Design, Analysis & Cost Development of a 220 Ton Geothermal HVAC System

Albert A. Koenig, Ph.D.

ARB/Geowell Systems

www.ARBgeowell.com

Presentation Outline

L.E.E.D. Building Design (Silver) Goals Load Modeling/Simulation HVAC Distribution Technology Hydronic System Scheme Site Information Load Design Spec The GeowellTM SCW Technology GeowellTM String Deployment 220 Ton Geothermal Field Layout Installed Cost & Payback

Building Design Standard

Basis: ASHRAE/IESNA Standard 90.1-2004 for building energy efficiency/sustainability and Standard 62 for ventilation

Bldg. envelope & systems designed to maximize energy performance, based on

– Computer simulation model (DOE-2, TRACE)– Identification & implementation of the most cost-effective

energy efficiency measures– Quantification of performance vs. baseline bldg.

20% renewable energy credit: geothermal

Building Operating Expense

Building Interior Daylighting

DOE-2: Model Bldg. Hourly Energy Use

Silver L.E.E.D. Design Goal

Targets: 280 KBTU/sqf =>180 KBTU/sqf annual energy use HVAC equipment: 250 tons => 180 tonsEquipment: Innovative active chilled beam ceilings for integral

room comfort using geothermal chilled water to provide 15°F ΔT (floor to ceiling)

73% efficient economizer with energy recovery wheel

Exposed Chilled Beam TechnologyEsp. Suited for Open Office Areas

Chilled Beam Bldg. Heat Transfer

Chilled Beam Bldg. HX

0

5

10

15

20

25

0 20 40 60 80 100

Heat Transfer (tons)

Flr

-Clg

dT

(F)

emis=.65

Chilled Beam Bldg. HX

0

0.2

0.4

0.6

0.8

1

30 40 50 60 70 80

Heat Transfer (tons)

Em

iss

ivit

y

dT=15F

Hydronic System Diagram

Building External HVAC Load: HDD/CDD

Bldg. Monthly Load

0

200

400

600

800

1000

1200

1 2 3 4 5 6 7 8 9 10 11 12

MM

BT

U

Heating

Cooling

Building HVAC Design Spec

80,000 sqf office building (7 floors) 220 tons (365 sqf/ton) Building Load:

– External Load: 92 tons – Internal Load: 128 tons

(lighting, people, equipment & air transport)

Site Information

20 acres wooded area (NJ/NY) Proximity to river for ground water recharge Ample water well records in vicinity Water 50-60’ from surface Excellent hydrogeology for geothermal

application

Rock Thermal Properties

0

0.5

1

1.5

2

2.5

3

Co

nd

ucti

vit

y (

BT

U/h

rftF

)

0.0

0.5

1.0

1.5

2.0

Dif

fusiv

ity (

Sq

f/d

ay)

Seasonal Heat Storage Measurement & Modeling/Simulation @ 50’/ton

Thermal Propagation in WellboreContinuous Heating

00.5

11.5

22.5

33.5

0 10 20 30 40 50 60 70

Time (hr)

Pro

pa

ga

tio

n L

(ft)

Avg. Formation TemperatureOver Thermal Penetration Distance

54

56

58

60

62

64

0 200 400 600 800 1000

Time (hr)

Ro

ck

Te

mp

. (F

)

ARB/Geowell Technology

A New Old Approach for Using Geothermal Water Wells for Building HVAC

Water Well Operation with Re-injection Wellbore Heat Transfer

Patented in-Well String Design for Fast Deployment & Maintenance

Impact of Polypipe Insulation on Wellbore Heat Transfer

Wellbore Heat Transfer

0

100

200

300

400

500

600

0 0.1 0.2 0.3 0.4 0.5 0.6

Insulation Thickness (in)

HT

C (

BT

UH

/sq

f F

)

Colburn

Von Karman

ε/D = .01

Heat Transfer Benefit of GeowellTM: 4-Fold Improvement Over Closed Loops

Thermal Analysis: Closed Loop vs GeowellRock Prop: k=1.87BTUH/ftF, diff=1.11sqf/day

3

4

5

6

7

0 500 1000 1500 2000 2500

Op. Time (hr)

Re

sis

tan

ce

Ra

tio

(clo

se

d/g

eo

we

ll)

The ARB/Geowell Technology

Patented SCW technology that insure: minimal geofield installed expense

• use of deep (nom. 1000’) wells to minimize footprint and the number of submersible pumps

• the entire 6” wellbore diameter and length are utilized in return water heat exchange

