Cool Solutions: Science and Engineering Help Address the Impacts of Climate Change
By T.J. Becker | Photography by Allison Carter
Among sobering statistics, 2018 was the fourth warmest year since 1880 (when consistent record-keeping began) with 2016, 2017, and 2015 ranking as the three hottest. Fallout from increased global temperatures includes melting polar ice, rising sea levels, coastal flooding, severe weather events, altered ecosystems, and species extinction.
“Climate change is one of the biggest challenges of our time,” said Kim Cobb, Georgia Power Chair and ADVANCE Professor in Georgia Tech’s School of Earth and Atmospheric Sciences and director of the Institute’s Global Change Program. “Impacts from global warming are detectable all across America, and they will get worse,” she points out. “But there’s also good news. It’s not too late to reduce greenhouse gas emissions and avoid the most damaging impacts of future climate change.”
“The time to argue about the causes of climate change has passed,” said G. Wayne Clough, president emeritus of Georgia Tech and senior advisor to the Global Change Program. “We need to focus on real solutions — and for the engineering community to step up. Climate change is not just a science problem; it’s also an engineering problem.”
“Granted, we’re dealing with a pretty miserable set of playing cards,” Clough added. “Yet what’s exciting is that we have a new scope of technologies to deal with these issues.” He points to a suite of solutions that Georgia Tech researchers are working on: removing carbon from the air, longer storage methods for renewable energy, novel approaches to air conditioning, and helping both urban and coastal communities respond to climate change.
Within the climate-mitigation arsenal, an emerging set of tools are negative emission technologies (NETs). Unlike carbon-capture methods that reduce emissions from power plants and industrial facilities, NETs remove carbon dioxide in the atmosphere and sequester it in the ground or other forms of long-term storage. Examples of NETs include reacting CO2 with various minerals, cultivating forest and croplands that take up carbon dioxide, and practices to enhance carbon storage in coastal and marine ecosystems.
Christopher Jones, a professor in the School of Chemical and Biomolecular Engineering, tests materials used to capture carbon dioxide directly from the atmosphere.
Researchers in Christopher Jones’ lab at Georgia Tech have been making advances in a type of NET known as direct air capture (DAC). “DAC is based on technologies with solid or liquid materials that selectively bind CO2 very strongly, so it can be plucked from the dilute mixture in the air like a pair of tweezers,” said Jones, professor and William R. McLain Chair in the School of Chemical and Biomolecular Engineering.
Jones’ team has developed an amine-oxide hybrid adsorbent material, which has been licensed by Global Thermostat, one of a handful of companies trying to commercialize DAC technology. “Their technology is a marriage between their proprietary process and our adsorbents,” Jones explained. “Once a stream of air moves past our material, which is bonded onto a ceramic monolith, it grabs the CO2. When the adsorbent reaches its capacity, low-temperature steam is brought into the system, providing the necessary energy to release the captured CO2, after which it is compressed and stored.”
Based in New York, Global Thermostat has established a research and development lab in Georgia Tech’s Advanced Technology Development Center, and the company is in the process of building its first commercial-scale plant near Huntsville, Alabama.
Because DAC can produce a source of concentrated CO2 from anywhere in the world, it eliminates the need for extensive piping or other complicated distribution systems. In addition to being sequestered, the carbon can be used as a feedstock in manufacturing food and beverages, plastics, building materials, and synthetic gases.
Although DAC technologies have great potential to clean up society’s CO2 waste, current costs ($200-$500 per metric ton of CO2) must be lowered to be competitive with existing point-capture technologies, which operate where the gas is generated. Yet Jones sees 2018 as a tipping point for two reasons: a federal tax credit that pays $50 per ton for carbon capture and storage, and California’s revised Low Carbon Fuel Standard, which now allows carbon capture and sequestration (including DAC) as a way for fuel suppliers to reduce their carbon intensity (credits that are about $100 per ton).
As a result, large oil and chemical companies are eyeing DAC with interest for the first time, Jones said. “If capital becomes available for young DAC companies to build plants, they can learn how to operate more efficiently and further reduce costs.”
Storing renewable energy
Georgia Tech researchers are also working on renewable hydrocarbons. These technologies use electricity generated from solar or wind power to produce hydrogen biofuels that could be used to mitigate transportation emissions.
“In the upcoming decades we’ll see an explosion in renewable electricity,” said Matthew Realff, a professor in the School of Chemical and Biomolecular Engineering. “Yet because solar and wind power can be produced abundantly at certain times of the year, and not so much at other times, we’re challenged to find a way to store renewable energy over long seasonal cycles.”
