Supersurface Could Shrink Power Plants

November 04, 2009

Sounds trippy, but it's true: mushrooms and lotus leaves are the inspiration for a superhydrophobic surface created by Duke University scientists that has the potential to make power plants super-efficient.

"In power plants, the majority of the space is taken up by bulky condensers," says Chuan-Hua Chen, assistant professor of mechanical engineering and materials science at Duke. Conventional condensers, which are needed to reject heat in power plants' cooling systems, rely on slick coatings and gravity. Chen and his team turned to nature for better ideas.

Water rolls right off a lotus leaf because its rough surface traps air under the droplets. When a mushroom reproduces, the discharge of spores is actually powered by the energy released when dew droplets merge on them. To replicate these effects, the scientists etched pillars a few microns tall into silicon and added carbon nanotubes that mimic the rough lotus leaf. When cooled, the synthetic surface causes water droplets to form quickly and jump--like a balloon bouncing off your hand.

Chen says this makes a condenser so efficient that its size could be reduced as much as 10 times what it is now. Plus, the surface doesn't need gravity to work so it could even be used in outer space. A Duke University video shows it in action:

Grad student Jonathan Boreyko is leading work on building miniaturized condensers with the superhydrophobic surface. Chen says that while there are ways to make such surfaces inexpensively, the focus now is on durability. With supersurfaces, we could get more out of the power plants we've already got, making each drop truly count.

Photo: Chuan-Hua Chen (right) and Jonathan Boreyko (left), demonstrate the superhydrophobic surface, located under the pipette. Credit: Duke University Photography.

Wide Angle: Tsunami-Proof Buildings Gaining Ground

October 20, 2009

Geotechnical engineer Yumei Wang, who works for Oregon state, warns that it's only a matter of time before a tsunami hits the Pacific Northwest. Yikes. I mean, YIKES!!! Fortunately for the vulnerable populace, Wang has a plan.

She proposes that low-lying communities collaborate to construct what she calls "tsunami evacuation buildings." I think "post-wave outposts" sounds better, but that's just me. Such a building would be made from reinforced concrete and have an 18-foot first floor, wide columns connected to a deep pile foundation, a wide external stairwell, and seawalls along the exterior to dissipate waves. An open plan would allow the building to have other daily uses.

As an engineer with the Oregon Department of Geology and Mineral Industries in Portland, Wang is meeting with officials in Cannon Beach about potentially constructing the nation's first tsunami evacuation building (PDF) by retrofitting the town hall. While the estimated cost is between $1 million and $2 million, doing nothing would be worse since around 100,000 people live in the state's risk areas. Maybe they could even use green concrete. A retrofit definitely beats my idea: water wings as fashionable accessories.

Photo: Walk this way: Shirahama tsunami evacuation structure in Japan. Credit: Nobuo Shuto.

German Solar Cube House Wins DC Decathlon

October 16, 2009

On the final, rainy, day of judging at the fourth Solar Decathlon in Washington, DC, I found myself busting a move with the German team in their solar house. Maybe that was what pushed them over the top.

Today, the U.S. Department of Energy announced that Team Germany from Technische Universität Darmstadt had won the competition, coming away with glory and bragging rights. For the uninitiated, the Solar Decathlon is a DOE-sponsored event where college teams from around the world design and build family homes on the National Mall that run solely on solar power.

When the judges aren't evaluating the homes in 10 different weighted categories, the public can traipse through for inspiration. Despite the cold and steady rain yesterday, the German house was packed with visitors drawn to its futuristic cube shape. The team had cleverly used photovoltaics on all sides for maximum power. Team member Patrick Tauchert told me that one of their strategies was to take features that worked and push them as far as they could go. Even on a gloomy day they still had an impressive surplus, but maintaining a comfortable temperature was key so the whole team danced in unison to generate more heat. I'm pretty sure they're still dancing, but this time in celebration. 

Photo: Visitors flock to the decathlon, and to the German house (far right). Credit: Stefano Paltera/U.S. Department of Energy Solar Decathlon.

