Browsing all articles tagged with energy

Nanoconfined chemistry for hydrogen storage

The main obstacle to building a ‘hydrogen economy’ – this much touted vision of a society where the main energy carrier is hydrogen – is the lack of efficient hydrogen storage. The research conducted in the hydrogen storage scientific community is aimed towards mobile applications. Hydrogen is a gas at ambient conditions and takes up a lot of space. For stationary storage facilities, for which available space is not an issue, hydrogen gas can be kept in large tanks at moderate pressures using already known technology. However, in order to utilize hydrogen for mobile applications i.e. to produce and be able to sell hydrogen fuelled cars on a large scale, it must be stored in a compact, safe, cheap and efficient way.

In 2009, the U.S Department of Energy (DOE) proposed on-board hydrogen storage system performance targets that have become widely accepted. So far, researchers haven’t been able to successfully demonstrate a material that is capable of simultaneously meeting all of the requirements and criteria set out by the DOE.

A European research team has now reported on a new concept for hydrogen storage using nanoconfined reversible chemical reactions. They demonstrate that nanoconfined hydride has a significant hydrogen storage potential. Research at the Nano Energy-Materials research group at Interdisciplinary Nanoscience Center (iNANO) at Aarhus University in Denmark, led by Flemming Besenbacher and Torben R. Jensen, focuses on the utilization of nanoporous materials as scaffolds for preparation and confinement of nanosized metal hydrides. This bottom-up approach limits the particle size of the hydride to the average pore size of the scaffold material, which allows for the direct production of smaller particles than obtainable mechanically. Furthermore, particle growth and agglomeration may be hindered by the compartmentalization of the nanoparticles within the scaffold material. Nanoconfinement may also mediate improved re-hydrogenation properties of complex metal hydrides.

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New prospects for solar cells

new solar cellsThe most efficient solar cells, composed of a semiconductor material such as silicon, have been developed in Switzerland in the early 90s. As in the case of conventional electrochemical batteries, solar cells consist of a cathode, a platinum-based catalyst, and an anode, a porous layer formed from titanium dioxide nanoparticles and coated with a dye absorbs sunlight. A conductive liquid, the electrolyte is placed between two electrodes.

Despite the use of materials for the most inexpensive, easy to manufacture and flexible, large-scale commercialization of these batteries confronts two major obstacles. The electrolyte is very corrosive, causing a deficiency in sustainability. It is also very colorful, preventing light from entering and effectively limiting the photo-voltage of 0.7 volts. Moreover, platinum is an expensive material, non-transparent and rare.

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Energy dissipation and transport in nanoscale devices

microelectronicsUnderstanding energy dissipation and transport in nanoscale structures is of great importance for the design of energy-efficient circuits and energy-conversion systems. This is also a rich domain for fundamental discoveries at the intersection of electron, lattice (phonon), and optical (photon) interactions. A review article published in NanoResearch presents the recent progress in understanding and manipulation of energy dissipation and transport in nanoscale solid-state structures.

Some of the greatest challenges of modern society are related to energy consumption, dissipation, and waste. Among these, present and future technologies based on nanoscale materials and devices hold great potential for improved energy conservation, conversion, or harvesting. A prominent example is that of integrated electronics, where power dissipation issues have recently become one of its greatest challenges. Power dissipation limits the performance of electronics from handheld devices (~10–3 W) to massive data centres (~109 W), all primarily based on silicon micro/nanotechnology.

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Chemically driven thermopower waves

nanotube conducting heatA team of scientists at MIT have discovered a previously unknown phenomenon that can cause powerful waves of energy to shoot through minuscule wires known as carbon nanotubes. The discovery could lead to a new way of producing electricity, the researchers say.

The phenomenon, described as thermopower waves, “opens up a new area of energy research, which is rare,” says Michael Strano, who was the senior author of a paper describing the new findings that appeared in Nature Materials. The lead author was Wonjoon Choi, a doctoral student in mechanical engineering.

A carbon nanotube (shown in the illustration made by Christine Daniloff) can produce a very rapid wave of power when it is coated by a layer of fuel and ignited, so that heat travels along the tube. Like a collection of flotsam propelled along the surface by waves travelling across the ocean, it turns out that a thermal wave — a moving pulse of heat — travelling along a microscopic wire can drive electrons along, creating an electrical current.

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Hydrogen storage


The automobile fleet is contributing significantly to air quality degradation in large cities. The use of hydrogen as a fuel is interesting since combustion delivers a lot of energy without polluting. However, some obstacles, like the efficient storage of this gas, remain before it can be implemented in the transportation industry.

Figure 1: Hydrogen powered car built by BMW

Figure 1: Hydrogen powered car built by BMW

Hydrogen storage solutions

The United States Department of energy (DOE) has fixed two targets for hydrogen storage solutions applied to automotive transportation. The first target requires a ratio of hydrogen weight / tank weight that is superior to 0,065 (6,5% weight). This target limits the weight of the tank. The second target requires a hydrogen volumetric density higher than 62 kg/m in order to limit the volume of the tank.

Four main solutions were proposed to solve this problem:

  • Compression or liquefaction of hydrogen
  • Metal hydrides
  • Chemical tanks
  • Adsorbent materials

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Hydrogen storage – literature

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Reference books

R. Saito, G. Dresselhaus and M. S. Dresselhaus, Physical Properties of carbon nanotubes, Imperial College Press, Londres, 1998

G. Gao, T. Cagin and W. A. Goddard III, Energetics, Structure, Mechanical and Vibrational Properties of Single Walled Carbon Nanotubes (SWNT), Foresight Institute, 1997 (pdf©)

D. Frenkel and B. Smit, Understanding molecular simulation: from algorithms to applications, Academic Press, San Diego, 1996

C. Ngô and H. Ngô, Physique statistique, Masson, Paris, 1995

R. A. Oriani, The physical and metallurgical aspects of hydrogen in metals, Fourth International Conference on Cold Fusion, 1993 (pdf)

Nanotube fabrication methods

S. Iijima, Helical microtubules of graphitic carbon, Nature 354 (1991), 56-58 (pdf©)

S. Iijima and T. Ichihashi, Single-shell carbon nanotubes of 1-nm diameter, Nature 363 (1993), 603-605 (pdf©)

A. Thess, R. Lee, P. Nikolaev, H. Dai, P. Petit, J. Robert, C. Xu, Y. H. Lee, S. G. Kim, A. G. Rinzler, D. T. Colbert, G. E. Scuseria, D. Tománek, J. E. Fischer and R. E. Smalley, Crystalline Ropes of Metallic Carbon Nanotubes, Science 273 (1996), 483-487 (pdf©)
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