Granted, a great deal of energy is needed to drive the electrolysis of water and produce hydrogen. Yet if electricity from renewable sources is used when production exceeds demand, the resulting hydrocarbon fuels can be used at a later time and serve as an energy storage medium.
Another positive, these hydrocarbon fuels can be plugged into our current distribution system, Realff pointed out. “This would eliminate the need to spend lots of money building an entirely new infrastructure for electric cars. People underestimate the value of not disrupting social patterns, and with these fuels no one would have to change cars or the patterns of their lives.”
Among renewable hydrocarbon projects:
- Georgia Tech is working with Global Thermostat and Algenol Biotech to remove CO2 from the air using DAC technology and deliver it to algae bioreactors, a $2.5 million project funded by the U.S. Department of Energy (DOE). The goal is to grow biomass for biofuel production that can be cost competitive with conventional fuels. “If successful, you could imagine a closed-loop CO2 cycle,” Jones explained. “Carbon dioxide is removed from the air and fed to algae. The algae grow and are then converted to a biofuel that we burn in planes or cars. When the carbon dioxide is reemitted, we can capture it again.”
- Another DOE-backed project looks at capturing CO2 emitted by power plants and directly converting it into xylenes, which are precursor chemicals to polyethylene terephthalate (PET) used in plastic bottles. Researchers in the Jones, Realff, and A.J. Medford labs aim to make the conversion process more efficient and less costly by developing catalysts that can perform two reactions in a single step.
This federal funding indicates expanded support for CO2 utilization projects — and investment in DAC for the first time, which is significant because DAC has been controversial. “Strident environmentalists fear it will reduce the urgency society feels to get off fossil fuels,” Jones explained. “Yet with the right balance of incentives and regulations, DAC is an opportunity to wean ourselves off fossil fuels and transition to an entirely renewable infrastructure without causing major damage to the economy.”
Addressing other climate change challenges, Georgia Tech researchers are focused on new cooling technologies.
Air conditioning is a twofold problem due to demand on the grid and refrigerant emissions that trap heat in the atmosphere. Hydrofluorocarbons (HFCs) used in refrigerants only represent about 2 percent of greenhouse gases, but have a much higher global warming potential than carbon dioxide, explained Shannon Yee, an assistant professor in the George W. Woodruff School of Mechanical Engineering. “What’s more, demand for air conditioning is increasing due to global population growth, urbanization, and greater access to low-cost electricity.”
Aravindh Rajan, one of Yee’s graduate students, has been exploring a new type of cooling — turning a battery into an air conditioner.
Ph.D. student Aravindh Rajan and Assistant Professor Shannon Yee are taking advantage of the endothermic reaction that occurs when batteries are charged. Their work could provide an alternative cooling technique.
Most battery research focuses on energy storage and concern about overheating and fire risks due to exothermic (heat releasing) reactions during discharge. “Yet what’s been overlooked is that batteries also have the potential to cool,” Yee said.
Rajan has developed a thermodynamic process to leverage the endothermic (heat absorbing) reaction that takes place when a battery is charged. Although still in its infancy, the technology shows potential for a high coefficient of performance.
How it works: In a lab prototype, two flow batteries operate at different temperatures (heating and cooling) next to two heat exchangers. The system pumps heat by circulating two battery fluids (an anolyte and a catholyte) in a closed-loop fashion, continuously charging and discharging the battery. “As the system goes through the exothermic and endothermic reactions, it can absorb heat from the ambient environment in a house and move it outside,” explained Rajan. “The system is similar to a heat pump, except there are no noisy compressors, and the heat transfer is done in a more compact framework.”
Yee’s team is also developing polymer-based thermoelectric (TE) materials for wearable devices to help people feel warmer or cooler on demand. “This is already possible using inorganic TEs, but results in bulky ceramic devices,” Yee said. “With polymers, we can literally paint or spray material, resulting in more comfortable and stylish options.” The polymer TE materials could either harvest body heat to generate electricity or be used to produce a cooling sensation by hooking up a flexible battery to the circuitry, he explained.
It’s still early days for the technology, but researchers have made strides with a new n-type polymer. In contrast to existing n-types that oxidize readily, this new polymer remains stable in air. For a proof-of-concept project, the researchers have created the first textile-integrated thermoelectric shirt, which features a Georgia Tech logo made from the novel polymers.
Albeit a niche application, Yee believes polymer TEGs could achieve significant savings. “Forty percent of electricity from power plants is used for heating and cooling, which we could utilize better,” he said. “If we can provide heating and cooling locally so individuals feel more comfortable, we may be able to use less energy to heat and cool open spaces.”
