efficiency, economic and environmental assessment of ground

Abstract� The energy use of a ground-source heat pump

(GSP) for heating, cooling and hot water in a Central Pennsylvania residence (namely, the author�s house) is analyzed, compared to a simulation of electricity and a heating-oil furnace (with electric cooling) for these same energy uses. Energy demands for space conditioning in the house are simulated by building a model of the house using the Transient Energy System Simulation (TNRSYS) tool. Overall, the efficiency gain for the ground-source heat pump compared to electricity is 43% for cooling and 81% for heating. For home heating and hot water, the ground-source heat pump has a 42% efficiency gain over a fuel-oil furnace. The system modeled in this paper has a payback period of between four and five years compared to an all-electric system. The payback period compared to a hybrid system of fuel-oil heat and electric cooling is between two and three years.

Index Terms�Ground-source heat pump, energy efficiency, distributed energy

I. INTRODUCTION eothermal energy is most often associated with steam extracted from subterranean reservoirs for the generation of central-station electricity. Since these steam reservoirs

are generally only found in geologically active areas (around fault lines or active volcanoes), the use of geothermal energy for electric power has naturally been limited. Where moderate geothermal resources are located, the steam has been used for distributed energy applications, such as district heating. A more widespread potential use of geothermal energy is for single-building residential heating and cooling via a ground-source heat pump. This application ties the residence to an electricity source to operate the heat pump, but since the climate-control energy itself comes from the earth, geothermal heat pumps have the potential for significant energy savings [1].

The performance of ground-source heat pumps for residential building applications has been studied in various controlled experiments in Turkey by Arif Hebpasli [2 � 5]. A simulation model developed for a Canadian climate in [6]

Seth Blumsack is with the Department of Energy and Mineral Engineering, The Pennsylvania State University, University Park, PA 18602 (e-mail: [email protected]).

Jeffrey Brownson is with the Department of Energy and Mineral Engineering, The Pennsylvania State University, University Park, PA 18602 (e-mail: [email protected]).

Lucas Witmer is with the Department of Energy and Mineral Engineering, The Pennsylvania State University, University Park, PA 18602 (e-mail: [email protected]).

suggests that ground-source heat pumps are �economically preferable� [6] to conventional energy sources, in the sense of having a higher net present value.

Rather than setting up a laboratory experiment, this paper attempts to estimate the relative efficiency and payback period of a ground-source heat pump used for space conditioning and hot water in an actual Central Pennsylvania single-family residence. This location is of interest for two reasons. First, as discussed in Section III, the region has four distinct seasons, with warm humid summers and relatively cool winters. The system performance discussed here might thus be thought of as �typical� for the Mid-Atlantic U.S., which has a high population density and relatively high residential energy costs. The second point of interest is that the residence discussed in this paper belongs to one of the authors, who is naturally curious whether the ground-source heat pump in his home is merely a curiosity to be discussed at cocktail parties, or represents a sound economic investment.

Three energy-source scenarios are modeled in this paper. The first uses the ground-source heat pump for all space conditioning and most hot water (electric resistance heating provides about 30% of the energy for hot water). The other two scenarios use electricity for all heating and cooling; and a hybrid system of electric cooling and fuel-oil heating. The ground-source heat pump provides a significant efficiency gain over either system. For heating, the ground-source heat pump is 42% more efficient than the fuel-oil furnace and 81% more efficient than electric heat. The efficiency gain over electric cooling is 43%.

II. GROUND-SOURCE HEAT PUMP TECHNOLOGY A ground-source heat pump functions nearly identically to

an air-source heat pump or other heat exchanger, except that it uses the earth as its energy source. In most locations, the frost line extends several feet beneath the surface, meaning that the ground below maintains an essentially constant temperature throughout the year. In Centre County, Pennsylvania, where the house is located, the frost line is estimated to be around 36 inches [7] and the ground temperature beneath the frost line is approximately 55º F.

