More Than Living

REALLY cut your computer screen’s energy use">Does Blackle save any power?How to REALLY cut your computer screen’s energy use

We’ve writ­ten about Blackle so many times that I’m run­ning out of cheap puns to use in my head­lines, but it’s clearly still rel­ev­ant: Charlie’s been seeing reg­u­lar dis­cus­sion of it via his Twit­ter­web, or whatever it is he gets up to these days.

For anyone who’s just joined us, Blackle provides a Google search, but it has a black back­ground rather than the usual white screen. The site addresses the idea that it takes less energy to dis­play a black screen than a white one, and that Google is one of the web’s most vis­ited sites. So it fol­lows that if enough people access the search engine through Blackle’s black screen, the energy sav­ings should be significant.

Well, I’m not con­vinced. As we’ve writ­ten before, nearly all modern com­puter dis­plays use LCD tech­no­logy, which uses the twist­ing and untwist­ing of liquid crys­tals to block light or allow it to pass. The back­light, which oper­ates at a con­stant bright­ness regard­less of what’s on the screen, is the most power-​​hungry part, typ­ic­ally using some­where around 10–20 watts. It takes a much smal­ler amount of power to twist the crys­tals, but doing so actu­ally causes light to be blocked, mean­ing that a dark LCD might use frac­tion­ally more power than a light one. In prac­tice, we can’t tell any dif­fer­ence using our power meter, which dis­plays con­sump­tion to the nearest watt.

Of course, older mon­it­ors used a cath­ode ray tube (CRT) like that of a con­ven­tional TV. These work by firing a stream of excited elec­trons at a spe­cial phos­phor coat­ing, which glows when the elec­trons hit it. A bright screen needs more elec­trons, which requires more energy, so there’s no doubt that a dark CRT saves a bit of power. But while we haven’t got one to test, I’m not sure that the sav­ings would be huge: much of the power a CRT uses goes to heat­ing up the elec­tron gun and cre­at­ing the mag­netic fields needed to steer the beam of elec­trons – only a por­tion is used to accel­er­ate elec­trons at the phosphor.

Blackle’s FAQ does tackle the change in mon­itor tech­no­lo­gies, point­ing out that plasma screens – which are very vaguely sim­ilar to LCDs in that they con­tain phos­phors and (mul­tiple) almost-​​electron guns – use more power to dis­play brighter images. It also says that organic light-​​emitting diode (OLED) screens, which don’t have a back­light, will use less power when dis­play­ing darker images.

I’ve no doubt that they’re right on both counts, and when we get the chance we’ll run some more tests to see just how much power Blackle can save with these sorts of screens, but there are better ways to make your mon­itor use less power. Before you worry about the colour of your desktop or the web pages you visit, con­sider turn­ing down the bright­ness of your screen and making sure that it’s set to power down when you’re away from your com­puter (see below).

That’ll make a small but appre­ciable dif­fer­ence, whatever type of mon­itor you use. Well, every pixel helps.

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If your mon­itor doesn’t already go blank when you leave your PC alone for a few minutes, right-​​click your desktop and choose Prop­er­ties, then click the Screen Saver tab. Click the Power button, and use the drop-​​down boxes to set a suit­able time after which your screen will go dark – try 10 minutes and see how you get on.

The screen should come back to life if you move your mouse. Very occa­sion­ally the screen on some com­puters will remain dark – if this hap­pens to you you’ll need to reset your com­puter, retrace the steps above and change the time period back to “never”.

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• New Laser-​​Driven Dis­plays Use 75 Per­cent Less Power Than Today’s Screens [Lpd] (giz​modo​.com)
• The Dif­fer­ences In Com­puter Mon­it­ors (pro2sell​.com)

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Ori­gin­ally posted 2009-​​08-​​25 12:28:00. Repub­lished by Blog Post Promoter

Tags: Blackle, Blackle.com, Cathode ray tube, Computer monitor, CRT, Google, Liquid crystal display, Television
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