The well-tuned geometry of the florets on the face of the sunflower head has inspired an improved layout for mirrors used to concentrate sunlight and generate electricity, according to new research.

The sunflower-inspired layout could reduce the footprint of concentrating solar power (CSP) plants by about 20 percent, which could be a boon for a technology that's limited, in part, by its massive land requirements.

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CSP plants employ arrays of giant mirrors, each the size of half a tennis court, to beam the sun's rays up to heat a tube of fluid in the top of a tower. This hot fluid drives steam turbines that generate electricity.

In the traditional layout, the mirrors are arranged in rows of circles that ripple out from the central tower. Some, such as the Spain's Gemsolar power-generating array, take up 185 acres. That plant, when complete in 2013, will provide power for about 25,000 homes.

This voracious appetite for land sent Alexander Mitsos, a mechanical engineer at the Massachusetts Institute of Technology, and colleagues in search of an improved layout.

They started with a computer model that evaluates the efficiency of layouts and tested it on a CSP plant in Andalucia, Spain, called PS10. They found its arrangement of mirrors results in shading and blocking of sunlight that dampens the plant's efficiency.

In a bid to increase the efficiency, Mitsos and colleagues used some numerical optimizations to tinker with the layout. They came up with a design where the mirrors are closer together, reducing the amount of land required by 10 percent.

The pattern, a team member noticed, had some elements that resembled the spiraling pattern in sunflowers and suggested they mimic the florets.

"We started looking into it and it turns out that was an excellent idea," Mitsos told me Wednesday.

This "a ha" moment, in turn, led them to a simulated field of mirrors that even more closely resembles a sunflower, with each mirror angled at 137 degrees with respect to its neighboring mirror, as mathematicians had previously found each sunflower floret is turned.

The result was a layout that takes up 20 percent less space than the PS10 layout and is more efficient to boot, Mitsos said.

"It is very scary that we did all the [numerical optimization] work and then we go back to nature," he noted. "We could have started there."

While the finding is based on computer simulations, Mitsos has no doubts it is correct.

"The thing to realize is that a plant like [PS10] costs many millions of dollars and it takes some time to build, so it is not an experiment you can do in the lab," he said.

But he hopes that developers in the CSP industry will adopt his design, saving land and money in the process.

More on solar power technology:

• World's largest solar plant gets U.S. OK
• China taps into solar thermal power plants
• Ant frying tech could make solar cheap
• Himalayas: The future of solar?
• 'Artificial leaf' makes real fuel

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Findings are published in the journal Solar Energy. 

John Roach is a contributing writer for msnbc.com. To learn more about him, check out his website. For more of our Future of Technology series, watch the featured video below.

 

 

A device that gets scorching hot as it captures and traps much of the sun's energy using a greenhouse-like approach could usher in an era of inexpensive electricity from the sun.

The breakthrough comes from a sunlight-absorbing material made of photonic crystals that are arranged to prevent the escape of most of the energy it captures from direct sunlight.

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The concept is similar to the way carbon dioxide molecules in the atmosphere trap the sun's energy, which keep the planet warmer than it would be if all the energy escaped to space.

In this case, infrared radiation from the sun enters the device through holes in the surface, but the reflected rays are blocked when they try to escape, explains Peter Bermel, an electronics researcher working on the device at the Massachusetts Institute of Technology. 

This blockage is achieved by a geometry that limits re-radiation of the sun's rays to a narrow range of angles — the solar disk and region right around the sun. The rest of the rays stay in the device and heat it up.

All this concentrated heat is focused on the production of high-energy photons, which are used to generate electricity via a thermophotovoltaic device.

Conventional photovoltaic cells are limited in their ability to convert sunlight into electricity due to the inefficient conversion of the broad spectrum of sunlight that hits the cells. 

This limit, known as Shockley-Queisser, is 31 percent. 

"What we're doing is a way around that limit … we are taking a very broad spectrum and then we are squeezing it, in some sense," Bermel told me.

That's because heat is absorbed across a broad range of wavelengths and then tailored to generate the high-energy photons needed to generate electricity. The approach, Bermel said, could reach efficiencies of 35 to 36 percent, which is higher than the Shockley-Queisser limit.

