A solar energy material that is remarkably durable and affordable is regrettably also unusable if it barely generates electricity, thus many researchers had abandoned emerging organic solar technologies. But lately, a shift in the underlying chemistry has boosted power output, and a new study has revealed counterintuitive tweaks making the new chemistry successful.

The shift is from "fullerene" to "non-fullerene acceptors" (NFAs), terms detailed below, and in photovoltaic electricity generation, the acceptor is a molecule with the potential to be to electrons what a catcher is to a baseball. Corresponding donor molecules “pitch” electrons to acceptor “catchers” to create electric current. Highly cited chemist Jean-Luc Brédas at the Georgia Institute of Technology has furthered the technology and also led the new study.

“NFAs are complex beasts and do things that current silicon solar technology does not. You can shape them, make them semi-transparent or colored. But their big potential is in the possibility of fine-tuning how they free up and move electrons to generate electricity,” said Brédas, a Regents Professor in Georgia Tech’s School of Chemistry and Biochemistry.

Gaining on silicon

In just the last four years, tuning NFA chemistry has boosted organic photovoltaic technology from initially converting only 1% of sunlight into electricity to 18% conversion in recent experiments. By comparison, high-quality silicon solar modules already on the market convert about 20%.

“Theory says we should be able to reach over 25% conversion with organic NFA-based solar if we can control energy loss by way of the morphology,” said Tonghui Wang, a postdoctoral researcher in Brédas’ lab and first author of the study.

Morphology, the shapes molecules take in a material, is key to NFA solar technology’s heightened efficiency, but how that works on the molecular level has been a mystery. The new study carefully modeled tiny tweaks to molecular shapes and calculated corresponding energy conversion in a common NFA electron donor/acceptor pairing.

Improved performance came not from tweaks to the metaphorical hand of the catcher nor from the donor’s pitching hand but from something akin to positions of the catcher’s feet. Some positions better aligned the “body” of the acceptor with that of the electron donor.

The “feet” were a tiny component, a methoxy group, on the acceptor, and two positions out of four possible positions it took boosted the conversion of light into electricity from 6% to 12%. Brédas and Wang published their study, Organic Solar Cells Based on Non-Fullerene Small Molecule Acceptors: Impact of Substituent Position, on November 20, 2019, in the journal Matter. The research was funded by the Office of Naval Research.

(The donor/acceptor chemical pair was PBDB-T / IT-OM-1, -2, -3, or -4, with -2 and -3 showing superior electricity generation. See the citation at bottom for a complete chemical name.)

Clunky silicon cells

Marketable NFA-based solar cells could have many advantages over silicon, which requires mining quartz gravel, smelting it like iron, purifying it like steel, then cutting and machining it. By contrast, organic solar cells start as inexpensive solvents that can be printed onto surfaces.

Silicon cells are usually stiff and heavy and weaken with heat and light stress, whereas NFA-based solar cells are light, flexible, and stress-resistant. They also have more complex photoelectric properties. In NFA-based photoactive layers, when photons excite electrons out of the outer orbits of donor molecules, the electrons dance around the electron holes they have created, setting them up for a customized handoff to acceptors.

“Silicon pops an electron out of orbit when photons excite it past a threshold. It’s on or off; you either get a conduction electron or no conduction electron,” said Brédas, who is also Vasser Woolley Chair in Molecular Design at Georgia Tech. “NFAs are subtler. An electron donor reaches out an electron, and the electron acceptor tugs it away. The ability to adjust morphology makes the electron handoff tunable.”

Not a fullerene

Like the name says, non-fullerene acceptors are not fullerenes, which are pure carbon molecules with rather uniform and geometric structures of repeating pentagonal or hexagonal elements. Nanotubes, graphene, and soot are examples of fullerenes, which are named after architect Buckminster Fuller, who was famous for designing geodesic domes.

Fullerenes are more ridged in molecular structure and tunability than non-fullerenes, which are more freely designed to be floppy and bendable. NFA-based donors and acceptors can wrap around each other like precise swirls of chocolate and vanilla batter in a Bundt cake, giving them advantages beyond electron donating and accepting – such as better molecular packing in a material.

“Another point is how the acceptor molecules are connected to each other so that the accepted electron has a conductive path to an electrode,” Brédas said. “And it goes for the donors, too.”

As in any solar cell, conduction electrons need a way out of the photovoltaic material into an electrode, and there has to be a return path to the opposite electrode for arriving electrons to fill holes that departing electrons left behind.

Highly impactful citations

Brédas’ accolades are numerous, but he has particularly gained attention for his Google Scholar h-index score, a calculation of the impact of a researcher’s publications. Breda’s current score of 146 likely places him in the 700 most-impactful published researchers in modern global history.

He has been a particularly noted leader in photoelectric and semiconductor research based on affordable and practical organic chemistry.

Also Read: The International Space Station tests carbon nanotube organic solar cells

The research was funded by the Office of Naval Research (award N00014-17-1-2208). Any findings, conclusions, or recommendations are those of the authors and not necessarily of the Naval Office of Research. PBDB-T is an abbreviation for: poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophen)-co-(1,3-di(5-thiophene-2-yl)-5,7-bis(2-ethylhexyl)benzo[1,2-c:4,5-c′]dithiophene)-4,8-dione)]

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If endangered air quality energy regulations and incentives fall flat, carbon gas emissions are predicted to accelerate. Additional pollutants from coal power plants would synergize with global warming to hamper the thus far successful fight against harmful ozone, according to a new study. Then ground-level O₃, which damages the human respiratory system, may eventually resurge.

Energy policy expert Marilyn Brown explained to Research Horizons online the current peril facing many emissions-related policies face. This is a companion article to one written about the study.

Brown is a Regents Professor and Brook Byers Professor of Sustainable Systems in the Georgia Institute of Technology’s School of Public Policy. She co-authored the new ozone study with researchers in the School of Civil and Environmental Engineering that modeled what stripping away the policies could do to future ozone levels.

Research Horizons: Before we get to emissions and energy regulations, there is a perhaps larger, very serious issue: What is happening to the generous tax incentives for people and companies who contribute to cleaner air and lower carbon emissions?

Marilyn Brown: Some incentives are being retired early like production and investment tax credits, which have been very influential in the spread of solar and wind power. A major one, the Investment Tax Credit gives a 30% tax reduction for investments in solar or wind farms or the purchase of solar rooftop panels by homeowners. The Production Tax Credit for utilities reduces tax liabilities by 23 cents for each kilowatt-hour of electricity generated by solar, wind or other renewable energy sources. These measures have been absolutely transformational in the U.S. power industry.

RH: Where did these incentives come from, and how long have they been in place?

Brown: They started spreading at the state level probably about 30 years ago. Iowa was the first state with its significant wind resources. With the Energy Policy Act of 1992, the incentives became national policy. Tax credits have been an on-and-off policy but mostly on, and they have really helped remake the energy landscape. But the incentives have to be renewed periodically, and then they go up for debate in Congress.

RH: Has this been a partisan issue? One party came up with the incentives, and the other has tried to knock them down?

Brown: That’s not what we’ve seen. These were not partisan agendas in particular in their implementation. For example, the last extension of the Production Tax Credits two years ago benefitted the economics of Plant Vogtle’s two new units, because nuclear power now qualifies as an eligible resource. These incentives have been on a planned gradual retirement trajectory.

In our new study, we just removed them entirely, along with other key policies under threat to see the effect on ozone levels with them completely gone. Such removal actions are occasionally debated in Congress, so it’s not unrealistic to see them suddenly disappear. The paper quantifies the resulting ozone penalty, and that is a first. Our results show that we would have less success fighting ozone, and eventually it would resurge, which would be bad for the health of many people. Costs would rise sharply for places in ozone non-attainment to try to meet healthy targets, and many of them would fail, as many do today.

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RH: But there was recently a more political back-and-forth over a plan by the previous administration, correct?

Brown: The last administration created the Clean Power Plan (CPP), and it was stayed – not approved – by federal courts in 2016, so it was not implemented. The current administration basically replaced it with the Affordable Clean Energy (ACE) plan. CPP would have phased out coal-fired electricity generation in favor of natural gas and sustainable energy solutions. ACE, on the other hand, emphasizes improvement in the efficiency of coal plants, but there is a strong a consensus that coal plants can’t be made much more efficient.

RH: Foundational clean air regulations, the iconic Corporate Average Fuel Economy, or CAFE, standards – first enacted in 1975 – are also under threat.

Brown: The CAFE standards are very much up in the air right now. They could be frozen or done away with, but the automobile industry appears to be divided on this. Seventeen auto makers – Ford and Honda among them – came out in support of CAFE’s progressive tightening of fuel standards because they said doing away with them could destabilize their industry. CAFE lays down a trajectory of improvement that car makers are already anticipating in their product engineering. But CAFE is also being litigated. Also, California has the right to have its own emissions standards, which have a strong influence on fuel economy for all cars sold in the U.S., and that’s being challenged, too.

RH: Why the concentration on ozone in the study as opposed to, say, particulates?

Brown: The Clean Air Act regulates many pollutants, but it seems that ozone is the one we are having the most trouble with. Thirty percent of Americans live with levels exceeding public health targets. Progress has been quite slow because ozone’s precursors come from coal plants, and those precursors are what have to be regulated. There are no new coal plants under construction or plans to build any, but many coal plants are still active, and they can boost capacity a lot. For example, you could get about 250% more coal being used in the Great Lakes region by 2050. That would come from existing coal plants being dispatched much more.

RH: It sounds like many things could converge at once.

Brown: If they did, it could make for a perfect ozone storm. But keep in mind that there are other forces at work like the market and technology as well as consumer choices and other innovations that could help keep the fight against ozone going — actually against many pollutants and greenhouse gases.

Also READ the main article: This study shows what could happen to harmful ozone levels if endangered federal energy-air quality regulations are not rescued.

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Pollutants from coal-fired power plants help make ground-level ozone, and a warming world exacerbates that. Recent rollbacks of U.S. energy regulations may speed climate change, keep pollutants coming, and thus slow the fight against harmful ozone, according to a new study.

Currently, 30% of the U.S. population lives with ozone levels that exceed government health standards. Though past environmental regulations have vastly helped clean the air and put the U.S. on a positive trajectory to reduce pollutants — including ozone — policy rollbacks back could slow the progress and even reverse it, researchers from the Georgia Institute of Technology said.

Continuing progress against ozone would pay off in better health and finances: The more ozone in the air, the more cases of respiratory illness and the higher the cost of meeting ozone level targets.

“Additional ozone is tough to control technologically. The costs would be very high — tens of billions of dollars,” said Ted Russell, a principal investigator on the study. “In the meantime, more people would die than otherwise would have.”

