Configure my PC to Save Electricity
Introduction
Computers use electrical power. Consequently, each computer in the University that is switched on contributes to the University's overall power consumption requirements. The more computers that are switched on, the more power that is needed to operate them and thus the University's power bill increases.
This is a simple cause and effect relationship.
The Need for Power
Most computers are comprised of two main units, each of which consumes electrical power. These units are: a) the system unit, housing the processor chip and its support chips, memory modules and disk drives, etc; b) the monitor for displaying information to users. Notebook computers can be an exception to this as they have a combined system unit and monitor format.
So what is the electrical requirement of a processor? Well, as processor speed increases so the need for electrical power also increases. Currently available processors are fitted with massive heat sinks to conduct away the heat generated by the electrical power they use. Without the benefit of a heatsink and, perhaps, a cooling airstream, a processor would incinerate itself very quickly. It is true to say that today's processors consume significantly more power than those of a few years ago. Designs are being talked about that may reduce the power consumption required (as in the Intel Centrino line of mobile processors) and these will become available from 2005 or 2006 onwards. Until then, though, there is a heat or power problem with processors.
What electrical power requirements do monitors have? These must be divided into two classes, as each has quite different electrical needs. The first class of monitor is based on Cathode Ray Tube (CRT) technology and consumes a reasonable amount of power, despite progress made in developing more efficient circuits and display tubes. The tubes themselves consume the bulk of the energy primarily in firing electrons at the display screen but also in forming the electro-magnets to move the electron beams around the screen. The larger the CRT display the more power it takes to drive it.
The second class of monitor is based on the Liquid Crystal Display (LCD) technology. Despite being more costly, these maonitors have gained a ready acceptance for two reasons: firstly, they are smaller, requiring much less desk space and, secondly, they consume somewhat less power. Thus the use of LCD monitors in computer systems has helped to redress the power balance as processors have become more power hungry.
Ways to Conserve Electrical Power
There are a number of things that can be done to reduce the daily power requirements of your computer(s) and these will now be explained. Please bear in mind that the usage patterns of a computer have to be taken account of in determining what power-saving measures might be employed. For instance, in Student Computer Centres (SCCs), PCs are operated from early morning to late at night. In the hours when a lab is closed the PCs are instructed remotely to enter a 'sleep' mode. This action reduces power consumption to a few watts per PC. They can then be 'awakened' again at a suitable time to refresh the software on the PCs before students start arriving for another day of work. No one needs to be onsite to do this. Because students and classes expect the computers to be immediately available for use, amongst other things, it is not practical to use many other power conservation methods during the day, although this is being re-examined again.
Screen Savers
Screen savers are thought of as power savers but they are not. Their main purpose is to prevent a regular pattern that is displayed on a CRT monitor from 'burning' the phosphors on the display face. If a rectangular line is constantly displayed on a CRT for several months, the phosphors that display the line will change colour slightly and their intensity will reduce. The pattern of the rectangle will be etched onto the screen and become very noticeable.
If a screen saver that causes little to be displayed, such as a blank screen, is used a little power may be saved.
LCD monitors use a different technology, a rectangular fluorescent lamp behind a mosaic array of coloured filters. When the screen is blank (dark) the fluorescent tube is still lit whereas in a CRT electrons have been inhibited from flowing. It is only the filters in an LCD panel that prevent the light from shining through. Again, some power will be saved because the screen elements are 'off'. Greater power savings may be made by reducing brightness to an acceptable level, though.
The main benefit of a screen saver lies in the associated security aspects. A screen saver has the ability to hid on-screen information and it can also force a user to retype a password to recommence a session. The length of the period of inactivity before a screen saver activates must be set when configuring the screen saver and a period of 5 to 10 minutes is usually adequate.
To invoke the screen saver in Windows, either right-click the mouse on the desktop background and select the Properties option or open the Control Panel by clicking on the Start button on the bottom left of the screen and select Control Panel. Depending on display settings, Control Panel might display as a list (see Fig 1) or as a collection of icons.
Fig 1
Within Control Panel select the Display option and then choose the Screen Saver tab (Fig 2).
Fig 2
There you will find a drop down box offering a number of screen saver schemes. Select the one you prefer (in this case the Blank screen saver). To invoke password protection, click the 'On resume, password protect' box and then set a wait time somewhere between 5 and 10 minutes. Click Apply to commit the change.
Power Settings for Monitors
Using Windows it is possible to put the monitor into a 'sleep' mode in which it uses little power. This option is invoked after a predetermined period of inactivity has elapsed and is really intended for notebook computers, where the need to conserve battery power is often very important. However, the settings can also be applied to desktop computers. When powered off via this mechanism, the monitor will power up again when computer activity recommences (it will take a number of seconds for the screen to warm up, so please be patient).