Thermophotovoltaic devices have existed since the 1950s, but the concentration of sunlight is traditionally done with giant and expensive arrays of mirrors. Bermel's approach, by contrast, can be made with inexpensive chip-manufacturing technology, he said.

A major expense, though, will come in the equipment needed to track the sun so that the device is always getting direct sunlight to take advantage of the selective-angle approach.

Other solar concentrators, such as the luminescent solar concentrators we reported on in November, get around the outlay for tracking technology by absorbing diffuse sunlight and pumping it to conventional solar cells.

However, some sunlight is still reabsorbed in the LSC technology and control of the wavelengths is difficult, Bermel noted.

"The nice thing about our angle-selective approach is that it can keep losses to extremely low levels, relatively speaking," he said.

What's more, the higher efficiencies of the thermophotovoltaics, in theory, could make up for the added costs of the tracking, he added.

To get there, though, will require more work on optimizing the angular selectivity of their material to reach the theoretical efficiencies.

"I don't want to oversell the research and say we've already figured it all out and it is going to be in your home in the next year or two," Bermel said. "That's not realistic."

Nevertheless, finding new ways to concentrate sunlight to generate electricity is welcome news as global concentrations of carbon dioxide reach new highs, raising worries about that other greenhouse effect.

More on solar energy breakthroughs:

• Ant frying tech could make solar cheap
• Technology could streamline solar power
• Pentagon may study space-based solar power
• Green energy ideas so crazy they just might work

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Bermel and colleagues describe their work in the journal Nanoscale Research Letters. 

John Roach is a contributing writer for msnbc.com. To learn more about him, check out his website. For more of our Future of Technology series, watch the featured video below.

A new breed of solar-powered flying truck is envisioned that can take off from and land on soccer fields, allowing the delivery of goods and services to regions of the world where no roads lead and few planes can land.

Fields big enough for a game of soccer are just about everywhere, reckons the team behind Toronto-based Solar Ship. The game is, after all, the world's most popular sport. It's played anywhere there's room to kick around a makeshift ball.

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The company is building a fleet of delta-shaped ships that are a hybrid between airships and airplanes. They're filled with helium gas, but not enough to lift them off the ground. Solar panels on their body generate electricity from the sun and provide the power to drive them forward and into the air.

According to specifications, the ships can fly up to 1000 kilometers in a day under the power of the sun, haul up to 12 tons of cargo and reach a top speed of 85 kilometers per hour. The company recently announced the successful flight of its first prototype ship. 

The video shows a helium-filled flying wing aircraft successfully taking off and landing. R&D continues to improve performance, attach solar panels and lightweight batteries. Further details on the status of the project are under wraps due to contractual obligations, a company representative told me.

Solar powered airplanes are nothing new. For example, in 2010 an aircraft called the Solar Impulse completed the first 24 hour flight, a feat that proved aircraft can collect enough energy during the day to stay aloft all night.

But the Solar Ship isn't really designed to compete against solar planes per se, which need a large runway to take off and land. Instead, they are more like delivery trucks designed to access areas with few roads, limited space to take off and land, and scant infrastructure to refuel.

In this sense, the prime competitor is the helicopter, but the range of whirlybirds is limited due to fuel requirements. 

A Solar Ship would have been helpful, for example, when the magnitude 7.0 earthquake struck Haiti in 2010, Solar Ship CEO Jay Godsall told the Toronto Star.

It took eight days, he noted, for aid to reach the city of Jacmel. Roads from the capital, Port-au-Prince, were blocked and the airstrip and fueling infrastructure in Jacmel were too damaged to accommodate supply flights from Miami, the closest U.S. city.

"Nobody could land," Godsall told the paper. "If we could make a similar run, and do it here in Ontario, it would an irrefutable demonstration of our aircraft."

We'll have to wait a while longer for that demonstration flight. In the meantime, check out the Solar Ship website and the video below to learn more about the concept.

