PV panels on the Mars rover Spirit were covered with dust over a two-year period. Credit: NASA/JPL.

Self-cleaning surfaces aren’t a particularly novel idea, and self-cleaning glass commercial products made by companies, such as Saint Gobain, have been around in various products for at least five years – but at a premium price. These technologies use a TiO₂ coating to photocatalyze organic dust that is then washed away by humidity and rain. However, for some dusty (e.g., nonorganic) materials, even this self-cleaning system doesn’t work.

The cost and performance problems with these existing systems are unfortunate, especially when it comes to photovoltaic solar panels and mirrors, particularly when one considers that many utility-scale solar energy systems are being located in desert areas that are prone to large amounts of non-organic dust. In some of these regions, even dragging out a hose or water truck to rinse off PV panels and mirrors is not practical nor economically feasible.

The effects of the dust on these solar energy system are tangible. “A dust layer of one-seventh of an ounce per square yard decreases solar power conversion by 40 percent,” explains MIT visiting professor Malay K. Mazumder. “In Arizona, dust is deposited each month at about four times that amount. Deposition rates are even higher in the Middle East, Australia and India.”

Mazumder knows something about dust. He has worked with NASA on a similar but more difficult problem: Extraterrestrial dust. When the problem is dust on surfaces somewhere lacking Earth’s atmosphere and weather – say, Mars or the moon – terrestrial technology just won’t cut it. Lunar dust was nasty stuff for astronauts to deal with and is described as tiny pieces, sharp and interlocking pieces of glass or coral that is everywhere on the lunar surface.

According to NASA, Mars dust isn’t quite so bad, but still a big problem:

Dust is also ubiquitous on Mars, although Mars dust is probably not as sharp as moon dust. Weathering smooths the edges. Nevertheless, Martian dust storms whip these particles 50 m/s (100+ mph), scouring and wearing every exposed surface. As the rovers Spirit and Opportunity have revealed, Mars dust (like moon dust) is probably electrically charged. It clings to solar panels, blocks sunlight and reduces the amount of power that can be generated for a surface mission.

NASA knew that dust interference with solar panel function could be catastrophic for Mars missions. Working with the agency, Mazumder and other researchers developed a novel self-cleaning solar panel technology for use in lunar and Mars missions.

Now, Mazumder says the time has come to apply the same technology on earth. “Solar panels powering rovers and future manned and robotic [NASA] missions must not succumb to dust deposition. But neither should the solar panels here on Earth,” he says

Mazumder describes the technology he has in mind as having three parts. The first part is thin layer of transparent, electrically sensitive material on the glass or plastic covering of a solar panel. The second part is a sensor to monitor dust levels on the surface of the panel. The third part is a system to send a brief electric charges over the surface of the panel. Because, like the stuff on moon and Mars, most Earth dust carries an electrical charge, delivering alternating electric fields acting through the thin layer on the panel dislodges, carries and deposits dust particles off and away from surfaces.

According to a news release, Mazumder says a two-minute process removes about 90 percent of the dust deposited on a solar panel. Further, his approach requires only a small amount of electric power, which can easily be supplied by the panel.

Artist’s conception of solar sail. (Credit: JAXA.)

Japan has successfully deployed a solar sail on a spacecraft, demonstrating for the first time that such technology can be used to convert the sun’s energy to the power needed to move a vessel in the cosmos. As an added feature, the IKAROS spacecraft uses LCD technology to alter its attitude using the pressure of sunlight – a first for solar sails.

The sail measures 20 meters diagonally, but is only 0.0075 millimeters thick - or about half the thickness of a human hair.

IKAROS launched in May, and soon after became the first solar sail to be propelled by sunlight. Liquid crystal devices along the outer edge of the sail are used to help steer the craft. These devices control the reflectivity of the outer sections of the sail; switching one on creates a mirror-like effect, allowing sunlight to push more on those parts. The sail can slowly be spun by turning the LCD devices on and off, synchronized to the spin cycle.

“With this we can control both the orbit and the attitude using only sunlight,” says Yuichi Tsuda of the Japan Aerospace Exploration Agency.

Compared with onboard thrusters, which remain the main method of steering spacecraft, the effect of the reflecting devices is slight. The sail can only change its attitude by about 1 degree per day, Tsuda says, and it gets less effective the faster the sail spins.

This short video displays images that IKAROS took of the solar sail from space. Try to ignore the Styx Muzak.

Ultrasensitive Nanomechanical Transducers Based on Nonlinear Resonance, one of ORNL’s 2010 R&D 100 award winners. (Credit: ORNL.)

R&D Magazine awarded DOE and other federal labs with 50 of its R&D 100 Awards. The awards, sometimes referred to as the “Academy Awards of Science,” are presented to those labs and companies that have been a major contributor to the development of “one of the 100 most technologically significant new products of 2010.”

