ASHRAE Journal - April 2013 - 17

Table 5: Monthly peak heating and cooling loads (kBtu/h) and monthly energy loads (kBtu)
are shown for a 100,000 ft2 (9290 m2) office building in Wichita, Kan.

Chilled Water, Ice Storage Tanks in GCHP System

April 2013

Heating kBtu
Heating kBtu/h

Cooling kBtu
Cooling kBtu/h

400,000

1,600
Office Building Load Profile – Without TES

300,000

1,200

250,000

1,000

200,000

800

150,000

600

100,000

400
200

0

Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sept. Oct. Nov. Dec.

400,000

Peak Monthly Loads (kBtu/h)

1,400

50,000

Monthly Energy Loads (kBtu)

350,000

0
1,600

Office Building Load Profile – With TES
350,000

1,400

300,000

1,200

250,000

1,000

200,000

800

150,000

600

100,000

400

50,000

Monthly Energy Loads (kBtu)

The instantaneous peak load of a chiller or water to
water heat pump system is one factor used to calculate
the size of a GHX required. This is demonstrated by
seeing the impact of energy storage on the loads and
the size of GHX needed for a 100,000 ft2 (9293 m2)
office building in Wichita, Kan.4
The peak cooling load of the facility is 1,329
kBtu/h (390 kW). Both peak heating loads and annual heating energy loads are about 60% lower than
the cooling loads. The building is cooling dominant
even before considering the electrical energy used
to power compressors, pumps and fans. Monthly
peak heating and cooling loads and monthly energy
loads are shown in Table 5 and graphically in Figure 1.
By adding TES, the capacity of the heat pumps or
chiller is reduced from 1,329 kBtu/h to 600 kBtu/h
(390 to 175 kW). The annual cooling energy loads do
not change, but smaller equipment operates for more
hours to meet the annual cooling loads of the building. The equipment is used during off-peak hours
to chill water or make ice in a storage tank. Stored
energy supplements the equipment cooling capacity
the following day.
However, the designer must ensure that the
equipment has the capacity to build enough ice or
chilled water during the off-peak hours available,
taking into consideration the lower cooling capacity when producing low temperature water or ice.
The designer should also take into consideration
that the efficiency of a heat pump is reduced by
approximately 10% to 15% when producing ice
or low temperature water.5 The reduced efficiency
while producing ice is partially offset in some situations if simultaneous heating and cooling options
are available (Figure 2e).

200

0

Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sept. Oct. Nov. Dec.

Peak Monthly Loads (kBtu/h)

runs at part load or is idle. To take
advantage of this pattern, chilled
water and ice storage tanks have
traditionally been used in areas
where the cost of electricity is
affected by high peak demand
charges and time of use rates.
Storage has been used to shift
peak electrical demand from periods of high cooling demand—and
high utility costs—to take advantage of off-peak rates overnight
that coincide with the reduced
building loads. Smaller, less expensive systems can satisfy the
building loads with the same (or
lower) energy costs.3

0

Figure 1: Office building load profile without thermal energy storage
compared to equipment load profile with the addition of thermal energy storage. Limiting the equipment cooling capacity to 600 kBtu/h does
not change the annual loads; it simply increases the equipment run hours.
Chilled water or ice built during off-peak hours supplements the cooling capacity of the equipment when required during times of peak cooling loads.
ASHRAE Journal