More on the future of flight:

• An electric plane you can (almost) buy
• Solar plane completes historic 24 hour flight
• Flying car cleared for the road
• Flying Humvee moves ahead
• Seven flights of fancy the fizzled

 

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John Roach is a contributing writer for msnbc.com. To learn more about him, check out his website. For more of our Future of Technology series, watch the featured video below.

 

 

Admit it. You fried an ant under a magnifying glass. It's OK. We did it too. Now scientists are reporting a breakthrough in a similar technology that could bring down the cost of solar power.

About 50 percent of the cost of solar power is due to the materials and manufacturing of solar cells, essentially pieces of silicon that convert sunlight into electricity. By concentrating the sunlight, you can get the same amount of power with fewer cells.

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One way to do this is with a magnifying glass, like we do when we fry ants. But this is a bit tricky when we want to concentrate sunlight all day long because we have to make sure the glass is directly aligned with the sun. 

"In order to do that, you have to track the sun … and that drives up the cost of your concentrating system," Chris Giebink, an assistant professor of electrical engineering at Pennsylvania State University, told me today.

Luminescent solar concentrators
The approach he and his colleagues are improving upon is a decades old technology called luminescent solar concentrators. These contraptions concentrate light by absorbing it with special dyes that re-emit about 75 percent of the light within the confines of a transparent slab of material.

The trapping effect is similar to the way optical fibers use light to transmit data. "It is trapped so it is guided towards the edges and that's where you stick your solar cells," Giebink explained.

The bigger you make the LSC, the more concentrated the light that's fed to the solar cells on the edges. In theory, these things can concentrate the light to the power of 100 suns — all without tracking the sun since they work at any angle and even concentrate diffuse light on cloudy days.

"On paper, it sounds really good," Giebink said. "In practice, the reason you don't see these things is because they don't work very well."

The biggest problem is that much of the sunlight that is absorbed by the dye and reemitted into the glass either bounces off the glass and gets reabsorbed by the dye and lost or reemitted in a direction where it is no longer trapped, which has about a 25 percent chance of occurring.

"Since we are bouncing through this thing hundreds of times, that adds up to a big problem. It has prevented these things from getting anywhere close to their theoretical potential," Giebink said.

Preventing re-absorption
He and his colleagues have now found a way to prevent the light from being reabsorbed by the dye en route to the edge of the glass.

To do this, they made an LSC with two very thin films stacked on a layer of glass. 

The first film — about 100 nanometers thick — is a luminescent layer containing the dye that absorbs and reemits sunlight. This layer sits on top of a low refractive index layer, "which essentially means from the standpoint of light it looks a lot like air," Giebink explained.

This combination creates what is called a microcavity. The researchers found if they changed the thickness of the luminescent layer, the microcavity would change in a way that prevents the light reemitted by the dye from being reabsorbed when it bounces off the bottom of the glass.

"We've changed the thickness of one of the films such that light essentially can't fit in that thin film anymore and as a result it is reflected back with very high efficiency, close to 100 percent," Giebink said.

Their experimental results suggest this approach allows them to get to about 25 suns for a window pane sized collector, which is 2.5 times greater than a conventional LCS.

Going forward, the researchers need to optimize the design so that it is both cheap to manufacture and has the desired effect. After all, it won't bring down the cost of solar power if the concentrator cost as much as the solar cells it's meant to replace.

"We've shown the general idea works, but how exactly to build one of these things is not entirely clear," Giebink said.

Complementary approach
The breakthough is compatible with another approach to this problem reported by researchers at the Massachusetts Institute of Technology in 2008 that focused on creating dyes that are less susceptible to reabsorbing the light they reemit.

"We took any dye that you want and decreased the probability of re-absorption a lot just by how we structure the concentrator itself," Giebink explained. "We ought to be able to combine the two approaches. That's the direction we are going now."

If it all works out, the researchers estimate it could reduce the cost of solar power systems by about a factor of two, he added, which could help make solar energy more price competitive with coal and oil, easing the transition away from fossil fuel energy.

