The NIST team used a powerful combination of microanalytic techniques that simultaneously image photoelectric current and chemical reaction rates across a surface on a micrometer scale. The target is a potentially efficient, cost-effective, photoelectrochemical (PEC) cell that’s essentially a solar cell that produces hydrogen gas instead of electric current.
Daniel Esposito, a NIST chemical engineer sets up the background with, “A major challenge with solar energy is dealing with solar intermittency. We demand energy constantly, but the sun’s not always going to be shining, so there’s an important need to convert solar energy into a form we can use when the sun’s not out. For large-scale energy storage or transportation, hydrogen has a lot of benefits.”
A simple PEC cell contains a semiconducting photoelectrode that absorbs photons and converts them into energetic electrons that are used to facilitate chemical reactions that split water molecules into hydrogen and oxygen gases.
Water splitting is not easy. Esposito explained he best PEC cell was been demonstrated with efficiency around 12.5% in the 1990s by the U.S. Department of Energy’s National Renewable Energy Laboratory. But, “it’s been estimated that such a cell would be extremely expensive – thousands of dollars per square meter – and they also had issues with stability,” he said.
One big problem is that the semiconductors used to achieve the best conversion efficiency also tend to be highly susceptible to corrosion by the cell’s water-based electrolyte. A PEC electrode that is efficient, stable and economical to be productive has been elusive.
The NIST team’s proposed solution is a silicon-based device using a metal-insulator-semiconductor (MIS) design that can overcome the efficiency/stability trade-off. The key is to deposit a very thin, but very uniform, layer of silicon dioxide – an insulator – on top of the semiconductor – silicon – that is well suited for doing the photon-gathering work.
On top of that is a polka-dot array of tiny electrodes consisting of platinum-covered titanium. The stable oxide layer protects the semiconductor from the electrolyte, but it’s thin enough and transparent enough that the photons will travel through it to the semiconductor, and the photo-generated electrons will “tunnel” in the opposite direction to reach the electrodes, where the platinum catalyzes the reaction that produces hydrogen.
The MIS device requires good production controls because the oxide layer in particular has to be deposited precisely. Esposito notes that they used fabrication techniques that are standard in the electronics industry, which has decades of experience in building low-cost, silicon-based devices.
To study the system in detail, the NIST team scanned the surface of the device with a laser beam, illuminating only a small portion at a time to record photocurrent with micrometer resolution. In tandem with the beam, they also tracked an “ultramicroelectrode” across the surface with scanning photocurrent microscopy (SPCM) and scanning electrochemical microscopy (SECM) to measure the rate of molecular hydrogen generation, the chemical half of the reaction. The combination allowed them to observe two bonus effects of the MIS photoelectrode design: a secondary mechanism for hydrogen generation caused by the channeling of electrons through the oxide layer, and a more efficient transport of electrons to the reaction site than predicted.
The NIST team calculates an efficiency of 2.9 percent for their device, which also exhibits excellent stability during operation. While this efficiency is far lower than more costly designs, they note that it is 15 times better than previously reported results for similar silicon-based MIS devices, and the new data from their microanalysis of the system points towards several potential routes to improving performance.
While today’s 2.9% isn’t gong to revolutionize the hydrogen production business, the possible improvements should get to numbers that may make economic sense.
We’re a long way from consumers choosing their own solar powered energy or fuel system from a long list of choices. Saving hydrogen for later use could make more sense than trying to buy electrical storage for storing photovoltaic energy.
Scientists with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (LBNL) have reported the first fully integrated nanosystem for artificial photosynthesis. The scientists have taken the “artificial leaf” as the popular term for such a system, to success as an “artificial forest.”
The DOE is under pressure politically as the climate crowd is claiming atmospheric carbon dioxide is now at its highest level in at least three million years. Due to the hype and a very successful sales job the research field has proceeded quite well.