The researchers published their results in One Earth, a Cell Press journal on Friday, October 25, 2019. The research was funded by the U.S. Environmental Protection Agency and by the National Science Foundation.

The study focuses on ground-level ozone people breathe to the detriment of their health, which should not be confused with the stratospheric ozone that protects us from the sun’s harmful radiation.

Goodbye environmental policies

In the last three years, various energy policies have been loosened, which should result in raised CO₂ emissions and continued emissions of ozone precursors in years to come, the study’s authors said.

“Incentives are being retired like production and investment tax credits, which have been very influential in solar and wind,” said Marilyn Brown, a Regents Professor in Georgia Tech’s School of Public Policy and a principal investigator on the study. “The Investment Tax Credit gives a 30% tax reduction for investments in solar or wind farms or the purchase of solar rooftop panels by homeowners. The Production Tax Credit for utilities reduces tax liabilities by 23 cents for each kilowatt-hour of electricity generated by solar, wind or other renewable energy sources.”

But one policy move in particular stands to keep more ingredients in the ozone-making cauldron: courts preventing the Clean Power Plan (CPP) from going into effect and its replacement with the Trump administration’s Affordable Clean Energy (ACE) plan.

ACE, which also has not been implemented, would make it easier to continue burning fossil fuels, particularly coal, according to Brown, who was a member of the Intergovernmental Panel on Climate Change, which received a Nobel Peace Prize in 2007. CPP would have phased out those generators, reducing nitrogen oxide gases, or NO_X, key reactants in the production of ozone.

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From NO_X to noxious

“The major target of the CPP was CO₂, but it had side effects on the reduction of NO_X because it shifted coal use to natural gas as well as to renewable sources,” said Huizhong Shen, a postdoctoral researcher in Russell’s group and one of the study’s first authors.

The study modeled atmospheric chemistry that produces O₃ around commonly predicted trajectories for greenhouse gas emissions and climate change paired with anticipated pollutant emissions, particularly of NO_X. The model’s output depicted “non-attainment” scores, which refer to the number of U.S. counties exceeding ozone targets and by how much.

The study modeled against official targets for ozone levels and in addition, against cleaner standards widely held to be attainable and much healthier for people. Models built around rolled-back environmental regulations and increased warming initially showed the current trajectory of progress against ozone levels continuing — but later reversing. Ozone levels then rose again, putting many more counties in non-attainment by or before 2050.

Nature’s surprise ingredient

Alongside human-produced NO_X, nature contributes ozone-making ingredients that aren’t harmful per se and often smell great, like the aroma of cut grass or of a pine tree. They are examples of volatile organic compounds (VOCs), of which nature produces hundreds.

VOCs get into the air easily and react readily with other chemicals. The warmer the air and the sun, the more vegetation produces VOCs that meet with raised levels of NO_X emissions to make ozone. It forms downstream from emissions sources, making it hard to regulate. 

“There are no ozone emissions, just precursor emissions,” Shen said. “So, emission controls for ozone have to mainly target NO_X emissions.”

Feedbacks and pile-ons

Keeping ozone around as the world warms will be more than just the sum of power plants still emitting NO_X plus boosted VOC emissions.

“If you heat up the air, it also speeds up photochemical reactions involved in ozone production,” Shen said.

“Ozone is a greenhouse gas, so it adds some climate change feedback, too,” said Russell, who is Howard T. Tellepsen Chair and Regents Professor in Georgia Tech’s School of Civil and Environmental Engineering. “You can also have increased vegetation emissions of ammonia. Some of this goes on to form particulate matter, which is also harmful to the lungs.” 

Passing the buck

When coal-fired power plants emit NO_X, the ozone strikes miles away.

“Ozone can occur hundreds of miles away, so if controls are loosened in one state to save industry money there, a state downstream may have to spend even more to try to meet ozone targets. You transfer the problem and the costs,” Russell said. “Most U.S. cities are already not in attainment, and this will likely make it harder for them to get there.”

Also READ the companion piece on policy: U.S. Carbon and Pollution Emissions Policies are ‘Up in the Air’

The co-authors of the research are: Yilin Chen, Yufei Li, Yongtao Hu, Mehmet Odman, Momei Qin, Abiola Lawal, Gertrude Pavur, and Marilyn Brown of Georgia Tech; Zhihong Chen of Georgia Tech and the Chinese University of Hong Kong; Jhih-Shyang Shih and Dallas Burtraw of Resources for the Future; Lucas Henneman of Harvard University; Shuai Shao and Charles Driscoll of Syracuse University; and Haofei Yu of the University of Central Florida. The research was funded by the U.S. Environmental Protection Agency (grant R835880) and the National Science Foundation (grant 1444745). Any findings, conclusions, or recommendations are those of the authors and not necessarily of the funding agencies. Ted Russell served on the Clean Air Scientific Advisory Committee during the administration of President Barack Obama.

DOI: https://doi.org/10.1016/j.oneear.2019.09.006 

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Email: ben.brumfield@comm.gatech.edu

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The U.S. Department of Energy (DOE) has announced that the National Alliance for Water Innovation (NAWI) has been chosen to lead a large research and development effort called the Energy-Water Desalination Hub. This effort is targeted at addressing water security issues in the United States by developing innovative water treatment technologies that can make “non-traditional” water sources available for a wide range of potable and non-potable uses. 

The Georgia Institute of Technology is a member of this multi-institutional public-private team, led by the Lawrence Berkeley National Laboratory. Total federal funding for this five-year research center is expected to reach $100 million. NAWI is a research network with more than 35 members, including Georgia Tech, and more than 180 organizations that will collaborate with the National Energy Technology Laboratory, National Renewable Energy Laboratory, and Oak Ridge National Laboratory.