Most ground-source heat pump applications are closed-loop systems (open-loop and pond systems are discussed in [1]). When called upon to provide space heating, a non-toxic chemical heat exchanger such as glycol is pumped through one or more parallel loops of underground piping (typically polyethylene). The basement furnace captures the heat and

Efficiency, Economic and Environmental Assessment of Ground-Source Heat Pumps in

Central Pennsylvania Seth Blumsack, Jeffrey Brownson and Lucas Witmer

G

Proceedings of the 42nd Hawaii International Conference on System Sciences - 2009

1978-0-7695-3450-3/09 $25.00 © 2009 IEEE

distributes it through the ductwork in the hompurposes, the process is essentially reverseextracted from the home and exchanged into the same piping loop. During the summer used for cooling, most ground-source heasome of the waste heat extracted from tdesuperheater) and use it to heat water. provide water heating in the winter by usinexchanger.2

Figure 1: Ground-source heat pump closed-loop condepicts a horizontal configuration, while panel (bconfiguration. Source: [1]

The piping is either arranged in

configuration, parallel to the plane of the gror in a �vertical� configuration, normal to ground (Figure 1b). The choice of a horizconfiguration is generally driven by the available and the character of the soil. Typicpipe network requires more land and is laidbelow the frost line. In a vertical configuratholes between 50 and 400 feet deep are boroughly five meters apart. A vertical pipe netused for larger buildings (where the land rehorizontal network would be prohibitive) andpoor quality (rocky or clayey) soil. Either crequire sufficient property rights (surface anaccommodate the network of pipes, whicpracticality of ground-source heat pumpsurban areas where land may not be avasubsurface excavation is problematic dunderground civil infrastructures (such asdistribution mains).

III. THE HOUSE AND ITS ENVIR

The residence used as a case study in this square-foot single-family dwelling in Pennsylvania (2,800 square feet above grouwas built in 2004 (it was purchased by the

1 The fact that the ground-source heat pump redistribution throughout the home does limit its applicatiohomes for geothermal heat, for example, may be cost-pro

2 The house analyzed in this paper has an air vcaptures stale air from indoors and brings in fresh air fromanufacturer of the unit, April-Aire, claims that the unitrecovery by capturing 40% of the heat in the stale months, before sending it outside. Since the author has nthese claims, the ventilator system is ignored in the modpaper.

me.1 For cooling ed � warm air is

the earth through when the unit is

at pumps capture the house (via a Many can also

ng a separate heat

figurations. Panel (a)

b) depicts a vertical

a �horizontal� ound (Figure 1a), the plane of the

zontal or vertical amount of land

cally, a horizontal d 12 to 24 inches tion, a number of ored in the earth, twork is generally equirements for a d in locations with configuration does nd subsurface) to

ch may limit the in high-density

ailable, or where due to existing s water and gas

RONS paper is a 3,600-Centre County,

und). The home author in 2007),

equires ductwork for ons. Retrofitting older ohibitive. ventilator system that om the outdoors. The t also assists in energy air during the winter not been able to verify

deling presented in this

and the ground-source heat pump wconstruction. Although the house sitthe rocky quality of the soil necessitpipe configuration for the heat pumpwells located on the property.

The house is framed with 2x6 clapboard siding and shingles, andicynene foam. All windows in thewith low-emissivity coating. Basedthe builder (also the original owner)R-value of 30.3

Centre County is located in tPennsylvania, amongst a series of lovalleys known as the Allegheny PPennsylvania has a fairly humid crugged and heavily forested terrelevations keeps summer high tempextremes seen in nearby cities (sWashington, DC), while the terraaverage rainfall [10].

A 25-year average monthly temp(the largest municipality in Centre Cyear monthly extreme temperatures in Figure 2.

Figure 2: 25-year monthly average tempeSource: National Climactic Data Center.