• minimal total drilled length to satisfy bldg. load specification• fast installation of each well string• minimal field installation time (pre-fab ext. plumbing)

minimal operating expense• minimal parasitic power utilization by employing a control algorithm

that activates on those well pumps that are needed to satisfy the load• well strings designed for ease of pump replacement

Fast In-Well Deployment

GeoWellTM Submersible Pump Housing and Docking Assembly

GeoWellTM Injected Molded Components

Lower installed cost ($1300 vs. $2300 per ton)

Smaller wellfield footprint (20% of closed loop)

Minimal parasitics: well row operational selectivity

Wellfield design using minimal number of pumps

Pre-fab plumbing kits to min. field installation expense & insure best practices

Fast installation of in-well components

Geowell Advantages

Applications

220 Ton Geothermal Field Layout

220 Ton Geowell Field Layout

220 Ton Design Specification

Based on drilling to a nom. depth of 800’ 20 water wells, operated 4 rows x 5 wells per

row, or 5 x 4 Well-well spacing 30’ Footprint: ⅓ acre Installed cost: $211,800

Field Plumbing Schematic

Installed Cost Breakdown

GeoWell Field Cost Breakdown

Drilling %

Electr %

Civil/Install %

Mech %

Installed Cost & Payback

Geowell Example: 220 ton bldg. loadInstalled loop (20 wells) price: $286,000[Heat Pumps (220 tons total): $176,000]less State Rebate ($/ton): ? - $ 77,000less Fed Tax deduction: - $ 48,000Net Cost: $161,000Annual Operating Savings: $ 22,850Discounted Payback: 6 yrs

Discounted Payback Analysis

NPV Analysis of Geothermal HVAC Applications0.027 Fuel Escalation Rate 220 ton Calculation of Annual HVAC Load0.035 Cost of Living 12 mean value (yrs) Heating mos. 5 COP0.05 Discount Rate 3 stand. dev. Cooling mos. 3 SEER

161000 Original Investment 20 Number Pumps Electric Rate ($/kWh) 0.093 avg. hr/mo. oper.86433.45 Annual Cost (NG/elect) NG Rate ($/MMBTU) 7.5456832.8 Annual Cost (Geowell)

29600.65 Annual Savings

Maintenance Expense Failure StatisticsYear Materials Labor Cash Flows Cumulative NPV Cumulative Failures No. Failed in Period

0 -$ -$ -$ -$ 0 01 -$ 281.52$ 30,118.35$ 28,684.14$ 0 02 -$ 291.37$ 30,929.29$ 56,737.92$ 0 03 -$ 301.57$ 31,762.05$ 84,175.17$ 0 04 -$ 312.13$ 32,617.21$ 111,009.43$ 0 05 -$ 323.05$ 33,495.38$ 137,253.94$ 0 06 -$ 334.36$ 34,397.17$ 162,921.64$ 0 07 -$ 346.06$ 35,323.22$ 188,025.19$ 1 18 1,011.31$ 716.34$ 34,904.70$ 211,650.07$ 2 19 1,046.71$ 741.42$ 35,833.30$ 234,748.53$ 3 1

10 1,083.34$ 767.37$ 36,786.50$ 257,332.25$ 5 211 2,242.51$ 1,191.34$ 36,246.56$ 278,524.87$ 7 212 2,321.00$ 1,233.03$ 37,197.75$ 299,237.96$ 10 313 3,603.35$ 1,701.58$ 36,547.14$ 318,619.69$ 13 314 3,729.47$ 1,761.14$ 37,491.47$ 337,555.43$ 15 215 2,573.34$ 1,367.08$ 40,202.18$ 356,893.37$ 17 216 2,663.40$ 1,414.93$ 41,256.11$ 375,793.27$ 18 117 1,378.31$ 976.30$ 44,203.87$ 395,079.27$ 19 118 1,426.55$ 1,010.47$ 45,378.53$ 413,934.98$ 20 1

Federal Tax IncentivesEPAct 2005 for Commercial Bldgs.

Tax deduction of up to $1.80/sqf for qualifying property (e.g.$144,000 for a 80,000 sqf bldg.)

Split three parts: ⅓ each for envelope, lighting and HVAC

Fully qualifying property must show (in a simulation) 50% energy & power savings over a reference bldg. that meets minimum Standard 90.1-2001

State Rebate ProgramGeothermal GSHP Installations

PA offers only Energy Harvest grant opportunities and Sustainable Development Fund (SDF) loan pool (7-9%) + PECO ($800 installation rebate)

NY: $150-800/ton under LIPA NJ: $370/ton DE: $600/ton capped at $25,000