Water Splitting Technique Efficiently Produces Hydrogen Fuel

An artist's conception of a commercial hydrogen production plant that uses sunlight to split water in order to produce clean hydrogen fuel. 

Credit: University of Colorado Boulder

A University of Colorado Boulder team has developed a radically new technique that uses the power of sunlight to efficiently split water into its components of hydrogen and oxygen, paving the way for the broad use of hydrogen as a clean, green fuel.

The CU-Boulder team has devised a solar-thermal system in which sunlight could be concentrated by a vast array of mirrors onto a single point atop a central tower up to several hundred feet tall.

Alan Weimer

The tower would gather heat generated by the mirror system to roughly 2,500 degrees Fahrenheit (1,350 Celsius), then deliver it into a reactor containing chemical compounds known as metal oxides, said CU-Boulder Professor Alan Weimer, research group leader.

As a metal oxide compound heats up, it releases oxygen atoms, changing its material composition and causing the newly formed compound to seek out new oxygen atoms, said Weimer.

The team showed that the addition of steam to the system -- which could be produced by boiling water in the reactor with the concentrated sunlight beamed to the tower -- would cause oxygen from the water molecules to adhere to the surface of the metal oxide, freeing up hydrogen molecules for collection as hydrogen gas.

"We have designed something here that is very different from other methods and frankly something that nobody thought was possible before," said Weimer of the chemical and biological engineering department.

"Splitting water with sunlight is the Holy Grail of a sustainable hydrogen economy."

Charles Musgrave

One of the key differences between the CU method and other methods developed to split water is the ability to conduct two chemical reactions at the same temperature, said Charles Musgrave, also of the chemical and biological engineering department.

While there are no working models, conventional theory holds that producing hydrogen through the metal oxide process requires heating the reactor to a high temperature to remove oxygen, then cooling it to a low temperature before injecting steam to re-oxidize the compound in order to release hydrogen gas for collection.

"The more conventional approaches require the control of both the switching of the temperature in the reactor from a hot to a cool state and the introduction of steam into the system," said Musgrave.

"One of the big innovations in our system is that there is no swing in the temperature. The whole process is driven by either turning a steam valve on or off."

"Just like you would use a magnifying glass to start a fire, we can concentrate sunlight until it is really hot and use it to drive these chemical reactions," said Christopher Muhich.

"While we can easily heat it up to more than 1,350 degrees Celsius, we want to heat it to the lowest temperature possible for these chemical reactions to still occur. Hotter temperatures can cause rapid thermal expansion and contraction, potentially causing damage to both the chemical materials and to the reactors themselves."

In addition, the two-step conventional idea for water splitting also wastes both time and heat, said Weimer, also a faculty member at CU-Boulder's BioFrontiers Institute. "There are only so many hours of sunlight in a day," he said.

With the new CU-Boulder method, the amount of hydrogen produced for fuel cells or for storage is entirely dependent on the amount of metal oxide -- which is made up of a combination of iron, cobalt, aluminum and oxygen -- and how much steam is introduced into the system.

One of the designs proposed by the team is to build reactor tubes roughly a foot in diameter and several feet long, fill them with the metal oxide material and stack them on top of each other.

A working system to produce a significant amount of hydrogen gas would require a number of the tall towers to gather concentrated sunlight from several acres of mirrors surrounding each tower.

Weimer said the new design began percolating within the team about two years ago. "When we saw that we could use this simpler, more effective method, it required a change in our thinking," said Weimer.

"We had to develop a theory to explain it and make it believable and understandable to other scientists and engineers." 

Journal Reference: C. L. Muhich, B. W. Evanko, K. C. Weston, P. Lichty, X. Liang, J. Martinek, C. B. Musgrave, A. W. Weimer. Efficient Generation of H2 by Splitting Water with an Isothermal Redox Cycle. Science, 2013; 341 (6145): 540 DOI: 10.1126/science.1239454

CAN Revolutionary laser system produce the next LHC

An international team of physicists has proposed a revolutionary laser system, inspired by the telecommunications technology, to produce the next generation of particle accelerators, such as the Large Hadron Collider (LHC) in CERN.

The International Coherent Amplification Network (ICAN) sets out a new laser system composed of massive arrays of thousands of fibre lasers, for both fundamental research at laboratories such as CERN and more applied tasks such as proton therapy and nuclear transmutation.

Lasers can provide, in a very short time measured in femto-seconds, bursts of energy of great power counted in peta-watts or a thousand times the power of all the power plants in the world.

Compact accelerators are also of great societal importance for applied tasks in medicine, such as a unique way to democratise proton therapy for cancer treatment, or the environment where it offers the prospect to reduce the lifetime of dangerous nuclear waste by, in some cases, from 100 thousand years to tens of years or even less.

Major Difficulties
However, there are two major hurdles that prevent the high-intensity laser from becoming a viable and widely used technology in the future.

• First, a high-intensity laser often only operates at a rate of one laser pulse per second, when for practical applications it would need to operate tens of thousands of times per second.

• The second is ultra-intense lasers are notorious for being very inefficient, producing output powers that are a fraction of a percent of the input power. As practical applications would require output powers in the range of tens of kilowatts to megawatts, it is economically not feasible to produce this power with such a poor efficiency.

Technological Consortium
To bridge this technology divide, the ICAN consortium, an EU-funded project initiated and coordinated by the Ecole polytechnique and composed of the University of Southampton Optical Research Centre (ORC), Jena and CERN, as well as 12 other prestigious laboratories around the world, aims to harness the efficiency, controllability, and high average power capability of fibre lasers to produce high energy, high repetition rate pulse sources.

The aim is to replace the conventional single monolithic rod amplifier that typically equips lasers with a network of fibre amplifiers and telecommunication components.