IV. MODELING THE RELATIVE EFFISOURCE HEAT PUM

For the one-year period June 200run a series of simulations to estimfor space conditioning and water house, under three scenarios:

1. The ground-source heat pum

conditioning and almost alspecifically, we assume thatheat the water to 100 degree

3 From the materials supplied by the bu

whether the R-value of 30 is a �whole-houR-value. The Icynene manufacturer [8] claim2x6 framing has an aggregate R-value of 2space bordering the outdoors is taken up by wR-values (around R-3, according to [9]).

was installed at the time of ts on 11 acres of farmland, tated a vertical closed-loop p. There are four 150-foot

construction, with wood d is insulated with spray e house are double-paned d on materials supplied by ), the home has an overall

he geographic center of ong, steep ridges and broad Plateau. This portion of continental climate. The rain at (relatively) high eratures from reaching the such as Philadelphia and ain contributes to above-

perature for State College County), along with the 25-

(highs and lows) is shown

eratures in State College, PA.

ICIENCY OF THE GROUND-P SYSTEM 07 through May 2008, we

mate the energy consumed heating in the simulated

mp is used for all space ll water heating. More t the heat pump can only es, with electric resistance

uilder, it is not completely clear use� R-value or a �whole-wall� ms that its insulation sprayed into 26. However, much of the wall windows, which have much lower


2

heating required to heat the water degrees. This represents the �basimulations and is similar to the ccurrently exists in the house.

2. Electricity is used for all space conditheating. We will refer to this scenelectric� scenario.

3. Electricity is used for cooling, but afurnace with an efficiency of 85% isheating and hot water. We will refer tthe �oil heat� scenario.

For each of the three scenarios, we assume

temperature setpoint of T* = 74 degrees arounwinter temperature setpoint is assumed to beshown in Figure 3. The figure shows that wheated to 75 degrees during the day in thwhenever heating is required), with short ramdowns in the early morning and evening.4

Figure 3: Winter thermostat set-points in the house. Figure 4 shows electricity use in the hous

of one year, along with the total electric bill kWh plus a $5 monthly fixed distribution chin June 2007. The usage data in the figurhomeowner�s monthly electric bill. The houan oil furnace, nor is there a natural gas disin the area of Pennsylvania where the house i

A. The Demand for Space Conditioning Heat transfer in and out of the home is

entirely conductive. Since the home is fairinfiltration (leakage through seals in doors not likely to be a significant source of heat trmay play a more significant factor in heaicynene insulation is not foil-backed, but is ne

Heat flux in and out of the house is following process [11]:

4 The winter indoor temperature setpoint of 75 de

reader as quite high, perhaps even bordering on profligaoffered by the author is that lower indoor temperatureorchids being grown in the house.

5 The furnace for the ground-source heat pump does electric strip heater as a backup (or supplement, in tweather). The strip heater has not been used since the ahouse.

an additional 25 ase case� set of configuration that

tioning and water nario as the �all-

a modern fuel-oil s used to provide to this scenario as

e a summer indoor nd the clock. The e time-varying, as we keep the house he wintertime (or mp-ups and ramp-

se over the course (at 7.33 cents per harge), beginning re came from the use does not have stribution network is located.5

modeled here as rly well insulated,

and windows) is ransfer. Radiation at loss, since the eglected here. governed by the

egrees may strike the ate. The only defense es would threaten the

have a backup 10 kW the case of very cold author moved into the

,R

MAQ ×=

Figure 4: Monthly electricity usage and total bills. where Q represents heat loss in or represents heat loss per unit timeconductive surface, in square feedifference (indoor temperature lessdegrees Fahrenheit and R is the Rsurface, and takes units of ft2×ºF×[value for Q indicates demand for

from the house), while a negativedemand for cooling (warm air is leak

While the house has 3,600 squarsquare feet are subterranean (theclimate-conditioned. The above-greight-foot ceilings; the ceiling heightabove ground. The outside dimensfeet by 32 feet. The simulation modincorporates the effects of the introoms and walls) as well as the cefirst and second floors, as well as the