To configure your monitor for this mode of operation, click on the Power button in the Properties Window (Fig 2) or click the Power options in the Control Panel (Fig 1). Another window will open (Fig 3).
Fig 3
Select the PowerSchemes tab and choose a suitable Power scheme from the drop down menu. Then select a time from the drop down menu after which the monitor will turn off (in this case 20 mins). Click the Apply button to commit the changes.
N.B. Setting this option requires administrator privilege.
Hard Disks
It is possible to configure the power settings so that the hard disk(s) will power off after a specified period of disk inactivity. Select a value from the Turn off hard disks drop down menu. Click OK to accept the change. Again, this setting is aimed primarily at notebook users to conserve battery power. If you use this setting on a desktop computer, be aware that it will take several seconds before disks which have stopped spin up and become available again. It may be better left for notebook computers, as they have slower disks requiring less startup power and generating less force to wear the bearings.
N.B. Setting this option requires administrator privilege.
Processor and System Board Sub-Systems
Once more this is a notebook setting that can be applied to a desktop computer. In the window depicted in Fig 3 , select the 'System standby' drop down menu and choose a suitable time interval. Click Apply or OK to commit the change. The computer will then power down after the selected period of inactivity has elapsed. The power button must be pressed to re-activate the computer and user's session.
Please note that all network connections will be broken when standby mode is entered. The importance of this to you depends upon the activities you were engaged in prior to standby mode being invoked.
Most people now perform antivirus scans of disks and download Windows updates automatically. It is important that you allow sufficient delay time before standby mode will commence, otherwise these and other similar functions, if they are active, will be stopped when your system enters standby mode. Only you will know how much time such activity requires and you will know the time when it is scheduled to happen. This will let you calculate a suitable delay time to accommodate the activity.
Use automatic entry into standby mode if you are regularly away from your computer for maybe an hour or more. But please save any work before going off, as data can be lost if power is interrupted whilst in standby mode.
Click on the Advanced tab in Fig 3 to bring up some advanced facilities (Fig 4).
Fig 4
For security reasons, set the 'Prompt for password' box to demand a password before the system will restart the suspended session.
Set the 'Always show icon' box if you wish to have an icon to bring up this dialogue box. From the 'When I press the power button' drop down menu, choose the setting you wish to apply. Normally you would choose the Shut down option but choose Standby if you wish to put your computer into standby mode manually.
Click on the Hibernate button if you wish to avail of the hibernate option (Fig 5).
Fig 5
Set the 'Enable hibernation' box and click OK to accept this option. This option can be selected even if standby has not been. The computer will then enter Hibernation mode when the hibernate time delay expires. You must set the System hibernate delay time prior to this (see Fig. 3).
Instead of entering standby mode, the state of the computer is saved to disk and the computer powers off. This is much safer than standby mode, where data can be lost if the power goes off. When the computer is next switched on, the system will restore its previous state from disc and continue on as though it had never been interrupted. Of course, it does take a minute or two to carry out this action. Please note the caution in the standby section (above) concerning the loss of network connections.
The hibernate function is useful if a computer will be left running after normal working hours to complete some task before switching the computer off. Allowing ample time for the task to finish, the computer will be put into hibernation mode automatically.
The cautions about allowing sufficient time to complete tasks in the standby section (above) also apply to hibernate. It should also be pointed out that the system will link hibernate and standby if both have been selected. The delay time the system waits before entering hibernate mode must exceed the delay time for standby mode and the system will offer you a restricted set of time options to enforce this.
Notice that Fig 5 will indicate both how much free space the system drive (C:) has available and the amount of space required to store the data associated with the hibernate process.
N.B. Setting these options requires administrator privilege.
Going Home
So far we have considered how power may be saved during working hours. When going home, unless there is a good reason for doing so, it is better to power down a computer and switch it off at the mains (using either the mains switch or a power switch if the power supply has one). During the off period, this will save approximately 14 x 5 (70) watt hours per weekday and 48 x 5 (240) watt hours per weekend compared to being in standby mode (assuming a consumption of 5 watts when in standby mode). This gives a total power saving of 590 watts per week, and at least 30,680 watt hours per annum, or 30.68 kilowatts.
If a computer is left on overnight each night and it consumes, say, 150 watts of power, the excess power requirement for the 14 hours (say) when not needed is 2,100 watt hours per workday and 6,000 watt hours during the week end. Assuming 45 working weeks in the year, this leads to a waste of 742,500 watt hours of electricity per year, or 743 kilowatts. A more powerful computer will increase this rate of waste and a less powerful one will reduce it.
These figures show that taking sensible power-saving measures is worthwhile.
During the day it is recommended that you use settings that do not cause undue delays when working. But at night time, please switch off your computer equipment unless there are good reasons for leaving it on or letting it enter standby mode. Also, switch off other peripherals that are not required to be left on overnight, such as printers and scanners.
