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Could the Next Kindle Be Battery-less? Probably Not

bezos[1] Does the nuisance of having to carry around a CPU and battery inside your ereader get you down? Amazon has a solution!

The US patent office has just unveiled a patent that Amazon filed back in September 2012. This patent takes the classic dumb terminal computer idea one step further:

Power and content would be delivered wirelessly from a nearby base station, according to the filing. That base station would also receive user input (for example, detecting a gesture or receiving voice commands from across the room) and handle the behind-the-scenes processing (sending a signal to the display to turn the page, for example).

The remote displays will be able to operate “for substantially longer periods and may not need to be recharged,” the filing explains. No more pesky power cords.

Amazon is thinking that this could be used by colleges and institutions:

For example, a college campus might have multiple primary stations located across campus. The primary stations located throughout campus basically establish a wireless power and data network, such that a student, using their portable display, can access data anywhere on campus. At the same time, the portable display constantly receives power from the network of primary stations while the student is on campus. Thus, the portable display may operate without requiring an independent power source (e.g., rechargeable battery). Similar to Wi-Fi services today that require a fee to access, users could be charged an access or usage fee to utilize the system including usage of the wirelessly transmitted power. [A] rechargeable battery may however provide additional benefits. If the data available to the student included the electronic version of the text books required by a class, a student might be able to view the electronic version of the text book while in class and may no longer need to carry multiple, heavy books around campus.

As cool as the idea might sound, I’m not sure how practical it is. First, I’m not sure this would work with an E-ink screen; I suspect they require too much power to rely on a remote source. (What?!?)

If you’re wondering why a screen that is regularly pitched as being low-power in fact requires a lot of energy then I suggest you look past the marketing hype and consider the engineering reality. An E-ink screen doesn’t need any power to maintain an image on the screen, but changing the screen contents is another matter. That actually takes a lot of energy. In fact, that brief spike in power usage is far higher than the averaged power demands for your average LCD screen.

The energy cost of updating the E-ink screen is its Achilles heel.  It’s part of the reason why video on E-ink will never have a practical commercial application; refreshing the E-ink screen 30 times a second would actually drain a battery faster than a similar-size LCD screen.

It’s the peak power demand that probably means that this battery-less display concept is impractical. At the very least the mobile display is going to require capacitors to store the beamed power needed to update the screen, and once you add those the display is arguably no longer battery-less.

I’m also not seeing any evidence that beamed power is practical on this scale. Sure, it’s now possible to charge your smartphone without plugging it in, and there is even an E-ink shipping label concept design that is powered by the RFID scanner used to read the RFID chip in the label, but those 2 ideas only transmit power for a few inches at best.

Transmitting power across a room, across a building, or across a campus is a completely different problem that I’m not sure anyone has solved.

It’s been a heavily researched topic since it was first proposed by Nikola Tesla around the turn of the century, but I can’t find evidence that there are any current commercial applications. The closest I could find was a hint that in 1964 a model helicopter was flown using beamed power. Unfortunately I cannot find any sign that in the following 50 years this idea was commercially developed.

So if E-ink screens require too much power and if beamed power doesn’t work outside of a lab then why did Amazon get this patent?

I would bet they have a concept design that works well in the controlled conditions of the lab. It’s almost certainly not a design that they think could be taken to market, but it might still be working in the lab.

And don’t forget, Amazon would not let us see the patent if they were planning to release this as a product. These things can be kept from the public view until awarded, so the fact we can see it is a sign that Amazon doesn’t care that everyone knows about it.


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fjtorres March 28, 2013 um 10:32 am

NASA has done and continues to do a lot of work on beam power for long duration aircraft and even for space launch applications.
The theory and prototypes say yes, it can work. Economics and engineering say, not yet.
For low-power devices, the term to look into is wireless power harvesting. The most common idea being to take advantage of all the E-M radiation in the environment to power RFIDs and other chip-level devices.

Patents last 17 years so we may see this one used in a product by 2030.
If not in a future eink device, then maybe in something electrofluidic.

Popup March 28, 2013 um 10:50 am

I was looking for numbers on the energy to refresh an e-ink screen, but couldn’t find any serious-sounding figures.
Do you have any numbers available?
How many ?J does it take to flip an e-ink pixel?

Nate Hoffelder March 28, 2013 um 11:19 am

I only have empirical data, not anything firm.

fjtorres March 28, 2013 um 11:22 am

The issue isn’t just the dye bubbles flipping; it’s the power the backplane consumes.
Eink panels use generic TFT backplanes from the LCD toolkit. Now that mobile displays are becoming key to so many products we re seeing moves to dramatically reduce backplane power consumption. The IGZO tech SHARP is working on allows extremely high resolution displays because, among other things, it’s transistors use lower power.
Qualcomm’s Pixtronix tech is another way the industry is looking to cut display power needs.
A Kindle powered by a future wifi standard is not imminent but down the road…?
Not impossible.

fjtorres March 28, 2013 um 12:01 pm

BTW "beam power" devices are old tech. 🙂

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