Heat Recovery at Alaska CenterHeat Recovery at Alaska Center for Energy and Powergy

Chuen-Sen LinChuen Sen LinVamshi K AvadhanulaRoss CoenUniversity of Alaska Fairbanks

Organic Rankine CycleOrganic Rankine Cycle

P ti th h• Power generation through use of an Organic RankineCycle (ORC) unit with heatCycle (ORC) unit with heat recovery from diesel generator.generator.• Laboratory and field tests.• Funded by Denali Commission and Alaska Energy Authority.

ORC TechnologyORC Technology

Project objectives:Project objectives:• To achieve ORC efficiency of 10% and corresponding f ff 3%fuel efficiency by ~3%.

• Reduced fuel consumption• Lower costsLower costs• Reduced greenhouse gas emissions

• To evaluate feasibility, operation / maintenance requirements, and economic impact.

• To develop guidelines for ORC application, particularly in rural Alaska.

Effect of ORC on overall efficiencyEffect of ORC on overall efficiencyStarting engine fuel efficiency (kw-hr/gal) 14.5 14.5 14.5

Gal fuel per 1000 kW hr 68 9655 68 9655 68 9655Gal fuel per 1000 kW-hr 68.9655 68.9655 68.9655

Cost per 1000 kW-hr (at $6.50/gal) $448.28 $448.28 $448.28

ORC efficiency improvement (%) 10 9 5

ORC fuel efficiency improvement (kW-hr/gal) 1.6675 1.50075 0.83375p ( W /g )

Net fuel efficiency (kW-hr/gal) 16.1675 16.00075 15.33375

Gal fuel per 1000 kW-hr 61.8525 62.4971 65.2156

Cost per 1000 kW-hr (at $6.50/gal) $402.04 $406.23 $423.90

Cost savings $46 24 $42 05 $24 38Cost savings $46.24 $42.05 $24.38

Potential cost savingsPotential cost savingsORC efficiency

10 9 5improvement (%) 10 9 5

Cost savings per 1000 kW-hr/gal $46.24 $42.05 $24.38

Hypothetical community with powergeneration = 4 million kW hr

Potential

generation = 4 million kW-hr

Potential annual savings with ORC

$184,960 $168,200 $97,520

ORC

Economic Analysis (payback time)y (p y )ORC unit cost = $128,000 / Fuel efficiency = 14 kw-hr/gal

ORC qualifies as “emerging g gtechnology”…

• ORC technology currently used in large-scale and industrial applications around the world.

• Few data exist on small-scale applications.

• NO data in Alaska.

• Alaska has unique environmental and climatic conditions. Rural villages have unique operating conditions.Rural villages have unique operating conditions.

• There is a need for laboratory / field performance data for optimal application and design improvementoptimal application and design improvement.

Heat Recovery StudyHeat Recovery from Diesel Exhaust for Heating1. Experimental study of feasibility, performance, and economic

analysis. 2. Development of a design and economic analysis computer

program for rural power plant engineers to conduct preliminary design and determine whether applying exhaust heat for heating to any of the village power plants is beneficial.g y g p p(Complete)

Heat Recovery for Power1. Experimental study of feasibility, performance, and economic

analysis.2. Development of a tool to make comments on design, to help

laying out test planlaying out test plan.3. Development of system maps for selecting appropriate diesel

generator and optimizing the system performance (for different engine operating and environmental conditions).

PotentialExhaust Heat energy recovery forExhaust Heat energy recovery for

heating: Heat recovery: 15% fuel energyFuel savings: 15% fuel used by engine

Ai AftWinter season onlyRestricted application (Only for heating)

H t f (f

Friction Radiation

7%

Air After Cooler

7%

Heat energy recovery for power (for generator set average load less than about 1 MW): Engine efficiency improvement: About

Power 38%Liquid jacket water 18%

g e e c e cy p o e e t bout4%Fuel savings: About10% (14.5kW-hr/gallon)M b f th h l

Exhaust 30%

May be for the whole yearFlexibility in application

Other ConsiderationsOther Considerations

• Infrastructure in existing power and heating systems• Infrastructure in existing power and heating systems. • Load patterns in power and heating usages.• Environmental and surrounding conditions (i.e. temperatures,

stream, etc.)., )• Operation loss.• Performance characteristics of individual technologies (e.g.

working fluid, positive pressure cooling).