B. The Demand for Hot Water When the house is being cooled

warm air from the house and uses it a desuperheater. During the winterprovide hot water in addition to waheat exchanger. Warm water from an insulated holding tank (not conne

(1)

cost from the author�s electricity

out of the home (thus, Qe), A is the area of the et, M is the temperature s outdoor temperature), in R-value of the conductive [time]×BTU-1. A positive heating (heat is escaping

e value for Q indicates a king into the house). e feet of living space, 800 basement) and are not round living spaces have t on the top floor is 20 feet sions of the house are 42 del we build for the house terior layout (location of eiling heights on both the e attic.

d, the heat pump captures to heat water, by means of

r, the heat pump is able to arm air using an auxiliary the heat pump is stored in ected to an electric heater)


3

at a temperature of 100ºF. As hot water is cais transferred from the holding tank to a sttank with electric resistance heating, wher120ºF. Since water enters the systemtemperature of 55ºF, the heat-pump system the necessary energy, while electricity supplie

The water�s temperature change is governe

,)( QTTUATSHm wbasww +−×=×× where m is the mass of water (lb), SHw is thwater (BTU×ºF-1×hr-1), Tw is the temperaturthe tank (ºF), Tbas is the ambient temperature(set at 67 ºF year-round), UA is an insulationhow quickly the water in the tank cools (anvalue for house insulation), and Q is the heatto the tank (BTU). The hot water heaterassumed to have a UA factor of 2.5.

Figure 5: Average hourly hot water usage for an Ame[14]

In this paper we assume that hot water usasimilar to that of a typical American family Figure 5. We do not differentiate betweendifferent applications (such as showering andeach of which may require water that is �mhot.� I assume that all hot water use repre120-degree water.

C. Simulation Procedure and System InformaThe simulations in this paper are run o

scales for the period June 1, 2007 to May 3each hour, the heat loss in the home (that iheating or cooling required for that hour) is cmodel of the house built with a simulatioTransient Energy Systems Simulation tTRNSYS is a modular tool built in FORTRAmeasured in units of BTU per hour. difference M is given by:

)()()( tTtTtM appset −= ,

6 More information on TRNSYS is available at www

alled for, the water tandard hot-water re it is heated to

m at the ground supplies 70% of

es the remainder. ed by [11 � 13]:

(2)

he specific heat of re of the water in e in the basement n factor governing nalogous to the R-t energy provided r in the house is

erican family. Source:

age in the house is [14], as shown in n water used for

d washing dishes), more hot� or �less esents demand for

ation over hourly time 31, 2008. During is, the amount of calculated using a n tool called the tool (TRNSYS). AN.6 Heat loss is The temperature

(3)

w.trnsys.com.

Where Tset is the thermostat setpoiabove and shown in Figure 3, and Ttemperature in State College, PA at National Climactic Data Center.

Total energy demanded in each hothe energy required for space conditenergy required for hot water. The has an hourly capacity of 42.1 MBMBTU for heating. During somedemanded may exceed the capacity pump. In this case, the simulations rto be met in the following hour. Ienergy demand Qtot(t) in hour t is wr

(

[ −−+

=

if)1(

(),(max

if(),(max

)(max

max

Q

tQQtQ

QQtQ

tQ

tot

tot

air

tot

air

tot

where Qair is the hourly enerconditioning, Qw is the hourly enerand Qmax is the hourly energy outpsystem.