Raise the Roof: Tiles Change With the Seasons

October 14, 2009

Looking at a sea of black-topped roofs during a city summer is maddening. They should be painted white! No wonder we're scorching! Then winter rolls around. Now scientists bring us roof tiles that go both ways.

A team of seven recent MIT grads from the Department of Materials Science and Engineering calling themselves Thermeleon created temperature-sensitive tiles made from commercial polymer sandwiched between flexible plastic layers. Cold causes the polymer to dissolve, exposing a dark layer at the back of the tile while heat makes it form droplets that coalesce into a white surface.

The team is still doing testing on the tiles to determine just how much energy savings they produce, and how durable they'll be. Plus they're experimenting with a paint form. They estimate the tiles could cost about the same as traditional roofing materials. While it's hard to compete with a green roof--in part because it seems like fun to hang out on one--Thermeleon tiles might morph into a viable alternative.

Photo: MIT grad Nick Orf turns up the heat on a roof tile. Credit: Patrick Gillooly.

Nanopower Springs Into Battery Territory

September 22, 2009

It sounds like magic: teeny tiny little springs made from carbon could store as much energy as lithium ion batteries. New research out of MIT shows it's possible, at least according to the theoretical models.

Carol Livermore, an associate professor of mechanical engineering at the Institute, led research to show through mathematical modeling and testing that carbon molecules coaxed into tiny spring shapes have the potential to store exponentially more energy for their weight than springs made of steel. The work was published recently in Nanotechnology and the Journal of Micromechanics and Microengineering.

The next step will be to work on making an energy storage device by assembling longer, thicker nanotube fibers than the ones created for the tests. If the scientists can achieve that, they'll open the door to a compelling lithium-ion battery competitor. Carbon nanotubes are durable, so the springs could conceivably work in extreme temperatures that batteries can't handle. While this nano-spring power is still years away from a commercial introduction, I think it's worth the effort to develop. After all, good things tend to come in small packages.

Photo: Carole Livermore (left) with graduate student Frances Hill (right) in the MIT lab where all the magic happens. Credit: Patrick Gillooly.

Nontoxic Water Screening System Blasts Off

September 15, 2009

University of Utah chemists have developed a new nontoxic water testing system that they recently sent via the Discovery shuttle to be tested over six months in the International Space Station.

Astronauts there have two water purification systems--the Americans use iodine and the Russians use colloidal silver. Too little of either means microbe growth while too much iodine can cause thyroid problems and too much silver turns the skin grayish-blue, permanently. To test the water, the astronauts usually send samples back to Earth and wait for the results. Until now.

University of Utah chemistry professor Marc Porter led the creation of a two-part water testing system ten years in the making. A water sample is injected into a cartridge containing a membrane-covered disc of a nontoxic reactive chemical--5-(dimethylaminobenzylidene) rhodanine (DMABR) for silver and polyvinylpyrrolidone (PVP) for iodine. The cartridge is then loaded into an industrial sensor usually used commercially to measure automotive paint color. The sensor can determine exactly how much iodine or silver is in the water sample. If all goes well, the astronauts will be able to correctly calibrate water disinfection in space.

The chemists are currently reworking their color-sensitive NASA system to detect levels of arsenic and heavy metals such as cadmium and lead in water on Earth. The inexpensive color-based detection systems out there now tend to be unreliable, says Lorraine Siperko, a senior research scientist on the University of Utah team. The chemists' goal is to create reliably reactive cartridges that cost less than a few dollars each.

"We want to make something that’s affordable and could be used in many parts of the world, especially where they have limited resources," Siperko says. "We want to make it easy, so you don’t have to be an astronaut."

Top: University of Utah chemist Lorraine Siperko has a zero gravity moment while testing a water monitoring system aboard a NASA aircraft. Bottom: Two of the color sensors. Credit: Courtesy of NASA.

Swedes Make High-Performance Battery With Algae

September 11, 2009

Scientists at Uppsala University in Sweden have created lightweight, flexible batteries from a nuisance algae that blooms globally.

