ms thesis: investigating the technical and commercial merits of zinc-air fuel cells for passenger...

INVESTIGATING THE TECHNICAL AND COMMERCIAL MERITS OF ZINC-AIR FUEL CELLS FOR PASSENGER ELECTRIC VEHICLES

by Denis Vasilescu

October 28th 2010Masters Degree of Science in Mechanical & Aerospace Engineering

Illinois Institute of Technology

Motivation

Tesla Roadster288 horsepower245 mile range6 hour @220/240 V 40A$109,000 MSRP

Nissan Leaf107 horsepower90 miles/hour100 mile range8 hr @220/240 V 40A

Motivation

Chevrolet Volt150 horsepower80 hp engine50 mile range4 hr @220/240 V

Coulomb Technologies IncCT2100 ChargePoint: 208/240V 30ACT3000 ChargePoint: 500V 125A

Motivation

Faster, more powerful charge stations?More lithium batteries per car?Change driver habits and routines?

“If I had asked people what they wanted, they would have said faster horses”

-Henry Ford

Outline

Literature Review Technical Concept Economic Analyses Sustainability Experiments Summary

Literature ReviewNet chemistry: the oxidation of zinc

Claim to fame: high energy density due to half the reactants available in air

Killer app: button batteries for hearing aids, watches, and calculators

Literature Review: Mechanically Rechargeable Batteries

Developed for military electronics in the 1960s

Research for vehicle propulsion in the 1970s


Commercialized in 1980s by Electric Fuel Ltd of Israel for fleet vehicles

Zinc cassettes swapped at depot in Germany, reprocessed at plant in Israel

First to implement a zinc cycle

Battery swap scheme now in use by A Better Place using lithium

Literature Review: Shell-and-Tube Slurry Fuel Cells

Developed in the 1970s by French General Electric Company (CGE)

Literature Review: Shell-and-Tube Slurry Fuel Cells

Fuel in granulated/particulate form

Constant mass of zinc within the control volume

Literature Review: Packed Bed Tapered Fuel Cell

Developed in the 1990s through 2000s at Lawrence Livermore National Lab

Planar geometry like the mechanically-rechargeable batteries

Continuous feed of particulate zinc like the shell-and-tube fuel cell

Used a taper for gradual feed of zinc


Developed six generations of design

Demonstrated on a tour bus, achieved 300 mile range

IP and personnel handed over to Power Air Corp for commercialization in 2004

Literature Review: Legacy

LLNL design by far the most researched and developed, but many questions still open-ended

How to improve power density? How to control the flows? How to manufacture? How to make the design robust? How will it be refueled? How will the oxide be reprocessed? How much will it cost? How sustainable is the whole system? Etc

Literature Review: Thesis Contributions

Design and analyze the aspects of a holistic system using centralized reprocessing

-Technologies and mechanisms-Cost analyses-Toxins and emissions

Design and analyze a control system for the fuel cell systems

-Analytically frame the problem-Experimentally probe the physics

Technical Concept: The Electrochemistry

Most ideal specific energy is the Gibbs free energy of zinc oxide, 1352 Wh/kg

Ideal efficiency, ε = ΔG/ ΔH = 91.4%. 80-90% for Li-ion and 55-80% NiMH

Practical specific energies depend on packaging and controls

Observed ZAFCs: 110-330 Wh/gObserved Li-ion: 160-190 Wh/gObserved NiMH: 70-80 Wh/kg


Zinc, immersed in alkaline electrolyte, undergoes intermediary reactions

Zinc hydroxide formation

Decomp. (I)

Decomposition (II)

Technical Concept: Fuel Cell Architecture

Three feeds: zinc, air, and electrolyte

Observe that high flow rates aid in chemical rates, but also convect heat away

Geometry is not all together homogenous

Technical Concept: Fuel Cell Architecture

Technical Concept: Fluids Management System

Determine optimal values of electrolyte flow rate and air flow rate experimentally rather than analytically


Air convected in between cells using fan

Cathode characteristicslimit power


Fuel and waste storage system

Technical Concept: Refueling Scheme

Centralized Reprocessing: Pump in zinc metal fuel at a gas station

Pump out zinc oxide waste

Zinc oxide shipped from station to rail depot to freight car to depot to reprocessing plant

Reprocessing plant uses renewable energy


Solar Generation

Rail DepotRail Depot

Service Station

Plant


Existing gas stations to be retrofit for ZAFCs by converting two underground tanks and associated pumps and meters

