overcoming hurdles integrated simulation-based design for geothermal heat pump systems xiaobing liu,...
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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
temperature
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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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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HP-8 HP-11
HP-15 HP-14
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HP-15 HP-14
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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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5,000
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25,000
30,000
Jul-06
Aug-06
Sep-06
Oct-06
Nov-06
Dec-06
Jan-07
Feb-07
Mar-07
Apr-07
May-07
Jun-07
To
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Bu
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kW
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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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Pe
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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)
12 ft 12 ft
Line-2 L-3 Rect-2X2
12 ft
12 ft
12 ft
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Time lapse from the beginning of a year [Hour]
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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?