17



ASHRAE Journal - April 2013

Table of Contents for the Digital Edition of ASHRAE Journal - April 2013

ASHRAE Journal - April 2013
Contents
Commentary
Industry News
Letters
Meetings and Shows
Feature Articles
Ground-Coupled Heat Pump and Energy Storage
Fan Efficiency Requirements for Standard 90.1-2013
Technology Award Case Studies:
Geothermal for 5 Ecosystems
Holistic HVAC Design
Standing Columns
Engineer’s Notebook
Data Centers
Emerging Technologies
IAQ Applications
Refrigeration Applications
Special Products
People
International Column
Energy Modeling
Products
Classified Advertising
Advertisers Index
ASHRAE Journal - April 2013 - ASHRAE Journal - April 2013
ASHRAE Journal - April 2013 - Cover2
ASHRAE Journal - April 2013 - 1
ASHRAE Journal - April 2013 - 2
ASHRAE Journal - April 2013 - Contents
ASHRAE Journal - April 2013 - Commentary
ASHRAE Journal - April 2013 - 5
ASHRAE Journal - April 2013 - Industry News
ASHRAE Journal - April 2013 - 7
ASHRAE Journal - April 2013 - 8
ASHRAE Journal - April 2013 - Letters
ASHRAE Journal - April 2013 - Meetings and Shows
ASHRAE Journal - April 2013 - 11
ASHRAE Journal - April 2013 - 12
ASHRAE Journal - April 2013 - 13
ASHRAE Journal - April 2013 - Ground-Coupled Heat Pump and Energy Storage
ASHRAE Journal - April 2013 - 15
ASHRAE Journal - April 2013 - 16
ASHRAE Journal - April 2013 - I1
ASHRAE Journal - April 2013 - I2
ASHRAE Journal - April 2013 - I3
ASHRAE Journal - April 2013 - I4
ASHRAE Journal - April 2013 - 17
ASHRAE Journal - April 2013 - 18
ASHRAE Journal - April 2013 - 19
ASHRAE Journal - April 2013 - 20
ASHRAE Journal - April 2013 - 21
ASHRAE Journal - April 2013 - 22
ASHRAE Journal - April 2013 - 23
ASHRAE Journal - April 2013 - Fan Efficiency Requirements for Standard 90.1-2013
ASHRAE Journal - April 2013 - 25
ASHRAE Journal - April 2013 - 26
ASHRAE Journal - April 2013 - 27
ASHRAE Journal - April 2013 - 28
ASHRAE Journal - April 2013 - 29
ASHRAE Journal - April 2013 - 30
ASHRAE Journal - April 2013 - 31
ASHRAE Journal - April 2013 - Geothermal for 5 Ecosystems
ASHRAE Journal - April 2013 - 33
ASHRAE Journal - April 2013 - 34
ASHRAE Journal - April 2013 - 35
ASHRAE Journal - April 2013 - 36
ASHRAE Journal - April 2013 - 37
ASHRAE Journal - April 2013 - 38
ASHRAE Journal - April 2013 - 39
ASHRAE Journal - April 2013 - Holistic HVAC Design
ASHRAE Journal - April 2013 - 41
ASHRAE Journal - April 2013 - 42
ASHRAE Journal - April 2013 - 43
ASHRAE Journal - April 2013 - 44
ASHRAE Journal - April 2013 - 45
ASHRAE Journal - April 2013 - 46
ASHRAE Journal - April 2013 - 47
ASHRAE Journal - April 2013 - Engineer’s Notebook
ASHRAE Journal - April 2013 - 49
ASHRAE Journal - April 2013 - 50
ASHRAE Journal - April 2013 - 51
ASHRAE Journal - April 2013 - 52
ASHRAE Journal - April 2013 - 53
ASHRAE Journal - April 2013 - Data Centers
ASHRAE Journal - April 2013 - 55
ASHRAE Journal - April 2013 - 56
ASHRAE Journal - April 2013 - 57
ASHRAE Journal - April 2013 - 58
ASHRAE Journal - April 2013 - 59
ASHRAE Journal - April 2013 - Emerging Technologies
ASHRAE Journal - April 2013 - 61
ASHRAE Journal - April 2013 - 62
ASHRAE Journal - April 2013 - 63
ASHRAE Journal - April 2013 - IAQ Applications
ASHRAE Journal - April 2013 - 65
ASHRAE Journal - April 2013 - 66
ASHRAE Journal - April 2013 - Refrigeration Applications
ASHRAE Journal - April 2013 - Special Products
ASHRAE Journal - April 2013 - People
ASHRAE Journal - April 2013 - International Column
ASHRAE Journal - April 2013 - 71
ASHRAE Journal - April 2013 - Energy Modeling
ASHRAE Journal - April 2013 - 73
ASHRAE Journal - April 2013 - Products
ASHRAE Journal - April 2013 - 75
ASHRAE Journal - April 2013 - 76
ASHRAE Journal - April 2013 - 77
ASHRAE Journal - April 2013 - 78
ASHRAE Journal - April 2013 - Classified Advertising
ASHRAE Journal - April 2013 - Advertisers Index
ASHRAE Journal - April 2013 - Cover3
ASHRAE Journal - April 2013 - Cover4
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