Central Geothermal

Trane Sales Webinar Central Geothermal Systems A System Overview

Trane Sales Webinar Lee Cline P.E. Senior Principal Systems Engineer

Trane

La Crosse, WI

3

Agenda

Overview

Multiple Chiller/ Heater Bi-directional Cascade

Single Chiller/Heater Configurations

Water-to-Water Heat Pump Configurations

A Few Lessons

Additional Resources

Q&A

3

5

Distributed Geothermal System

heat pumps

water pumps vertical-loop ground heat exchanger (borefield)

WSHPs

Dedicated outdoor air units

Optional fluid cooler

Water pumps

Geo heat exchanger

5

Central Geothermal System

Chillers provide heating and cooling

Ground couple for an efficiency boost

Central air handlers

VAV terminals

Water pumps

Auxiliary boilers

Fluid or dry cooler

Air handlers

chiller/heaters

Geothermal loop (borefield)

VAV boxes

6

7

Central Geothermal Customer Benefits Compared to Distributed

Premium efficiency (LEED EA Credit #1) Efficient central equipment

Bi-directional cascading

VAV

Air economizing

Better heat recovery management

Easy to maintain Central equipment, few cooling units

Uses equipment rooms, no access to occupied space required

Simpler coil condensate collection

7

8

Central Geothermal Customer Benefits Compared to Distributed

Low space noise (ASA 12.60) Fans and compressors away from occupied space

Noise paths can be more easily attenuated

Good IAQ Many filtration options available (LEED EQ 5 MERV 13)

Easier to deliver 30% more outdoor air (LEED EQ 2)

8

10

Vertical Markets

Education Primary and secondary

Colleges and universities

Government Federal sector

State and county level

Long-term owners Accept extended payback periods

Interested in embracing green technologies

Usually have space for a borefield

11

Incentives

Utility

Reimbursement

Tax (if private)

www.dsireusa.org

12

Central Geothermal System Types

System Type Capacity Range Target Market

Single chiller/heater

systems

(based on typical industry units)

K / 12 Schools

Simpler / Smaller

Premium Efficiency

cascading

multi-chiller/heater

systems


High School / Secondary Ed

> 36,000 sq. ft

Super Premium Efficiency

Water-to-water

heat pump system


Small Building Large Volume 80% of Buildings < 25,000 sq ft

Premium Efficiency

150-1500 tons

70-250 tons

5-200 tons

13

Agenda

Single Chiller-Heater Central Geothermal Systems Four-pipe distribution system configuration

Two-pipe distribution system configuration

Multiple Unit Cascading Systems

Water-to-Water Heat Pump Based Systems

14

Central Geothermal Systems

Single Chiller-Heater

Allow screw compressor chiller-heater based CGS systems down to 70-75 tons

Simple configurations

Simpler operation

Two basic distribution configurations:

4-pipe simultaneous heating/cooling

2-pipe changeover heating/cooling

15

P-GS

4-pipe distribution / Constant flow (3-way control valves)

aux heat

cond

evap

CHR-1

Chiller/Heater

P-CH

P-HT

heating loads

cooling loads

Single Chiller-Heater CGS

to

ground

source

from

ground

source VAL-1 / VGS

16

P-GS

aux heat

cond

evap

CHR-1

Chiller/Heater

VAL-1 / VGS

P-CH

P-HT

heating loads

cooling loads Standard chilled water

system maybe constant

flow, primary/secondary or

variable primary flow

Single Chiller-Heater CGS 4-pipe distribution / Constant flow (3-way control valves)

to

ground

source

from

ground

source

17

P-GS

aux heat

cond

evap

CHR-1

Chiller/Heater

VAL-1 / VGS

P-CH

P-HT

heating loads

cooling loads Heating water system will

likely be constant flow or

primary/secondary

4-pipe distribution / Constant Flow (3-way control valves)


