Handbook of air conditioning and refrigeration / Shan K

● Secondary-loop systems using brine as the cooling medium and distributed systems in which
compressors are close to the display case have far less refrigerant leakage than DX systems.
● The use of greenhouse gases as blow agents should be minimized.
The selection of environmentally-friendly refrigerant with low ozone depletion and global
warming effect should be considered. From Table 9.1, compare the following refrigerants:
According to Baxter et al. (1998), the energy use of centrifugal chiller using HCFC-123a as refrigerant
is only about 87 percent of that using HFC-134a as refrigerant. More research is required to
determine a suitable alternative refrigerant for chillers when ODP, HGWP, and energy use are all
considered at the same time.
25.3 ENERGY EFFICIENCY
Federal Mandates
Energy Use Intensities
ENERGY MANAGEMENT AND GLOBAL WARMING 25.5
Ozone depletion potential Halocarbon global warming
(ODP) potential (HGWP)
HFC-134a 0 0.28
HFC-404A 0 0.95
HFC-407A 0 0.47
HCFC-123 0.016 0.02
According to Cox and Miro (1998), the U.S. government is the single largest energy user. In late
1990s, the federal government provided energy to approximately 500,000 buildings with a floor
area of about 3.1 billion ft 2 (288 million m 2 ). Energy was needed in HVAC&R, lighting, and other
building services. Approximately 77 percent of the floor area was used for housing, office, storage,
and other purposes; the remaining 23 percent belonged to hospital, school, prison, and other uses.
Many federal buildings constructed before the energy crisis of 1973 are not energy efficient. The
president’s Executive Order 12759 in 1991 and the National Energy Policy Act of 1992 (EPAct) required
federal buildings to reduce enery use by 20 percent from 1985 levels in the year 2000. In addition,
Executive Order 12902 called for an energy efficiency improvement of 30 percent over the
1985 level by the year 2005.
The Federal Energy Management Program (FEMP) was established in 1974 to provide guidance
and assistance to improve energy efficiency in implementing energy management plans. It
has focused on the energy bill and potential for improvements. The Energy Policy Act established
the fiscal year (FY) 1995 goal of improving energy efficiencies in federal buildings by 10
percent from 1985 levels on a Btu/gross ft 2 (W/m 2 ) of floor area. This goal is exceeded in FY
1994 with a total reduction in federal buildings of 11.2 percent. In addition, energy costs were
$3.8 billion in FY 1994, and that was $1.5 billion less than in FY 1985. The federal government
accumulated an energy savings of $9.8 billion and reduced federal building petroleum-based fuel
use by 45.4 percent.
Energy use intensity (EUI) is the annual energy use per unit floor area, in MBtu/ft 2 � yr
(kWh/m 2 � yr). The EUI depends mainly on the locations of buildings, building characteristics, operating
characteristics, and the HVAC&R system characteristics. According to DOE/EIA (1992),
the abridged EUIs for commercial buildings in 1989 were as follows: