hey, i've been looking for those numbers for years! where did you get them?
the particular memory lcd i have is 35mm × 58mm, which is 20cm², so at 7½ millijoules per square cm, updating the same area of epaper would require 150 millijoules to update if it were epaper. the lcd in fact requires 50 microwatts to maintain the display. so, if it updates more than once every 50 minutes, it will use less power than the epaper display, by your numbers. (my previous estimate was 20 minutes, based on much less precise numbers.) at one frame per second it would use about a thousand times less power than epaper
so in this context epaper is ultra high power rather than ultra low power. and the olpc pixel qi lcds, excellent as they are, are even more power-hungry
pixel qi and epaper both have the advantage over the memory lcd that they support grayscale (and pixel qi supports color when the backlight is on)
the particular memory lcd i have is 35mm × 58mm, which is 20cm², so at 7½ millijoules per square cm, updating the same area of epaper would require 150 millijoules to update if it were epaper. the lcd in fact requires 50 microwatts to maintain the display. so, if it updates more than once every 50 minutes, it will use less power than the epaper display, by your numbers. (my previous estimate was 20 minutes, based on much less precise numbers.) at one frame per second it would use about a thousand times less power than epaper
so in this context epaper is ultra high power rather than ultra low power. and the olpc pixel qi lcds, excellent as they are, are even more power-hungry
pixel qi and epaper both have the advantage over the memory lcd that they support grayscale (and pixel qi supports color when the backlight is on)