Georgia Tech has researchers with expertise in specialties that will prove vital to the success of this effort, such as water treatment systems analysis (John Crittenden, director, Brook Byers Institute for Sustainable Systems), and advanced manufacturing (Chris Saldana and Thomas Kurfess, professors in the George W. Woodruff School of Mechanical Engineering). Marta Hatzell, professor in the School of Mechanical Engineering, and Rich Simmons, senior research engineer at the Strategic Energy Institute, were technical liaisons during the two-year proposal development process, offering expertise in water research related to electric power generation and thermal systems.  

Following the negotiation of the final award, the NAWI team and DOE will work together to develop a research roadmap. It is expected that Georgia Tech researchers in additional disciplines such as thermal systems, materials separation and cooling for electric power generation will be called on to contribute as well. 

“Working with the NAWI team, we will enable a secure set of next-generation water treatment technologies, ensuring a safe and plentiful supply of water for the United States,” Kurfess said. “The work will also have implications on legacy systems providing a path toward modernization. With this team in place, the future of this critical resource is in great shape.”

"This initiative is a great opportunity for our team to leverage new distributed sensing and analytics methods, as well as rapidly maturing manufacturing capabilities based on additive and hybrid manufacturing, to address major challenges in scalable and effective water treatment,” Saldana said.

The overarching goal for NAWI is to develop a range of novel technologies within 10 years to treat the vast majority of non-traditional water resources, such as brackish water, seawater, and water that comes from oil drilling operations — known as “produced waters” — at a cost that is competitive with conventional water treatment. 

“Current technologies for desalination are among the most energy intensive methods for water purification that we employ,” Crittenden said. “Innovating desalination technologies for greater energy efficiency and smaller scale will drastically improve the sustainability of water resources, not only in the U.S., but globally as well.”

Achieving this goal will also transform water treatment from a linear economic and use model to a circular model. Water treatment is usually thought of in the context of drinking water, but treating non-traditional water sources can yield resources that are safe and suitable for a variety of non-potable uses, such as agriculture, industry, energy utilities, oil and gas production, and others. 

NAWI plans to reach its goal by focusing on technologies and manufacturing processes that apply to small-scale, affordable, decentralized, energy-efficient, and purpose-specific desalination systems. Placing purification systems where water is used will make it possible to use the same water resource multiple times, or even indefinitely, in a cost-effective manner, thus reducing the burden on potable water infrastructure. 

In keeping with the philosophy of similar DOE hub-scale initiatives, NAWI will pursue a comprehensive research agenda that spans fundamental to applied research and development, through demonstration and initial scale up. As such, the Hub’s strategy includes a focus on early-stage and enabling research, which is often costly or complex for established manufacturers and suppliers of desalination systems. Likewise, the Hub will emphasize research that addresses manufacturing challenges and emerging capabilities to accelerate the transition of technology from the lab to the marketplace.  

Lack of fresh water presents enormous implications on quality of life, including wellness and economic development in the U.S. and beyond. The award for the Energy-Water Desalination Hub to the National Alliance for Water Innovation represents a major effort by the U.S. public and private sectors to support major innovations that will lead to long-term water security. 

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Writers: Brent Verrill and Alyson Powell Key

Using a new time-based method to control light from an ultrafast laser, researchers have developed a nanoscale 3D printing technique that can fabricate tiny structures a thousand times faster than conventional two-photon lithography (TPL) techniques, without sacrificing resolution.

Despite the high throughput, the new parallelized technique — known as femtosecond projection TPL (FP-TPL) — produces depth resolution of 175 nanometers, which is better than established methods and can fabricate structures with 90-degree overhangs that can’t currently be made. The technique could lead to manufacturing-scale production of bioscaffolds, flexible electronics, electrochemical interfaces, micro-optics, mechanical and optical metamaterials, and other functional micro- and nanostructures.

The work, reported Oct. 3 in the journal Science, was done by researchers from Lawrence Livermore National Laboratory (LLNL) and The Chinese University of Hong Kong. Sourabh Saha, the paper’s lead and corresponding author, is now an assistant professor in the George W. Woodruff School of Mechanical Engineering at the Georgia Institute of Technology.

Existing nanoscale additive manufacturing techniques use a single spot of high-intensity light — typically around 700 to 800 nanometers in diameter — to convert photopolymer materials from liquids to solids. Because the point must scan through the entire structure being fabricated, the existing TPL technique can require many hours to produce complex 3D structures, which limits its ability to be scaled up for practical applications.

“Instead of using a single point of light, we project a million points simultaneously,” said Saha. “This scales up the process dramatically because instead of working with a single point that has to be scanned to create the structure, we can use an entire plane of projected light. Instead of focusing a single point, we have an entire focused plane that can be patterned into arbitrary structures.”

To create a million points, the researchers use a digital mask similar to those used in projectors to create images and videos. In this case, the mask controls a femtosecond laser to create the desired light pattern in the precursor liquid polymer material. The high-intensity light causes a polymerization reaction that turns the liquid to solid, where desired, to create 3D structures.

Each layer of the fabricated structure is formed by a 35-femtosecond burst of high-intensity light. The projector and mask are then used to create layer after layer until the entire structure is produced. The liquid polymer is then removed, leaving behind the solid. The FP-TPL technique allows the researchers to produce in eight minutes a structure that would take several hours to produce using earlier processes.

