Table 1. Scenario Assumptions for Carbon Analysis of District Cooling.
1
Scenario
23
4
Region
North America or Europe
Middle East
District cooling technology1
Percentage of total capacity
Electric centrifugal
Gas engine-driven centrifugal
Percentage of annual cooling energy
Electric centrifugal
Gas engine-driven centrifugal
Annual electricity efficiency including
distribution pumping (k W/ton)
Electric centrifugal
Gas engine-driven centrifugal
Annual gas efficiency for engine-driven
chillers (Btu/hr per ton)
Conventional building technology
Percentage of total capacity
Electric centrifugal
Air-cooled reciprocating
Annual electricity efficiency (k We/ton) 2
Power grid technology mix
Percentage of annual electric energy
New natural gas combined-cycle
New pulverized coal
Annual average fuel to power efficiency
(generation, transmission and distribution) 3
New natural gas combined-cycle
New pulverized coal
X
X
X
X
100%
-
100%
-
100%
-
50%
50%
100%
-
100%
-
100%
-
20%
80%
Rating System™ created by the U.S. Green
Building Council (USGBC) has become a
significant factor in commercial building
design in North America and is of growing
interest worldwide. There is a growing
number of subcategories of the LEED
standard, most significantly LEED for New
Construction (LEED-NC) and LEED for
Existing Buildings (LEED-EB). Although the
USGBC has made progress in addressing
issues relevant to district energy in LEED-NC, both LEED-NC and LEED-EB continue
to have significant defects relative to the
treatment of district energy.
0.90
-
0.90
-
0.90
-
0.90
0.26
-
-
-
7317
100%
-
1.05
100%
-
1.05
-
100%
1.65
-
100%
1.65
Although the USGBC has made
progress…both LEED-NC and
LEED-EB continue to have
significant defects relative to
the treatment of district energy.
100%
0%
0%
100%
100%
0%
100%
0%
46.2%
35.5%
46.2%
35.5%
43.8%
35.5%
43.8%
35.5%
Notes
11. All district cooling technologies are assumed to be water-cooled.
22. Conventional building cooling system efficiencies are projected efficiencies after five years of
operation. Typical maintenances practices often result in performance below modeled performance. In addition, in the Middle East, there is significant performance degradation due to harsh
operating conditions.
33. All power grid technologies are assumed to be efficient new technology.
Source: Analysis by FVB Energy Inc.
Table 2. Carbon Dioxide Reductions With District Cooling.
1
Scenario
23
4
Reduction in CO2 emissions
Lb/ton-hr
Percentage
Value of CO2 emission reduction
(US cents/ton-hr) at given CO2 value
in US dollar/metric ton
0 per metric ton
$ 50 per metric ton
$ 100 per metric ton
0.13
14%
0.30
14%
0.69
45%
0.47
31%
-
0.3
0.6
-
0.7
1. 3
-
11. 6
3. 1
-
11. 1
22. 1
Source: Analysis by FVB Energy Inc.
The steps taken to date by USGBC
include the “CHP Calculation Methodology
for LEED-NC v 2. 2 EA Credit 1” released
in November 2005. This document estab-lishes an exceptional calculation method
(ECM) to provide LEED energy-efficiency
credits to buildings supplied with thermal
energy from district energy systems using
CHP. An ECM was required because of the
fundamental structure of the LEED standard,
which is building-focused and cost-based
rather than based on total energy efficiency
and/or environmental impact.
Although the CHP calculation method
was a useful step forward, the fundamental
LEED-NC structure, which is based on the
ASHRAE Standard 90.1 Performance Rating
Method, has continued to create significant
barriers to certification of new buildings
proposing to use district energy. An attempt
to resolve these issues resulted in “Required
Treatment of District Thermal Energy in
LEED-NC version 2. 2 and LEED for Schools”
released in May 2008.
This methodology essentially treats
the fuel and electricity inputs to the district energy system as pro rata inputs to
the building and compares the district
energy inputs to the fuel and electricity
required for in-building heating and/or
cooling systems. This treatment corrects
a huge problem with the cost-based
ASHRAE 90.1 method by ensuring that