“The large number of winners from the Department of Energy’s national labs every year is a clear sign that our labs are doing some of the most innovative research in the world. This work benefits us all by enhancing America’s competitiveness, ensuring our security, providing new energy solutions, and expanding the frontiers of our knowledge. Our national labs are truly national treasures, and it is wonderful to see their work recognized once again,” says Energy Secretary Steven Chu.

U.S. federal labs have a history of being highly recognized for technological developments and materials innovation through these awards. Here are the labs that are winners this year:

• Ames National Lab
• Argonne National Lab
• Idaho National Lab
• Lawrence Berkeley National Lab
• Lawrence Livermore National Lab
• Los Alamos National Lab
• NASA Glenn Research Center
• National Energy Technology Lab
• National Renewable Energy Lab
• Oak Ridge National Lab
• Pacific Northwest National Lab
• Sandia National Lab
• Army Engineer R&D Center

The biggest winner is the Lawrence Livermore National Lab which is recognized with 10 awards.

ACerS Corporate Member Toyota Central R&D Labs was also recognized by R&D Magazine for their Permanently Engaged Gear Starting Mechanism for Stop and Start System (Mechanical Devices).

All of the award winners can be seen here.

Credit: JACerS and Colombo,Mera, Ridel and Sorarù.

A quartet of researchers from Italy and Germany have published an fascinating overview of polymer-derived ceramics in the most recent edition of JACerS. Paolo Colombo, Gabriela Mera, Ralf Riedel and Gian Domenico Sorarù write in “Polymer-Derived Ceramics: 40 Years of Research and Innovation in Advanced Ceramics” (free access), that:

“The polymer precursors represent inorganic/organometallic systems that provide ceramics with a tailored chemical composition and a closely defined nanostructural organization by proper thermal treatment (curing and thermolysis processes) under a controlled atmosphere. The PDCs route is an emerging chemical process as attested by the increasingly commercial development of preceramic polymers to produce near-net shapes in a way not known from other techniques. Moreover, PDCs are additive-free ceramic materials possessing excellent oxidation and creep resistance up to exceptionally high temperatures.”

It’s easy to understand the growing interest in PDCs because, at least In principle, the preceramic polymers can be produced and shaped using familiar techniques such as injection molding, coating from solvent and extrusion. The preceramic polymers still have to be converted to a true ceramic, something that is accomplished by components by heating to a temperature that that it consolidate the elements contained in the polymer structure to a ceramic. PDCs also have excellent oxidation and creep resistance.

Over the years, PDCs have grown from binary systems, such as Si₃N₄, SiC, BN, and AlN, to ternary systems that include SiCN, SiCO and BCN, and quaternary systems, such as SiCNO, SiBCN, SiBCO, SiAlCN, and SiAlCO.

Credit: JACerS and Colombo,Mera, Ridel and Sorarù.

Regarding applications, the authors sum up the remarkable evolution of PDCs:

“Initially the research on PDCs was focused mainly on dense bulk materials and fibers for mechanical applications at high temperatures. Nowadays, nano powders and porous PDCs with pore sizes in the range between several microns and few nanometers for applications such as catalyst support and for liquid and (hot) gas separation processes are gaining increasingly importance. Moreover, the polymer-to-ceramic transformation is a suitable technology to produce a broad spectrum of ceramic-based composite materials with adjusted chemical, mechanical, and physical properties. PDCs can also be processed to thin films for optoelectronic applications and to thick films, e.g. for hard coatings, environmental barrier coatings, and others. The great flexibility in terms of processing and forming of preceramic polymers into shaped-ceramic components has also enabled them to play an important role in several other applications.”

They also discuss how PDCs are being used in cutting-edge areas such as anode material for solid oxide fuel cells (SiCN), glow plugs, temperature and pressure sensors, high-temperature brake pads (to compliment the new ceramic composite brake disks) and space mirror mock-ups.

According to a NASA Tech Brief, the Next Generation Space Telescope - aka, the James Webb Space Telescope – will be using electrostrictive ceramic actuators that can function at low temperatures to control the shapes of mirrors.

The actuators, developed by two ACerS members, Maureen L. Mulvihill and Mark A. Ealey of Xinetics, a division of Northrup Grumman in Devens, Mass., can achieve a relatively large stroke in the low-temperature ranges that the telescope will encounter, i.e., in the area of 30–60 K. This stroke will be used to adjust the shape of the mirrors used by the telescope.

Unlike the Hubble telescope that used a single primary mirror, the JWST will a mirror composed of 18 hexagonal segments, which will unfold and be adjusted after the telescope is launched.

According to Mulvihill and Ealey, besides use in deep space, the electroactive ceramic material may be of interest to companies for fine control of the positions of objects in cryogenic laboratory apparatuses and in industrial cryogenic (including superconducting) systems.

NASA offers a download of a Xinetics PowerPoint presentation on Xinetic’s work here.