More on solar power technologies:

• Technology could streamline solar power
• Liquid batter could harness, store solar energy
• Chicago getting a tower of power – solar power
• Pentagon may study space-based solar power
• Green energy ideas so crazy they just might work

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The researchers, who included Giebink and Gary Widerrecht and Michael Wasielewski with Argonne-Northwestern Solar Energy Research Center and Northwestern University, published their findings in current issue of Nature Photonics.

John Roach is a contributing writer for msnbc.com. To learn more about him, check out his website. For more of our Future of Technology series, watch the featured video below.

The high peaks of the Himalayas may soon be a beacon for adventurous solar power entrepreneurs, suggests a new study that identified the lofty region as having some of the world's greatest potential to capture energy from the sun.

Other regions not traditionally considered hotbeds of solar power potential include the Andes of South America and Antarctica, note Takashi Oozeki and Yutaka Genchi with the National Institute of Industrial Science and Technology in Japan. 

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In addition to copious amounts of sunlight, these regions are chillier than the usual suspects such as the southwestern United States and the deserts of North Africa. Colder temps increase the operational efficiency of certain photovoltaic solar cells, which turn sunlight into electricity.

"The Himalayan region is especially attractive because it is near regions with large future energy demands such as China and India," the pair writes in Environmental Science and Technology. 

The finding is based on a global analysis of photovoltaic potential that takes into account the effect of ambient temperature, something the team says has not been done before. 

Plopping solar cells high up in the rugged mountains will require addressing additional challenges such as building and maintaining the transmission infrastructure to bring the electricity to the cities where it is most needed, the pair notes.

But overcoming those challenges may be worth the hassle especially when factors such as global climate change are added to the equation. China, for example, adds the equivalent of two 500 MW coal fired power plants per week, according to a 2007 MIT report. 

"Because CO2 emissions per unit electricity in China and India are larger than those in the developed countries, using PV energy in these regions could have a large mitigation effect on climate change," write Oozeki and Genchi.

Big solar in Antarctica, the team adds, doesn't make much sense — at least with current technology — given the low population there and the fact that it's dark for half the year.

"If some way can be developed to store the generated energy, e.g. in the form of hydrogen or refined metals, then it may be possible to utilize the large potential in this region in the future," the team notes.

More stories on solar power potential:

• Algeria sees its desert as solar industry
• Chicago getting a tower of power – solar power
• Space solar power crowd bets on Obama
• 'Arab Spring' to juice power project?
• Green machine takes root in Jordan

Also in msnbc.com's Future of Technology section:

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John Roach is a contributing writer for msnbc.com.

It doesn't look like the leaves changing colors and piling up on the lawn, but a nature-inspired "artificial leaf" technology has taken a notable step toward the goal of producing storable and clean energy to power everything from factories to tablet computers.

The leaf is a silicon solar cell coated with catalytic materials on its side that, when placed in a container of water and exposed to sunlight, splits the H2O into bubbles of oxygen and hydrogen. The hydrogen can be stored and used as an energy source, for example to power a fuel cell.

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"The device both captures the solar energy and stores it in the chemical bonds of the hydrogen and oxygen that are produced from the water," Steven Reece, a research scientist with Sun Catalytix and lead author of a paper describing the breakthrough, told me Friday.

 

You can check out the device in action the video below.

The artificial leaf is made entirely with earth-abundant, inexpensive materials — mostly silicon, cobalt, and nickel — and it works in ordinary water. Other attempts have required more expensive catalysts such as platinum and/or extremely caustic water, noted Reece.

"What was really novel about our work is that we were able to integrate our earth-abundant catalysts with this commercial triple junction solar photovoltaic technology that would then operate under benign conditions without wires and a reasonable efficiency," he said

The breakthrough was led by Daniel Nocera at the Massachusetts Institute of Technology and was reported Thursday in the journal Science. Reece worked in Nocera's lab before moving to Sun Catalytix, which was started by Nocera to commercialize his solar energy inventions.

This new paper is the latest step in a process that has generated buzz over the years.

In 2008, the team reported on the cobalt part of the equation, which releases oxygen from water. They've now coated the other side of the silicon sheet with the nickel-molybdenum-zinc alloy, which releases hydrogen from water molecules.