The heating season is assumedthrough May each year, while the cto run from June through Octobercooling is demanded during the heatis demanded during the cooling seas

The ground-source heat pump syGSUJ-042 with an EER rating of 18of 5.3. The cost of the system,assumed to be $12,000. The all-electric heating and cooling with anaverage rating for Energy Star air cof $6,000. The oil furnace systeheating efficiency of 85% (coolingthe all-electric scenario) and a total c

Figure 6: Heat rate curve for fossil generators

int at time t, as discussed Tapp is the apparent outdoor

time t, as recorded by the

our (in BTU) is the sum of tioning plus the sum of the

ground-source heat pump BTU for cooling and 29.8 e hours, the total energy of the ground-source heat

require this excess demand n equation form, the total

ritten:

)

]−>−

−−+

−≤−+

)1()1()1(

)()(

)1()1()()(

max

max

max

tQt

tQtQt

tQttQt

w

w

, (4)

rgy demand for space rgy demand for hot water put capacity of the energy

d to run from November cooling season is assumed r. In the simulations, no ting season, and no heating on. ystem modeled is a Trane and a corresponding COP including installation is

-electric scenario assumes n EER rating of 10.3 (the onditioners) at a total cost m is assumed to have a

g efficiency is identical to cost of $5,000.

s in the PJM system.


4

Since all three systems rely on the electdegree, the total system efficiency will be iefficiency with which electricity is generatedpower plants. We assume that all electricity fpurchased from plants in the PJM system, anefficiency of the generating plants in PJMdata on average heat rates for fossil generatiorate curve for PJM is shown in Figure 6.

We measure the generation efficiency forequired by each home energy system in twoway is to simply use an average heat rageneration in the PJM system. This simple a12,335 BTU/kWh. The second method economic dispatch curve for PJM, and determof the marginal generator dispatched in eacmethod described in [16]. Particularly oveyear, whether the efficiency of the PJM syson an average or marginal basis does not masimulation results.

V. SIMULATION RESULTS AND DISC

This section contains the results of the hsimulations. The ground-source heat pcompared to the all-electric system and thesystem (with electric cooling) in terms of relative efficiency and cost.

A. Energy Use and Relative Efficiency This section contains the results of the h

simulations. The ground-source heat pcompared to the all-electric system and thesystem (with electric cooling) in terms of relative efficiency and cost.

Figure 7: Cumulative energy use distribution curves for tsystems over the course of one year. GSP denotes thpump system. The horizontal axis stops at 6,000 hounumber of hours where energy demand is close to zero.

Figure 7 shows a cumulative distributhourly energy use in each of the three simwhile Figure 8 shows a cumulative distributhe hourly differences in total energy uefficiency for power purchased from the calculated using the �average heat rate� mefigure demonstrates that the all-electric syst

tric grid to some influenced by the

d at central-station for each system is

nd we measure the M using published

on [15]. The heat

or the grid power o ways. The first ate for all fossil

average is equal to is to build an

mine the heat rate ch hour using the er the course of a stem is calculated aterially affect the

CUSSION hourly energy-use pump system is e fuel-oil heating total energy use,

hourly energy-use pump system is e fuel-oil heating total energy use,

the three home energy

he ground-source heat urs because of a large

tion function for mulated systems, ution function for use. Generation

PJM system is ethodology. The tem is by far the

least energy-efficient. The energy-iheating, relative to fuel oil, is the poverall inefficiency of the electric ssource heat pump. For heating ansource heat pump is 42% more esystem and 81% more efficient tsystem. For cooling, the ground-smore efficient than the electric coothe all-electric and fuel-oil scenarios

Figure 8: Cumulative distribution curves for tground-source heat pump (GSP) energy useelectric and oil-heat systems. The horizontal of a large number of hours where energy dem

B. Economics of Ground-Source HeFor each hour, the cost of primary

three systems was calculated. Thewas $4 per gallon. The total cost ofour different components: gdistribution and ancillary servicdisaggregated based on informationbill from Allegheny Power, and smonthly bill also includes taxes charge, which are neglected in this a

TABLE 1: LINE ITEMS FROM THE AUTHOR

We calculate the total cost of ele

conditioning and hot water under tThe first assumption is that the genebased on the cost of service.7 The stime pricing: the generation charge the locational marginal price (LMP

7 This is the assumption reflected in tAllegheny Power will not transition out oJanuary 1, 2011.

intensive nature of electric primary contributor to the system versus the ground-nd hot water, the ground-efficient than the fuel-oil than the electric heating source heat pump is 43% oling system (used in both s).

the hourly difference between the e and the energy use of the all-axis stops at 6,000 hours because

mand is close to zero.

eat Pumps y energy to run each of the e assumed cost of fuel oil of electricity is the sum of generation, transmission, ces. These costs are n in the author�s monthly shown in Table 1. The and a fixed distribution

analysis.

