In Jan 2007 someone genuinely thought that changing the Google default search pages into a black background with white or other color text would save 3000 MW-hours of energy every year for mankind. The post got Dugg, the server survived, someone got smug and lots of discussion ensued.
Now we have Blackle.com, the suggested Black Google, which suggests in its About page
We encourage you to set Blackle as your home page. This way every time you load your Internet browser you will save a little bit of energy. Remember every bit counts! You will also be reminded about the need to save energy each time you see the Blackle page load.
Help us spread the word about Blackle by telling your friends and family to set it as their home page. If you have a blog then give us a mention. Or put the following text in your email signature: “Blackle.com - Saving energy one search at a time”.
It further proclaims in the first paragraph of the About page
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
Talk of contextual citing to suit ones purpose.
For instance, the above cited text appears in page 15, paragraph 2, of the above cited paper. Let us download the pdf article and quote from it again, but with one extra follow up sentence this time
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. Displayed image affects on power more in CRTs than LCDs, as discussed in detail below.
Eh!
So it is not all monitors that are going to help “Blackle.com - Saving energy one search at a time”
In my understanding, after discussing the issue with some of my EE and ME department colleagues, the Cathode Ray based monitors (CRTs) do use variable power to generate different colors in each pixel hence the energy savings is a possibility if one were to use a black background (no pixel is lit to “generate” this color). However, if one were to use the Liquid Crystal Displays (LCD) based screens in computers (the “flat panel” screens and all the laptops), I doubt there is any energy savings in the lines suggested. The LCD screen uses a lamp with a constant power source behind the LCDs and the color is generated more by the relative orientation of the crystals with respect to the path of the light beam.
The article cited “contextually” by Blackle suggests this aspect correctly from the experiments reported. In page 19 of the article, the data in Table 8 clearly suggests LCDs don’t have a significant variation in wattage for variable color display. In fact the authors themselves conclude below the Table 8 thus
The data in Table 8 seem to indicate that on power is more variable in CRTs than LCDs (the ratio of maximum to minimum on power ranges from 118-188% in CRTs, compared to 103-108% in LCDs. Among CRTs, maximum on power appears to be associated with a white display, or a maximum-sized application window (which approximates a white display). Among the few LCD monitors in the table, the power used to display a white screen is indistinguishable from power used to display the desktop. Thus, it appears that display color is a significant determinant of on power for CRTs, but not for LCDs.
Instead of hair-splitting about energy savings through colors, one may safely venture into using LCD instead of the CRT, an act that can be more energy saving, barring the procuring cost. For a 15″ display resolution, LCD in power “ON” condition requires about 16 W while a CRT requires about 65 W. See Table 8 in the cited paper above.
[As an aside, there are other interesting things that this article throws up, which is worth noting. For instance, a desktop computer using AMD athlon of processor speed 1200 MHz requires about 100 W (Fig. 7, page 27) while it requires only 60 W if it uses a Pentium 4 processor for achieving comparable speed. No wonder my laptop using AMD burns my arms much more quickly (more the power required, usually, more the heat dissipated from the electronics). Do take a look at the article - and yes, thank Blackle for giving it publicity.]
Here is one more pertinent comment that almost got lost in the comments section of the follow-up post for the original post that started all of this. (wouldn’t you agree why I have come to despise the comments section? Pertinence and good discussions seem to be usually mired in the prevailing euphoria or irrelevance). Eric explains tersely, the consequences of blindly following the perhaps well-intended suggestion of possible energy saving through black google.
My gosh this is disinformation. The comment by Susan just scares me - it’s the same kind of “we don’t need to bothered with data” mentality that leads to things like Iraq wars and teaching intelligent design as science in schools.
The vast majority of power consumed by an LCD panel is used by the backlight. It takes roughly the SAME amount of energy to maintain liquid crystals in ANY orientation. There isn’t a concept of “off” or “on”. LCs work because the light from the backlight is polarized. Twist the LC in one orientation (perpendicular to the polarized light), and it doesn’t pass. Twist it in the other direction, and light passes.
[...]
The US alone generates 4,100,000,000 Megawatt hours per year. 3,000 Megawatt hours amount to about 0.00007% of US energy consumption. Reduce that number by 75% (because it only applies to CRTs), and we’re talking about 0.00001% of the US energy generation for a year.
I’m quite sure it would take MUCH MORE energy to “spread the word” about this “issue” than it would save in energy. Don’t know if this is hype for the sake of hype, or some misinformed person genuinely trying to do the “right thing”, but I think there are better ways to go about encouraging energy consumption that to lobby for COLOR usage on websites.
To round off my argument, I don’t have exact figures but, from my experience of using LCD based computers for the past four years even in my “third world” institute, my guess would be that the world at large is using mostly LCDs or fast converting to that. CRTs are becoming obsolete.
Blackle, in my opinion, can pretty soon, serve to improve the business of ophthalmologists.
Before I close, there is one local issue. There seems to be a free advertisement to use Blackle championed even by some of my engineering students in their blogs, GTalk message tag lines, links etc. Hope they know the perspective of when Blackle saves energy because, reading at least one such advertising blog post makes one wonder it may not be the case (of course, not linking to that post).
As knowledgeable engineers that we are, instead of a simple “Use Blackle” in our GTalk message tag line, we could use a “Use Blackle if you use CRTs” and follow it up with a “Use Friend to use Blackle”. Or to be in sync with the suggested “Blackle.com - Saving energy one search at a time” we could use a “LCD.comp - Saving energy one computer at a time”
An even better GTalk tag-line to save energy for mankind would be “Switch off the computer now and read a good book”.