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Carbon Nanotubes Could Help Us Store And Use Solar Energy Even After The Sun Has Set

This Invention Could Help Us Use Solar Energy Even After The Sun Has Set
Mother Nature Network
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This story originally appeared on Mother Nature Network.

Scientists at MIT and Harvard University have revealed a novel way to store solar energy in molecules that can be used as fuel to heat homes or used for cooking, reports The Atlantic.

According to the researchers, the large-scale use of solar energy will require significant advances in storage technologies to meet the demands of an energy-hungry population. Other than liquid fuels, they say, existing energy-storage materials do not offer the necessary mix of high energy density, high stability, easy handling, transportability and low cost.

But it looks like that could change with the use of "photoswitching" molecules. The molecules comprise a set of innovative materials that absorb energy, store it, and then release it when needed.

“Some molecules, known as photoswitches, can assume either of two different shapes, as if they had a hinge in the middle,” said the MIT researchers. “Exposing them to sunlight causes them to absorb energy and jump from one configuration to the other, which is then stable for long periods of time.”

To release that energy for use, the molecules simply need to be exposed to a small amount of light, heat or electricity, making them switch back to their other shape and radiate heat. “In effect, they behave as rechargeable thermal batteries: taking in energy from the sun, storing it indefinitely, and then releasing it on demand,” the scientists said.

At the heart of the research is a photoswitching chemical compound called azobenzene, which they attached to substrates of carbon nanotubes. When packed together in correct proportions, the azobenzene molecules formed “teeth” on the nanotubes, which gripped teeth on nearby nanotubes, resulting in a mass able to create a viable amount of energy storage.

If the technology can be brought out of the lab and into the commercial world, the storage would most likely take a liquid form, which would be easy to transport, said Timothy Kucharski, the paper’s lead author.

“It would also enable charging by flowing the material from a storage tank through a window or clear tube exposed to the sun and then to another storage tank, where the material would remain until it's needed,” Kucharski wrote. “That way one could stockpile the charged material for use when the sun's not shining.”

The scientists say the new technology could be put to great use in places where inhabitants burn wood or dung for cooking, which can lead to deleterious indoor air quality as well as contributing to deforestation and climate change.

“For solar cooking, one would leave the device out in the sun during the day,” said Kucharski. “One design we have for such an application is purely gravity driven – the material flows from one tank to another. The flow rate is restricted so that it's exposed to the sun long enough that it gets fully charged. Then, when it's time to cook dinner, after the sun is down, the flow direction is reversed, again driven by gravity, and the opposite side of the setup is used as the cooking surface.”

The research team is now looking into other photoswitching molecules and substrates, “with the aim of designing a system that absorbs more of the sun's energy and also can be more practically scaled up.”

Here’s to putting the sun to good use, 24 hours a day.