Peidong Yang, a chemist with Berkeley Lab’s Materials Sciences Division, who leads the research explains the overview, “Similar to the chloroplasts in green plants that carry out photosynthesis, our artificial photosynthetic system is composed of two semiconductor light absorbers, an interfacial layer for charge transport, and spatially separated co-catalysts. To facilitate solar water- splitting in our system, we synthesized tree-like nanowire heterostructures, consisting of silicon trunks and titanium oxide branches. Visually, arrays of these nanostructures very much resemble an artificial forest.”
Yang, who also holds appointments with the University of California Berkeley’s Chemistry Department and Department of Materials Science and Engineering, is the corresponding author of a paper describing this research in the journal NANO Letters. The paper is titled “A Fully Integrated Nanosystem of Semiconductor Nanowires for Direct Solar Water Splitting.” Co-authors are Chong Liu, Jinyao Tang, Hao Ming Chen and Bin Liu.
The LBNL press release refreshes with the reminder that there’s enough energy in one hour’s worth of global sunlight to meet all human needs for a year. While its quite difficult to imagine a planetary sized solar collector, the lure of free source energy is enticing. It’s the harvesting and production of some useful fuel that’s the problem.
Artificial photosynthesis, in which solar energy is directly converted into chemical fuels, is regarded as one of the most promising of solar technologies. A major challenge for artificial photosynthesis is to produce hydrogen cheaply enough to compete with fossil fuels. Meeting this challenge requires an integrated system that can efficiently absorb sunlight and produce charge-carriers to drive separate water reduction and oxidation half-reactions.
Yang retakes the explanation with, “In natural photosynthesis the energy of absorbed sunlight produces energized charge-carriers that execute chemical reactions in separate regions of the chloroplast. We’ve integrated our nanowire nanoscale heterostructure into a functional system that mimics the integration in chloroplasts and provides a conceptual blueprint for better solar-to-fuel conversion efficiencies in the future.”
When sunlight is absorbed by pigment molecules in a chloroplast, an energized electron is generated that moves from molecule to molecule through a transport chain until ultimately it drives the conversion of carbon dioxide into carbohydrate sugars.
This electron transport chain is called a “Z-scheme” because the pattern of movement resembles the letter Z on its side. Yang and his colleagues also use a Z-scheme in their system only they deploy two Earth abundant and stable semiconductors – silicon and titanium oxide – loaded with co-catalysts and with an ohmic contact inserted between them. Silicon was used for the hydrogen-generating photocathode and titanium oxide for the oxygen-generating photoanode. The tree-like architecture was used to maximize the system’s performance. Like trees in a real forest, the dense arrays of artificial nanowire trees suppress sunlight reflection and provide more surface area for fuel producing reactions.
“Upon illumination photo-excited electron−hole pairs are generated in silicon and titanium oxide, which absorb different regions of the solar spectrum,” Yang says. “The photo-generated electrons in the silicon nanowires migrate to the surface and reduce protons to generate hydrogen while the photo-generated holes in the titanium oxide nanowires oxidize water to evolve oxygen molecules. The majority charge carriers from both semiconductors recombine at the ohmic contact, completing the relay of the Z-scheme, similar to that of natural photosynthesis.”
Under simulated sunlight, this integrated nanowire-based artificial photosynthesis system achieved a 0.12-percent solar-to-fuel conversion efficiency. Although comparable to some natural photosynthetic conversion efficiencies, this rate will have to be substantially improved for commercial use.
However, the modular design of this system allows for newly discovered individual components to be readily incorporated to improve its performance. For example, Yang notes that the photocurrent output from the system’s silicon cathodes and titanium oxide anodes do not match, and that the lower photocurrent output from the anodes is limiting the system’s overall performance.
Yang said, “We have some good ideas to develop stable photoanodes with better performance than titanium oxide. We’re confident that we will be able to replace titanium oxide anodes in the near future and push the energy conversion efficiency up into single digit percentages.”