“The parallel two-photon system that has been developed is a breakthrough in nanoscale printing that will enable the remarkable performance in materials and structures at this size scale to be realized in usable components,” said LLNL’s Center for Engineered Materials and Manufacturing Director Chris Spadaccini.

Unlike consumer 3D printing that uses particles sprayed onto a surface, the new technique goes deep into the liquid precursor, allowing the fabrication of structures that could not be produced with surface fabrication alone. For instance, the technique can produce what Saha calls an “impossible bridge” with 90-degree overhangs and with more than a 1,000:1 aspect ratio of length to feature size. “We can project the light to any depth that we want in the material, so we can make suspended 3D structures,” he said. 

The researchers have printed suspended structures a millimeter long between bases that are smaller than 100 microns by 100 microns. The structure doesn’t collapse while being fabricated because the liquid and solid are about the same density — and the production happens so quickly that the liquid doesn’t have time to be disturbed.

Beyond bridges, the researchers made a variety of structures chosen to demonstrate the technique, including micro-pillars, cuboids, log-piles, wires and spirals. The researchers used conventional polymer precursors, but Saha believes the technique would also work for metals and ceramics that can be generated from precursor polymers.

“The real application for this would be in industrial-scale production of small devices that may be integrated into larger products, such as components in smartphones,” he said. “The next step is to demonstrate that we can print with other materials to expand the material palette.”

Research groups have been working for years to accelerate the two-photon lithography process used to produce nanoscale 3D structures. The success of this group came from adopting a different way of focusing the light, using its time-domain properties, which allowed production of very thin light sheets capable of high resolution — and tiny features.

Use of the femtosecond laser allowed the research team to maintain enough light intensity to trigger the two-photon process polymerization while keeping the point sizes thin. In the FP-TPL technique, the femtosecond pulses are stretched and compressed as they pass through the optical system to implement temporal focusing. The process, which can generate 3D features smaller than the diffraction-limited, focused light spot, requires that two photons hit the liquid precursor molecules simultaneously. 

“Traditionally, there are tradeoffs between speed and resolution,” Saha said. “If you want a faster process, you would lose resolution. We have broken this engineering tradeoff, allowing us to print a thousand times faster with the smallest of features.”

At Georgia Tech, Saha intends to continue advancing the work with new materials and further scale-up of the process.

“So far, we have shown that we can do pretty well on speed and resolution,” he said. “The next questions will be how well we can predict the features and how well we can control the quality over large scales. That will require more work to understand the process itself.”

CITATION: Sourabh K. Saha, Dien Wang, Vu H. Nguyen, Yina Chang, James S. Oakdale, Shih-Chi Chen, “Scalable submicrometer additive manufacturing.” (Science 2019). http://dx.doi.org/10.1126/science.aax8760

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Media Relations Contact: John Toon (404-894-6986) (jtoon@gatech.edu).

Writer: John Toon

Brook Byers Professors Bert Bras and Marc Weissburg have been awarded a $100K National Science Foundation Engineering Research Center (ERC) Planning Grant, along with their co-principal investigators Srinivas Garimella and Shannon Yee, also from Georgia Tech, and Scott Turner from The State University of New York. The ERC is a highly competitive, large, multi-year award centered on translating a research topic from the laboratory to commercialization. The ERC Planning Grant is intended to build capacity amongst a research community around a topic with the ultimate aim of elevating the quality of proposals submitted to the ERC program.

The title of this group’s proposed ERC is “Biologically Inspired Realizable Design for Building Energy Eco-Systems (BIRDBEES).” The Center’s focus will be to develop self-sustaining, carbon-neutral building energy systems. The BIRDBEES investigators aim to accomplish this by looking to nature for inspiration in a systematic and scientific way. From this perspective, buildings are framed as living, breathing organisms with coupled fluid flow, heat and mass transfer, water and moisture transfer, complex control systems, etc. This approach is known as Biologically-Inspired Design.

Biologically-Inspired Design (BID) is an innovation method that seeks sustainable solutions by emulating nature's time-tested patterns and strategies with the goal of creating products, processes, and policies—new ways of living—that are well-adapted to life on Earth over the long haul. BID employs life's principles, such as build from the bottom up, self-assembly, optimize rather than maximize, use free energy, cross-pollinate, embrace diversity, adapt and evolve, use life-friendly materials and processes, engage in symbiotic relationships, and enhance the biosphere.

Areas of research that the BIRDBEES team sees as promising are: fundamental energy systems technology components (such as heat exchangers, pumps, insulation, building skins, and energy storage); new building systems that integrate the various components with biologically inspired controls; leveraging the clustering of buildings as ecosystems that provide even larger energy reductions through interaction of mutually beneficial bio-inspired energy systems. The ultimate goal for the BIRDBEES ERC is to show the efficacy of such an approach with real test-beds at the building and community levels. It is then hoped that such validation will lead to the commercialization of BIRDBEES technologies.

Prof. Bert Bras has held various organizational leadership positions, including interim school chair and director of an interdisciplinary research center. Prof. Marc Weissburg is a world renowned biologically inspired design expert and co-director of Georgia Tech’s Center for Biologically-Inspired Design (CBID). Prof. J. Scott Turner studies heat flow and thermal management in species like alligators, black desert beetles, termite mounds, etc. Prof. Garimella holds a Hightower Chair in Engineering and is a leading expert in building energy systems and heat transfer.

Platinum has long been used as a catalyst to enable the oxidation reduction reaction at the center of fuel cell technology. But the metal’s high cost is one factor that has hindered fuel cells from competing with cheaper ways of powering automobiles and homes.

Now researchers at the Georgia Institute of Technology have developed a new platinum-based catalytic system that is far more durable than traditional commercial systems and has a potentially longer lifespan. The new system could, over the long term, reduce the cost of producing fuel cells.

In the study, which was published July 15 in the ACS journal Nano Letters, the researchers described a possible new way to solve one of the key causes of degradation of platinum catalysts, sintering, a process in which particles of platinum migrate and clump together, reducing the specific surface area of the platinum and causing the catalytic activity to drop.

To reduce such sintering, the researchers devised a method to anchor the platinum particles to their carbon support material using bits of the element selenium.

“There are strategies out there to mitigate sintering, such as using platinum particles that are uniform in size to reduce chemical instability among them,” said Zhengming Cao, a visiting graduate student at Georgia Tech. “This new method using selenium results in a strong metal-support interaction between platinum and the carbon support material and thus remarkably enhanced durability. At the same time, the platinum particles can be used and kept at a small to attain high catalytic activity from the increased specific surface area.”

The process starts by loading nanoscale spheres of selenium onto the surface of a commercial carbon support. The selenium is then melted under high temperatures so that it spreads and uniformly covers the surface of the carbon. Then, the selenium is reacted with a salt precursor to platinum to generate particles of platinum smaller than two nanometers in diameter and evenly distributed across the carbon surface.

The covalent interaction between the selenium and platinum provides a strong link to stably anchor the platinum particles to the carbon.

“The resulting catalyst system was remarkable both for its high activity as a catalyst as well as its durability,” said Younan Xia, professor and Brock Family Chair in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University.

Because of the increased specific surface area of the nanoscale platinum, the new catalytic system initially showed catalytic activity three and a half times higher than the pristine value of a state-of-the-art commercial platinum-carbon catalyst. Then, the research team tested the catalytic system using an accelerated durability test. Even after 20,000 cycles of electropotential sweeping, the new system still provided a catalytic activity more than three times that of the commercial system.

The researchers used transmission electron microscopy at different stages of the durability test to examine why catalytic activity remained so high. They found that the selenium anchors were effective in keeping most of the platinum particles in place.

“After 20,000 cycles, most of the particles remained on the carbon support without detachment or aggregation,” Cao said. “We believe this type of catalytic system holds great potential as a scalable way to increase the durability and activity of platinum catalysts and eventually improve the feasibility of using fuel cells for a wider range of applications.”

Part of the research was supported by the U.S. Department of Energy through the electron microscopy work performed at the Center for Nanophase Materials Sciences. The work was also supported by the China Scholarship Council through the graduate student fellowship. The content is the responsibility of the authors and does not necessarily represent the official views of the sponsoring agencies.

CITATION:  Haoyan Cheng, Zhenming Cao, Zitao Chen, Ming Zhao, Minghao Xie, Zhiheng Lyu, Zhihong Zhu, Miaofang Chi and Younan Xia, “Catalytic System Based on Sub-2 nm Pt Particles and Its Extraordinary Activity and Durability for Oxygen Reduction,” (Nano Letters, July 2019). http://dx.doi.org/10.1021/acs.nanolett.9b01221

The way a ladybug folds its wings can help aerospace engineers design more compact satellites. Studying how ants dig tunnels could help us create our own tunnels more efficiently.

The idea of using nature’s examples to develop products and designs that benefit society is the cornerstone of a new project at Georgia Tech that aims to get more high school students interested in engineering.

Funded by the National Science Foundation (NSF), the $3 million effort will put high school engineering teachers in research labs at Georgia Tech for five weeks. The teachers will be embedded with engineers and scientists, working at the forefront of what’s called biologically inspired design, and creating a curriculum for the teachers to use in their classrooms.

“Lots of people think animals and what they do is insanely cool  — and the internet agrees — which means we can engage interest in engineering by making a link to biology as a way to solve engineering challenges,” said Marc Weissburg, project leader and professor in the School of Biological Sciences. “The act of trying to see how an animal might help find a solution to a problem is a very creative process. It challenges the notion that engineering is boring. High school engineering experiences vary widely, but they generally do not include the most cutting-edge topics, like bio-inspired design, which gets people really excited,” he said.

For the next four years, Weissburg will collaborate with researchers Meltem Alemdar, Michael Helms, Roxanne Moore and Michael Ryan at Georgia Tech’s Center for Education Integrating Science, Mathematics and Computing. They’ll create and assess units for 10th, 11th and 12th graders that explore bio-inspired design in the context of problems that are relatable to teenagers.

In particular, the researchers see their approach as a way to reach girls, who may not have considered engineering as a potential career. Weissburg pointed to data from the Center for Digital Education that showed 24% of male high school students expressed interest in engineering. For young women, the number was just 11%.

“Too often, engineering is depicted as applied math and science, which completely neglects how human-centered engineering is,” said Weissburg, who also co-directs the Center for Biologically Inspired Design at Georgia Tech and is a Brook Byers Professor.

The project will generate a curriculum with design and build exercises, background materials for teachers, examples to spark discussion, tests, and other resources that can be used by teachers across the country. Researchers will examine how well the curriculum engages students, particularly those from groups underrepresented in engineering.

