The Tide Is High: Generating Energy From Waves, Tides, and Currents
Solar and wind power have been used as renewable energy for years, but what about waves, tides, and currents? Kevin Haas, a professor in the School of Civil and Environmental Engineering, has been on the forefront of ocean energy for over a decade.
“This is an emerging industry — it's basically where the wind industry was about 30 years ago, and we’re trying to develop technologies to capture the energy,” he said. “We must find the resource, estimate and calculate how much energy we can get from it, locate energy extraction sites, and identify which type of market would be able to use it.”
Certain locations are better for energy extraction. For tides, the most effective source is inland, where tidal currents are concentrated, leading to higher velocity flows, like New York’s East River. Researchers are also experimenting with using smaller devices for more localized power sources, like buoys. Like wind power, turbines are the best tool to extract energy from tides. Wave energy, by contrast, can either be close to shore for immediate energy or on offshore farms, but this variability means the most effective tool for extraction still hasn’t been proven.
Although renewable energy is key in cutting carbon emissions, tides and waves are also affected by climate change. Part of Haas’ work is predicting how much reliable energy production can be expected from these sources. Climate change could affect the Gulf Stream, so Haas must take that into consideration, as well as how energy extraction itself could alter the ocean ecosystem.
“A big part of my work is creating the modeling to learn what could happen to the Gulf Stream when you start extracting energy from the tides or full ocean currents,” he said.
To do these calculations, Haas develops numerical models to simulate the physics of tides. He is also testing a hybrid method that deploys instrumentation to measure tidal currents over a 90-day period. In an ideal world, there would be measurements at every turbine location, but this is not financially feasible, so the hybrid method deploys one permanent instrument and uses a boat to capture measurements in the area and subsequently predicts tides based on the model.
“Working in the ocean is much more challenging than terrestrial settings. We've already accomplished a lot in the area of ocean research, and now we're realizing the energy resource in the ocean is actually much bigger than we even thought.”
Ocean to Ocean: Connecting Ecosystems Using Modeling of Currents
The entire ocean is connected. Species like coral can be similar in entirely different parts of the ocean because those waters share characteristics like salinity, temperature, and nutrients. But how did this shared DNA travel in the first place? Currents connect ecosystems, and understanding their flow could help to rebuild other ecosystems. That’s the focus of the research from School of Earth and Atmospheric Sciences Professor Annalisa Bracco.
“Corals spread through larvae, which are transported by ocean currents. This is something that naturally happens and is, in the case of corals, definitely quite beneficial,” Bracco said. “If the coral gets bleached and dies, other coral DNA can come in the form of larvae and recolonize the territory.”
Bracco’s research is about more than just following these currents. She also determines how they could be used to rejuvenate weakened or destroyed ecosystems. Marine protected areas in the Gulf of Mexico could be expanded to deliver more flora and fauna larvae to repopulate stressed or damaged areas.
“We need to preserve ecosystems that are diverse, but also well connected, so they can transfer that diversity if something happens in another place,” Bracco said.
Data is limited for some areas, like the Gulf, so Bracco’s group uses ocean computer models and simulates currents and the coral larvae that could spread genetic material through them. Many corals spawn in a limited time frame, so the researchers simulate the circulation around that time of year, then trace how far the larvae can go, where they arrive, and which area they can colonize. Many ocean basins, like the Pacific, have more observations of ocean temperatures than continuous observations of coral reefs’ conditions, so the researchers rely on machine learning to establish how reefs are connected by ocean currents from temperatures alone. The machine learning models can determine which area should be monitored and protected to preserve biodiversity.
Bracco partners with other labs who collect coral samples to determine if and when reefs are genetically connected and validate her model. This collaboration between geneticists and modelers is rare in her field but has strengthened both research areas.
“In the models we have a lot of parameters that are unconstrained, but once we compare the models with the genetic data, it's really helped us to put everything together,” Bracco said. “The goal is to build a system that is so well constrained by what is in the observation that you can use it to intervene in ecosystems in the future.”
“In the models we have a lot of parameters that are unconstrained, but once we compare the models with the genetic data, it's really helped us to put everything together. The goal is to build a system that is so well constrained by what is in the observation that you can use it to intervene in ecosystems in the future.”