Research is needed for the development of appropriate methods and tools to assist the selection of best fit technology to optimize the benefit to individual villages.p g

Heat Recovery Unit for Power:General Components in Application

Heat Recovery for Power

Ammonia –water system (VS ORC):Theoretically it is more efficient (Need real life data to

approve it).It can use positive pressure for cooling sideIt can use positive pressure for cooling side.It needs a separator and an absorber.Other factors needs to be considered include:

Heat exchanger design.Ammonia concentration limit (at high ambient temperature).Etc.

Current Projects: Ammonia-Water Cycle

Heat Source: System Performance VS Heat Source Temperatures with Ammonia Concentration X= 0 87Temperatures with Ammonia Concentration X= 0.87

Performance at Different Heat Source Temperatures (X= 0.87)

600 8 6

500

600

W)

8.2

8.4

8.6

300

400

Tur

bine

Pow

er (k

W

7.6

7.8

8

ency

(%)

Source Heat RateTurbine Power

200

Hea

t Sou

rce

(kW

),

7

7.2

7.4

Effic

ie Efficiency

0

100

6.4

6.6

6.8

93.33333 100 121.1111 140 155 170

Heat Source Temperature (C)

Heat Source: Efficiency versus Ammonia Concentration and S T tSource Temperatures

Efficiency versus Ammonia Concetration for Different Heat Source Temperatures

7.50

8.50

6.50

cy (%

) T18 = 200FT18=250FT18=311F

4.50

5.50

Effy

cien

c T18=311F

2.50

3.50

0 6 0 65 0 7 0 75 0 8 0 85 0 9 0 95 10.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1Ammonia Concentration (kg/kg)

Heat Source: Efficiency versus Source Flow Rate and Ammonia ConcentrationConcentration

8.00

6.00

4.00

ycie

ncy

(%)

40GPM80GPM160GPM

0.00

2.00Effy

-2.000.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1

A i C t ti (k /k )Ammonia Concentration (kg/kg)

Heat Sink: Turbine work vs. Pressure ratio for and Ammonia C t ti f li t t f 40oFConcentration for cooling temperature of 40oF

35

X=0.7

25

30

)

X=0.75

X=0.8689

X=0 9

20

25

Wor

k ou

tput

(kW

) X 0.9

15

Turb

ine

W

5

10

1 8 2 2 2 2 4 2 6 2 8 3 3 2 3 41.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4Pressure Ratio

Heat Sink: Coolant flow rate vs. Pressure ratio and Ammonia Concentration for Cooling temperature of 40oFConcentration for Cooling temperature of 40 F

100

80

90 X=0.7

X=0.75

X=0.8689

X=0 9

50

60

70

low

rate

(GPM

)

X=0.9

30

40

50

Coo

lant

Fl

10

20

30

101.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4

Pressure Ratio

Heat Sink: Turbine work vs. Pressure ratio and Ammonia Concentration for cooling temperature of 100oFConcentration for cooling temperature of 100 F

23

25

19

21

23 X=0.7

X=0.75

X=0.8689

X=0.9

15

17

ork

outp

ut (k

W)

9

11

13

Turb

ine

Wo

5

7

9

1.8 2 2.2 2.4 2.6 2.8 3 3.2Pressure Ratio

System MapMajor Components:

Heat source, heat sink, power system.Assumptions and calibration.Assumptions and calibration.

Selected Independent Parameters for Maps:Heating fluid temperature and flow rateHeating fluid temperature and flow rate Cooling fluid temperature System ammonia concentration and turbine

dpressure drop.

Dependent Parameters: pSystem net efficiency, turbine work, input heat rate, cooling flow rate, cooling rate.(More if needed)( )

Design Consideration and Testing (O ti ) C t S l ti(Operation) Components Selection

Heat exchanger sizeHeat exchanger size Ammonia concentrationFluid flow controlsFluid flow controls PumpsCooling device for heat sinkCooling device for heat sink

(e.g. dry cooler, cooling tower, river, ground water)water)

Heat source temperatureScrew expander characteristicsScrew expander characteristics

ORC System - Soon