It has taken a while to get the technical details right, but at long last iSolutions is able to put all 1800 of its Common Learning Space PCs (the ones in lecture halls and workstation areas) to sleep overnight. Hallelujah! The problem was that although they went to sleep without difficulty, some of them just wouldn’t wake up and needed to be physically switched off and on again. I know from bitter experience that re-starting a CLS PC takes several minutes, especially as it always wants to to install Windows updates, new software and virus definitions if it has been switched off for a few days. It is all very frustrating if you have a roomful of students and no time to waste. As a consequence, the old power scheme merely powered down the display after 30 minutes, reducing their consumption from 80W to 47W – so a 50% saving, but still a lot of wasted electricity.
Now, after thorough testing, those technical issues have been overcome, and the new power plan has just been rolled out to those 1800 PCs. The energy savings are hard to calculate due to the unpredictable use of the PCs, but I used my PC power saving Excel spreadsheet to estimate the savings based on the following assumptions:
- the PCs are ‘in use’ from 9am-9pm (some workstation rooms are open later, some close earlier, and most teaching rooms are unused after 6pm)
- while they are ‘in use’ they are actually only used for 75% of that time (ie 9 hours, which I suspect is being generous)
- they wake up and reboot at 2am to install software updates, but are asleep again at 2.30am.
- they wake up and reboot at 6am, but are asleep again by 6.30. This is needed because some software requires a reboot to complete installation.
- they stay asleep until used, so will remain asleep across weekends and holidays.
- I ignored minor savings generated by the new scheme shaving a few minutes off the screen and hard disk sleep times.
I calculate that the annual savings across all 1800 PCs are 473 MWh of electricity, equivalent to 258 tonnes of CO2 and a cost saving of £57,000. Merry Christmas!
Sleepy mouse image by wilkolak3dh from DeviantArt