“States have different standards, and teacher goals and classes have to be responsive to their unique student audience,” Weissburg said. “Our series of resources, all of which will be online, will allow teachers to easily slot in material that fits for them. It will allow them to talk to us and each other about best practices.”

The research team has partnered with Gwinnett County Public Schools to identify the first group of teachers they’ll invite to participate. Weissburg said that will happen in late Spring 2020.

“Bio-inspired engineering is a unique way of thinking, and so we have to help the teachers understand how to encourage this in their students.”

There’s a shiny black espresso machine prominently displayed in Shannon Yee’s office in Georgia Tech’s George W. Woodruff School of Mechanical Engineering. 

While Yee is indeed a coffee drinker, there is a more important reason for the machine’s presence: Its compact and efficient design may hold the key to meeting the needs of the approximately 2.5 billion people worldwide who now lack improved sanitation. An associate professor specializing in energy technologies, Yee is leading a $13.5 million effort funded by the Bill & Melinda Gates Foundation to reinvent the toilet — technology that hasn’t changed much in more than a century. 

High pressure, heat, and control of liquids are essential to making a good cup of espresso. They are also critical for a 21st-century toilet able to reduce human waste to clean water and benign solids, operating with no plumbing or sewerage connections – and an amount of electricity that could potentially be provided by a single solar panel.

Shifting Away from Treatment Plants

Existing toilets still rely on a key innovation patented in 1775: the S-trap, which holds water in the toilet bowl to prevent sewer gases from entering buildings containing flush toilets. It’s not that the system doesn’t work well, but the world’s poorest cannot afford the sewage treatment infrastructure necessitated by existing toilets.

“The Reinvent The Toilet Challenge (RTTC) wanted to create a momentous global shift away from sewerage systems,” said Yee. “It can no longer be about running pipes to a central treatment plant.”

Centralizing the Engineering Efforts

Research to reinvent the toilet was launched by the Gates Foundation eight years ago and those efforts have made significant progress toward this goal. But gaps remain, and the broader team will have 42 months to bridge those gaps to produce a minimum of six reinvented toilet prototypes ready for a commercial manufacturer.

The new initiative is nicknamed Generation 2 Reinvented Toilet (G2RT). It will build on the exceptional innovations developed during the original RTTC program. The goal will now be to bring the dispersed efforts together to focus on demonstrating prototypes of a single user reinvented toilet (SURT) that the world’s poorest regions can afford.

“We will have to hit a certain reduction in pathogenic markers like E. coli bacteria, and we will also have to control, treat, and handle the nitrates and phosphates associated with waste,” Yee explained. “It’s a pretty aggressive goal and those metrics will be hard to hit at a cost point of $450. And each SURT will have to operate for less than 15 cents per day.”

The G2RT project has formed three engineering teams, two of them headed by researchers from the Georgia Tech Research Institute (GTRI) – Georgia Tech’s applied research group – and one from Helbling Technik, the Swiss engineering company that designed Yee’s espresso machine. The GTRI teams will be led by Principal Research Scientist Kevin Caravati and Senior Research Scientist Ilan Stern, both of whom have been involved in creating new products. The Helbling team is being led by Christian Seiler, who holds the title of Head Of Development Process Technologies at the company.

The engineering teams are joined by researchers from other institutions, including:

• Cranfield University, led by Professors Ewan McAdam and Leon Williams
• Duke University, led by Professor Brian Stoner and Research Scientist Brian Hawkins
• University of Kwazulu Natal in South Africa, led by Professor Chris Buckley 
• University of Applied Sciences in Northwestern Switzerland (FHNW), led by Professor Frederic Vogel 
• Scion, a New Zealand company, led by Environmental Engineer Daniel Gapes

At Georgia Tech, GTRI Research Engineer Paula Gómez and microbiologist Stephanie Richter, along with Ph.D. students Bettina Thomas and Amanda Lai and undergraduate student Magdalena Ravello, will develop concepts for features that will serve women, children, seniors, and those with special needs.

The research teams will be reviewing all that has been developed so far and asking existing researchers to discuss concepts that may have been discarded along the way. Centralizing the engineering should help accelerate progress toward the G2RT finish line.

“We want to take the best concepts that have been developed and try to integrate them,” Yee said. “We will look at the problem holistically and try to deliver a series of prototypes tailored for various culturally acceptable use cases.”

Controlling Cost, Creating Value

Cost targets will require some engineering compromises, of course. Instead of using mechanical solenoids common in the developed world, for instance, the SURT will use simpler technology – perhaps a camshaft to control actuation. In addition to being inexpensive and easy to deploy, the SURT will have to be simple to maintain and repair.

For homeowners around the world, having an indoor toilet provides perceived value well beyond the cost. “How much are you willing to pay to have a toilet in your house versus the alternative? Once they have clean water and electricity, people start looking at sanitation,” Yee observed. 

That perceived value provides the basis for what could be a very large market. And that doesn’t include the value of preventing disease, improving dignity, and offering better safety.

Initially, the new toilets will likely be purchased and installed by non-governmental organizations and governments to demonstrate the potential. Then it will be up to homeowners and others to see the value and make the investment.

There are multiple engineering alternatives for what can happen to human waste inside the reinvented toilet. Suffice to say that heat and pressure will be required, and that the result will be water and a dry, odor-free sanitized solid that can be placed into municipal landfills, buried or even burned.

The Laws of Thermodynamics

Yee’s interest in the project stems from the thermodynamic issues involved. At Georgia Tech, he has pursued new methods of converting heat into useful energy and developing new cooling technologies. Success of the toilet project will depend on working within the limits of the first and second laws of thermodynamics – using the energy in solid waste, supplemented by a minimal amount of electricity, in the most efficient manner. 