R�S MONTHLY ELECTRIC BILL

ectricity required for space two different assumptions. eration charge is regulated, second assumption is real-for each hour is equal to

P) in the Allegheny Power

the charges shown in Table 1. of regulated retail pricing until


5

Zone of PJM.8 The transmission, distributservices costs are identical under both assump

The total annual primary energy cost for escenario is shown in Table 2. The annual cosource heat pump are lower than the all-elroughly a factor of six, and are lower than thby more than a factor of nine. Note that eveheat system is more efficient than the all-eleFigures 7 and 8), the consumer costs of the onearly 50% higher than the all-electric system

TABLE 2: ANNUAL COSTS OF EACH HOME ENER

To calculate whether the lower energy co

source heat pump system are worthwhile, present discounted value of the costs of eacperiod of ten years, assuming that energy cosusage remain constant in each year. The casystem was assumed to be incurred in year not discounted), while the energy costs of ediscounted annually, with a discount rate of 5

Figure 9: Present discounted cost of each home energy flat regulated generation charge from Table 1. GSPsource heat pump system. Crossover points denote the ground-source heat pump system and other systems.

The cumulative present discounted costs o

shown in Figure 9, assuming a flat disgeneration rate, and in Figure 10, assuming The intersection of the discounted cost curv

8 As discussed in [16], under real-time pricing

significantly higher bills during periods of peak usarespond in some way to these higher bills. In this aneffects of a nonzero price elasticity of demand and assuremains unchanged.

9 PJM currently uses market-based pricing for somWe are thus assuming that the charges for ancillary setheir current levels.

tion and ancillary ptions.9 each home energy sts of the ground-lectric system by he oil-heat system en though the oil-ectric system (see il-heat system are

m.

RGY SYSTEM

sts of the ground-I calculated the

ch system over a sts and our hourly apital cost of each

zero (and thus is each system were 5%.

system, assuming the denotes the ground-payback period of the

of each system are scounted electric real-time pricing.

ve for the ground-

consumers will see age and are likely to alysis, we neglect the ume that energy usage

me ancillary services. ervices will remain at

source heat pump (denoted GSP) witwo systems determines the paybasource heat pump. Under flat-generation, the ground-source heat pits second year of operation, compaThe payback period relative to thbetween three and four years. SincZone of PJM are, on average, highergeneration rate, the payback periodselectricity are slightly shorter, as sho

Figure 10: Present discounted cost of each real-time pricing of electricity. GSP denotesystem. Crossover points denote the paybaheat pump system and other systems.

VI. ENVIRONMENTA

Our simulation results in Sectioground-source heat pump system rinput energy than either the all-elecsystem of fuel-oil heating and electresults of our energy-use simulatioemissions reductions associated witpump system relative to the other tw

We focus on emissions of carbdioxide (SO2), and the various oxidalso investigated the potential for rebut the magnitudes of mercury involare so small that any comparison oenlightening. Average annual emelectricity system (in pounds of generation) are taken from [15]. emissions factor for each pollutant fweighted by generator size and capaaverage emissions rates used in this 2.21 lbs/MWh of NOx, 8.51 lbs/Mlbs/MWh of CO2.10

Burning fuel oil also results in Cour analysis we use figures from lbs/MMBTU of CO2 and 0.376 lbs/M

Using these figures, we calculfootprint of the home under each ofThe results are summarized in Tab

10 We calculate an average emission rate

the level of a single household, the mercury fomit mercury from our emissions analysis.