Ice Ice Baby: Modeling the Future of Glaciers and Ice Sheets
Retreating glaciers and the animals who live on them have become highly visible symbols of climate change. They are also a key to predicting its future. Alex Robel, an assistant professor in the School of Earth and Atmospheric Sciences, uses computational modeling to better understand how ice reacts to climate change and how, in turn, that causes global sea level to rise. His research group creates equations to explain how ice not only responds to climate change, but also how it flows, fractures, and melts.
“Unlike other fields, we don't have the standard set of equations that describe how ice sheets and glaciers work,” Robel said. “We use high-performance computing to simulate real glaciers on Antarctica and Greenland and try to understand how they have changed in the past and predict how they will change in the future.”
Not all ice is created the same. While sea ice freezes over a few feet of the top of the ocean in wintertime, glaciers are formed by the accumulation and compression of snow on land over long periods of time to depths of hundreds, even thousands, of feet. When enough accumulates, ice can start to flow like honey under its own weight and then is considered an ice sheet.
Developing these equations must account for how glaciers and ice sheets are exposed to the volatile climate system — and measuring conditions at the bottom of a glacier is no easy task. The field comes with a lot of inherent uncertainty that Robel’s group must plan for.
“What makes the speed of modern climate change challenging from the point of view of making predictions is that the best analog we have of ice sheet change is at the end of the Ice Age,” Robel said. “But the speed of those natural climate changes was much slower than what we're currently causing now due to greenhouse gas emissions.”
Despite the uncertainty involved, industries and communities are relying on predictions to make decisions about how to build coastal infrastructure or which drinking sources communties can rely on, so having any model is beneficial.
“Quantifying uncertainty is our role in helping people make better informed decisions about what will be happening in their communities in the future. We are in the business of arming people with good information, but then also educating Georgia Tech students who are going to take the lead on designing and building this infrastructure.”
- Alex Robel
Sensors Working Overtime: Tracking Coastal Sea Rise in South Georgia
One of the key ways to fight climate change is to monitor its effects. This empowers scientists to make better predictions and solutions and citizens to understand just what’s at stake. Since 2017, Russ Clark, a senior research scientist in the Institute for People and Technology, and his team have installed 64 sensors, with more to come, along the South Georgia coast to track rising sea levels. Part of Georgia Tech’s Smart Cities and Inclusive Innovation initiative, the Coastal Equity and Resilience Hub isn’t just an effort to track how climate change is affecting coastal cities, but it’s also an opportunity to involve the community in the research. Since its inception, the researchers have partnered with everyone from Chatham County Emergency Management to the Black environmental justice organization, the Harambee House.
“A lot of academics helicopter in, gather a bunch of data, and then they go home and write a paper, but they never come back and help actually address any of the problems,” Clark said. “This really requires relationship building and going to meetings in person that we don't normally make time for in a traditional academic environment. It’s part of why the community trusts us and continues to work with us. They can rely on us to show up and be there.”
Now, the team is hiring community partners like Kait Morano, a former Savannah government urban planner who used the project’s data to develop an emergency management portal tool and forecast flooding based on the sensor system. In her role with Georgia Tech, she focuses on equity and resilience.
“This project pairs researchers with community members as core partners from the beginning and has an actual dialogue with them about their needs and goals and how we can help them achieve those things,” Morano said. “The data that the sensors in these communities provide is something tangible that the community can then take to local governments or other partners to address this flooding.”
Although the project has mostly focused on Savannah and its surrounding area, the team is adding sensors to Brunswick and hopes to expand what they can measure, including air quality, temperature, and urban heat. The project has also expanded to include measuring rainwater and even adding better communication infrastructure to Sapelo Island, which currently has no reliable internet connectivity. Eventually, the researchers hope to partner with meteorologists from the National Weather Service to use the data collected with the sensors to validate inundation forecasts during hurricanes.
“With the sensor data, we can look back at storms from prior years and then run a forecast model to see how well it forecasted,” Clark said. “You can't have good forecast algorithms without lots of data to validate it, and that's the business we're in.”
Mitigating climate change is a complex, ever-evolving challenge, but Georgia Tech researchers plan for unpredictability and help everyone else navigate it.
This story was originally published by the Georgia Institute of Technology.