The about one eighth of a percent efficiency is only a start that shows the concept functions. Still, efficiency is just one part of the equation to get to market acceptance. Efficiency is inversely proportional to cost. If technology is really low cost the efficiency need not be high or if technology is expensive it has to be very efficient.
The vague addressing of the technology end product is a little disconcerting. The press release mentions hydrogen as a product a well as carbon dioxide to carbohydrate sugars. Today it is still much more market worthy to get to a carbon fuel than chase the hydrogen dream.
This is a good-looking technology. It doesn’t seem to use costly materials. The question then goes back to the efficiency vs. cost matter. If it’s low cost and produces sugars the LBNL folks might just have a major success.
Norwegian research scientists are now working on the concept of storing electricity at the bottom of the sea. The energy will be stored with the help of high water pressure. It’s a new idea invented by a German engineer who has spent much of his professional life working in aerospace technology.
Rainer Schramm, inventor and founder of the company Subhydro AS said, “Imagine opening a hatch in a submarine under water. The water will flow into the submarine with enormous force. It is precisely this energy potential we want to utilize. Many people have launched the idea of storing energy by exploiting the pressure at the seabed, but we are the first in the world to apply a specific patent-pending technology to make this possible.”
Schramm has joined forces with SINTEF, the largest independent research organization in Scandinavia to research the concept. “SINTEF has experts in the fields of energy generation, materials technology and not least offshore and deep-water technology, which means we have all the expertise we need in one place,” he said.
To use the water pressure at the seabed in practice, the mechanical energy is converted by a reversible pump turbine, as in a normal pumped storage hydroelectric plant.
Schramm explains, “A pumped storage power plant is a hydroelectric plant that can be “charged” up again by pumping the water back to the upper reservoir once it has passed through a turbine. This type of power plant is used as a “battery”, when connected to the power grid.”
In this pumped storage power plant a turbine will be connected to a tank on the seabed at a depth of 400-800 meters. The turbine is fitted with a valve, and when this is opened, water flows in and starts turning the turbine. The turbine drives a generator to produce electricity. One can connect as many tanks as one might wish. In other words, it is the number of water tanks that decides how long the plant can generate electricity, before the energy storage capacity is exhausted.
“When the water tanks are full, the water must be removed from the tanks,” Schramm explains. This is achieved by running the turbine in reverse, so that it functions as a pump. The process consumes energy from the power grid, just as when one charges an ordinary battery. Although a bit more energy is used to empty the water tanks than can be recovered from flooding them, the degree of efficiency of this type of power plant is just as high as that of a conventional, onshore plant. According to Schramm, calculations indicate an electric storage efficiency of approximately 80% per power emptying cycle.
Another advantage of the system is that equipment can be scaled according to users’ requirements, both as regards the turbine size and the number of water tanks. A plant of normal size will produce roughly 300 megawatts for a period of 7-8 hours. This is enough energy to supply just over 200,000 (British measure) households with electricity for the same time.
Schramm said, “We envisage that this type of storage plant will function well in conjunction with, for example, wind farms. At strong wind conditions, excess electricity is sent subsea to pump water out of the storage tanks. In periods with little wind, energy can be obtained from this underwater plant instead. The same applies to solar generation: the pumped storage power station can contribute to constant electricity production at night time when there is no sunshine to run a solar power plant.”
In addition to the number of tanks, the sea depth also determines the effectiveness of the plant: the deeper the equipment is located, the greater is the pressure difference between the sea surface and the seabed, and the more energy is stored in a single tank.
Schramm explained, “This is part of the reason why we want to try out the technology in Norway.” In his native country Germany the sea is too shallow for the system to be profitable, but there are many parts of the world where great water depths are located close inshore, such as the marine areas around Italy, Portugal and Spain, as well as North and South America.
This where SINTEF comes in. One of the challenges is to develop a type of concrete that can be used to cast the water tanks, which are placed on the seabed. Tor Arne Martius-Hammer at SINTEF Building and Infrastructure is an expert on strong, light concrete types.