to

ground

source

from

ground

source

18

aux heat

heating water by-pass

chilled water by-pass

VAL-1 / VGS

P-CH

P-CD

heating loads

cooling loads

cond

evap

CHR-1

Chiller/Heater

VAL-1 / VGS

P-HT

Primary/secondary

heating water system

- for expanded

distribution delta T

and variable flow

4-pipe distribution / Decoupled pumping


to

ground

source

from

ground

source P-GS

19

aux heat

cond

evap

CHR-1

Chiller/Heater

VAL-1 / VGS

P-CH

P-HT

heating loads

cooling loads

Ground-source loop should be variable flow

for controllability and pumping efficiency

4-pipe distribution / 3-way control valves


to

ground

source

from

ground

source P-GS

20

Central Geothermal System Options

Auxiliary heating

NOT OPTIONAL for single unit systems

Auxiliary heat rejection

Auxiliary cooling

Contingency cooling connections

21

P-GS

Contingency Cooling

Connections

aux ht reject

Central Geothermal System Options

aux heat

cooling loads

cond

evap

aux cooling

heating loads

Chiller/Heater

P-CH

P-HT

to

ground

source

from

ground

source VAL-1 / VGS

Single Chiller/Heater


23



V1

cond

evap

Chiller/

Heater

V2

auxiliary heat

V3

building loads

to

ground

source

from

ground

source

P-GS

P-DS

V4

24

Single Chiller-Heater CGS 2-pipe distribution / Constant Flow (3-way control valves)

Cooling only mode

V1

cond

evap

Chiller/

Heater

V2

auxiliary heat

V3

building loads

to

ground

source

from

ground

source

P-GS

P-DS

V4

Chilled water distribution

will likely be constant flow

or primary/secondary

25


Cooling only mode

V1

cond

evap

Chiller/

Heater

V2

auxiliary heat

V3

building loads

to

ground

source

from

ground

source

P-GS

P-DS

V4

Ground-source loop

providing cool water to the

chiller/heater condenser

26



Heating only mode

V1

cond

evap

Chiller/

Heater

V2

auxiliary heat

V3

building loads

to

ground

source

from

ground

source

P-GS

P-DS

V4

Heating water distribution

will likely be constant flow

or primary/secondary

27


Heating only mode

V1

cond

evap

Chiller/

Heater

V2

auxiliary heat

V3

building loads

to

ground

source

from

ground

source

P-GS

P-DS

V4

Ground-source loop

providing warm water to the

chiller/heater evaporator

Multi-Chiller/Heater Cascading


29

cooling

load

On

Cool

PLc

PC PLe

M

M M

A

cond

evap

On

Heat

M

PH

B

cond

evap

heating

load



VAL-2

/ VEC

VAL-3

/ VCC

M

M

VAL-1 / VGSC

PB

to

ground

source

from

ground

source

30

Multi-Chiller/Heater Cascading Review

Number of Chiller-Heaters 2-6 Units

Nominal 80-250 ton unit capacity Actual 150-1500 ton plant size

Operating conditions 38 leaving chilled water

140 leaving condenser water (lower is better)

Not at the same time!

Cascading has the potential to increase plant efficiency

The energy transfer loops increase plant controllability

31

PB

VAL-2

/ VEC

VAL-3

/ VCC

M

M

VAL-1 / VGSC

cooling

load

On

Cool

PLc

PC PLe

M

M M

A

cond

evap

On

Heat

M

PH

B

cond

evap

heating

load

Multi-Chiller/Heater Cascading Introduction

to

ground

source

from

ground

source

32

VAL-2

/ VEC

VAL-3

/ VCC

M

M

VAL-1 / VGSC

Cooling system

cooling

load

On

Cool

PLc

PC PLe

M

M M

A

cond

evap

On

Heat

M

PH

B

cond

evap

heating

load


Standard Chilled Water

System may be:

constant flow primary/secondary or variable primary flow

to

ground

source

from

ground

source PB

33

PB

VAL-2

/ VEC

VAL-3

/ VCC

M

M

VAL-1 / VGSC

Heating system

cooling

load

On

Cool

PLc

PC PLe

M

M M

A

cond

evap

On

Heat

M

PH

B

cond

evap

heating

load


Heating Water System will

likely be constant flow or

primary/secondary

to

ground

source

from

ground

source

34

VAL-2

/ VEC

VAL-3

/ VCC

M

M

VAL-1 / VGSC

cooling

load

On

Cool

PLc

PC PLe

M

M M

A

cond

evap

On

Heat

M

PH

B

cond

evap

heating

load

Ground-source loop


Ground-source loop

should be variable

flow for pumping

efficiency

to

ground

source

from

ground

source PB

35

VAL-2

/ VEC

VAL-3

/ VCC

M

M

VAL-1 / VGSC

cooling

load

On

Cool

PLc

PC PLe

M

M M

A

cond

evap

On

Heat

M

PH

B

cond

evap

heating

load

Condenser Energy Transfer Loop


Condenser Energy Transfer

Loop brings cooling water to

condenser from ground-source

loop or heater evaporator

to

ground

source

from

ground

source PB

36

PB

VAL-3

/ VCC cooling

load

On

Cool

PLc

PC PLe

M

M M

A

cond

evap

On

Heat

M

PH

B

cond

evap

heating

load

Evaporator Energy Transfer Loop


VAL-2

/ VEC

M

M

VAL-1 / VGSC

Evaporator Energy Transfer

Loop brings warm water to

evaporator from ground-source

loop or chiller condenser

to

ground

source

from

ground

source

37

PB

VAL-2

/ VEC

VAL-3

/ VCC

M

M

VAL-1 / VGSC

cooling

load

On

Cool

PLc

PC PLe

M

M M

A

cond

evap

On

Heat

M

PH

B

cond

evap

heating

load

Single Chiller-Heater Operation

Multiple chiller-heater systems

can and will provide simultaneous

cooling and heating with one unit.


to

ground

source

from

ground

source

38


Water To Water Heat Pump

WWHP Simple piping - dedicated pumps

PH

Cooling load

To wellfield

Heating load

PC

From wellfield

PW

P P P P

Water-to-Water

Heat Pumps

evap

cond

evap

cond

cond

evap

On

Cool On

Cool On

Heat Off

39

40

Key Design Issues

Geothermal vs Heat Recovery

Optimizing life cycle costs Borefield sizing

Supplemental heating Auxiliary heat rejection

Load shedding economizer

Application Comparison

Geothermal vs Heat Recovery

Geothermal

Separate heating and cooling seasons

Relatively balanced

Real estate for ground source system

Capital availability for ground-source system

Energy savings driven

Heat Recovery

Significantly cooling dominant

Relatively low peak or average heating load

Right-sized heat recovery unit

Energy and ROI driven

41

42

optimizing life cycle costs

Ground-Source Sizing

Must consider Peak building demand

Annualized building energy balance

Optimization Reduce peak demand cooling and heating

Balance annual heating and cooling loads

Consider a hybrid system design

Fluid cooler

Pond / lake system

43

Heating Dominate Seasonal Load Profile

Building Load Profile

0

600000

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total

Month

Energ

y

Cooling

Heating

44

Cooling Dominate Seasonal Load Profile

Building Load Profile

0

500000

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total

Month

Energ

y

Cooling

Heating

Total vs. monthly?

45

Addressing Load Profile Imbalance

A cooling dominate building Reduce solar loading and/or interior loads

Auxiliary energy rejection (e.g. fluid cooler)

Add heat load to system (e.g. domestic hot water)

A heating dominate building Auxiliary heating system (e.g. condensing boiler)

Thermal solar heating

Optimize the building life cycle cost Reducing borefield size

Increasing borefield utilization for energy efficiency

46

cooling

load

On

Cool

PLc

PC PLe

M

M M

A

cond

evap

On

Heat

M

PH

B

cond

evap

heating

load


VAL-2

/ VEC

VAL-3

/ VCC

M

M

VAL-1 / VGSC

PB to

ground

source

from

ground

source

47

Packaged Central Geothermal Plants

48

A Few Lessons

Do not oversize the plant! Do a computerized load analysis not rule of thumb Size for block loading - not sum of the coil peaks

Apply optimization principles

Pump pressure optimization

Load based setpoint resets

Have auxiliary / backup heat in single unit systems

Watch the condenser minimum flow in heating

Fully and carefully document control system sequence of operation

Do not leave the details to the controls field technician

49

Additional Resources

Applications Engineering Manual - SYS-APM009-EN includes single and multiple chiller/heater configurations.

Documents

Central Geothermal