It was first in July that Blackle came to my attention with an enquiry from a mate who works at a large accounting/consulting company into the claims of reduced power consumption resulting from using its services over google.
Could this be true? The energy saving I mean.
For those worried with energy consumption and all its downsides, when your screen is white, being it an empty word page, or the Google page, your computer consumes 74 watts, and when its black it consumes only 59 watts.
Mark Ontkush wrote an article about the energy saving that would be achieved if Google had a black screen, taking account of the huge number of page views, according to his calculations, 750 mega watts/hour per year would be saved.
In a response to this article Google created a black version of its search engine, called Blackle, with the exact same functions as the white version, but with lower energy consumption, check it out.
So I headed over to the site to see whether the claims being made were based in a sense of reality and not some fictional fairytale. After delving into the site a little I came across both an FAQ page and an about page. There was a link from there to the main document that Heap Media use to make their claims: Energy Use and Power Levels in New Monitors and Personal Computers. They managed to distill thirty six pages of analysis on the consumption of a variety of monitors down to a single figure that they could use to support their claims – for everyone using the Google search spin off.
The research was undertaken at the University of California by a collection of people for the United States Department of Energy (USDoE) and presented in their paper dated July 2002 (some five years before Blackle arrived on the scene). The actual study was carried out in 2000 and 2001 on both the bulky Cathode Ray Tube monitors and the early thin Liquid Crystal Displays being driven by a variety of sources, such as embedded computers, personal computers and macintoshes.
The sample of thirty-five monitors selected had the following characteristics:
- Ninteen (54%) Cathode Ray Tube
- Sixteen (46%) Liquid Crystal Display
- CRT: $US270 to $US1,000
- LCD: $US380 to $US920
- Ten Manufactured in 2000
- Twenty-five Manufactured in 2001
- Fifteen metered in Retail Showrooms
- Twenty metered in Offices (LBNL, UC Berkeley Campus or the City of Berkeley)
- Operating System
- Three were connected to Macintosh desktop computers
- Thirty-two connected to personal computers running Windows OS (Windows 98: 8; Windows NT: 1; Windows 2000: 11; Windows ME: 5; Windows XP: 7)
The report is rather thorough, covering the different switching modes of the monitors (such as off, deep sleep, sleep and on), their power used during these different modes, the usefulness of operation in any of the modes and the correlation, if any, of size and type to power used.
The parts of interest to Mark Ontkush were the area where the team looked at the impact of extremes of display on power consumption. For a monitor, there are two extremes to show: where all the pixels are fully on, that is white, and when they are all fully off, that is black.
Graph: Additional power required for White versus Black
As can be seen here, the CRT monitors suffer when displaying an all white screen far more than their LCD counterparts. The worst case sees nearly a doubling in power consumption to run the CRT monitor at fully white when compared to a fully black state. This is due very much to the methods employed to give the user the visual interface that appears as an image to them. The different methods inherently have different power consumption requirements when pixels are either fully on or fully off.
Why this is so?
The two methods used to display images will be explored here.
The Cathode Ray Tube
A cutaway of a CRT (Image: Wikipedia)
The Cathode Ray Tube is one of the oldest electrical display methods that we have used. Dating back to the #DATE# where an evacuated glass tube had electrons fired onto a phosphorous screen not much has changed. The Cathode Ray Tube display still fires electrons at a screen, though changes have been made for colour screens such that there are three “sub-pixels” per pixel (red, green and blue). Where it is black the electron beam is not fired at all, where the colour is not bright the electron beam intensity is reduced. The problem with this technique is that the illumination caused by the electron striking the screen is not permanent and decays with time, hence the requirement for a refresh rate – the frequency with which the screen is repeatedly bombarded with electrons. Also, these devices have a single electron gun that must sweep, pixel by pixel, from the top left to the bottom right to create a single refresh. To prevent “flicker” in the screen engineers must ensure that the refresh rate is high enough such that our eyes cannot recognise the decay in intensity between refreshes (anyone who has seen an amateur video that has a CRT monitor will recognise the flickering and scan lines as the capture rate of the video differs from the refresh rate of the monitor).
As is obvious, the brighter a colour, up to full white, the higher density of electrons are required, needing more power. Under a black screen, the scanning of the electron gun is still undertaken by the monitor, however, as no electron beam is needed, the power required is lower.
Want to know more? Try Wikipedia.
The Liquid Crystal Display
A cutaway of an LCD (Image: Wikipedia)
The LCD monitors are completely different to the CRT displays. Where a CRT will fire electrons at a screen to produce light, the “screen” of an LCD acts as a filter and thus requires a light source. LCD monitors have traditionally employed a fluorescent light source with a mirror to ensure the maximum amount of light goes forward, though some manufacturers have recently been using LEDs.
In order to filter different colours, and to different levels of intensity, a voltage is applied across each “sub-pixel” (again, red, green and blue) which twists the liquid crystal, and with the use of a polarising filters, allows light to pass through. The main power consumption comes not from the colours on the screen, but rather from the high intensity white light source that is needed to drive the output.
Want to know more? Try Wikipedia.
Blackle’s Claims: fact or fallacy?
Blackle’s home page claims that 266,315.662 watt hours (one million watt hours is a megawatt hour and the average residential property in Australia is claimed to use around 6.6 megawatt hours per year according to the Australian Institute of Energy). Given that web servers cannot differentiate between a user with a CRT monitor and one using an LCD monitor and further give no indication of their assumptions on patronage from users of each, their claim of any savings cannot be proven. Given that they are marketing the site’s use on reducing power consumption, it is their case to prove that the user base is as they have assumed for the assumptions of energy savings.
Given all the media hype coming from ill informed and evidently illiterate journalists, and the blogging community too, who failed to read let alone comprehend the report that formed the basis of the claims being made, much of Blackle’s success has come from ignorance.
The Broader Goals
Blackle’s goals may be considered to be benign or even positive, that of raising awareness about energy efficiency. This awareness campaign, however, was not combined with an education campaign. Many of the posts that I have read, and the multi-forwarded emails too, do not contain any information that would lead me to believe that the users of Blackle are informed enough to realise that using an LCD monitor leads to savings that are minute at best.
The winner here however is Heap Media, the company behind Blackle. Heap Media set up Blackle with an intended goal of:
to remind us all of the need to take small steps in our everyday lives to save energy
What is not noted is the income that Heap Media has derived from Google, nor has this been disclosed. Further, given the highly dubious figures being used on the site and the lack of any accompanying notice that LCD monitor users may not be making any energy efficiency gains. Given that this site makes no comment on embodied energy (such as for the additional servers and support required to run Blackle, with no savings seen by Google as they still are required to provide the engine on which Blackle rests), more energy gains would be made with a switch to an LCD monitor than by using the Black screen of Blackle.
A Note on Thin Film Technologies
The report on which Heap Media makes its claims is over half a decade old. The monitors selected for analysis were made in 2000 and 2001. This was a time when the Pentium III was reigning supreme, when the 2GHz mark was a dream and when a terabyte of storage cost many thousands of dollars. During this time advances in energy efficiency have been made, but more telling, there has been a marked shift to the use LCD monitors in the Western world. New computers have been packaged with these thin displays as standard for nearly half a decade. Beyond that there have also been developments in thin film technologies that may work their way into the computer monitor market in the future. These include the OLED that has been used on a smaller scale for some time. Whether we see a migration to another generation of display technologies faster than the shift from the CRT to the LCD is yet to be seen.