Much has been made this week of Apple's patent filing for solar panels embedded into the screens of gadgets. In the diagram accompanying the application, we see a layer of solar cells tucked safely behind the glass and the LCD layer, presumably to juice, say, an iPod's battery as you use it.

Most likely this is one of the many patent filings made when an engineer has an idea. Often there is no intention to pursue the design, but you file anyway, just in case.

But would a solar panel inside an iPod really work? After all, we have had solar powered watches and calculators for years. It's doubtful. Fortune spoke to Michael Filler, an expert in photovoltaics, and he said that you'd need the solar cells from almost one million watches to power an iPod.

This is slightly disingenuous: It is indeed possible to power an iPod by the sun, you just use a better solar unit. Brunton's Solaris i6 will put out up to six watts, which is plenty to power a USB device (using P=VI, six watts should give five volts at half an ampere). At $210, though, it costs around the same as the iPod you'll be using it to charge. And as you can see in the picture, it's a lot bigger than the iPod's screen.

Clearly powering something as demanding as a modern iPod by the light of the Sun is impractical. Forbes goes on to discuss the solar-sandwich design:

Sandwiching the solar cells inside the device would block some light out and knock down power conversion efficiency even further

The UK Times is a little more enthusiastic:

The patent, should it be awarded, has the potential to make the iPhone a truly portable device, dispensing with the need for it to be connected to a power supply by wires

But despite all the expert testimony, we can't help but think that everybody is missing the point. Those facts again: First, the power from a panel the size of an iPod screen would be woefully inadequate. And even if a laptop screen is bigger, so are its power needs. Second, and almost perversely if the panel is meant to suck up photons from the Sun, the cells are hidden behind the LCD screen, which is designed to block light. And third, how often is a gadget in bright light anyway? The iPod is almost always in your pocket, and if you use a MacBook in the sun, good luck actually reading the screen.

The point that everybody seems to have missed is that these panels might be intended to soak up light from the actual screen backlight itself. Think about the way a hybrid or electric car works. When braking, the energy that would go to waste is sent into a flywheel which then returns a little charge to the battery.

What if Apple is planning on using all the light which goes to waste, normally absorbed by a colored liquid crystal, and converting it to give a little juice back to the batteries? It wouldn't be much, but it's free power, recycling from within, and as we know, every little bit of power saving helps battery life.

This, if you think about it, makes a lot more sense than leaving your iPhone on the dashboard, roasting in the sun. I did ask Apple about this but, according to the PR people, there was nobody available to comment.

Solar LCD Powered iPods, iPhones and Laptops? [MacRumors]
iPhone 2.0: Solar-Powered Mobility [Forbes]
Apple raises prospect of solar-powered iPhone [Times UK]

by Charlie Sorrel for Wired.com

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