Before You Go

10 Hot Green Innovations
Bike Shares(01 of10)
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Bike share programs have revolutionized transportation in some of the country's largest cities, like Washington D.C., Minneapolis, Miami Beach and Boston. For a daily or annual fee (usually around $7 or $75 respectively), users can check out a bike for about 30 minutes at a stand-alone kiosk, ride it around the city, and then check it in at any other kiosk in the system with no extra charge.The idea has been popular overseas since 2007 and there are now massive programs in cities like Paris (16,000 bikes), London (8,000), and Hangzhou, China (65,000). New York launched it's own 10,000-bike version, Citi Bike, earlier this year. Many other cities (like Portland, Seattle, Detroit, Chicago, and Los Angeles) have programs in the works. (credit:AP)
The Electric Car(02 of10)
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Electric cars are finally starting to gain some traction and become reasonably affordable. The Tesla Model S, subject to some recent bickering, has a range of about 275 miles on a single charge and a starting price tag around $50,000.The Chevy Volt, an electric hybrid vehicle, has a range of about 35 miles before a gas engine kicks in. The all-electric Nissan Leaf gets an equivalent to 99 mpg.But the main concern is the youth of the industry. At home charging stations are recommended for most electric vehicles, but there isn't a widespread public system that can rival gas stations, making long distance trips more difficult. (credit:AP)
LEED Building Standards(03 of10)
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The U.S. Green Building Council's Leadership in Energy and Environmental Design system (LEED, for short) has revolutionized eco-conscious building initiatives across the globe. Companies looking to pump up their environmental track record are spending time and money to have their buildings certified green.LEED projects are in progress in 135 different countries, and more than half of certified square footage is outside the U.S.A USA Today report criticized the system as being too lenient for some buildings, which only need to get 40 points out of 100 to receive a certification. (credit:AP)
Cheaper Alternative Energy(04 of10)
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The cost for renewable energy continues to fall and is starting to become much more economically competitive with fossil fuels. New reports from the International Renewable Energy Agency show the cost of solar falling more than 60 percent in the past few years alone.Increasing competition has helped push the price down, particularly with solar as U.S. and European manufacturers struggle to keep up with the pricing of Chinese solar panels.Wind power has also gotten consistently cheaper. (credit:Getty Images)
Reusable Bags/Plastic Bag Bans(05 of10)
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Single-use plastic bags have been outlawed in a few major cities across the country like Seattle and San Francisco, and others like Washington D.C. have instituted a per-bag tax. China imposed a nationwide ban in 2008.Why get rid of them? They're rarely recycled, according to the EPA. They take a really, really long time to break down. And we humans use between 100 billion and a trillion annually. But people should be wary and keep grocery bags clean - a 2012 study found a connection between reusable bags and a spike in E. coli infections. (credit:Getty Images)
Sustainable Fashion(06 of10)
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Sustainable fashion has been in vogue and on the radar since the early 1990s, but it's only gone mainstream recently.Synthetic fibers like polyester produce significantly more carbon emissions than organic cotton, and quite a few large brands were found to use some harsh chemicals to dye and manufacture their garments.Either way, ethical and ecological clothing is catching on. H&M is the biggest user of organic cotton in the world, and brands like Nike and Zara have followed suit. (credit:Getty Images)
Better Ways To Throw Stuff Away(07 of10)
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The average American throws about 40 percent of their food away every year, and nearly 100 cities have launched composting programs to try and keep it out of landfills. Curbside composting has spread across the country from uber-green San Francisco, which started their program 15 years ago and now collects more than 600 tons of compost daily. Of the 250 million tons of trash created in the U.S. in 2010, 34 percent of it was diverted to composting or recycling programs, according to the EPA. (credit:AP)
LED Lighting(08 of10)
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Lightbulbs have changed quite a bit lately. Compact fluorescent lamps were introduced as highly efficient alternatives to traditional bulbs before 100, 75, 60 and 40-watt incandescent lightbulbs are phased out of production by 2014.But now, the new lighting revolution is in LED. These high-tech bulbs last upwards of 20 years and use minimal energy. But, the new Philips 10-watt bulbs cost $60. Each.The good news is that the bulb is so efficient that if every 60-watt incandescent in the country were replaced, $3.9 billion and 20 million metric tons of carbon emissions would be saved in one year. (credit:AP)
Community Gardens / Local Food Movement(09 of10)
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Community gardening isn't really that new, but the local food movement is. The demand for plots in p-patches or local green spaces has skyrocketed in the past few years as people opt out of GMOs and out-of-season produce (which some argue is actually more carbon friendly).Hyper-dense New York has plans to reclaim vacant lots for urban agriculture under Mayor Michael Bloomberg's PlaNYC initiative.The U.S. Department of Agriculture estimated the local food industry to be $4.8 billion in 2008 and upwards of $7 billion in 2011. (credit:WikiMedia:)
Greener Funerals(10 of10)
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Death isn't the best thing for the environment. Cremation sends more than 6.8 million tons of carbon emissions into the atmosphere every year, caskets take a long time to biodegrade and burial leads to methane emission (the second most prevalent greenhouse gas).But environmentally-friendly burial options are becoming more prevalent. Wicker and cardboard coffins can replace traditional wood, and dry ice is used rather than formaldehyde. And green burial services are popping up around the globe to curb post-mortem emissions. (credit:Getty Images)
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