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

Our planet is changing …

Trift Glacier, Switzerland

From left to right: 1948, 2002, 2006 Glacier retreating Greenland's ice sheet is thinning by up to 1m per year Image: NASA Sea level raising Strong Hurricanes increasing as Global Warming worsens Image: NASA More and severer hurricanes, heat waves, floods, droughts, and tornadoes occurring

What can we do to protect our sweet home – Earth?

“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

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

Geothermal Heat Pump System

A smart solution for energy efficiency

Uses solar energy stored in the earth and takes advantage of the nearly constant temperature just below the surface

Geothermal Heat Pump System

Equivalent to

“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) 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 Estimate building loads using various tools/software ” Size ground heat exchanger using OTHER tools/software • Test and optimize GHP system by evaluating its performance in virtual reality

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/

Integrated Simulation-Based Design

(Continued)

What kind of tool do We Need?

• • • Credible – Building load calculation – GHX modeling – HVAC system simulation User-friendly Cost effective

Enhancements of eQUEST/DOE-2.2

Other GHX models Dedicated GHP reports

Water-air Heat pump library * Advanced GHX modeling technology * Improved water-air heat pump simulation 

Enhancements of eQUEST/DOE-2.2

Advanced model for vertical ground loop heat exchangers (VGLHE)

  Based on extended G-function algorithm Various borehole field configurations 45 40 35 30 25 20 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 15 10 5 0 -5 -16 -15 -14 -13 -12 -11 -10 -9 -8 -7 -6

Ln (t/ts)

-5 -4 -3 -2 -1 0 1 2 3 4  Analytical borehole thermal resistance calculation accounting for grouting material, borehole geometry, anti-freeze

Enhancements of eQUEST/DOE-2.2

Wizard Interface for Specifying VGLHE

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

Water-to-Air Heat Pump Library

• • 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

Example of Performance Curves

1.4000

1.2000

1.0000

0.8000

0.6000

0.4000

0.2000

0.0000

0 20 40 CF_TC 60 80

EFT [F]

CF_SC 100 Non-dimensional heating capacity as a function of entering fluid temperature 1.5000

140 1.0000

0.5000

0.0000

0 Non-dimensional total and sensible cooling capacity as a function of entering fluid temperature 20 40

EFT [F]

60 80 100

Enhanced eQUEST/DOE-2.2

• • • • •

Key Features

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

Verification and Validation

Approaches

• 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 *

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

Verification and Validation

VGLHE Model Verification

75 23 21 19 17 15 eQUEST Results (previous model) HVACSIM+ Results 70 65 60 Previous eQUEST (DOE 2.1E GLHE model)

vs.

HVACSIM + (extended g-function model) 13 55 11 9 7 6/13/2005 0:00 6/14/2005 0:00 6/15/2005 0:00 6/16/2005 0:00 6/17/2005 0:00 6/18/2005 0:00 45 New eQUEST (extended g-function model)

vs.

HVACSIM + (extended g-function model) 50 17 15 eQUEST Results (new model) HVACSIM+ Results 13 11 9 49 47 7 6/13/2005 0:00 6/14/2005 0:00 6/15/2005 0:00 6/16/2005 0:00 6/17/2005 0:00 6/18/2005 0:00 45 57 55 53 51 65 63 61 59

Verification and Validation

Validation with Meter Level Data (1)

Garrett Geothermal Buildings 20,000 sf office conditioned by 50 ton GSHP VGLHE 40 boreholes 5 by 8 grid 250’ deep 20’ spacing 4.5” bore diameter ¾” PE U-tube Standard grout Zoning Two floors 7 perimeter zones each floor 1 core zone each floor Each zone conditioned with individual water-air heat pump

Verification and Validation

Validation with Meter Level Data (2)

30,000 Monthly Electric Use (kWh) Measured Data (06-07) eQUEST Prediction 25,000 20,000 15,000 Garrett Geothermal Building Thermal Model 3-D view in eQUEST 10,000 5,000 0 Jul 06 Aug 06 Sep 06 Oct 06 Nov 06 Dec 06 Jan 07 Feb 07 Mar 07 Apr 07 May 07 Jun 07 Annual Total Electric Use (kWh) Metered Predicted Error 249,920 236,790 5%

Applications

HVAC Systems Comparison (1)

     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

Applications

HVAC Systems Comparison (2)

1: PTAC ($ 69,012) 2: GHP ($ 45,834)

Applications

HVAC Systems Comparison (3)

Fan Pump Cooling Heating PTAC GHP DHW More energy savings if heat pump condensing heat is used for DHW

High electric demand means lager transformer and wires Subject to demand charge

Applications

HVAC Systems Comparison (4)

Peak Electric Demand [kW]

250 200 150 100 400 350 300 PTAC GLHP 50 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

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)

Unit 4 (3 stories) Unit 1 (3 stories) Unit 2 (3 stories) Unit 3 (2 stories)

Dwelling Unit

Index Area ft2 1 2 3 4 2,698 2,630 2,045 2,698

Heat Pump

Clg Tons SF/Ton 5.5

4.5

3.0

5.0

491 584 682 540

Config Rect-2X2 L-3 Line-2 Rect-2X2 Num. of bore 4 3 2 4 Bore depth 360 300 320 320

VGLHE

Total bore length bore length / ton 1440 900 640 1280

262 200 213 256

Min LFT 51.9

50.5

51.5

51.1

Max LFT 96.5

96.0

96.5

95.7

12 ft 12 ft

Line-2 L-3 Rect-2X2

Applications

GHP System Design (3)

100 90 80 70 60 50 40 30 20 10 0 0 Leaving Fluid Temperature Thermal Loads 1000 2000 3000 4000 5000 6000 7000

Time lapse from the beginning of a year [Hour]

8000 Thermal Loads of VGLHE and Leaving Fluid Temperature 60000 50000 40000 30000 20000 10000 0 -10000 -20000 700 600 500 400 300 200 100 0

Temperature range [F]

600-700 500-600 400-500 300-400 200-300 100-200 0-100 Jul Jan Mar May Sep Nov

Applications

GHP System Design (4)

Annual Max. & Min. VGLHE Leaving Fluid Temp. [F] 110 100 90 80 70 60 50 40 30 20 10 0 0 5 10 Max LFT Min LFT 15 20

Years of operation

25 30 35

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

Prospects

• • • • 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 Intelligent Drilling

Advanced bits

Borehole Televiewer

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 You!

Questions?