Urban areas, home to 55 percent of the human population (a number expected to hit 68 percent by 2050), have unique vulnerabilities when it comes to climate change, points out Brian Stone, a professor in Georgia Tech’s School of City and Regional Planning and director of the Urban Climate Lab (UCL).
One of the few groups in the country to focus on urban warming, UCL researchers have discovered that temperatures in large U.S. cities are rising at more than twice the global rate (with Atlanta ranked third among the most rapidly warming metro areas). This “heat island effect” occurs for four reasons:
- Loss of natural vegetation, which reduces shading and water vapor released by plants.
- Asphalt, concrete, and other construction materials increase the earth’s capacity to absorb, store, and reemit more heat.
- Waste heat generated from industry, transportation, and buildings.
- Tall building and street canyons trap solar radiation, making it difficult to escape.
A network of 30 weather sensors like this one monitors climate trends on the Georgia Tech campus.
As a result, urban residents face greater risks to their health and infrastructure. Yet there is also an opportunity. “Because cities control land use within their boundaries, they don’t need an international climate regime or the U.S. Congress to take action,” Stone explained.
UCL researchers not only evaluate cities’ rate of warming, but also find ways to mitigate heat. One method is the use of “cool materials” (construction materials that are engineered for high surface reflection and store less heat energy).
Natural solutions also come into play. For example, working with officials in Dallas, Texas, UCL determined that significant cooling and health benefits could be achieved by planting 250,000 trees. In fact, the trees would be 3.5 times more effective in lowering temperatures than cool materials.
Emory University students Miranda Mitchell and Elena Jordanov describe their research during a poster session conducted as part of the Carbon Reduction Challenge. Mitchell recently graduated with a master's degree in epidemiology, and Jordanov is a public health student and graduate intern in Emory's Office of Sustainability Initiatives.
Precise measurement and modeling at the neighborhood level are the keys to making such recommendations, Stone said. “For cities to adopt ordinances and programs that mitigate urban warming, you have to have very detailed, actionable numbers.”
Closer to home, UCL has installed a network of weather sensors around the Georgia Tech campus to monitor climate trends and assess the benefits of recently added vegetation and cool materials. “Although there are a few larger networks in the country, we believe ours to be the densest, with 30 sensors spread across a single campus,” said Stone.
Reducing companies’ carbon footprint
Climate change affects businesses in a wide variety of ways, from their ability to operate in areas with severe weather, to water scarcity or extreme temperatures, to benefiting from energy efficiency, said Beril Toktay, the Brady Family Chair in Management and faculty director of the Ray C. Anderson Center for Sustainable Business in the Scheller College of Business, and co-director of the Carbon Reduction Challenge.
The challenge helps companies find ways to both reduce energy consumption and embrace more renewable sources. This award-winning program began as a class project initiated by Professor Kim Cobb in 2007, and then in partnership with Toktay, it was expanded two years ago to include students in Georgia Tech co-op and internship programs. Participants talk with employees in various departments at companies to devise strategies for reducing carbon emissions and simultaneously saving money.
For example, one team looked at the carbon footprint of employee travel at a company where the default option for rental cars was a medium-sized vehicle. Students showed that if only 50 percent of employees went with a compact model, the company could reduce carbon emissions by 100,000 pounds and save $40,000 per year.
Since the program’s inception, student recommendations implemented by companies have saved more than 40 million pounds of carbon dioxide — equivalent to removing 4,000 cars from roads for an entire year.
“The program shows how both student interns and employees can be sustainability ambassadors within their organizations — even if sustainability isn’t in their job title,” said Toktay. “We’ve also had interest from other universities in the U.S. and Europe to implement this program, and we’re excited to have even broader impact.”
Helping communities adapt
Last August, Georgia Tech researchers began developing a network of internet-enabled, water-level sensors on bridges and other critical infrastructure across Chatham County on the Georgia coast. A partnership between Georgia Tech, Chatham Emergency Management Agency, and the City of Savannah, the sensors provide real-time data on coastal flooding for use in emergency planning and response.
High-water events are becoming more frequent in Savannah and Chatham County. These events include blue sky flooding not associated with storms.
“During a storm or high-water event, water can compromise bridges and other transportation infrastructure, which engineering teams must inspect before declaring safe to use,” explained Russell Clark, a senior research scientist in Georgia Tech’s School of Computer Science. “The sensors tell officials which bridges need to be inspected so we can focus inspectors and get roads opened more quickly.”
Beyond major storm events, the network also provides data on blue sky flooding (caused by the moon’s gravitational pull), which is becoming more common. “Flooding typically varies across the region depending on wind direction, amount of rain, and other factors,” Clark said. “The idea is to have a high density of data points so we can see what’s going on in every neighborhood, street, dock, and river throughout a community.”
