Power/Performance Bits: Dec. 5

Solar jet fuel
Researchers at ETH Zurich demonstrated the ability to use solar energy to create the precursor to jet fuel from water and carbon dioxide, a process that could lead to carbon-neutral air travel.

The scientists performed 295 consecutive cycles in a 4 kW solar reactor, yielding 700 standard liters of hydrogen and carbon monoxide (syngas), the precursor to kerosene and other liquid fuels. The syngas was refined into kerosene, the jet fuel used by airplanes, by Shell Global Solutions in Amsterdam.

Sunlight, H₂O and CO₂ make for an essentially unlimited feedstock for all the liquid fuels currently used for transportation, which are just various molecular recombinations of hydrogen and carbon.

To split the H₂O and CO₂, the team used a high-temperature concentrated solar reactor containing a reticulated porous ceramic structure made of ceria (CeO2), which facilitates molecule splitting.

The scientists performed 295 consecutive cycles in a 4 kW solar reactor during the SOLAR-JET project, yielding 700 standard liters of syngas. (Source: SolarPACES)

“Ceria is the state-of-the-art material,” said Philippe Furler, a post-doc researcher at ETH Zurich. “It has the ability to release a certain amount of its oxygen and then in the reduced state it has the capability of splitting water and CO₂.”

“In the first step, at 1500°C, we release a fraction of the oxygen contained in the material, thereby a pure stream of oxygen leaves the reactor as a valuable by-product,” he explained.

“The second step takes place at a lower temperature, about 1000°C, and H₂O and CO₂ are introduced. The ceria wants to uptake the oxygen which it previously held. Since there is no oxygen it needs to split H₂O and CO₂ in order to access its oxygen, so it splits the water and carbon-dioxide into hydrogen, carbon-monoxide and oxygen to access the oxygen. Now it uptakes the oxygen, and thereby it resumes its initial state, and the product is a mixture of hydrogen and carbon monoxide can be extracted from the reactor.”

The team envisions the process using CO₂ extracted from air, making the solar jet fuel carbon neutral, as the CO₂ used in the fuel production is equivalent to the CO₂ released in combustion.

There is still a ways to go. The researchers have boosted the efficiency of the solar process from 2% to 5% by moving to vacuum extraction on the 4 kW reactor. Their two-step solar thermochemical conversion with ceria shows a long-term efficiency potential of beyond 30%.

The next goal is to raise the efficiency to 15%, by incorporating an advanced system to recover heat from the process, and then to scale up.

Ultimately, industrial-scale solar fuels production systems would be run using megawatt-scale reactor-systems on solar towers with heliostats (mirrors) concentrating suns on the receiver, similar to, but running at much higher temperatures than current commercial solar tower plants. According to the SOLAR-JET Project Coordinator at Bauhaus Luftfahrt, Dr. Andreas Sizmann, a solar reactor with a 1 square kilometer heliostat field could generate 20,000 liters of kerosene a day. This output from one solar fuels refinery could fly a large 300-body commercial airliner for about seven hours.

Furler has founded the ETH spin-off Sunredox to commercialize the technology.

Arm for HPC
The U.S. Department of Energy’s Argonne National Laboratory will explore a future high-performance computing (HPC) system based on 64-bit Arm processors with the help of Hewlett Packard Enterprise (HPE).

Several efforts are now underway to develop a robust HPC software stack to make Arm processors capable of supporting the multithreaded floating-point workloads that are typically required by high-end scientific computing applications.

Argonne and HPE will evaluate early versions of chipmaker Cavium (recently acquired by Marvell) Arm ThunderX2 64-bit processors for the Arm ecosystem as a cost-effective and power-effective alternative to x86 architectures based on Intel CPUs, which currently dominate the high-performance computing market.

Argonne will install a 32-node Comanche Wave prototype ARM64 server platform in its testing and evaluation environment, the Joint Laboratory for System Evaluation, in early 2018. Argonne researchers from various computing divisions will run applications on the ecosystem and provide performance feedback to HPE and partnering vendors.

Argonne’s goal is to produce custom architectures optimized for scientific and engineering research. These architectures not only feature custom processor systems, but novel interconnects, software stacks and solutions for power and cooling, among other things.

ICs printed on fabric
Researchers at the University of Cambridge, Politecnico di Milano, and Jiangnan University printed washable, stretchable and breathable electronic circuits made of graphene and hexagonal-boron nitride on fabric.

The circuits were made with cheap, safe and environmentally friendly inks, and printed using conventional inkjet printing techniques. They were able to survive up to 20 cycles in a typical washing machine.

A sample circuit printed on fabric. (Source: Felice Torrisi)

“Digital textile printing has been around for decades to print simple colorants on textiles, but our result demonstrates for the first time that such technology can also be used to print the entire electronic integrated circuits on textiles,” said Professor Roman Sordan of Politecnico di Milano. “Although we demonstrated very simple integrated circuits, our process is scalable and there are no fundamental obstacles to the technological development of wearable electronic devices both in terms of their complexity and performance.”

Based on earlier work on the formulation of graphene inks for printed electronics, the team designed low-boiling point inks, which were directly printed onto polyester fabric. Additionally, they found that modifying the roughness of the fabric improved the performance of the printed devices. The versatility of this process allowed the researchers to design not only single transistors but all-printed integrated electronic circuits combining active and passive components.