Overcoming Hurdles

Integrated Simulation-Based Design for Geothermal Heat Pump Systems

Xiaobing Liu, Ph. D.

ClimateMaster

Agenda• Background• Geothermal heat pump• Overcoming hurdles• Integrated simulation-based design

– Enhancements of eQUEST/DOE-2.2

– Verification and validation

– Applications

• Summary and prospects

2007 Nobel Peace Prize goes to Al Gore and the U.N.'s IPCC for their efforts to spread awareness of man-made climate change, and to lay the foundations for the measures needed to

counteract it. Global Warming Map Animation by NA

More and severer hurricanes, heat waves, floods, droughts, and tornadoes occurring

Strong Hurricanes increasing as Global Warming worsens

Image: NASA

Our planet is changing …

Sea level raising

Greenland's ice sheet is thinning by up to 1m per year Image: NASA

Glacier retreating

Trift Glacier, SwitzerlandFrom left to right: 1948, 2002, 2006

What can we do to protect our sweet home –

Earth?

How we use our resources and energy today makes difference in our world in the future

“Humankind has not woven the web of life. We are but one thread within it. Whatever we do to the web, we do to ourselves.

All things are bound together. All things

connected.”

- Chief Seattle

Uses solar energy stored in the earth and takes advantage of the nearly constant

temperature just below the surface

Geothermal Heat Pump SystemA smart solution for energy efficiency

“the most energy-efficient, environmentally clean, and cost-effective space-conditioning system”

“produce the lowest carbon dioxide emissions, including all source effects, of all available space-conditioning technologies”

(EPA, 1993)

Geothermal Heat Pump System

Equivalent to

More trees

Fewer cars

Greater clean power

Overcoming Hurdles

• Hurdles in initial cost• Hurdles in design

– Cumulative loads required for sizing ground heat exchanger (GHX) is much more complicated to calculate than the peak loads

– Performance of various type of GHX is affected by many factors and their design heavily relies on computerized calculation

– Lack of GHX design required geology information

– Unfamiliar with GHX related drilling and grouting technology • Hurdles in the field

– Struggles between GHX installation and other construction processes

– Challenges in quality control/assurance of drilling and grouting

– Intensive requirements for flushing, purging, and pressure testing of underground piping

Integrated Simulation-Based Design

• No hassles any more in transferring data among individual programs

• Test and optimize GHP system by evaluating its performance in virtual reality

Estimate building loads usingvarious tools/software

Size ground heat exchanger usingOTHER tools/software

Integrated Simulation-Based Design“Under one roof”

Integrated Simulation-Based Design (Continued)

• Documented energy performance rating is required for LEED certification and energy efficiency incentives

• Integrated building energy system requires integrated design process

Zero Energy Home GSHP

ERV

PV panel

Better insulation

Double low-e windows

Compact Fluorescent Lights

Energy efficient appliances

The above illustration is from http://www.ideal-homes.com/

• Credible– Building load calculation– GHX modeling– HVAC system simulation

• User-friendly• Cost effective

Integrated Simulation-Based Design (Continued)

What kind of tool do We Need?

Water-air Heat pump library *

Enhancements of eQUEST/DOE-2.2

Advanced GHX modeling technology*

Improved water-air heat pump simulation

Dedicated GHP reports

Other GHX models

Based on extended G-function algorithm

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Short-time g-function

Long-time g-function for 10X6 borehole field

Long-time g-function for 20X3 borehole field

Long-time g-function for 5X3 borehole field

DOE-2.2 g-function for 5X3 borehole field

Enhancements of eQUEST/DOE-2.2

Advanced model for vertical ground loop heat exchangers (VGLHE)

Various borehole field configurations

Analytical borehole thermal resistance calculation accounting for grouting material, borehole geometry, anti-freeze

Soil/rock Types Main Ground-Source HP Equipment Screen GHX Configurations

Grout Types

Fluid Types

Enhancements of eQUEST/DOE-2.2

Wizard Interface for Specifying VGLHE

For each heat pump• H/C capacities, EER,

COP, airflow, water flow, pressure drop, ESP, and etc at ARI/ASHRAE/ISO rated conditions

• Eight curves for performance at off-rated conditions

Water-to-Air Heat Pump Library

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Non-dimensional total and sensible cooling capacity as a function of entering fluid temperature

Non-dimensional heating capacity as a function of entering fluid

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Water-to-Air Heat Pump Library

Example of Performance Curves

• Wizard interface with intelligent defaults • Hourly building loads calculation• Size and simulate almost all HVAC

systems including GHP system• Graphical display and summary reports

– Energy consumption– Peak Demand– Utility bill (based on given utility rates)

• Detailed comprehensive reports

Key Features

Enhanced eQUEST/DOE-2.2

• Verification of newly implemented g-function based VGLHE model

• Sensitivity study through parametric runs• Validate predicted whole building and GHP system

energy consumption with monitored meter level data• Validate predicted whole building and GHP system

performance (including energy consumption, loop/room temperature, and etc) with detailed component level data *

Verification and Validation

Approaches

* Ongoing process using monitored data from a fully instrumented Zero Energy Home.

