Office equipment that can process information by utilising electrical energy existed as early as 1890's [24]. At that time, U.S. Census Bureau sponsored a contest to find out an efficient method to tabulate census data. Herman Hollerith won the contest with his machine that used an electric current to sense holes in punched cards and that also could keep a running total of data. These type of machines soon flourished and a whole new industry that designed, manufactured and marketed computing machines was born.
53 Soon after this, other types of devices followed such as electric accounting machines, electric writing machines etc.
In the 70's, wide adoption of computers allowed software to become a different industry on its own thanks to the development of programming languages. The availability of thousands of computer programs enhanced the position of computers in work environments even more. 1980's saw the birth of personal computers (PC's). During these years, photocopy machines, fax machines, digital telephony devices all started to change the work environment. These devices became so essential that offices became overly dependent on their functioning.
1990's brought huge technological advances in network infrastructures where large mainframe computers were being used to serve PC's that were now available to nearly every office worker. Internet caused enormous expansion in network equipment market. Today, internet is the driving force in the computing world.
2.2.5.1. Office Equipment and Energy Consumption
In the U.S. non residential office and telecomms equipment accounted for 3% of national electricity consumption in 2000. 9% of electricity consumed in the commercial buildings was because of these [25].
Roth et al [26] have categorised office equipment into eight groups:
Computer Monitors and Display
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Server Computers
Copy Machines
Computer Network Equipments
Telephone Network Equipment
Printers
Uninterruptable Power Supplies
These equipment types accounted for 90% of the total annual office equipment energy consumption in the U.S. Their research also shows that five categories which are PC's, monitors, servers, copiers and printers constitute approximately 70% of the overall annual energy consumption of office equipment (Figure 7).
2.2.5.2. Power consumption of PC's and Monitors
Developments in computing technology allowed laptop computers to overtake desktop computer sales [27]. Nonetheless, office environments still have a combination of both
55 desktop PC's and laptops [28] where desktops are still dominant. When it comes to energy consumption of computers, desktops consume up to three times as much as laptops. The paper [29] lists the studies that were carried out to identify the power consumption of computers. According to the research, desktop computers consume between 50 to 70 watts when active compared to Laptops which consume 10 to 20 watts when active.
Just like PC's themselves, display devices such as monitors and TV's have seen radical changes in the past decade. The introduction of cheap colour Liquid Crystal Displays (LCD's) not only allowed significant space savings but also reduced energy consumption of computers as well. On average, a cathode ray tube (CRT) monitor requires 65W – 135W while working whereas an LCD monitor requires just 30W while working [29].
2.2.5.3. Power consumption of servers
A server is a computer that is dedicated to run specific programs which are designed to serve the requests of other computers. Depending on the type of service that it is designed for, a server can be database server, file server, web server, gaming server etc. Servers provide services to either users across local intranet or to public via internet.
A comprehensive report by Koomey [30] gives valuable information about the global trends in server technologies as well as power consumption of an average server. He indicates that the substantial increase in the usage of internet has caused the number of servers and the data centres (which are dedicated buildings that host many servers) to multiply in the recent years. Also, the energy consumed by servers has doubled between
56 2000 and 2005 throughout the world. Most of this is caused not by the energy consumption of individual servers themselves but by the increase in the number of servers installed in offices and data centres.
The number of servers is also required to calculate the power consumption caused by servers in an office environment. In [30], the authors have carried out surveys in commercial and public buildings in various cities in the U.S. According to their survey, approximately 89 servers exist for 1453 computers. This shows that the computer/server ratio is approximately 16. Their study also shows the fact that most servers are kept in 'On' status even after hours. Therefore they usually contribute to the base-load of a building's electricity consumption.
2.2.5.4. Power consumption of Copiers, Printers and MFD's
Printers have two dominant technologies that are still in competition today. These are toner based (laser) printers and inkjet printers. Toner based printers use xerography whereas inkjet printers use paper ink. There are two major differences between laser printers and inkjet printers. Laser printers are fast with up to 50 paper per minute print rate. However they consume more power. Inkjet printers are much slower (up to 20 papers per minute print rate) but they consume less power.
According to [31], small power equipment loads for copiers is 850 watts and for printers is 150 watts. However, it is also indicated in this resource that peak power of printing equipment does not give clear indication on the overall energy consumption of these devices since these devices are most likely to be idle.
57 In this case, printing habits of employees would give a good indication of how and when these devices operate at their rated power. The survey [32] revealed that an average UK office worker prints 45 pages a day. Combining this information with an average of 40 papers per minute speed rate, a printer profile that shows electrical power consumption of a typical printer (or a multi function device) can be obtained.
Finally multifunction devices (MFD's) are usually devices that are capable of printing, scanning, copying and faxing. These devices have become popular in recent years because of their practicality. Their power profiles though, are similar to laser or inkjet printers.