Martius-Hammer explains the SINTEF work with, “The challenge is to find the optimal balance between strength and cost. If we achieve the goal of creating a concrete that will withstand at least 5 times as high loading as ordinary concrete, we can reduce the wall thickness by 75%. This is a critical factor. We need to reach production and installation costs which make storage of energy economical in relation to the price of electrical energy. One of the solutions SINTEF will work on is reinforcing the concrete with thin steel fibers instead of the normal steel rebar. This will result in a significant simplification of the production process. Concrete is in existence at present which can be used, but our job is to develop a cheaper alternative.”
It all seems elegantly simple to use gravity and pressure to achieve high energy storage efficiency. As the team in Scandinavia is figuring out, its much more of an engineering exercise of the extreme.
Eighty percent efficiency look quite attractive. No battery, chemistry problems, or life cycle issues other than wear and tear. The concrete tanks could last indefinably. The physics are quite simple with no problems such as compressing air that would loss energy to thermal loses. One simply needs to be near a deep body of water.
Lets hope the thin steel fibers replacing the normal steel rebar work out great.
One’s first impression is – it won’t work. But some innovative and enterprising folks have driven the wind through a funnel idea to what seems to be a successful field trial.
Brian Wang’s NextBigFuture site spotted the small firm’s press release and ran a post. That in itself is an acknowledgment the technology is interesting.
Simply put SheerWind’s Invelox wind energy system captures the breeze from an above ground portal and funnels the wind through a tapering passageway that “naturally” accelerates its flow. Near the end a venturi effect is introduced and the now fast moving breeze passes through a conventional turbine.
Lets say it works, and it probably does, the user is looking at a much different installation and performance scenario.
Up front the cost of producing electricity is less than 1 cent per KWH, making it more than competitive with natural gas and hydroelectric powered generation. At this cost level the system wouldn’t need government subsidies to be profitable. The basic unit wouldn’t have moving parts, the generating set is near the ground suggesting a 50% reduction of operating costs compared current wind turbine technology/
An Invelox funnels wind energy to ground-based generators. Instead of snatching bits of energy from the wind as it passes through the blades of a rotor, wind is captured with a funnel and directed through a tapering passageway that naturally accelerates its flow. This stream of kinetic energy then drives a generator that is installed safely and economically at ground level.
The premise is to bring the airflow from the top of the tower to ground level and allow for greater power generation with much smaller turbine blades. It could also allow for networking, allowing multiple towers to direct energy to the same generator. The unit is about 50% shorter than traditional wind towers and uses a ground-based turbine with blades that are 84% smaller. Fewer generators are required in a network, so equipment and maintenance costs would be lower. Most importantly, energy output is greater.
So far the technology has been reviewed and validated by the company’s technical advisory board and a team from City University of New York. Prototypes were tested under controlled laboratory conditions, and test results were used to build and validate full-scale computational fluid dynamic (CFD) models.
The first small-scale unit was installed in a field near SheerWind’s facility in Chaska, Minnesota. The unit incorporates the instruments for full speed and power data collection. Preliminary speed data have validated CFD model predictions.
A larger-scale (Commercial-grade) field demo unit has also been completed. Data collection and testing has exceeded expectations.
Perhaps the SheerWind’s Invelox best use is to uprate wind speeds. Chaska, Minnesota is generally considered a class 1 or 2 wind area, which is verified by free stream wind. The wind speeds recorded inside the venturi section of the Invelox show that winds are converted to class 3.
The firm’s web site has additional information. With designs for both single wind direction and all direction winds plus the advantages of more operating time should see the firm gain some market traction.
We’ll assume here that it works as described, and wish the folks there the best. They’re going to need it. It’s a large imposing structure running a rather small generator. What it would cost is still an unknown. But if it does perform to expectations there isn’t anything like it for competition.
