Geothermal Systems Using Water Source

Heat Pumps Northrich Company / Roberts Mechanical

Presentation FocusTypes of Systems• Building types and advantages

Water Loop• Different types of loops

System Ideas• Heat Pumps

• Heat Recovery

• System Schematics

• Fully Package Geothermal Skid

Cost Benefit Examples• Up front cost vs. life cycle cost

What Type of Buildings use Geo

Systems?Virtually Any Building can use a Geothermal Heating and Cooling System

• Schools (Terminal units, AHU, VAV, multi-zone, unit vents)

• Office Buildings (Terminal units, AHU, VAV, fan coils)

• Hotels (AHU, fan coils)

• Government Buildings (AHU, VAV, fan coils)

• Residential homes

Advantages of Geothermal

• Environmentally friendly

• Design flexibility – Terminal units– Central Plant

• Low energy costs – eliminate or reduce natural gas usage

• Long term Solution – extended life cycle

– Majority of equipment is indoors

– Ground loops last a long time

• Lower maintenance

– No cooling tower or boiler

– No chiller

Earth - Heat Sink and Heat Source

Heat Sink - Summer

• Geothermal systems use the ground as a heat sink in the summer – excess energy is rejected into the ground via a water loop

Heat Source - Winter

• Geothermal systems use the ground as a heat source in the winter– energy is added to the building via a water loop

Ground is Heat Sink

Ground is Heat Source

Water LoopWater Loop

Water Loop Variables

• **Cooling & Heating load (ventilation)

• **Equipment Performance (EER & COP)

• Load diversity

– Loops can be oversized if building diversity is not accounted for

• Site characteristics

– Land available?

– Pond or Lake?

– Soil Conditions?

The Water Loop - 4 Main Types

• Closed Loop Boiler/TowerClosed Loop Boiler/Tower– Cooling Tower to reject heat in summerCooling Tower to reject heat in summer

– Boiler to add heat in winter Boiler to add heat in winter

– System temperatures typically range from 60 to 95System temperatures typically range from 60 to 95

– Tower and boiler maintenanceTower and boiler maintenance

• Geothermal LoopGeothermal Loop – Closed loopClosed loop

• HorizontalHorizontal

• VerticalVertical

• Closed PondClosed Pond

– System temperatures range from 35 to 90System temperatures range from 35 to 90

• Open LoopOpen Loop– ““Pump and Dump” Pump and Dump”

• Directly into the heat pump with suitable waterDirectly into the heat pump with suitable water

• Intermediate heat exchanger if the water is a problemIntermediate heat exchanger if the water is a problem

– System temperatures typically range from 40 to 90System temperatures typically range from 40 to 90

• Hybrid LoopHybrid Loop – Any combination of the two – typically a boiler and/or Any combination of the two – typically a boiler and/or

cooling tower attached to a closed loopcooling tower attached to a closed loop

– Lower first cost due to smaller loopLower first cost due to smaller loop

– Popular with Geo retrofitsPopular with Geo retrofits

The Water Loop - 4 Main Types

Vertical Loops

Most common for large commercial projects

Vertical Loops

• Smaller Land Requirement– 150 to 250 feet per ton –

depth depends on thermal

– 250 square feel per ton (15 foot centers)

• Soil borings

– Thermal conductivity of soil will dictate the amount of pipe

• Vertical bores– Well drilling machinery

– Polyethylene pipe

– Pipe is joined by heat fusion that make the joints stronger than the pipe itself

Vertical Loops

• Vertical bores– 4.5 to 6.5 inch bore holes

– Grout is pumped down the bore holes

– Reverse return

• Freeze Protection– Average water temps 33 to 90

– Methanol, Ethanol, or Propylene

• Design– Systems should be designed &

installed by a certified Ground Loop Engineer

Can be placed under a parking lot

Closed Pond

• Ground Water

• Pond or Lake

• Man made or natural

• 10 to 12 feet minimum

• 10 to 50 tons per acre

• Average Water Temperature 35 to 87

• Evaporative effect of water in summer

• Thermal conductivity of the earth in the winter

Closed Pond

Traditional Plastic Pipe on Pond Floor

• 300 to 350 feet of plastic pipe per ton

• Pipe coils separated by spacers

• Reverse Return piping

• Float out the pipes and then fill them with water to sink to the floor of the pond

