@twobob
I thought about that too. That charging circuit can be so much smaller that it would fit in the kindle even with the umts modem installed. So you wouldnt need Electricity at all. Now let's add more sophisticated Software like an email client to it and: you have your solar powered mobile tablet. This is really what I'm dreaming of and I still hope that some day android will be running on my kindle.
If you equip the kindles with a solar cell right when you buy them at amazon, you can use polycrystalline cells that are more efficient and cheaper. I had to use a flexible cell due to the roundet surface of the kindle. That could be adapted for stock solar kindles. Thus the whole construction would not be that much more expensive than the usb wall charger everyone has to buy extra now.
@ geekmaster
Thermal insulation for the kindle touch is a rather complex problem
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Our sun can be approximated as a so called "black body", that means it emits radiation (energie) according to Plancks law (yellow in the graph). This radiation has its peak somewhere at 600 nm (greenish yellow). If you place an infrared filter over your kindle, you would cut of the amount of energy (=surface in the graph) right from the point where it says "IR". But this energy has to be reflected (e.g. mirror). If you place an absorbing filter on your kindle, it just heats up your filter and the filter heats up your kindle.
Once the sunlight hits your kindle it is being absorbed, that means your kindle heats up. Now the following happens: Your peak wavelength is no longer at ~600nm, but somewhere at ~10,000nm (that is the wavelength of the maximum intensity for a black body at ~300K (your kindle). Look for Wien's displacement law if you are interested). This wavelength is waaaay on the right side (IR-Part) of your spectrum. Besides of that the general shape of the spectrum will still be the same (that little hill that is steeper on the left than on the right and it would be very flat and wide). Here is an example:
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Now if you still have your IR-Filter in place, congratulations, this energy will never escape and heat up your kindle. You built an energy trap
After that point where the solar energy reached your kindle, you can't win on the radiation side (i.e. reflecting covers, ir filters etc.). All you can do is fight against conduction to the battery/circuits and let the cover heat up.
The only (pracical) way to reduce the energy reaching the kindle is to cover the area that is not covered with the solar cell with a reflective foil (for example the emergency blanket that you mentioned) This blanket will reflect almost all energy that hits that area, reducing the amount of energy that heats up your kindle. You can't do anything against the solar cell being heated up and heating up your kindle.
The other (non pracitcal way) would be to place an IR-filter somewhere in front of the kindle (but not attaching it directly to it. That would reduce the amount reaching your kindle by lets say 25% without reducing the efficiency of your solar cell significantly. If your filter is not placed directly on your kindle, some energy still can be emitted as this emission is omnidirectional and your IR-Filter would only cover a specific area. The area covered by the filter (=the filter itself) would just heat up from the energy emitted from the kindle, but you wouldn't care as it is away from your kindle.
I hope this is clear, please let me know if there are any questions.