ASHRAE Journal - May 2011 - 31

erally calculated based on the nameplate data on the computers proven to provide an appropriate balance to cover potential and other electronic equipment. In the late 1980s, computer use future loads while not introducing significant over-design in began to become more widespread. In this era, the authors ob- building systems. served that it was not uncommon for air-conditioning systems to be sized for plug loads of 3 to 5 W/ft2 (32 to 54 W/m2). Trends to Date A 1991 ASHRAE Journal article1 reported on research This approach and recommended load factor have remained done in Finland where the actual load from computers and roughly the same since the mid-1990s. Computer technology other equipment was measured and compared to nameplate has certainly changed since that time but until recently, there data. This relatively modest effort revealed that the measured was no need to change the use of 1 W/ft2. In fact, a compreload of this equipment was typically only 20% to 30% of the hensive study was conducted by Koomey, et al,6 and reported nameplate data. This revelation provided the first hard evi- in December 1995 where it was predicted that plug loads in dence of this issue and changed the way that plug loads were office buildings would decrease modestly through at least considered in load and energy calculations. 2010 (Figure 1). Next, Wilkins and McGaffin in 19942 reported measureThis decrease was expected to be due to technical advances ments in five U.S. General Services Administration (GSA) that would result from ENERGY STAR and other related prooffice buildings in the Washington, D.C. 1.000 area. Their work included informal measurement of a large sample of individual equipment items, as well as measurements at panels that served computer 0.750 equipment within a given area of the building. The results provided further verification of the nameplate discrep0.500 ancy of individual equipment, provided measured data for the determination of the load factor of an area and, for the first 0.250 time, allowed the load diversity factor to be derived based on measured data. ASHRAE followed up this informal 0.000 research with the execution of two re1990 1995 2000 2005 2010 search projects: RP-822 (1996), “Test Method for Measuring the Heat Gain Figure 1: Plug load index, 1990 – 2010.6 and Radiant/Convective Split from Equipment in Buildings” and RP-1055 (1999), “Measurement grams. Their predictions were based on energy use, not peak of Heat Gain and Radiant/Convective Split from Equipment in load values, but it is believed that these trends would be simiBuildings.”3,4 The experimental results corroborated the ear- lar and, in fact, history has proven this to be the case. Office lier findings but did so in a more formal and traceable manner. equipment has become more efficient, and overall plug load All of this work led to a widely referenced ASHRAE Journal intensity has decreased. article in 2000.5 This data was incorporated into the ASHRAE Handbook—Fundamentals starting in 1997 and then signifi- Current State of Plug Loads cantly expanded in the 2001 edition. Predicting the future of the information technology (IT) world is not attempted here, but recent studies, as described Current ASHRAE Handbook Data later, have provided new data that gives a clearer picture of the Data presented in the 2009 ASHRAE Handbook—Funda- current state of plug loads. It is important to understand the mentals, Chapter 18, Nonresidential Cooling and Heating current state of the equipment that contributes to plug loads Load Calculations, relative to office equipment loads (or plug and how this equipment now in use differs from equipment loads) is based largely on the research and publications cit- in use at the time 1 W/ft2 (10.8 W/m2) was found to be an aped previously. Data is presented in a number of formats and propriate load factor. Hosni and Beck have recently completbreakdowns but can be best summarized by considering Table ed the latest ASHRAE-sponsored research project RP-1482, 11 in Chapter 18, which states that a “medium density” of- “Update to Measurements of Office Equipment Heat Gain fice building will have a plug load of 1 W/ft2 (10.8 W/m2). Data,”7 where measurements were obtained from an up-toIt is believed that this value of 1 W/ft2 (10.8 W/m2) has been date sample of office equipment including notebook computwidely used in the industry since the mid 1990s. The authors ers (laptops) and flat screen (LCD) monitors. believe this value is, and always has been, somewhat conserTable 1 shows how this most recent data compare to previvative when used in office environments. However, its use has ously referenced work, as well as some other data from KawaMay 2011
Index (kWh/ft2·yr)