“This is very much a thermodynamics and heat transfer problem,” said Yee. “It comes down to the flow of energy and how we can heat things locally to accomplish what we need with the toilet. I would say we are working at the intersection of thermodynamics, heat transfer, and chemistry.”

The strategy will require keeping solids separate from liquids, a practice that conventional sanitation systems abandoned long ago. Existing sewerage systems combine solids and liquids for transport to central treatment plants, where they must be separated – consuming large amounts of both water and energy in plants that are costly to build and operate.

“A lot of our systems today are based on having large volumes of water to transport the dilute waste streams,” Yee said. “But when you treat human waste, it’s a lot easier to treat a high solid concentration and a high liquid concentration separately.”

Originally, the reinvented toilets were supposed to work without electricity. “However, in the last decade, we have seen a dramatic decline in the cost of distributed energy from solar and other sources,” Yee said. “When you look at how rural electrification efforts are going, this electricity input seems reasonable.”

Recruiting Existing Manufacturers

The project will recruit and work with existing manufacturers – companies that can afford to invest $100 million in developing the product for manufacturing – to take over once prototypes have been built. The actual products will depend on cultural norms for each market, but will use common processing technologies.

“It’s potentially a very large market, but the entry point will be difficult,” Yee admits. “We want to work with large companies that are aligned with the Gates Foundation’s goals of global access and societal good, and help these companies access the $10 billion-per-year market with our technologies.”

But fielding reinvented toilets is only part of the battle. They will have to be maintained to keep them working. While that may seem like a major challenge in parts of the world without home repair centers nearby, it could actually provide a new source of employment, Yee noted.

“Some maintenance is required, but that’s not necessarily a bad thing,” he explained. “You can imagine having a service technician who visits periodically to change a filter.”

Opportunities in a Grand Challenge

While entrepreneurship still attracts students to universities, Yee is seeing a shift toward the excitement of tackling grand challenges like this one. “The climate is changing at universities and students seem to be focused on the big problems of the world,” he said. “We are getting into this at just the right time.”

While the main technological challenges for G2RT may require professional engineering to reduce risk for manufacturing, components of the challenge will also be open to student design projects. For instance, integrating odor control technologies and potentially including health monitoring may be projects for students to take on.

“It is quite an honor that the Gates Foundation believes we can tackle this grand challenge,” Yee said. “We are very fortunate to have the infrastructure and past investments that will allow us to do this.”

Lessons for the Developed World

While the Gates Foundation and the G2RT effort are focused on parts of the globe without improved sanitation, the reinvented toilets may ultimately find applications in large cities like Atlanta, Seattle, San Francisco, or Washington where sewerage systems may be in need of replacement. 

“It is going to be far too costly to replace all of that infrastructure at the end of its lifetime,” Yee said. “Cities in the developed world may ultimately want to move in this direction, too.”

This publication is based on research funded by the Bill & Melinda Gates Foundation. The findings and conclusions contained within are those of the authors and do not necessarily reflect positions or policies of the Bill & Melinda Gates Foundation.

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“In an era of U.S. energy abundance, the persistently high energy bills paid by low-income households is troubling.”  So begins the abstract to a new paper authored by Brook Byers Professor Marylin Brown and several co-authors.  Prof. Brown is also a Georgia Regents’ Professor, Director of the Georgia Tech Climate and Energy Policy Laboratory, and a Nobel Laureate.  The paper was recently published in the open access journal Progress in Energy, the full title of which is “Low-income Energy Affordability in an Era of U.S. Energy Abundance.”

This paper is a review of the current literature on energy costs in low-income households in the U.S.  The review reveals that socio-economic factors of the energy landscape put an onerous burden on poor households.  Programs meant to alleviate the burdens of energy insecurity are not particularly effective.  The authors draw four general conclusions:

• Energy burden is highest among low-income households.
• Low-income energy burden is worsening despite programs and funds tasked to help.
• Low-income households cannot take advantage of many of the policies and programs that promote energy efficiency and renewable energy technologies.
• Low-income utility customers receive a disproportionately small share of the funding targeted to improve residential energy efficiency.

The authors point out that the most common models for policy interventions into energy poverty were begun in the 1970’s.  Few innovations or adjustments have been made to them despite a changing energy environment.   Currently, short term solutions, like financial assistance with utility bills, vastly outweigh programs with longer term effects such as weatherization or appliance replacement programs.  The focus on the short-term financial needs of low-income rate payers tends to perpetuate energy insecurity, rather than offering efficiency investments, which have proven to be a more durable solution.

Many other policy solutions are suggested in the paper including inter-agency coordination, targeting low-income multi-family housing, implementing technology solutions such as smart thermostats, and innovations in the financing of energy upgrades.  The authors also emphasize that some programs result in additional benefits which aren’t usually accounted for.  For example, members of households that undergo a weatherization process have better overall health than those that receive other energy help.  Weatherization results in improved indoor air quality, which is thought to lead to better overall health.  This, in turn, results in multiplying the financial benefits due to reduced sick days and lower healthcare costs. 

Insights, like the one outlined above, prompted the authors to suggest more holistic and scalable approaches to addressing energy poverty in conjunction with other health and poverty related issues.  Professor Brown and her collaborators conclude that the transition to a sustainable energy future need not leave behind those at the low end of the income spectrum.