vast potential of floating offshore windfarms in the United States by improving understanding of wind-wave-turbine interactions, which if not accounted for properly, can greatly reduce the power output of a group of wind turbines.

The project combines developing a new computational method for enhancing the accuracy of Large Eddy Simulations (LES) – a mathematical computer model that depicts the wind field within floating offshore windfarms, with advanced experimental techniques using a state-of-the-art wind tunnel/wave tank facility at PSU. By integrating both computational and experimental methods, which are usually used separately in offshore wind research, the team aims to develop more accurate tools for the design and optimization of wind farms in the deep ocean.

“One of the challenges to floating offshore windfarms is we don’t have test beds. You can’t go out to sea, build a test windfarm, and see how it performs. It’s just too expensive,” said project Co-Principal Investigator Dennice Gayme, a professor of mechanical engineering at the Whiting School of Engineering and member of the Ralph O’Connor Sustainable Energy Institute (ROSEI) leadership council. “Most studies focus on LES simulations or lab experiments and don’t look at how to bridge the gap between the two, which is key to developing a complete understanding of the system.”

The JHU-PSU team’s project is the first to receive funding through the U.S. National Science Foundation (NSF) and the Department of Energy’s (DOE) Wind Energy Technologies Office (WETO)’s partnership in wind energy.

“This proposal is exciting because it’s incredibly well-rounded and brings together a pair of universities that have a history of excellence in wind energy research,” said Ben Hallissy, a technology manager with WETO. “It uses a combination of modeling advancements and scaled experimental results to answer some fundamental questions; for example, how do we better predict the interaction of the wind, waves, and turbines, and how do we learn as much as possible from cost-effective small-scale experiments in the laboratory before scaling up and putting turbines in the ocean?”

Ron Joslin, the program director for the NSF fluid dynamics program, added “NSF and DOE often have complementary roles in fostering US research and innovation, and together we move discoveries from the academic lab to commercial implementation. NSF has partnered with WETO to co-fund groundbreaking research in wind renewable energy to increase the U.S. capacity for renewable energy. This partnership gives us greater flexibility to award new projects with the funds available at each agency.”

Unlike traditional offshore wind turbines that are attached directly to the ocean floor, floating windfarms stand on buoyant structures that are anchored to the ocean bed by mooring lines. This allows placement in deep ocean waters, where about two-thirds of U.S. offshore wind energy potential exists, according to WETO. 

But turbines on platforms that move with the water make it difficult to design windfarms in a way that maximizes their energy potential. Computationally, a major challenge to creating LES for effective windfarm design is accurately reflecting wind flow over always-moving waves with multiple wavelengths and complicated shapes.

Project Principal Investigator Charles Meneveau, a professor of mechanical engineering at WSE and an associate researcher with ROSEI, explains two conventional methods for representing wind flow over moving water. The classic method assigns a general “roughness length” number to it, allowing for quicker but less precise simulations. The other method uses a computational grid that adapts to the wave. This approach offers greater accuracy but is quite difficult and time-consuming to create, making it impractical for most common use.

In this work, Meneveau and Gayme propose an intermediate approach, combining a less precise grid that doesn’t follow the waves, with a variable forcing term that represents the pressure force along the water’s surface.

“We can get accurate results using this model by combining the better features of both the faster less accurate method, as well as the slower more exact one,” Meneveau said. “Our model reflects different moving waves with peaks and troughs but does so quickly and accurately. It can also factor in a moving platform with a turbine on top of it. It works quickly but provides the critical details.”

The experimental aspects of the project will be led by Raúl Bayoán Cal, a professor of mechanical and materials engineering at PSU. His lab facility features a test length that is five meters long, with a wave tank with multiple small turbines floating on the water surface. Most groups studying wind turbines are limited to testing a single turbine at a time, making it more challenging to see how the turbines interact with each other.

“What we have is much smaller than an actual floating wind farm, but our platform enables the measurement of many different factors simultaneously, including dynamics of turbines, power extracted from turbines, motion of the waves, and the flow behind the turbines,” Cal said. “We can also recreate various environments where the wind and waves are forced in different ways, meaning my group can study a multitude of conditions that are observed in offshore wind farms, helping us prepare a wind farm for a given scenario.”

Before joining the faculty at PSU, in the late 2000s, Cal was a postdoctoral fellow advised by Meneveau at Hopkins, leading to this and many other collaborations between the two groups, including one of the first scaled windfarm experiments to ever happen in a wind tunnel.

“A big reason that you don’t see collaborations between groups that work in the computational and lab spaces is relationships. Knowing how myself, Charles, and Dennice all work has played a big part in us partnering,” Cal said. “When working with both computational and experiments, the questions need to be really defined and within that we can say ‘What are the computational elements that can be exploited in a lab experiment and vice versa.’ It’s easier to find answers to those questions when you have a history with your partners.”