Gerard Mourou

Gerard Mourou of Ecole polytechnique who leads the consortium says: "One important application demonstrated has been the possibility to accelerate particles to high energy over very short distances measured in centimetres rather than kilometres as it is the case today with conventional technology."

"This feature is of paramount importance when we know that today high energy physics is limited by the prohibitive size of accelerators, of the size of tens of kilometres, and cost billions of euros."

"Reducing the size and cost by a large amount is of critical importance for the future of high energy physics."

Dr Bill Brocklesby

Dr Bill Brocklesby from the ORC adds: "A typical CAN laser for high-energy physics may use thousands of fibres, each carrying a small amount of laser energy."

"It offers the advantage of relying on well tested telecommunication elements, such as fibre lasers and other components."

"The fibre laser offers an excellent efficiency due to laser diode pumping. It also provides a much larger surface cooling area and therefore makes possible high repetition rate operation."

"The most stringent difficulty is to phase the lasers within a fraction of a wavelength."

"This difficulty seemed insurmountable but a major roadblock has in fact been solved: preliminary proof of concept suggests that thousands of fibres can be controlled to provide a laser output powerful enough to accelerate electrons to energies of several GeV at 10 kHz repetition rate - an improvement of at least ten thousand times over today's state of the art lasers."

Such a combined fibre-laser system should provide the necessary power and efficiency that could make economical the production of a large flux of relativistic protons over millimetre lengths as opposed to a few hundred metres.

Societal Application
One important societal application of such a source is to transmute the waste products of nuclear reactors, which at present have half-lives of hundreds of thousands of years, into materials with much shorter lives, on the scale of tens of years, thus transforming dramatically the problem of nuclear waste management.

CAN technology could also find important applications in areas of medicine, such as proton therapy, where reliability and robustness of fibre technology could be decisive features.

Fungi Can Quickly Mutate to Produce an Infectious Ability

Fungi have significant potential for "horizontal" gene transfer, a new study has shown, similar to the mechanisms that allow bacteria to evolve so quickly, become resistant to antibiotics and cause other serious problems.

This discovery, to be published March 18 in the journal Nature, suggests that fungi have the capacity to rapidly change the make-up of their genomes and become infectious to plants and possibly animals, including humans.

They are not nearly as confined to the more gradual processes of conventional evolution as had been believed, scientists say. And this raises issues not only for crop agriculture but also human health, because fungi are much closer on the "evolutionary tree" to humans than bacteria, and consequently fungal diseases are much more difficult to treat.

The genetic mechanisms fungi use to do this are different than those often used by bacteria, but the end result can be fairly similar. The evolution of virulence in fungal strains that was once believed to be slow has now been shown to occur quickly, and may force a renewed perspective on how fungi can behave, change and transfer infectious abilities.

"Prior to this we've believed that fungi were generally confined to vertical gene transfer or conventional inheritance, a slower type of genetic change based on the interplay of DNA mutation, recombination and the effects of selection," said Michael Freitag, an assistant professor of biochemistry and biophysics at Oregon State University.

"But in this study we found fungi able to transfer an infectious capability to a different strain in a single generation," he said. "We've probably underestimated this phenomenon, and it indicates that fungal strains may become pathogenic faster than we used to think possible."

Flax And Yellow Flowers Can Produce Bioethanol

Surplus biomass from the production of flax shives, and generated from Brassica carinata, a yellow-flowered plant related to those which engulf fields in spring, can be used to produce bioethanol. This has been suggested by two studies carried out by Spanish and Dutch researchers and published in the journal Renewable and Sustainable Energy Reviews.

"These studies evaluate, from an environmental point of view, the production of bioethanol from two, as yet unexploited sources of biomass: agricultural residue from flax (for the production of paper fibres for animal bedding), and Brassica carinata crops (herbaceous plant with yellow flowers, similar to those which carpet the countryside in spring)", Sara González-García, researcher of the Bioprocesses and Environmental Engineering Group of the University of Santiago de Compostela (USC), explains to SINC.

González-García, along with other researchers from USC, the Autonomous University of Barcelona and the University of Leiden (Holland), has confirmed that if bioethanol is produced from these two types of biomass "both CO2 emissions and fossil fuel consumption will be reduced, meeting two of the objectives established by the European Union to promote biofuels".

These works have analysed the environmental load associated with the different stages of the process: the harvesting of flax or Brassica; the production of ethanol (through enzymatic hydrolysis followed by fermentation and distillation); mixing it with petrol (in varying proportions); and its use in passenger automobiles.

The results of both studies, published in the journal Renewable and Sustainable Energy Reviews, show that the use of ethanol-based fuels can help to mitigate climate change (by reducing greenhouse gases).

However, these fuels also "contribute to acidification, eutrophication, the formation of photochemical oxidants and toxicity (for people and the environment)". According to the experts, these negative effects could be lessened with the use of high-yield crops, as well as through optimisation of agricultural activity and better use of fertilisers.

Which is better: flax or Brassica?
The studies developed by the researchers reveal that flax (which is richer in cellulose) can produce up to 0.3 kg of ethanol for every kg of dry biomass, compared with 0.25kg/kg of Brassica. However, when the whole production cycle is analysed, the yellow-flowered plant offers a greater production of biomass per hectare and has a lesser environmental impact.

The biofuel produced from these two plants is "second generation bioethanol", which is obtained from forest or agricultural residues, or from herbaceous crops, and does not enter into direct competition with agricultural crops intended for animal or human consumption.

The European Union and the International Monetary Fund are promoting the development of these types of biofuels. Spain is the third largest producer of bioethanol in Europe, after France and Germany, although its use still only represents 0.4% of total energy consumption.