ASHRAE Journal

31



ASHRAE Journal - May 2011

Table of Contents for the Digital Edition of ASHRAE Journal - May 2011

ASHRAE Journal - May 2011
Contents
Commentary
Industry News
Letters
Meetings and Shows
Feature Articles
Seismic Restraint
Plug Load Design Factors
Technology Award Case Studies:
State-of-Art School
Green School Lab
Eco-Friendly, Affordable, School
Building Sciences
Special Section
InfoCenter
Solar NZEB Project
Emerging Technologies
IAQ Applications
Washington Report
International Column
Products
People
Classified Advertising
Advertisers Index
ASHRAE Journal - May 2011 - Intro
ASHRAE Journal - May 2011 - ASHRAE Journal - May 2011
ASHRAE Journal - May 2011 - Cover2
ASHRAE Journal - May 2011 - 1
ASHRAE Journal - May 2011 - 2
ASHRAE Journal - May 2011 - Contents
ASHRAE Journal - May 2011 - Commentary
ASHRAE Journal - May 2011 - 5
ASHRAE Journal - May 2011 - Industry News
ASHRAE Journal - May 2011 - 7
ASHRAE Journal - May 2011 - 8
ASHRAE Journal - May 2011 - 9
ASHRAE Journal - May 2011 - 10
ASHRAE Journal - May 2011 - 11
ASHRAE Journal - May 2011 - 12
ASHRAE Journal - May 2011 - 13
ASHRAE Journal - May 2011 - Letters
ASHRAE Journal - May 2011 - 15
ASHRAE Journal - May 2011 - 16
ASHRAE Journal - May 2011 - 16a
ASHRAE Journal - May 2011 - 16b
ASHRAE Journal - May 2011 - 17
ASHRAE Journal - May 2011 - Meetings and Shows
ASHRAE Journal - May 2011 - 19
ASHRAE Journal - May 2011 - Seismic Restraint
ASHRAE Journal - May 2011 - 21
ASHRAE Journal - May 2011 - 22
ASHRAE Journal - May 2011 - 23
ASHRAE Journal - May 2011 - 24
ASHRAE Journal - May 2011 - 25
ASHRAE Journal - May 2011 - 26
ASHRAE Journal - May 2011 - 27
ASHRAE Journal - May 2011 - 28
ASHRAE Journal - May 2011 - 29
ASHRAE Journal - May 2011 - Plug Load Design Factors
ASHRAE Journal - May 2011 - 31
ASHRAE Journal - May 2011 - 32
ASHRAE Journal - May 2011 - 33
ASHRAE Journal - May 2011 - 34
ASHRAE Journal - May 2011 - 35
ASHRAE Journal - May 2011 - State-of-Art School
ASHRAE Journal - May 2011 - 37
ASHRAE Journal - May 2011 - 38
ASHRAE Journal - May 2011 - 39
ASHRAE Journal - May 2011 - 40
ASHRAE Journal - May 2011 - 41
ASHRAE Journal - May 2011 - 42
ASHRAE Journal - May 2011 - 43
ASHRAE Journal - May 2011 - Green School Lab
ASHRAE Journal - May 2011 - 45
ASHRAE Journal - May 2011 - 46
ASHRAE Journal - May 2011 - 47
ASHRAE Journal - May 2011 - 48
ASHRAE Journal - May 2011 - 49
ASHRAE Journal - May 2011 - 50
ASHRAE Journal - May 2011 - 51
ASHRAE Journal - May 2011 - Eco-Friendly, Affordable, School
ASHRAE Journal - May 2011 - 53
ASHRAE Journal - May 2011 - 54
ASHRAE Journal - May 2011 - 55
ASHRAE Journal - May 2011 - 56
ASHRAE Journal - May 2011 - 57
ASHRAE Journal - May 2011 - Building Sciences
ASHRAE Journal - May 2011 - 59
ASHRAE Journal - May 2011 - 60
ASHRAE Journal - May 2011 - 61
ASHRAE Journal - May 2011 - 62
ASHRAE Journal - May 2011 - 63
ASHRAE Journal - May 2011 - 64
ASHRAE Journal - May 2011 - 65
ASHRAE Journal - May 2011 - 66
ASHRAE Journal - May 2011 - 67
ASHRAE Journal - May 2011 - InfoCenter
ASHRAE Journal - May 2011 - 69
ASHRAE Journal - May 2011 - 70
ASHRAE Journal - May 2011 - 71
ASHRAE Journal - May 2011 - 72
ASHRAE Journal - May 2011 - 73
ASHRAE Journal - May 2011 - 74
ASHRAE Journal - May 2011 - 75
ASHRAE Journal - May 2011 - 76
ASHRAE Journal - May 2011 - 77
ASHRAE Journal - May 2011 - Solar NZEB Project
ASHRAE Journal - May 2011 - 79
ASHRAE Journal - May 2011 - 80
ASHRAE Journal - May 2011 - 81
ASHRAE Journal - May 2011 - 82
ASHRAE Journal - May 2011 - 83
ASHRAE Journal - May 2011 - 84
ASHRAE Journal - May 2011 - 85
ASHRAE Journal - May 2011 - 86
ASHRAE Journal - May 2011 - 87
ASHRAE Journal - May 2011 - 88
ASHRAE Journal - May 2011 - 89
ASHRAE Journal - May 2011 - Emerging Technologies
ASHRAE Journal - May 2011 - 91
ASHRAE Journal - May 2011 - 92
ASHRAE Journal - May 2011 - 93
ASHRAE Journal - May 2011 - 94
ASHRAE Journal - May 2011 - 95
ASHRAE Journal - May 2011 - IAQ Applications
ASHRAE Journal - May 2011 - 97
ASHRAE Journal - May 2011 - 98
ASHRAE Journal - May 2011 - 99
ASHRAE Journal - May 2011 - 100
ASHRAE Journal - May 2011 - 101
ASHRAE Journal - May 2011 - Washington Report
ASHRAE Journal - May 2011 - 103
ASHRAE Journal - May 2011 - International Column
ASHRAE Journal - May 2011 - 105
ASHRAE Journal - May 2011 - 106
ASHRAE Journal - May 2011 - Products
ASHRAE Journal - May 2011 - 108
ASHRAE Journal - May 2011 - People
ASHRAE Journal - May 2011 - Classified Advertising
ASHRAE Journal - May 2011 - 111
ASHRAE Journal - May 2011 - Advertisers Index
ASHRAE Journal - May 2011 - Cover3
ASHRAE Journal - May 2011 - Cover4
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