• Labor intensive

• AWEBB Supply - Baton Rouge, LA

• Stainless steel plates connected to building

• Mounting– Feet

– Skids

– Floating

Closed Pond

Geo Lake Plate from Slim Jim

Closed Pond

Geo Lake Plate from Slim Jim• Long lasting

• Simple

• Custom configurations

• Lower labor costs

200 Tons8 Tons on skid

Open Loop

• “Pump and Dump”

• Colder water in cooling

• Filter out debris in the water

• Intermediate heat exchanger

What is a Heat Pump?

A heat pump is a traditional compressor driven air conditioner with a refrigerant reversing valve. When engaged the reversing valve reverses the flow of the refrigerant through the liquid line changing the evaporator into the condenser and vice versa.

Types of Heat Pumps

1. Air to air – some commercial applications – mainly a residential product.

2. Water to Air – water in one side – hot or cold air out the other side (3.0 GPM/Ton)

3. Water to Water – water in one side – hot or cold water out the other side (3.0 GPM/Ton)

Vocabulary

• Source Temperature

– Temperature of geo loop

• Load Temperature

– Temperature of building side of the system (typically used with water to water product)

• Cooling Capacity

– Amount of cooling at a certain source water temp

• Heating Capacity

– Amount of heating at a certain source water temp

• KW

– Electricity used at a certain source water temp

– Used to calculate EER in cooling mode

– Used to calculate COP in heating mode

Vocabulary

• EER

– Cooling Capacity (BTU) / (KW)

– Inverse of KW/Ton (( 1 / EER) X 12)

• COP

– Heating Capacity (BTU) / (KW input X 3412 BTU/KW)

• Heat of Extraction– Energy taken out of the loop in heating mode

• Heat of Rejection

– Energy added to the loop in cooling mode

ARI/ISO Ratings

• Old ARI Conditions

– ARI 320-93 Boiler/Tower (85 Cooling / 70 Heating)

– ARI 325-93 Ground Water Open Loop (70 Cooling / 50 Heating)

– ARI 330 – 93 Geothermal Closed Loop ((77 Cooling / 32 Heating)

• ARI/ISO 13256 joint Standard

– Boiler/Tower (86 Cooling / 68 Heating)

– Ground Water Open Loop (59 Cooling / 50 Heating)

– Geothermal Closed Loop (77 Cooling / 32 Heating)

EER and COP data is certified at ARI/ISO conditions

Geothermal Heat Pumps

• Extended Range– Heat generated at low source temperatures – 30 F or lower

• Better construction– Designed for longer life

– Coated evaporator coils

– Painted cabinets

• New equipment on the market due to 410a refrigerant– ECM motors

– Higher EER’s

– Enhanced control capabilities

Different Different SystemsSystems

Geothermal Pump Skid

– Integrated boilers– Integrated domestic water (IWH)– Integrated controls– System Flexibility– Maximize the use of your boilers and

equipment– Complete redundancy– Minimize – Installation, start-up, integration

costs

Selecting a proper boiler– Look closely at efficiency curves

– Control sequencing must be reviewed• MODULATION IS CRITICAL TO EFFICIENCY ON

MODULATING BOILERS• RETURN WATER TEMPERATURES ARE CRITICAL TO

EFFICIENCY ON CONDENSING BOILERS.

– First determine boiler ‘type’.• CONDENSING (LOW RETURN TEMP)

• COPPER MODULTING (MID RETURN TEMP)• COPPER OR STEEL 85% (HIGHER RETURN TEMP)

Condensing Boiler– 90% - 99% efficient at

return temperatures below 120F

– A good choice could eliminate redundant controls

– Flow to control temperature and delta tee.