If metering keeps atomic flow rates equal, customer is only charged the price of electricity and shipping

Economic Analyses: Capital Costs for EV

Onboard systems: Fuel Cell

Multiple cells (12)Cathode

Fluids Management System2 pumps, air fan, hydrocyclone, storage tank

Power Electronics & DriveDC motor, controller, pedal assembly

Secondary Battery PackNiMH pack for peak powerCharger, mating electronics

Zinc & Electrolyte


How much zinc to carry depends on fuel economy. Use EPA highway and city dynamometer tests


City fuel economy summary

Total Secondary Energy Spent (Wh) 4169.536

Estimated ZAFC Energy Expenditure (Wh) 5486.232

Zinc Required for Test (kg) 4.058

Miles Driven (mi) 10.257

Zinc Required for 300 mi (kg) 118.689

Energy Required for 300 mi (Wh) 160467.847

Energy Required for 300 mi (J) 577684247.439

Energy Density of Gasoline (MJ/kg) 44.400

Mass of Gasoline Equivalent (kg) 13.011

Density of Gasoline (kg/m^3) 719.700

Volume of Gasoline Equivalent (m^3) 0.018

Volume of Gasoline Equivalent (gal) 4.776

MPG equivalent (mpg) 62.817

Total Secondary Energy Spent (Wh) 2186.584

Estimated ZAFC Energy Expenditure (Wh) 2877.084

Zinc Required for Test (kg) 2.128

Miles Driven (mi) 7.450

Zinc Required for 300 mi (kg) 85.688

Energy Required for 300 mi (Wh) 115849.693

Energy Required for 300 mi (J) 417058896.588

Energy Density of Gasoline (MJ/kg) 44.400

Mass of Gasoline Equivalent (kg) 9.393

Density of Gasoline (kg/m^3) 719.700

Volume of Gasoline Equivalent (m^3) 0.013

Volume of Gasoline Equivalent (gal) 3.448

MPG equivalent (mpg) 87.010

Highway fuel economy summary

Full tank = 160kWh, 119 kg ZnFuel economy = 87 MPGe city, 63 MPGe highway

Economic Analyses: Capital Costs for EVEV capital cost summary

Subsystem ItemMaterial Cost Rate

AmountLabor Cost Rate

Time Quantity Total Cost

12-Celled Zinc-Air Fuel Cell

Glass-filled Nylon Channel Plate

$0.56 /g 93 g$100.0

0/hr 1 hr 12 $1,824.96

1/4" Acrylic Front Plate $0.21 /in^2 72 in^2 $60.00 /hr 1 hr 12 $901.44

1/4" Acrylic Back Plate $0.21 /in^2 72 in^2 $60.00 /hr 1 hr 12 $901.44

Cobalt Based Catalyzed Carbon Air Cathode

$0.05 /cm^2 151 cm^2 12 $90.78

Copper Anode Current Collector

$0.54 /in^2 23.5 in^2 12 $152.77

RTV Silicone Sealant $1.60 /oz 1 oz 12 $19.20

Fluid Management System

Zinc Peristaltic Pump $242.35 1 1 $242.35

Electrolyte Centrifugal Pump $314.48 1 1 $314.48

Air Fan $28.99 1 1 $28.99

Hydrocyclone $0.00 1 1 $0.00

PVC Tubing $10.95 /ft 12 ft 1 $131.40

Power Electronics

DC Brush Motor$1,775.0

01 1 $1,775.00

Motor Controller$1,850.0

01 1 $1,850.00

Hall Effect Accelerator Pedal $140.00 1 1 $140.00

Dashboard Display Module $260.00 1 1 $260.00

Secondary Battery SystemLead-Acid Battery $26.95 1 16 $431.20

Charge Pump 1 1 $0.00

Fuel Supply

Zinc Pellets $1.03 /lb 262 lb 1 $270.22

Potasium Hydroxide $27.90 /kg 7.12 kg 1 $198.62

Water $0.01 /gal 3.81 gal 1 $0.02

Total $9,532.87

Economic Analyses: Capital Costs for Station

Summary of capital costs to station owner

Subsystem Item Material Cost Rate Amount Labor Cost Rate Time Quantity Total Cost

