ASHRAE Journal - April 2013 - 14

Ground-Coupled Heat Pump
And Energy Storage
By Ed Lohrenz, Member ASHRAE; and Sergio Almeida, P.Eng., Member ASHRAE

G

round-coupled heat pump (GCHP) systems consume less purchased
energy than an HVAC system using fossil fuel and electricity di-

rectly for heating and cooling.1 However, the cost of building the ground

heat exchanger (GHX) often prevents acceptance of GCHP systems.
The incremental cost of a GCHP is
driven primarily by the cost of building
the GHX. The size of the GHX needed
for a project is determined by four factors: peak heating and cooling loads, annual heating and cooling energy loads,
geology, and configuration of the GHX.
A designer has no control over the
geology or size and configuration of
the site. The GHX must be designed for
the project. A designer can have some
control over the building and systems.
The purpose of this article is to illustrate how integration of thermal energy
storage (TES) with a GCHP system can
reduce the cost of a GHX and reduce
energy cost. Hypothetical examples
14

ASHRAE Journal

based on actual projects illustrate the
integration of a GCHP system with
TES to produce domestic hot water
or provide cooling more cost effectively and efficiently in certain types of
GCHP projects.

Energy Storage
You very likely took advantage of
TES during your morning shower. A
hot water tank with 10,000 Btu/h (3
kW) heating capacity, heats 11.5 gallons (43.5 L) of water for your fiveminute shower, using 5,750 Btu (1.65
kWh) of energy. An on-demand water
heater would require a 69,000 Btu/h
(20.2 kW) element to heat 50°F (10°C)
ashrae.org

water to 110°F (43°C) to supply 2.3
gpm (0.14 L/s).
If your teenager wants a shower at
the same time, you will need a second
69,000 Btu/h (20.2 kW) on-demand water heater. But if you have a storage tank
full of hot water, the same 10,000 Btu/h
(3 kW) heater would work for just over
an hour to provide hot water for both
showers before you head out.
If no one else uses hot water for a
few hours, a 30 gallon (113 L) tank easily meets your hot water needs using a
10,000 Btu/h (3 kW) heater instead of a
69,000 Btu/h (20.2 kW) heater.
Energy storage also has implications
on the design of the energy supply to
your home. Wires connecting your
home to the grid, electrical panel, circuit
breakers and size of the wires to your
water heater are all affected. It may have

About the Authors
Ed Lohrenz and Sergio Almeida, P.Eng., are partners in Geo-Xergy Systems Inc., in Winnipeg, MB,
Canada.

April 2013



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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