"You just drop it in a glass of water, and it starts splitting it," Nocera said in a statement. 

He added that the device is not ready for commercial production as the systems to collect, store, and use the gases remain to be developed. "It's a step," he said. "It's heading in the right direction."

The collection and storage of the sun's energy as hydrogen fuel is a key step in overcoming one of the limitations of solar power — it generates energy when the sun is shining, but it needs to be stored somewhere to be useful at night and in cloudy weather. 

Batteries are one place to store the energy, but battery technology, while improving, is limited. Storing solar energy as hydrogen fuel could be an answer.

"Nobody disputes the beauty of the chemistry," reads a Nature News article about the technology. "But whether the system is actually useful will come down to how expensive the hydrogen is to make, and how efficiently the system can use the available energy from sunlight."

More on energy technology:

• Up a tree no more, a 'real' artificial leaf debuts
• Fuel cell breakthroughs reported
• Scientists develop self-healing solar cells
• Green energy ideas so crazy they just might work

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John Roach is a contributing writer for msnbc.com.

 

 

The recent uprisings in North Africa have rattled the short-term prospects for a multi-billion dollar project to generate massive amounts of solar energy in the Sahara and ship a portion of it to Europe.

Long term, though, the establishment of new democracies throughout the region may set the stage for the project's long-term success, argued some participants at a project conference this week in Berlin, Germany.

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"Socioeconomic development and the development of democracy go hand-in-hand," Kirsten Westphal, an energy expert at the German Institute for International and Security Affairs, told Spiegel Online.

In her view, the solar energy project would bring the kind of economic development that could consolidate democratic structures. 

Harnessing the sun
The project, known as Desertec, would harness the abundant sun falling on the Sahara and use it to meet electricity demand across North Africa and Middle East, as well as 15 percent of Europe's.

The project calls for construction of solar thermal power plants in the Sahara and high-voltage transmission lines to ship the power to the people. Cost estimates are around $566 billion.

The concept is being promoted by the nonprofit Desertec Foundation and the Desertec Industrial Initiative, an industrial consortium consisting of such heavyweights as E.on and the re-insurer Munich Re.

At first, the solar power would be used locally, though eventually project promoters envision a portion shipped to Europe.

Such an ambitious project requires a certain level of stability in North Africa to be successful. Unrest scares off investors, for one, and providing extra security for the massive infrastructure would be too costly, noted conference participants. 

Neocolonial hurdle
The Arab Spring, as the revolts to establish democracy across the Middle East and North Africa are called, represent the latest hurdle to the project, which has been questioned as too expensive and technically challenging to ever work. 

In addition, the concept is seen by some as sort of neocolonialism — European nations coming into North Africa and the Middle East to siphon its resources for their own gain, Spiegel Online noted.

This type of fear isn't farfetched. Writing in the magazine Foreign Policy this week about the geopolitics of food, Lester Brown, president of the Earth Policy Institute, details how rich nations are already tying up land in developing countries to grow grain for themselves. 

"Most of these land acquisitions are in Africa, where some governments lease cropland for less than $1 per acre per year … That the governments of [Ethiopia and Sudan] are willing to sell land to foreign interests when their own people are hungry is a sad commentary on their leadership," Brown writes.

According to the Spiegel Online article, attendees at the Desertec conference are well aware of the neocolonial fears and are encouraging an open and transparent process to show that their motives are honorable.

"Until the project takes shape, however, doubts are likely to remain," notes Spiegel Online. " 'Desert Power for the People' was the title of the Berlin event. But it's perhaps understandable if stakeholders in North Africa and the Middle East find themselves asking the question: Which people?"

More stories on green energy: 

• Solar power from North Africa for Europe 
• Europe's supergrid gets a boost 
• Green machine takes root in Jordan 
• Green energy ideas so crazy they might just work

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John Roach is a contributing writer for msnbc.com. Connect with the Cosmic Log community by hitting the "like" button on the Cosmic Log Facebook page or following msnbc.com's science editor, Alan Boyle, on Twitter (@b0yle).