VGLHE Model Verification

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eQUEST Results (previous model) HVACSIM+ Results

Previous eQUEST (DOE 2.1E GLHE model)

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HVACSIM+ (extended g-function model)

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eQUEST Results (new model) HVACSIM+ Results

New eQUEST (extended g-function model)

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Verification and Validation

Validation with Meter Level Data (1)

2” PE Zone Supply Header - Return Similar3/4” PE bore piping back toheader

Notes:- 40 bores on 20 foot centers each with 3/4” PE pipe- Short header manifold in center of each loop zone of 10 bores- Each bore must have the same overall pipe length for balanced flow

(Coil excess piping in the header trench)- Loop zone supply and returns done in same fashion- Bores must be grouted when completed

Short headerlocation

Typical bore250 ft deep

VGLHE40 boreholes5 by 8 grid250’ deep20’ spacing4.5” bore diameter¾” PE U-tubeStandard grout

Garrett Geothermal Buildings20,000 sf office conditioned by 50 ton GSHP

Verification and Validation

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ZoningTwo floors7 perimeter zones each floor1 core zone each floorEach zone conditioned with

individual water-air heat pump

Validation with Meter Level Data (2)

Verification and Validation

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Measured Data (06-07) eQUEST Prediction

Monthly Electric Use (kWh)

Annual Total Electric Use (kWh)

Metered Predicted Error

249,920 236,790 5%Thermal Model 3-D view in eQUEST

Garrett Geothermal Building

Applications

Building Type: Hotel

Area: 66,000 sf

Candidate HVAC systems

PTAC with electric heater

GHP with VGLHE

Equipment efficiency

PTAC: EER 8.8

GSHP: EER 18.5; COP 4.0

Utility rates: OG&E PL-1 SL-5

HVAC Systems Comparison (1)

1: PTAC ($ 69,012)

2: GHP ($ 45,834)

Applications

HVAC Systems Comparison (2)

PTAC

GHP

Applications

HVAC Systems Comparison (3)

FanPump

Cooling

Heating

DHW

More energy savings if heat pump condensing heat is used for DHW

Peak Electric Demand [kW]

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Applications

HVAC Systems Comparison (4)

High electric demand means lager transformer and wires

Subject to demand charge

Applications

GHP System Design (1)

157 town homes grouped in 18 buildings

Varying in height from 2 to 4 stories

Ranging in size from 1600 sf to 3517 sf

Over twenty-six floor plans

Challenges in design

Boreholes are limited in garage only

Attached homes but with individual loop for each home

Very short time for design

Solution

Integrated simulation with customized VGLHE modeling

Result

VGLHE size varies from 230 – 280 ft/ton depending on location, orientation, window/wall ratio of each town home

Applications

GHP System Design (2)

Index Area ft2 Clg Tons SF/Ton Config Num. of bore Bore depth Total bore length bore length / ton Min LFT Max LFT1 2,698 5.5 491 Rect-2X2 4 360 1440 262 51.9 96.52 2,630 4.5 584 L-3 3 300 900 200 50.5 96.03 2,045 3.0 682 Line-2 2 320 640 213 51.5 96.54 2,698 5.0 540 Rect-2X2 4 320 1280 256 51.1 95.7

Heat PumpDwelling Unit VGLHE

Unit 4 (3 stories)

Unit 2 (3 stories)

Unit 3 (2 stories)

Unit 1 (3 stories)

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Line-2 L-3 Rect-2X2

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Leaving Fluid Temperature

Thermal Loads

Thermal Loads of VGLHE and Leaving Fluid

Temperature

Applications

GHP System Design (3)

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Annual Max. & Min. VGLHE Leaving Fluid Temp. [F]

Applications

GHP System Design (4)

Summary

• To overcome hurdles in GHP system design, eQUEST has been enhanced to facilitate the integrated simulation-based design process

• Extensive efforts have been conducted to validate the enhanced eQUEST and more intensive validation is ongoing

• The enhanced eQUEST is making revolutionary change in GHP system design

Prospects

• Further validation and development of eQUEST– Prediction of GHP system long-term performance – Hybrid GHP systems: combination of a variety of

heat sink and/or source– Geothermal water-water heat pump with integrated

domestic hot water heater– Other types of GHX, including horizontal loop,

pond/lake, standing column well, and other emerging technologies

Tremendous opportunity for GHP, if:

• More energy-efficiency incentives

• More knowledgeable and responsible drillers

• More cost-effective drilling and grouting technologies

• Advanced procedure and equipment for GHX installation and testing

Prospects

Borehole Televiewer

Intelligent Drilling

Advanced bits

From Craig E. Tyner at SNL

Since their introduction in the 1980’s, nearly 1 million Geothermal Heat Pumps have been installed in the United States

This is equivalent to:

• Planting 1 million acres of trees• Taking 2 Million cars off the road

We Can do More…

Thank Thank You!You! Questions?Questions?