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Solar Cell and Capacitor in One
Roland Piquepaille writes "Solar cells can convert solar energy to electricity, but that's about all they can do. You need batteries to store, and then release, this electricity. But this extra-step might soon no longer be necessary. According to PhysicsWeb, Japanese scientists have developed a new type of solar cell which integrates an electricity storage device. No more batteries or recharger! The 'photocapacitor,' as they call this new device, is also twice more efficient than a typical silicon-based solar cell when used on cloudy days. So apparently, you'll soon be able to travel lighter by leaving your various rechargers for your many handheld devices at home. Read more for other details and references."
This is very exciting, alternative sources of energy are getting closer and closer to becoming more viable. After reading an article about how rising oil prices are helping alternative energy, I think the stage is getting set for a real revolution. Being realistic, we have a long way to go,
Brandon PetersenGet Firefox!
It doesn't use batteries, which store electrical power in chemical reactions, it uses a capacitor, which stores static charges on two electrically separate plates. It actually appears to use an electrolytic capacitor, which will eventually wear out, but should last much longer than a battery. However, they store less energy, and they tend to lose charge faster.
I'm not sure what the benefit is supposed to be. It seems almost certain to be less efficient, less resistant to damage, and shorter lived than a separate device designed specifically for energy storage, which doesn't have to be manufactured in a thin layer. The articles claim it is more efficient in dim light than silicon cells, but don't give any reason why...I wonder if they are using some faulty measurement of "efficiency", such as output voltage. (It might charge to the same voltage on an open circuit in dim light, even though it can't deliver as much power.)
However, it seems to truly be a completely different type of solar cell: it's not just a silicon cell layered with a capacitor. It is possible that it really does behave better in low light conditions. The reference to the photoreceptor dyes makes me wonder how it'll stand up to full sunlight for prolonged periods, though.
Cool. However, the impression you give is a little inaccurate...these are just an improvement on the Peltier junctions already used to cool processors. That "1 square inch coolchip" doesn't provide the energy to cool your freezer, it just converts electrical energy produced somewhere else into a temperature difference. And you could use the temperature difference generated to produce power, but that would impede the cooling and just waste power overall...rather than powerchips, the hot side should have a heat sink and fan to dissipate heat as quickly as possible.
Also, operation produces no waste products, but what about manufacturing and lifetime? You have the same questions as you have for solar cells. However, I think this is a more viable source than solar for most of the world, and maybe for extracting more useful power from the waste heat of power plants and industry...and it'd be very helpful in spacecraft powered by radiothermal generators, such as Cassini. RTG's are heavy, this could allow much smaller ones to generate the same power.
One of the problems with standard solar cells is that you have to disconnect them from the battery when the light levels drop, or they will discharge the battery
Not too hard to avoid, simply connect it to a diode, so that the electrons only flow one way. You should probably use a schottky diode which has an extremely low voltage drop (more info) since you probably won't be producing too high of a voltage to start with if it's a single solar cell.