Qiaoqiang Gan, University at Buffalo assistant professor of electrical engineering and his team are developing a new generation of photovoltaic cells that produce more power and cost less to manufacture than what’s available today.
Gan is working on the use of plasmonic-enhanced organic photovoltaic materials. These devices don’t match traditional solar cells in terms of energy production but they are less expensive and – because they are made (or processed) in liquid form – can be applied to a greater variety of surfaces.
Gan’s team detailed the progress of plasmonic-enhanced organic photovoltaic materials in the May 7 edition of the journal Advanced Materials. An image of a plasmonic-enhanced organic photovoltaic device made the journal’s front page. Co-authors include Filbert J. Bartoli, professor of electrical and computer engineering at Lehigh University, and Zakya Kafafi of the National Science Foundation.
Today’s solar panels produce power with either thick polycrystalline silicon wafers that are expensive to manufacture or thin-film solar cells made up of inorganic materials such as amorphous silicon or cadmium telluride that are somewhat less, but still costly to manufacture.
Gan’s research involves thin-film solar cells, too, but unlike what’s on the market he is using organic materials such as polymers and small molecules that are carbon-based and less expensive. “Compared with their inorganic counterparts, organic photovoltaics can be fabricated over large areas on rigid or flexible substrates potentially becoming as inexpensive as paint,” Gan said.
There are drawbacks to organic photovoltaic cells. They have to be thin due to their relatively poor electronic conductive properties. Because they are thin and, thus, without sufficient material to absorb light, it limits their optical absorption and leads to insufficient power conversion efficiency.
Gan points out the power conversion efficiency needs to be 10 percent or more to compete in the market.
To achieve that benchmark, Gan and other researchers are incorporating metal nanoparticles and/or patterned plasmonic nanostructures into organic photovoltaic cells. Plasmons are electromagnetic waves and free electrons that can be used to oscillate back and forth across the interface of metals and semiconductors.
Recent material studies suggest they are succeeding, he said. Gan and the paper’s co-authors argue that, because of these breakthroughs, there should be a renewed focus on how nanomaterials and plasmonic strategies can create more efficient and affordable thin-film organic solar cells.
Gan is continuing his research by collaborating with several researchers at UB including: Alexander N. Cartwright, professor of electrical engineering and biomedical engineering and UB vice president for research and economic development; Mark T. Swihart, UB professor of chemical and biological engineering and director of the university’s Strategic Strength in Integrated Nanostructured Systems; and Hao Zeng, associate professor of physics.
The idea that photovoltaic cells could one day be applied to surfaces as easily as paint is to walls had great appeal. Polls suggest when the questions are carefully set forth that most Americans want the U.S. to place more emphasis on developing solar power.
The handling of the solar panel power to grid alternating current would be the remaining investment expense. The Buffalo team deserves to have the progress seen and considered. They do have an argument on their hands, solar is in the doldrums and needs a boost. Really very low cost panel constructions and lower power conversion investments are going to come. The question is who can make the breakthroughs in a very tight research-funding environment.
Ramaraja Ramasamy, assistant professor in the University of Georgia (UGA) College of Engineering said, “We have developed a way to interrupt photosynthesis so that we can capture the electrons before the plant uses them to make sugars.” Ramasamy is also a member of UGA’s Nanoscale Science and Engineering Center.
The sun is the largest source of energy on the planet. However, only a tiny fraction of the solar radiation on Earth is converted into useful energy. The UGA researchers looked to nature for inspiration, and they are now developing a new technology that makes it possible to use plants to generate electricity directly.
During photosynthesis, plants use sunlight to split water atoms into hydrogen and oxygen, which produces electrons. These newly freed electrons go on to help create sugars that plants use much like food to support growth and reproduction.
Ramasamy’s technology involves separating out structures in the plant cell called thylakoids, which are responsible for capturing and storing energy from sunlight. Researchers manipulate the proteins contained in the thylakoids, interrupting the pathway along which electrons flow.