Underground Tank Retrofit

Underground Tank Corrosion Lining

$0.04 /ft^2 483.00 ft^2 1 $17.88

6" Diameter 20' Auger $3,250.00 1.00 1 $3,250.00

Nozzle-and-Metering Unit

Fuel/Waste Metering Peristaltic Pump

$242.35 2.00 1 $484.70

Pumping Nozzle $116.67 2.00 1 $233.34

Lost Revenue Gasoline $3.00 /gal 1428.57 gal 1 $4,285.71

Installation Skilled professional $100.00 /hr 24 hr 5 $12,000.00

Total $20,271.63

Economic Analyses: EV Maintenance Costs

Cathode seals may wear out, need replacement

Electrolyte must be topped off if hydrocyclone isn’t 100% efficient

Maintenance Event Time Between EventsExpected Number of Events per Year

Cost Per Event Yearly Cost

Cathode Replacement 12000 hr 0.73 $90.78 $66.27

Secondary Battery Replacement 5 years 0.20 $431.20 $86.24

Electrolyte Top Off (99% Efficient) 300 miles 33.33 $1.99 $66.33

Total $218.84

Secondary batteries will wear out

Economic Analyses: Cost to Reprocess Zinc

Set up daily cash flow charts for the station and the plant

Service Station Cash Flow: Day 1

Item Value Unit

Volume of Oxide Tank 5000 gallons

Volume of Zinc Oxide 14.01359441 m^3

Mass of Oxide 78560.21026 kg

Mass of Zinc 63114.6049 kg

Freight Cars for Shipping 4

Number of Barrels per Car 50

Volume per Barrel 0.070067972 m^3

Mass per Barrel 392.8010513 kg

Shipping Rate to Chicago $119.08 /barrel

Distance to Chicago 45.7 miles

Shipping Cost to Chicago -$23,816.00

Account Balance -$23,816.00

Zinc Plant Cash Flow: Day 2

Item Value Unit

Mass of Zinc to be Produced 63114.6049 kg

Energy Required to Produce 29786.57881 kWh

Cost to Produce using Coal -$2,382.93

Cost to Produce using Solar -$10,127.44

Market Value of Zinc $143,318.20

Credit to Station for Oxide using Coal -$117,896.98

Credit to Station for Oxide using Solar -$109,378.02

Account Balance using Coal -$117,896.98

Account Balance using Solar -$109,378.02

Look at solar energy versus coal



Item Value Unit

Plant Credit from Coal $117,896.98

Plant Credit from Solar $109,378.02

Account Balance using Coal $94,080.98

Account Balance using Solar $85,562.02


Item Value Unit

Mass of Zinc Sold 63114.6049 kg

Volume of Zinc Sold 8.839580518 m^3

Freight Cars for Shipping 4

Number of Barrels per Car 50

Volume per Barrel 0.044197903 m^3

Mass per Barrel 315.5730245 kg

Shipping Rate to Joliet $114.00 /barrel

Distance to Joliet 45.7 miles

Shipping Cost to Joliet -$22,800.00




Item Value Unit

Debit to Plant for Zinc -$143,318.20





Item Value Unit

Credit from Station $143,318.20

Account Balance using Coal $2,621.22

Account Balance using Solar $11,140.18Service Station Cash Flow: Day 6

Item Value Unit

Mass of Zinc Obtained 63114.60 kg

Zinc Usage per EV 118.69 kg

Break-Even Cost per EV using Coal -$92.59

Break-Even Cost per EV using Solar -$108.61

Resale Profit 10.00 %

EV Tank Refill Price using Coal $101.85

EV Tank Refill Price using Solar $119.47

Refueling Cost per Exchanged Zinc using Coal $0.86 /kg

Refueling Cost per Exchanged Zinc using Solar $1.01 /kg

The rail shipping costs dominate the final price to the customer

Cost of solar versus coal close to each other

Total cost to fill up tank with reprocessed zinc = $102/$119

Competitive at $10/gal

Economic Analyses: Ownership Cost Comparison

Compare the costs of owning a conventional pick-up, a conventional economy car, a hybrid, or a ZAFC EV

Vehicle MSRP RebateFederal Tax Credit

City MPG

Hwy MPG

Avg MPG

Fuel Consumption per Year

Annual Fuel Cost

Annual Maintenance Cost

Cost Over Entire Ownership

Savings Over Entire Ownership

2004 Chevrolet S-10 $24,660 $0 $0 17.0 23.0 20.0 435 gal $1,521.74 $0.00 $44,905.69 $0.00

2008 Honda Civic $17,760 $0 $0 25.0 36.0 30.5 278 gal $972.22 $0.00 $31,016.63 $13,889.06

2008 Toyota Prius $22,875 $0 $0 48.0 45.0 46.5 222 gal $777.78 $0.00 $34,871.71 $10,033.98

ZAFC Powered S-10 $32,967 $0 $7,500 87.0 62.8 74.9 3966.7 kg $2,380.00 $218.84 $57,370.70 ($12,465.01)