A network of sensors is helping officials understand the issues governing flooding in the complex waterways of Chatham County.
The sensor package developed by Georgia Tech leverages LoRa, a wireless radio technology with extremely long range and low power requirements, which drastically reduces costs. Though traditional water-level sensors used by NOAA and other weather agencies cost thousands of dollars, price tags for the LoRa sensors run about $300 apiece.
“Instead of being submerged, our ultrasonic sensors read the water level from above, which greatly simplifies installation and maintenance,” Clark said, noting that the low power requirements of the LoRa technology enable sensor batteries to last up to five years. “Compared to previous technologies, this gives us the ability to install sensors at much greater densities, providing a far more detailed picture of what’s going on in the community so we can both forecast and respond better.”
Another hallmark of the project is its educational component. Students at Savannah’s Jenkins High School are assembling and testing some of the sensor packages as part of an engineering course. The information about what’s going on in the waterways will also be incorporated into lesson plans for sixth-grade students.
Fifty sensors will be deployed by this summer. “Yet this is just the beginning,” Clark said. “The network architecture can be used for other applications. We can monitor environmental parameters such as air quality, water temperature, and salinity levels — and tell a richer story about what’s going on ecologically.”
A network of 50 low-cost sensors is being installed on bridges in the Chatham County area to help understand what's happening in the waterways.
Improving energy infrastructure
Better data can also improve design and deployment of energy infrastructure. “Power plants are long-lived assets, so policy and decisions we make about fuel use matter for a long time,” pointed out Emily Grubert, an assistant professor in Georgia Tech’s School of Civil and Environmental Engineering.
In an analysis of the U.S. electric system’s evolution, Grubert has developed a digital map that shows existing power plants (the oldest dating back to 1891), which can be filtered by capacity, age, and fuel type. Grubert’s next step is to add emission numbers at both the plant and utility levels. Among its uses, the map helps visualize the influence of policymaking on the electrical grid. Case in point: A 1992 production tax credit dramatically accelerated wind farms and a 2005 investment tax credit resulted in a proliferation of solar-energy plants.
Grubert is also investigating how dams can be used to support intermittent renewable energy on the grid. Armed with five years of flow data (7 million hours) from U.S. dams, she is identifying priorities that may restrict or facilitate their use for electricity generation. For example, do communities use a waterway for navigation or trade? “The goal is to provide data for more realistic modeling of what the hydro system can do — and a better sense of cost and technology hurdles that need to be met,” she explained.
“Tension around climate solutions often stems from people’s concern that one priority will cause something else they really care about to be ignored,” Grubert added. “Yet by being conscious that these massive systems have a lot of interactions, we can make policy choices and design things that address more than one priority.”
A map developed by Emily Grubert shows the locations of U.S. power plants and their capacity, age, and fuel type.
New engineering challenges
Indeed, climate change requires a new way of thinking, especially from civil engineers, Clough stressed. He points to a recent report from the National Academies of Sciences, Engineering, and Medicine, “Environmental Engineering for the 21st Century: Addressing Grand Challenges,” which identifies climate change among the top five global problems. A comprehensive analysis of these issues and the evolving role of engineers, the study calls for greater interdisciplinary research, diverse collaborations, and stronger partnerships with communities and local stakeholders.
“It’s important for engineers to be more holistic — and much more conscious of social and political issues,” said Clough, who served on the committee that authored the report, along with John Crittenden, director of Georgia Tech’s Brook Byers Institute for Sustainable Systems. “For example, if you’re working on a new building, it can’t be a standalone project. You have to think about how that site connects with everything else in the area.”
Engineers must also become more adept at dealing with increasing uncertainty, he added. “Scientists may predict that sea level will be 2 to 4 feet higher in the future, but for an engineer, the difference between 2 and 4 feet is huge.”
Educational reforms will be important in addressing these new demands. Engineering students need in-depth training in scientific subspecialties as well data science, systems analysis, social sciences, global culture, policy, and law. “This is clearly about research and knowledge discovery, but it’s also about equipping young people with the skills needed for future innovations,”
Clough said. “Right now, we’re just scratching the surface.”
Resolving climate change is part mitigation and part adaptation, Clough concluded: “We’ve got to work both sides of the coin, and engineers have a leadership role in both. Because we bring a systems-level perspective to the table, engineers can serve as a bridge across disciplines to develop and implement effective solutions.”
T.J. Becker is a freelance writer based in Michigan. She writes about business and technology issues.