ith the curves for the other ack point for the ground--rate pricing of electric pump pays for itself during ared to the oil-heat system. he electric heat system is ce LMPs in the Allegheny r than my current regulated under real-time pricing of

own in Figure 10.

home energy system, assuming

es the ground-source heat pump ack period of the ground-source

AL IMPACTS on V demonstrate that the requires significantly less ctric system or the hybrid ric cooling. Based on the ons, we can estimate the th the ground-source heat

wo systems. bon dioxide (CO2), sulfur es of nitrogen (NOx). We

educed mercury emissions, lved for a single household of energy systems was not

missions data for the PJM pollutant per MWh of

We calculate an average for the whole PJM system, acity factor. The resulting portion of the analysis are

MWh of SO2 and 1,256.08

O2 and NOx emissions. In the U.S. EPA of 161.44

MMBTU of NOx. [17] late the hourly emissions f the three energy systems. le 3, which shows annual

of 0.04 lb/GWh for mercury. At footprint will be so small that we


6

emissions of CO2, SO2 and NOx from enerconditioning and hot water in the house. Ndoes not include energy use for other plighting, nor does it include the emisstransportation, since we assume that these enremain constant, no matter what system waconditioning and hot water.

TABLE 3: EMISSIONS IMPACTS FROM EACH ENERGY S

CONDITIONING AND HOT WATER (SHORT TO

The GSP system reduces CO2 emissions b

compared to the hybrid system of heatingpower, and by a factor of five compared tsystem. Emissions of SO2 and NOx are remagnitudes, though the total emissions of thefrom household energy use are orders of mthan CO2. In the event that the U.S. begins toprice carbon dioxide emissions at the consumsystem would offer additional savings.

VII. CONCLUSIONS AND FUTURE WDespite up-front capital costs that are m

those of oil-heat or all-electric home eneground-source heat pump appears to have binvestment. Using a detailed simulation mofor climate control and hot water in a Censingle-family home, we found that the grpump has yielded significantly lower cefficiencies. Emissions related to space condwater heating in the home are reduced signifto the fuel-oil or all-electric systems.

Particularly for suburban and rural areaheat pumps have the potential to lower both energy costs for homeowners and small comm(whether these systems are appropriate for laan interesting question, but beyond the scopUsage of these systems also lowers stresstransmission and distribution infrastructures, the risk of localized or widespread interruptions. Ground-source heat pumps arsilver bullet. The land requirements, even fwith vertical closed-loop configurations, mayhigh-density urban areas. In addition, the syrequires either new construction or existingcost-effective. The costs of retrofitting (particularly older homes) will affect thground-source heat pumps and likely varieslocation.

VIII. ACKNOWLEDGMENT The authors thank David Riley and Jeff

comments and suggestions, and Erin Whitin

rgy use for space Note that Table 3 purposes such as ions impacts of nergy uses would as used for space

SYSTEM FOR SPACE ONS/YEAR)

by more than half g oil and electric to the all-electric

educed by similar ese two pollutants

magnitude smaller o tax or otherwise

mer level, the GSP

WORK more than double ergy systems, the been a fairly good del of energy use

ntral Pennsylvania ound-source heat

costs and higher ditioning and hot-ficantly compared

as, ground-source average and peak

mercial customers arger customers is pe of this paper). s on the electric which may lower electric service

re not, however, a for small systems y be prohibitive in ystem as modeled g ductwork to be

existing homes he economics of widely based on

f Rayl for helpful ng for allowing us

to publicize the fact that she heats tthe wintertime.

IX. REFEREN

[1] U.S. Department of Energy, Office of EEnergy, �Buyer�s Guide to http://www.eere.energy.gov/consumer/yg/index.cfm?mytopic=12640

[2] A. Hepbasli, O. Akdemir, and E. Hancioof a Closed Loop Vertical Ground SouConversion and Management 44:4, pp.

[3] A. Hepbasli and O. Akdemir, 2004. �EGround Source Heat Pump,� Energy Copp. 737 � 753.