ZAFC Powered Civic $26,067 $0 $7,500 87.0 62.8 74.9 3966.7 kg $2,380.00 $218.84 $49,362.97 ($4,457.28)

At $3.50/gallon gasoline, $0.60/kg zinc, 10 year ownership, 10,000 miles driven per year, i = 1.5%

ZAFC EV not cost competitive at all

Economic Analyses: Ownership Cost Comparison

If everything stays the same except shipping rates go down by 10x, cost of refueling by solar is $0.28/kg zinc

ZAFC EV is cost competitive at $3.50/gallon

Vehicle MSRP RebateFederal Tax Credit

City MPG

Hwy MPG

Avg MPG

Fuel Consumption per Year

Annual Fuel Cost

Annual Maintenance Cost

Cost Over Entire Ownership

Savings Over Entire Ownership

2004 Chevrolet S-10 $24,660 $0 $0 17.0 23.0 20.0 435 gal $1,521.74 $0.00 $44,905.69 $0.00

2008 Honda Civic $17,760 $0 $0 25.0 36.0 30.5 278 gal $972.22 $0.00 $31,016.63 $13,889.06

2008 Toyota Prius $22,875 $0 $0 48.0 45.0 46.5 222 gal $777.78 $0.00 $34,871.71 $10,033.98

ZAFC Powered S-10 $32,967 $0 $7,500 87.0 62.8 74.9 3966.7 kg $1,110.67 $218.84 $43,785.38 $1,120.31

ZAFC Powered Civic $26,067 $0 $7,500 87.0 62.8 74.9 3966.7 kg $1,110.67 $218.84 $35,777.65 $9,128.04

Sustainability: Safety

Zinc is a mild irritant, partially flammable, dust can cause nausea

Zinc oxide is a mild irritant, not flammable

Potassium hydroxide is a harsh irritant to skin in high molarity and poses the risk of burns

Sustainability: Availability Zinc is plentiful around the world, including the United

States

United States produces 150,000 metric tons of surplus zinc ore each year

Zinc consumption down since 2009 in all countries except China and India

Sustainability: Availability

London Metals Exchange highest 2009 price = 94¢/lb

US yearly surplus of ore, if refined based on zinc content, can produce enough zinc for 1,206,000 ZAFC EVs

Total hybrid and EV sales by 2014 expected to be 1.5 million vehicles; surplus can allocate to compete with that

In order to produce 600 million ZAFC Evs (replacing the global automobile fleet), 75 million metric tons are needed, or 37.5% of known world zinc reserves

Sustainability: Availability Lithium not as plentiful or evenly distributed; vast majority in

Bolivia, Chile, and Argentina. No US surplus, net importer

Total yearly US lithium consumption can only produce 800,000 Tesla Roadsters. Depleting total US reserves can only build 9 million Roadsters

Zinc: abundant, evenly distributed, surplus Lithium: rare, single source, material deficit

Sustainability: Emissions

Electric vehicle itself has zero emissions

There are emissions associated with refining the surplus ore into zinc metal for the vehicles, the manufacture of the vehicles themselves, and the logistics of reprocessing zinc oxide back into zinc metal

Determine emissions of these subsystems of the zinc economy using Economic Input-Output Life Cycle Assessment (EIOLCA), a mathematical model using real price and cost information from the US economy in previous years across multiple industries

Essentially a set of operations on very large matrices of industrial data and their interdependencies, with economic activity ($) as the input


Refining the US surplus of zinc ore into zinc metal for ZAFC EVs-150,000 tonnes @ $0.94/lb = $63,955,500 economic activity

Manufacturing 603,000 ZAFC EVs-Half the processed surplus for vehicle supply, half for station supply-603,000 * MSRP of $22,875 = $13 billion in activity

SectorTotal (T CO2 Equivalent)

CO2 Fossil (T CO2 Equivalent)

CO2 Process (T CO2 Equivalent)

CH4 (T CO2 Equivalent)

N2O(T CO2 Equivalent)

HFC/PFCs (T CO2 Equivalent)

Total for all sectors 68200.0 51000.0 8060.0 3240.0 429.0 5480.0









The logistics of moving material in between reprocessing plants and service stations