– Primary secondary often not required.

– AL29-4C!

Copper Modulating Boiler– 89% to 85% based on

modulation.– Return temps to 115F

acceptable, 100F with proper piping and accessories.

– Primary / Secondary always required.

– Modulation controls CRITICAL and should not be left to the BMS.

– AL29-4C!

Copper Mid Efficiency Boiler– 85% flat line efficiency curve.

– Return temps to 115F acceptable, 100F with proper piping and accessories.

– Primary / Secondary always required.

– Simple staging. Desirable with multiple boilers.

– Category I or III venting acceptable.

Steel Boilers

– 80% to 85% but can lose efficiency based on age. (Scale/Soot)

– Return temps to 140F.– Available with built in low

temp heat exchanger.– Forced draft Category III.

Other boiler considerations– Seasonal efficiency

• Some condensing fire most the season below 85% when temperatures are above 140F.

• Load vs. Savings (life cycle payback)– Boiler manufacturers

• Scaled down controls (residential type)• True Freeze Protection.• Small tubing to attain efficiency• Communication ability

– Support and Service• Local service and support• National backbone• Proprietary combustion controls• Ignition systems / reliability

– Footprint vs. Service Clearances• Height!!• Depth of piping and venting

Conceptual Layout Options

Boiler Vent & Combustion Air Elevation

– NTS

Elevations can be from 4’-6’ off the floor.

Vents should stagger off the back of the boiler to leave through the wall at the same height (AL29).

Combustion air to be PVC and may be common connected.

18”

HYDROTHERM KN6 CONDENSING BOILERS Geothermal Suggested Piping - NTS

From Building

200 GPM

Boilers @ 100 GPM each 10F Delta Tee / 2.7 psi drop

To Building

HX1

CT-1

ST1

System shall flow through the boilers. The boilers shall sense the temperature and be set to fire below 50F. Boilers will be wired to each other and modulate together on the highest point of the efficiency curve.

This drawing is for conceptual purposes and should not be used for installation. The drawing does not include many required accessories such as expansion air elimination, etc.

Critical Spec Items – Heat Pumps• Heat pump performance capabilities: EER: 30.0; COP: 5.0 (Part load at

ARI/ISO 13256-1 (Ground Loop Heat Pump) minimum 23.0 EER cooling and 4.0 COP heating) Temperature range

• Loop design is based on Heat Pump performance. WSHP not meeting ARI certified operating performance requirements are responsible for added ground loop requirements.

• Insulated coaxial heat exchanger - extended range of temperatures eliminates condensation

• 410A refrigerant (Ozone depletion)• Dual speed compressor – for energy & eliminates auxiliary heat requirement• Multi-speed ECM Motor – for energy, and to monitor & control humidity• Foil faced cabinet insulation• Painted cabinet – longer life• Microprocessor control

Critical Spec Items – GeoSkid

• Pump performance (VIL for long life)• Proper boiler selection• Proper control selection• Boiler efficiencies• Single point responsibility:

– Pumps– Boilers– Controls– Integration

LEED POINTS• Meet all minimum pre-requisites for Energy & Atmosphers• Energy performance above minimum ASHRAE 90.1 standards

– 1-10 point possible for optimum energy performance– ASHRAE requires EER-12, WFI operates at EER-23 at ARI standards 30-50%

increase makes you eligible for highest point rating– 10 points

• Ozone Depletion – R410A– 1 point

• Materials & resources – locally manufactured– 1 point

• Indoor environmental Air Quality – minimum ASHRAE– 1 point

• Monitor/control humidity – ECM motor & Microprocessor– 1 point

• Innovation & design – geothermal skid– 1 point

ConclusionsConclusions Compare Safety

I nstallation Cost

Operating Cost

Maintenance Cost

Life-Cycle Cost

Combustion-based

A Concern

Moderate Moderate High Moderate

Heat pump Excellent Moderate Moderate Moderate Moderate

Geoexchange Excellent High Low Low Low