Then the modified thylakoids are immobilized on a specially designed backing of carbon nanotubes, cylindrical structures that are nearly 50,000 times finer than a human hair. The nanotubes act as an electrical conductor, capturing the electrons from the plant material and sending them along a wire.
In small-scale experiments, this approach resulted in electrical current levels that are two orders of magnitude larger than those previously reported in similar systems.
Plants are the undisputed champions of solar power. After billions of years of evolution, most of them operate at nearly 100% quantum efficiency, meaning that for every photon of sunlight a plant captures, it produces an equal number of electrons. Converting even a fraction of this into electricity would improve upon the efficiency seen with solar panels, which generally operate at efficiency levels between 10 and 20 percent.
Ramasamy said, “This approach may one day transform our ability to generate cleaner power from sunlight using plant-based systems.”
Ramasamy cautions that much more work must be done before this technology reaches commercialization, but he and his collaborators are already working to improve the stability and output of their device.
“In the near term, this technology might best be used for remote sensors or other portable electronic equipment that requires less power to run,” he said. “If we are able to leverage technologies like genetic engineering to enhance stability of the plant photosynthetic machineries, I’m very hopeful that this technology will be competitive to traditional solar panels in the future.”
“We have discovered something very promising here, and it is certainly worth exploring further,” he said. “The electrical output we see now is modest, but only about 30 years ago, hydrogen fuel cells were in their infancy, and now they can power cars, buses and even buildings.”
The study paper was co-authored by UGA graduate student Jessica Calkins and postdoctoral research associate Yogeswaran Umasankar.
It’s quite a scientific leap to developing bio-electrodes based on immobilized plant cell structures to harvest light energy. Such electrodes used in photosynthetic electrochemical cells that convert direct into electricity with no external fuel would be revolutionary.
Ramasamy is right at the leading edge of research carving a new potential path for solar harvesting. One hundred percent efficiency is the potential and the plant based science looks like it could get very close to harvesting it all.
Stay on target there at UGA – the potential is huge and the challenges immense.
Ionic liquid pretreatments show great potential as a biomass pretreatment for dissolving lignocellulose and helping to hydrolyze the resulting aqueous solution into fuel sugars. But the best of these ionic liquids so far have required the use of expensive enzymes.
Blake Simmons, a chemical engineer who heads the Joint BioEnergy Institute’s (JBEI) Deconstruction Division has taken another step towards meeting this challenge with the development of a new technique for pre-treating cellulosic biomass with ionic liquids – salts that are liquids rather than crystals at room temperature.
The new technique requires none of the expensive enzymes used in previous ionic liquid pretreatments, and makes it easier to recover fuel sugars and recycle the ionic liquid.
Simmons said, “Most of our ionic liquid efforts at JBEI have focused on using enzymes to liberate fermentable sugars from lignocellulosic biomass after pretreatment, but with this new enzyme-free approach we use an acid as the catalyst for hydrolyzing biomass polysaccharides into a solution containing fermentable sugars. We’re then able to separate the pretreatment solution into two phases, a sugar-rich water phase for recovery and a lignin-rich ionic liquid phase for recycling. As an added bonus, our new pretreatment technique uses a lot less water than previous pretreatments.”
Simmons is the corresponding author of a paper describing this research that has been published in the journal Biotechnology for Biofuels. The paper is titled “Production and extraction of sugars from switchgrass hydrolyzed in ionic liquids.” Co-authoring it were Ning Sun, Hanbin Liu Noppadon Sathitsuksanoh, Vitalie Stavila, Manali Sawant, Anaise Bonito, Kim Tran, Anthe George, Kenneth Sale, Seema Singh and Bradley Holmes.
The pitch at JBEI is advanced biofuels – liquid fuels synthesized from the sugars in cellulosic biomass – offer a clean, green and renewable alternative to gasoline, diesel and jet fuels. Bringing the costs of producing these advanced biofuels down to competitive levels with petrofuels, however, is a major challenge.
