geothermal heat pump systems presentation

7/28/2019 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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geothermal heat pump systems presentation

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