- The cost to the station owner amounts to $108.61 per tank-$65,491,830

Total carbon dioxide equivalent is 7.905 megatonnes, or 13 tonnes per vehicle including their manufacture, but 240 kg per vehicle without









In comparison, the US automobile fleet (~200 million cars) produced 3,277 megatonnes of CO2 or 16.4 tonnes per vehicle if manufacturing is considered

Without manufacturing, US autos produced 0.819 megatonnes or 8.9 tonnes per vehicle

ZAFCs are slightly cleaner, but not much due to unsustainable manufacturing

Experiments

Implement a test version of the control system

Design experiments that vary the flow rates and measure specific energy indirectly through voltage measurements

Determine characteristics if not the actual optimum values

“Re-invent the wheel” for LLNL design

Experiments: Prelab Activities

Experiments: Optimization Trails

Experiments varying electrolyte flow rate versus voltage were mired by leaks, slow flows, low power under loads

Experimental work took a detour to explore the nature of hindered flow

Experiments: Pressure Differential

Experiments: Pressure DifferentialHigh pressure drops given slow flow rate

Back-calculate k from data finds it to be 10-7cm2, more like very fine sand not gravel

Trial #

Pump Power Setting (W)

Volume of Beaker Filled (milliliters)

Elapsed Time (seconds)

Calculated Flow Rate (m^3/s)

Calculated Pressure Drop ΔP (Pa)

Theoretical Fuel Cell ΔP (Pa)

1 1.17E-01 900 223 4.04E-06 2.55E+04 2.54E-01

2 1.17E-01 900 197 4.57E-06 2.22E+04 2.87E-01

3 1.17E-01 900 240 3.75E-06 2.77E+04 2.36E-01

4 1.17E-01 1000 294 3.40E-06 3.09E+04 2.14E-01

5 1.09E-01 900 225 4.00E-06 2.39E+04 2.51E-01

6 1.09E-01 900 258 3.49E-06 2.79E+04 2.19E-01

7 1.09E-01 900 429 2.10E-06 4.87E+04 1.32E-01

8 1.09E-01 900 335 2.69E-06 3.73E+04 1.69E-01

9 4.11E-02 1000 551 1.81E-06 1.93E+04 1.14E-01

10 4.11E-02 900 552 1.63E-06 2.18E+04 1.02E-01

11 4.11E-02 930 480 1.94E-06 1.79E+04 1.22E-01

Experiments: Post MortemDecision to open up the fuel cell

5 Failure modes discovered: serpentine channel clog, cathode seal rupture, catalyst damaged, copper patina, zinc fusion

Experiments: Post Mortem

Serpentine channel for electrolyte inflow almost entirely clogged with black RTV silicone sealant


Seal between zinc chamber and air chamber using the air cathode broke along the bottom


Catalyst side of the air cathode punctured and scarred


Copper anode current collector panel, on the taper, covered with patina


Zinc pellets fused into solid wedges at the bottom, possibly herniating the cathode

Experiments: SEM Analysis

All failures likely the result of poor assembly practices except zinc pellets fusing

Possibly zinc ions, zinc oxide, or zinc hydroxide plating back on to the pellets

Send the fused pellet to the scanning electron microscope to identify the material of fused surfaces


Fused zinc pellets, adjacent to the air cathode, x90


Fused zinc pellets, adjacent to the air cathode, x1,000


Fused zinc pellets, adjacent to the air cathode, x10,000


Spectrometry finds that the octahedrons are 27.7% atomically zinc, 72.3% atomically oxygen; 2.6 O per 1 Zn

Spectrometry finds the dendrites are 57% atomically oxygen and 40% atomically zinc; 1.4 O per 1 Zn

Could be explained by complexes or hydrates

Is zinc fusion the result of a series of unfortunate events, or is this a fundamental aspect of the chemistry?

Summary of Achievements

Designed, analyzed the aspects of a holistic system using centralized reprocessing

-Technologies and mechanisms-Cost analyses-Toxins and emissions

Designed, analyzed a control system for the fuel cell systems

-Analytically frame the problem-Experimentally probe the physic

Final Remarks

Zinc economy: centralized reprocessing cost prohibitive and unsustainable without control over logistics and emissions

Fuel cell control: quality engineering and deeper electrochemistry need to be addressed

ms thesis: investigating the technical and commercial merits of zinc-air fuel cells for passenger...

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