For sample-and-hold panel technologies like LCD and OLED, refresh is about updating the pixel state (color). There is a process that takes place for that even when the pixel data remains unchanged between frames. However, the pixels still need to emit light between refreshes, which for LCD is a backlight but for OLED are the pixel themselves. The light emission is often regulated using PWM at a higher frequency than the refresh rate. PWM frequency affects power consumption as well. Higher PWM frequency is better for the eyes, but also consumes more power.

E-ink displays can do this. That's why they're used in ereaders. Display in TFA OTOH emits light, so definately not.

It does, especially with LCDs like this, where the backlight is the primary driver of the power consumption of the panel.

I'm not even sure how they got their 48% figure. Sounds like a whole-system measurement, maybe that's the trick.

If the screen is only refreshing once per second, less energy is used to refresh the screen. The pixel uses the same amount of power.