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Sep 22

Reported by Tom Abate in Stanford News Report, 16 September 2013.

An interdisciplinary team has created a “microbial battery” driven by naturally occurring bacteria that have evolved to produce electricity as they digest organic material.

The tubular growth depicted here is a type of microbe that can produce electricity. Its wire-like tendrils are attached to a carbon filament. This image is taken with a scanning electron microscope. More than 100 of these 'exoelectrogenic microbes' could fit side by side in a human hair. Credit: Xing Xie, Stanford Engineering.

Engineers at Stanford have devised a new way to generate electricity from sewage, using naturally occurring “wired microbes” as mini power plants, producing electricity as they digest plant and animal waste.

In a paper published in the Proceedings of the National Academy of Sciences, co-authors Yi Cui, a materials scientist, Craig Criddle, an environmental engineer, and Xing Xie, an interdisciplinary researcher, call their invention a microbial battery.

They hope it will be used in places such as sewage treatment plants, or to break down organic pollutants in the “dead zones” of lakes and coastal waters where fertilizer runoff and other organic waste can deplete oxygen levels and suffocate marine life. Continue reading »

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May 08

Reported by Ellis Simon, in City College of New York News, May 4, 2012.

The CUNY Energy Institute, which has been developing innovative low-cost batteries that are safe, non-toxic, and reliable with fast discharge rates and high energy densities, announced that it has built an operating prototype zinc anode battery system. The Institute said large-scale commercialization of the battery would start later this year.

Zinc anode batteries offer an environmentally friendlier and less costly alternative to nickel cadmium batteries. In the longer term, they also could replace lead-acid batteries at the lower cost end of the market. However, the challenge of dendrite formation associated with zinc had to be addressed. Dendrites are crystalline structures that cause batteries to short out.

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Jan 16

Reported by Jennifer Chu, MIT News Office, 11 Jan. 2012.

A new sunflower-inspired pattern increases concentrated solar efficiency.

Just outside Seville, in the desert region of Andalucia, Spain, sits an oasis-like sight: a 100-meter-high pillar surrounded by rows of giant mirrors rippling outward. More than 600 of these mirrors, each the size of half a tennis court, track the sun throughout the day, concentrating its rays on the central tower, where the sun’s heat is converted to electricity — enough to power 6,000 homes.

The sprawling site, named PS10, is among a handful of concentrated solar power (CSP) plants in the world, although that number is expected to grow. CSP proponents say the technology could potentially generate enough clean, renewable energy to power the entire United States, provided two factors are in ample supply: land and sunlight.

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Jan 11

Reported by Mark Brown, Wired UK, 4 Jan. 2012.

For NASA’s Martian rovers, it seems that bigger is better. The $2.5 billion (£1.6 billion) Curiosity — which is currently whizzing towards the red planet following its November 2011 launch — is five times bigger than twin predecessors Spirit and Opportunity.

In fact it’s taller than most basketball players at 2.2 meters high, and is about the size of a small SUV with its three-meter length. Add on its humongous robot arm, which can reach out another 2.2 meters, and you’ve got only seriously huge rover.

To power such a beast needs a lot of energy and the robot packs a radioisotope power system that generates electricity from the heat of plutonium’s radioactive decay. It will fuel the enormous rover for at least 687 Earth days (one Martian year).

But at the US Naval Research Laboratory, space roboticists are researching planetary explorers at the other end of the size spectrum. While Curiosity weighs about the same as a giraffe (900kg), these autonomous micro-rovers would be lighter than a bag of sugar, at just one kilogram. Continue reading »

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Sep 22

Reported by Ars Technica, in Wired Science, 21 Sep. 2011.

Most of the renewable energy sources that are under consideration involve an obvious source of energy — light, heat, or motion. But this is the second time this year there has been a paper that has focused on a less obvious source: the potential difference between fresh river water and the salty oceans it flows into. But this paper doesn’t simply use the difference to produce some electricity; instead, it adds bacteria to the process and takes out a portable fuel: hydrogen.

The process is still fundamentally electrochemical. Sea water and fresh water are placed on opposite sides of a membrane that allows ions through, but prevents the passage of water molecules. The ions will move to the fresh water to balance osmotic forces, which will create a charge difference that can be harvested for various purposes. The voltage produced in a single one of these cells is small, but the source of the power is essentially unlimited and is available 24 hours a day.

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Sep 13

Reported by Mark Brown, Wired UK, 13 Sep. 2011.

A team of researchers from universities across America are rooting through millions of molecules to hunt down a material that can create efficient and cost-effective solar cells — and they need your computer power to do it.

Currently, the cost of electricity from silicon solar cells is about ten times that of other energy sources. So to put solar on level pegging researchers are hunting down organic materials that have a conducting efficiency of 10 to 15 percent and an average lifetime of more than a decade.

Organic cells also have the ability to be molded into different shapes, they can be made semi-transparent and are much lighter than inorganic materials. They’re cheaper and easier to produce, too, and are non-hazardous.

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Feb 03

Reported by Winifred Bird in New Scientist, 02 February 2011.

The future of energy production (Image: Luis Louro/Alamy).

The way a dragonfly remains stable in flight is being mimicked to develop micro wind turbines that can withstand gale-force winds.

Micro wind turbines have to work well in light winds but must avoid spinning too fast when a storm hits, otherwise their generator is overwhelmed. To get round this problem, large turbines use either specially designed blades that stall at high speeds or computerised systems that sense wind speed and adjust the angle of the blade in response. This technology is too expensive for use with micro-scale turbines, though, because they don’t produce enough electricity to offset the cost. That’s where dragonflies come in.

As air flows past a dragonfly’s thin wings, tiny peaks on their surface create a series of swirling vortices. To find out how these vortices affect the dragonfly’s aerodynamics, aerospace engineer Akira Obata of Nippon Bunri University in Oita, Japan, filmed a model dragonfly wing as it moved through a large tank of water laced with aluminium powder. He noticed that the water flowed smoothly around the vortices like a belt running over spinning wheels, with little drag at low speeds.

Obata found that the flow of water around the dragonfly wing is the same at varying low current speeds, but, unlike an aircraft wing, its aerodynamic performance falls drastically as either water speed or the wing’s size increases. As air flow behaves in the same way as water, this would explain the insect’s stability at low speeds, Obata says.

Obata and his colleagues have used this finding to develop a low-cost model of a micro wind turbine whose 25-centimetre-long paper blades incorporate bumps like a dragonfly’s wing. In trials in which the wind speed over the blades rose from 24 to 145 kilometres per hour, the flexible blades bent into a cone instead of spinning faster. The prototype generates less than 10 watts of electricity, which would be enough to recharge cellphones or light LEDs, the researchers say.

“It’s a clever leap,” says David Alexander, a biomechanics specialist at the University of Kansas. “In some ways it’s more appropriate than using an animal wing model for an airplane. A wind turbine blade is just a wing, only it’s designed to go in tight circles.”

But Wei Shyy of the Hong Kong University of Science and Technology believes that while the dragonfly-inspired design may be more stable, it will also experience more energy loss in terms of drag.

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