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metalslug

Blackle - "Google with a smaller carbon footprint..."

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Blackle

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In January 2007 a blog post titled Black Google Would Save 750 Megawatt-hours a Year proposed the theory that a black version of the Google search engine would save a fair bit of energy due to the popularity of the search engine. Since then there has been skepticism about the significance of the energy savings that can be achieved and the cost in terms of readability of black web pages.

Blackle saves energy because the screen is predominantly black. "Image displayed is primarily a function of the user's color settings and desktop graphics, as well as the color and size of open application windows; a given monitor requires more power to display a white (or light) screen than a black (or dark) screen." Roberson et al, 2002


Source

I'm no engineer. Is "750 Megawatt hours a year" a realistic estimate ?
Is there any real-world advantage to this "saving"? It really seems to be a drop in the ocean compared to the global carbon footprint of everything else.

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Bull hockey. Given that a great number of monitors today are lcd, and a fair more crt's will be replaced with lcd's, it's a load of manure.

The lcd backlight stays on as long as you are using the computer. It just switches pixels on and off. Cost savings? Little to none.

Crt's aren't much different. They are still powered on if you're using the computer, regardless of the colors on the screen.

Screen saver mode? Yep, saves the screen from burn in, but it's still powered on.

Want to save energy? Change your dispay settings to put the monitor to sleep with 5 minutes of idle time, instead of the hours it's probably set for, if it actually powers down at all.
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Crt's aren't much different. They are still powered on if you're using the computer, regardless of the colors on the screen.



The deflection circuits and CRT heaters run the same regardless of what's being displayed.

Beam current varies from 0 to perhaps a few miliamps depending on what's being displayed. 1 mA * 35,000V * 3 guns = 105W for white versus nothing for black.

With total power consumption of a couple hundred Watts, easily half a CRT's load could come from what's on the screen.

Power supply sag is visible on old cheap computer CRTs, wher e a mostly bright screen causes the image to shrink horizontally because the power supply sags and can no longer get full deflection.

Televisions got over-scan where the edges of the image are off the screen so they could get away with weak unregulated power supplies without visible efects.

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Screen saver mode? Yep, saves the screen from burn in, but it's still powered on.



With the screen in standby (not displaying a pretty picture) there should be a lot less power consumed because you're not dumping enough power into the inductive horizontal deflection yoke to run it across the screen 100,000 times a second (that whole dv/dt thing)

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OK, you got me on the CRT's.

Can't remember the last time I saw one on a shelf though. I do have one here, for test purposes, but that will be replaced by an lcd soon too.
It's your life, live it!
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RB#684 "Corcho", ASK#60, Muff#3520, NCB#398, NHDZ#4, C-33989, DG#1

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