The press release continues with the burning of fossil fuels adding 9 billion metric tons of excess carbon dioxide to the atmosphere each year, so the need for carbon neutral, cost-competitive renewable alternative fuels has never been greater. Advanced biofuels, produced from the microbial fermentation of sugars in lignocellulosic biomass, could displace gasoline, diesel and jet fuel on a gallon-for-gallon basis and be directly dropped into today’s engines and infrastructures without impacting performance. If done correctly, the use of advanced biofuels would not add excess carbon to the atmosphere.
Environmentally benign ionic liquids are used as green chemistry substitutes for volatile organic solvents. With great potential as a biomass pretreatment for dissolving lignocellulose and helping to hydrolyze the resulting aqueous solution into fuel sugars, the best of these ionic liquids so far have required the use of expensive enzymes.
The state of the art when Simmons group published the study paper showed that acid catalysts, such as hydrochloric or Brønsted, can effectively replace enzyme-based hydrolysis, but the subsequent separation of sugars and ionic liquids becomes a difficult and expensive problem that can require the use of significant amounts of water.
Simmons team was guided by molecular dynamics simulations carried out at DOE’s National Energy Research Scientific Computing Center. Simmon’s team solved this problem by deploying the ionic liquid imidazolium chloride in tandem with an acid catalyst.
Simmons explains, “Imidazolium is the most effective known ionic liquid for breaking down lignocellulose and the chloride anion is amenable with the acid catalyst. The combination makes it easy to extract fermentable sugars that have been liberated from biomass and also easy to recover the ionic liquid for recycling. By eliminating the need for enzymes and decreasing the water consumption requirements of more traditional ionic liquid pretreatments we should be able to reduce the costs of sugar production from lignocellulose.”
Complete separation of the pretreatment solution into sugar-rich water and lignin-rich ionic liquid phases was attained with the addition to the solution of sodium hydroxide. The optimized sodium hydroxide concentration for both phase separation and sugar extraction was 15-percent, resulting in the recovery of maximum yields of 54-percent glucose and 88-percent xylose. The team believes optimizing the process conditions and using more advanced methods of phase separation and sugar recovery can increase these sugar yields.
Looking ahead Simmons said, “After optimizing the process conditions, our next step will be to scale the process up to 100 liters,” Simmons says. “For that work we will use the facilities at the Advanced Biofuels Process Demonstration Unit.”
Ionic liquid ideas have been popping up in papers and press releases over the past months with great hope for a low cost breakthrough for biomass to fuel processes. The Simmons team looks like the leader in two respects; it’s a process development and reduces inputs.
There remains one over riding question, just what does say a hundred thousand gallons cost and what would be involved for a facility to be built? Then the feedstock, transport and all the functional issues come into play.
The Simmons team looks to be getting to a point where those kinds of issues need considered. And that is a breakthrough of it own.
Donald Sadoway, the John F. Elliott Professor of Materials Chemistry at MIT found that a process called molten oxide electrolysis could use iron oxide from the lunar soil to make oxygen in abundance, with no special chemistry. He tested the process using lunar-like soil from Meteor Crater in Arizona – which contains iron oxide from an asteroid impact thousands of years ago – finding that it produced steel as a byproduct.
If you’ve seen photos or videos of the huge red-hot cauldrons in which steel is made, fueled by large amounts of energy that smoke and burn away impurities wouldn’t be surprised to learn that steel making is one of the world’s leading industrial users of energy and produces a nasty mix of effluent gas and particulates.
Sadoway’s new process offers two side benefits: The resulting steel should be of higher purity, and eventually, once the process is scaled up, a lower operating cost.
Sadoway’s paper, co-authored by Antoine Allanore, the Thomas B. King Assistant Professor of Metallurgy at MIT, and former postdoc Lan Yin (now a postdoc at the University of Illinois at Urbana-Champaign), has just been published in the journal Nature.
