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Science Roundup

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The Cassini spacecraft starts its swan song after more than a decade orbiting Saturn, a partnership between industry and education points to a breakthrough for rechargeable batteries, and a new way to collect sunlight could make solar cells significantly more productive.

These are some of the top stories in the world of science today.

Cassini’s Long Goodbye

After a 20-year mission, the Cassini spacecraft is about to plunge into the misty depths of Saturn’s hydrogen atmosphere. On April 22, Cassini started a series of tight orbits of the ringed planet that will mark the end of its mission.

Cassini is almost out of gas and NASA officials worried that if they let it die out in space it might bash into one of Saturn’s moons — primarily Titan or Enceladus — that could harbor life, and infect it with leftover earthy biological material. So they came up with the idea of letting it do 22 close-in orbits during the next few months. Cassini will orbit inside Saturn’s rings, gather samples of the planet’s atmosphere and rings, and go where no spacecraft has gone before. It’s possible that area inside the rings could be full of little bits of rock and ice that could pelt Cassini into an early end, but if not, the probe will say its last goodbyes in September when it disappears into Saturn’s atmosphere.

Self-Charging Batteries

Lithium-Ion batteries charge almost all of our portable electronic devices. They’re powerful, and small, but they need recharging, a lot of recharging. That’s the price for carrying your world in your pocket.

New tech could mean an end to scenes like this.

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To solve the problem, students from McGill University and researchers from Hydro-Québec’s research institute began working on a battery that collects the sun’s rays and recharges itself.

What they came up with is an entirely new concept in battery technology. The team coats the battery in “photo-harvesting dye molecules.” That turns the outside of the battery into a little solar cell.

That’s phase one of the project. The team just got a grant of more than $500,000 to start phase two, finding a way to get the battery to collect and store the sunlight.

“We have done half of the job,” says Professor George P.Demopoulos, co-senior author of the paper with Hydro-Québec’s Dr. Karim Zaghib, a leading expert on batteries. “We know that we can design the electrode that absorbs light.”

Scientists will now have to build an anode, the storage component, which will close the device’s circuit, allowing pwer from the energy-collecting dye to be transferred and stored. The concept was published last week in the journal Nature Communications.

If they can get that done, they’ll have created a self-charging battery with no need for plugs, or chargers.

Dr. Andrea Paolella, a researcher at Hydro-Québec and the study’s lead author, says she thinks phase two is doable. “I’m an optimist” she says, “and I think we can get a fully working device.” The trick after that, of course, will be making the whole thing small enough to incorporate into our phones, or any other devices that run on Lithium-Ion batteries.

Better Solar Cells

Solar cells appear simple: take the energy from the sun and convert it into electricity. But it is hard the process to make cost effective.

Part of the reason is because your basic solar cell, called a single junction solar cell, can only absorb the energy from a narrow part of the light spectrum. The rest of that light energy is lost. That means, on its best day, a solar cell is only about 30 percent efficient.

A new highly efficient generation of solar cells may be just a few years away.

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So scientists started creating multi-junction solar cells, made of semiconductors of several materials that absorb different parts of the light spectrum. That can increase solar cells’ efficiency to as high as 46 percent. Not great, but better, and even more expensive.

Now, in some new work described in Nature Communications, Professor Kita Takashi and Assistant Professor Asahi Shigeo at Kobe University present a new way to create more efficient solar cells.

They took that single junction solar cell, and created a way to make it absorb energy from more than one wavelength of light.

According to their research, this allows them to create solar cells with up to 63 percent efficiency. Their work hasn’t passed the experimental phase yet, but if their prototype makes it to the production line, it could change the face of energy production.

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