The scientists had originally studying Cladophora algae's potential as a thickening agent for pharmaceutical uses, but discovered that its unique nanostructure made it ideal for energy storage. They coated algal cellulose with a conducting polymer and achieved promising charge-time and storage capacity.

Nanotech professor and research lead Maria Strømme told the university's news service that their work opens up new possibilities for inexpensive, environmentally friendly, and lightweight energy storage systems. The interdisciplinary group published their findings in the September 9 issue of Nano Letters. Gas 2.0 editor Nick Chambers points out that when the algae batteries have been optimized, they should have similar storage capacity as lithium-ion batteries.

Hat tip to my Discovery colleague Michael Reilly for sending this news my way. Cladophora algae blooms worldwide and has been particularly problematic in the Great Lakes. With all the challenges still facing lithium-ion batteries, I'm all for tapping a widespread algae that has a tendency to slime our waterways.

Photo: This "grönslick" (algae) is helping the Swedes break records with their battery. Credit: Uppsala University.

Australians Break Solar Power Record

August 25, 2009

In a record reminiscent of a 100-meter dash, scientists at the University of South Wales in Sydney, Australia, have created the world's most efficient solar power cell ever...by a hair.

Professor Martin Green and his colleague Anita Ho-Baillie led a team of U.S. researchers to victory with a multi-cell combination that is able to convert 43 percent of sunlight into electricity. The previous record was 42.7 percent.

To capture light at the red and infrared end of the spectrum, the researchers threw everything into the cells--gallium, phosphorous, indium, and arsenic, plus silicon. While a bunch of the semiconductors used are expensive, the scientists did raise the efficiency bar.

Ho-Baillie and Green broke a different solar record with a silicon solar cell last October. If they continue to combine their efficient cells with technology from the folks at the National Renewable Energy Lab and Emcore, maybe they'll make ones that can convert 50 percent. I can't wait for the sunny day when that happens.

Photo: The fast ones: Ho-Baillie and Green with last year's (different) record-breaking solar cells. Credit: University of New South Wales.

Who Needs An Air Conditioner Anyway?

August 21, 2009

Even the most efficient air conditioning unit is still going to draw more power than a piddly electric fan. The electric bills this summer better reflect this because I've gone AC-free in New York City.

This little experiment began with an unseasonably cool summer and evolved into laziness about installing the window unit that I take out every fall to prevent heat loss in the cold months. The nice folks at Discovery Earth asked how I was coping so we put together a slide show that includes some tips for fellow AC-freers.

Several people told me they regularly go without AC. I know I'll never be as strong as they are. Are you going without AC? How are you coping? Or, if you recently bought an ultra-efficient and affordable window unit, please share. I might be too wimpy to try this next summer.

Photo: Breeze please! Credit: Alyssa Danigelis.

Crazy-Cool: AC Unit Blows Away the Competition

August 17, 2009

A Denver air conditioner company called Coolerado (ba-dum-bum) recently conquered a UC Davis cooling challenge with a rooftop unit that uses less than half the energy of a standard one.

The Western Cooling Challenge started last summer as a way to encourage manufacturers to make more efficient products and help get them into use. Coolerado's H-80 rooftop unit is intended for 1,500 to 3,000 square feet in a light commercial building. UC Davis put the unit through hardcore testing at the U.S. Department of Energy's National Renewable Energy Laboratory (NREL).

The contest organizers were just hoping to see units reduce energy use by 40 percent, but Coolerado's entry achieved nearly 80 percent energy savings and 60 percent peak-demand savings. With rebates, tax incentives, and energy savings, the unit's return on investment is two years, Coolerado CEO Mike Luby told UC Davis. UC Davis has plans to test units from five more manufacturers in the next few months so we'll have to see how Coolerado ultimately fares against energy-efficient competition.

Earlier this year Coolerado made the news with a solar-powered AC unit that provides 6 tons of cooling using 600 watts--enough for 3,000 square feet. All this AC sounds infinitely better than the ice pack I've been hugging while counting the days until fall, but at least I'm saving energy.

Photo: Coolerado CEO Mike Luby with one of the company's solar-powered AC units. Credit: Kathleen Levine, Denver Business Journal.