Worldwide steel production currently totals about 1.5 billion tons per year. The prevailing process makes steel from iron ore in the form of mostly iron oxide by intense heating with coal and blasts of air to uprate the temperature. The process forms carbon dioxide as a byproduct. Production of a ton of steel generates almost two tons of CO2 emissions, according to steel industry figures, accounting for as much as 5% of the world’s total greenhouse-gas emissions.
Additionally the process produces slag, ash and lots of particulate matter that is costly to remove and find uses for.
The industry has met little success in its search for carbon-free methods of manufacturing steel. The idea for the new method, Sadoway says, arose when he received a grant from NASA to look for ways of producing oxygen on the moon – a key step toward future lunar bases.
Sadoway’s method used an iridium anode, but since iridium is expensive and supplies are limited, that’s not a viable approach for bulk steel production on Earth. But after more research and input from Allanore, the MIT team identified an inexpensive metal alloy that can replace the iridium anode in molten oxide electrolysis.
It wasn’t an easy problem to solve, Sadoway explains, because a vat of molten iron oxide, which must be kept at about 1600 degrees Celsius, “is a really challenging environment. The melt is extremely aggressive. Oxygen is quick to attack the metal.”
Many researchers had tried to use ceramics, but these are brittle and can shatter easily. “I had always eschewed that approach,” Sadoway says.
Allanore takes up the explanation, “There are only two classes of materials that can sustain these high temperatures – metals or ceramics.” Only a few metals remain solid at these high temperatures, so “that narrows the number of candidates,” he says.
Allanore, who worked in the steel industry before joining MIT, says progress has been slow both because experiments are difficult at these high temperatures, and also because the relevant expertise tends to be scattered across disciplines. “Electrochemistry is a multidisciplinary problem, involving chemical, electrical and materials engineering,” he says.
The anode problem was solved using an alloy that naturally forms a thin film of metallic oxide on its surface: thick enough to prevent further attack by oxygen, but thin enough for electric current to flow freely through it. The answer turned out to be an alloy of chromium and iron – constituents that are “abundant and cheap,” Sadoway says.
The main benefit is the process produces no emissions other than pure oxygen and the process lends itself to smaller-scale factories: Conventional steel plants are only economical if they can produce millions of tons of steel per year, but this new process could be viable for production of a few hundred thousand tons per year, he says.
In addition to eliminating the emissions, the process yields metal of exceptional purity, Sadoway says. What’s more, it could also be adapted to carbon-free production of metals and alloys including nickel, titanium and ferromanganese, with similar advantages.
The third party observation chosen for the MIT press release, Ken Mills, a visiting professor of materials at Imperial College, London, says the approach outlined in the paper “seems very sound to me,” but he cautions that unless legislation requires the industry to account for its greenhouse-gas production, it’s unclear whether the new technique would be cost-competitive. Nevertheless, he says, it “should be followed up, as the authors suggest, with experiments using a more industrial configuration.”
Sadoway, Allanore and a former student have formed a company to develop the concept, which is still at the laboratory scale, to a commercially viable prototype electrolysis cell. They expect it could take about three years to design, build and test such a reactor.
It is also reported that the research was supported by the American Iron and Steel Institute and the U.S. Department of Energy. It’s good to see industry directly backing beneficial basic research.
The iron ore blast furnace has only been incrementally improved for decades since the idea burst forth over 100 years ago with a few standouts like the Swedish electric design that is known for very high quality steels.
The MIT team looks to have something quite a large evolutionary step ahead. With about 2000 years of humans working iron another big improvement is due. The mass involved in making iron ore to steel involves big numbers measured by millions of tons. Spreading the work out with no or very low pollution looks like a good step to get more competition, better quality and more innovative alloys.
The energy used will replace primarily coal with electric current. That opens the door to a drive to the lowest cost power generation. Let the battle begin driving down electricity and steel costs.