geothermal heat pump systems presentation
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Steve Lowe, PE, CEM, LEED AP BD+CMechanical Engineer
Reynolds, Smith, and HillsNorfolk, VA
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Thank you for having me
Please set phones to vibrate
Please ask questions when you think of
them
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What is Geothermal? How does it work?
What are appropriate applications of
Geothermal Heat Pump systems?
What are the major components of a
Geothermal Heat Pump system?
How do Geothermal Heat Pump systems
save money?Design and construction considerations
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Heat from the Earth
Using the earths internalthermal energy to
generate steam
NOT what we are talking
about today
Earth as a heat sink
Using the earth toabsorb, store and
release heat for seasonal
cooling and heating
This is the focus oftodays presentation and
is known as
GeoExchange
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REJECTING/STORING HEAT EXTRACTING HEAT
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PROS CONS
Balanced Loads
Plenty of Real Estate
Long Term Facility
Ownership
Unbalanced Loading
Tight site, urban setting
Short payback
requirements (less than 7-10 years)
What can we do to influence these
factors?
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Load balance is important to avoid long term depletion or saturation ofthe well-field.
Climactic Extremes Cold Climates Is there a refrigeration or other cooling process from which we can
capture heat?
Hot and/or humid climates Is there a heating process to which we can dump waste heat?
Internal Loads Occupancy, electronic equipment, processes
Can process loads be addressed with a separate system?
Can an internal or process load be used to balance a climactic load?
Additional Considerations Understand load profile of a well insulated building
Be wary of the effect of air side energy recovery
Balancing the load is a detailed engineering process, not a quickexercise!
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The simplest way to reduce cost, payback
period, and space requirement is with a
Hybrid System more on this later.
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Geothermal Heat Exchanger Boreholes Distribution Piping
Pumping System
Pumps Air Removal
Filtration
HVAC Equipment Heat Pumps, Chillers, Water HeatersControls
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Borehole Components Drilled hole
Factory Fabricated U-bend andpipe
Thermally Enhanced BentoniteGrout
Tremie pipe for grouting (this is a
tool, not a permanent component)
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Zones
Trenching
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DESIGN PARAMETERS SPECIFICATIONS
Soil Characteristics
Volumetric Heat Capacity
Thermal Conductivity
Undisturbed Temperature Heating and Cooling Load
Profiles
Field Configuration
Depth
Spacing
Diameter
Quantity Tube Size
Double or Single U-bend
Layout
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Pumping Arrangement
Primary only (okay for smallsystems on a tight budget) Primary-Secondary (much
more reliable and efficientfor larger systems)
Air Removal pipingsystem is very large, thisis a significant
considerationFiltrationBalancing more on this
later
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Balancing Reverse Return Sub-field
piping
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Balancing Balancing valves for piping
to zones and sub-fields
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Water-to-Air Heat Pumps Dedicated Outdoor Air Units
Zone Heat Pumps
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Water-to-Water Heat Pumps Chillers
Heaters
Chiller/Heaters
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Cooling Towers (closed circuit coolers,
fluid coolers, etc.)Boilers
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Distributed Water Source Heat Pumps Most common application
Heat pumps cool/heat space and reject/extract
heat to/from the loop
Recommendation: Use a dedicated outdoor airunit unitary heat pumps do not handle much
outdoor air
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Geothermal Central Systems Chillers generate hot and chilled water to be
used in air handler coils
Similar to a four-pipe central plant, but with
additional controls and no boilers or coolingtowers
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DISTRIBUTED CENTRAL
Lower first cost
Unitary equipment is
simpler to operate and
maintain Single pumping loop
simplifies design
Centralized Maintenance
Better acoustical
performance equipment
located in mechanical room Better humidity control
More complex design and
operation
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Hybrid Systems can be applied to central or
distributed geothermal heat pump system System utilizes a boiler or cooling tower in
addition to the geothermal heat exchanger toaddress load imbalance or peak operation
Frequently the best option Lower cost
More predictable long term performance
Flexibility
Recommendation: Always include provisions forfuture connection of a cooling tower and/orboiler.
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Load shifting
Turning off equipment Improving Equipment Efficiency
Reducing Maintenance and Repair
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Load shifting
Moving heat from one part of the building toanother
Inherent to all water source heat pump systems
(geothermal or not) Essentially a thermal storage system
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Turning off equipment
Turn off boilers in winter
Turn off cooling towers in summer
Downside more pumping energy
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Improving Equipment Efficiency
Water source is generally more efficient than airsource due to improved delta T and heat transfer
coefficient.
Geothermal systems have lower condenserwater temperatures, especially early in their life,
this results in higher seasonal energy efficiency
ratio (SEER).
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Reducing Maintenance and Repair
Equipment is indoors longer life
Better delta T reduces the lift on the compressor
The geothermal heat exchanger requires zero
maintenance
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Well field life
Insulate condenser water pipeSystem Configuration
Pumping Arrangement
Equipment Selection
Hybrid or not
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Construction Sequence
Well field installation is a major undertaking! Well field occupies large percentage of the site
Coordination with other site work and lay-down areas
Well field is often placed under storm water management
ponds, recreation fields, and parking lotsQuality Control
Factory tested U-bends
Field test every well
Field test every connection
Require test reports from the contractor
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