February 13, 2006

Rings turn out hydrogen

Hydrogen promises to be a clean fuel, if scientists can find clean ways of generating it. One of the most promising methods is using sunlight to split water into oxygen and hydrogen. Although it may sound simple, making the process practical is a challenge.

A researcher at Sandia National Laboratories have literally got the wheels spinning with a proposed mechanical solar water splitting device. Solar water splitters use a chemical catalyst to speed the reaction that breaks down water molecules. These are usually stationary.

The Counter Rotating Ring Receiver Reactor Recuperator is a horizontal stack of rings made from iron oxide mixed with the oxide of another metal like cobalt, magnesium or nickel. First the rings rotate through concentrated sunlight, where oxygen is stripped from the rings. They then pass through the cold side of the device, where they remove oxygen from water, leaving hydrogen. Each ring rotates in the opposite direction of its neighbors, which transfers heat between them to conserve energy.

The device would be used with solar collectors, which resemble large dish antennas with mirrored interiors. They could be used to produce hydrogen gas that could be used as fuel for hydrogen-powered vehicles.

(unpublished research reported in Sandia Lab News, February 3, 2006)

Nanotubes hold more electricity

Capacitors are capable of delivering large bursts of electricity but hold much less energy than batteries. Carbon nanotubes could change that, bringing about energy storing devices that combine the best of both worlds.

Researchers have been using carbon nanotubes to boost the storage capacity and performance of batteries and capacitors in recent years. (See Nanotubes pack power, TRN, February 27, 2002)

An MIT research team has designed an ultracapacitor that uses dense vertical arrays of single-walled carbon nanotubes as an electrode to store charge. The nanotube electrode promises to give capacitors storage capacities comparable to batteries. The nanotubes, each only a few millionths of a millimeter in diameter, provide a much larger surface area than the traditionally used porous carbon electrodes.

The technology could eventually be used to provide longer running times for electric cars and portable devices like computers and cellphones, which use capacitors to supply sudden power needs.

(Carbon Nanotube Enhanced Ultracapacitor, 15th International Seminar on Double Layer Capacitors and Hybrid Energy Storage Devices, Deerfield Beach, Florida, December 5-7, 2005)

Bits and pieces

Nanotubes boost solar cells

Ordered arrays of titanium oxide nanotubes make for efficient solar cells and have the potential to reach efficiencies comparable to today's silicon chip-based solar technology. The nanotube devices are easier to manufacture than silicon solar cells and have the potential to make photovoltaics commercially viable for a wide range of electricity needs.

(Use of Highly-Ordered TiO2 Nanotube Arrays in Dye-Sensitized Solar Cells, Nano Letters, February 8, 2006)

We follow the herd, culturally

A study has shown that when it comes to buying cultural items -- music, books, movies -- we are strongly influenced by choices others have made. This not only assures that popular items sell well -- the rich get richer phenomenon -- but it makes it hard to predict what people will buy.

(Experimental Study of Inequality and Unpredictability in an Artificial Cultural Market, Science, February 2006)

Multilevel optical disk scheme

A design for recording data in as many as eight layers in optical read-only disks could boost DVD storage capacity to 20 gigabytes, and even higher if shorter-wavelength lasers are used to record data. Twenty gigabytes is more than four times the capacity of today's DVDs.

(Modeling and Realization of a Multilevel Read-Only Disk, Optics Express, February 6, 2006)

Motion sensor on a chip

A low-power motion sensor that crams an accelerometer, gyroscope and wireless transmitter on a three-square-millimeter chip could be used in cellphones and other portable devices, clothing and even implanted in the body.

(Low-Power CMOS Wireless MEMS Motion Sensor for Physiological Activity Monitoring, IEEE Transactions on Circuits and Systems, December 2005)