[4] O. Ozgener and A. Hepbasli, 2004Analysis of a Solar-Assisted Ground-Heating System,� Energy and Buildings

[5] O. Ozgener and A. Hepbasli, 2005. Solar Assisted Ground-Source HeEngineering 25:10, pp. 1459 � 1471.

[6] P. F. Healy and V. I. Ugursal, 1998Feasibility of Ground-Source Heat International Journal of Energy Researc

[7] Northeast Regional Climate Center, Extremes for the Northeastern United St

[8] Icynene Corporation product http://www.icynene.com/assets/documeulas.pdf.

[9] U.S. Department of Energy, Office of EEnergy, �The R-Valuewww.eere.energy.gov/consumer/your_hcfm/mytopic=11340

[10] National Climactic Data Center, �PeAvailable at climate.psu.edu/data/ncdc_

[11] D. Q. Kern, 1990. Process Heat Transf[12] N. P. Chopey, 1994. Handbook of Che

McGraw-Hill. [13] C. H. K. Goh and J. Apt, 2004. �Con

Electric Water Heaters Under DynamElectricity Industry Center working pap

[14] ASHRAE, 1995. ASHRAE HandbookConditioning, Typical Residential Fami45.10.

[15] Environmental Protection Agency, EmIntegrated Database (eGhttp://www.epa.gov/solar/egrid/index.ht

[16] A. Newcomer, S. Blumsack, J. Apt, L2008. �The Short Run Economic aCarbon Tax on U.S. Electric GeneratioTechnology 42:9, pp. 3139 � 3144.

[17] U.S. Environmental Protection AgencyInventory,� available http://epa.gov/climatechange/emissions/

X. BIOGRAPH

Seth Blumsack is Assistant Professor of EnThe Pennsylvania State University, Universitdegree in Economics from Carnegie MellEngineering and Public Policy from Carneinterests are regulation and deregulation of planning and pricing, and complex networenergy and electric power.

Jeffrey Brownson is Assistant Professor of at The Pennsylvania State University, UnivPh.D. from The University of Wisconsin in 2the areas of inorganic materials for advanced

Lucas Witmer is a MS student in Energy Pennsylvania State University, University Par

the house to 75 degrees in

NCES Energy Efficiency and Renewable

Geothermal Heat Pumps,� your_home/space_heating_coolin

oglu, 2003. �Experimental Study urce Heat Pump System,� Energy 527 � 548. Energy and Exergy Analysis of a onversion and Management 45:5,

4. �Experimental Performance -Source Heat Pump Greenhouse s 37:1, pp. 101 � 110. �Exergoeconomic Analysis of a at Pump,� Applied Thermal

. �Performance and Economic Pumps in a Cold Climate,�

ch, 21:10, pp. 857 � 870. Atlas of Soil Freezing Depth

tates. specifications, available at nts/PDFs/Spray_and_Pour_Form

Energy Efficiency and Renewable e of Insulation,� home/insulation_airsealing/index.

ennsylvania Climate Narrative.� _pa.pdf. fer, McGraw-Hill. emical Engineering Calculations,

nsumer Strategies for Controlling mic Pricing,� Carnegie Mellon er CEIC-04-02. k: Heating, Ventilating and Air ily�s Hourly Hot Water Use, at p.

missions & Generation Resource RID), available at tm. L. B. Lave and M. G. Morgan,

and Environmental Effects of a on,� Environmental Science and

y, 2008. �U.S. Greenhouse Gas online at

/usinventoryreport.html.

HIES

ergy and Mineral Engineering at ty Park PA. He received the M.S. lon in 2003 and the Ph.D. in gie Mellon in 2006. His main network industries, transmission rks and systems, especially for

Energy and Mineral Engineering ersity Park PA. He received his 006. His research interests are in photovoltaics.

and Mineral Engineering at The rk PA.


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efficiency, economic and environmental assessment of ground

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