[membrane science and technology] ion exchange membranes - fundamentals and applications volume 12...

Energy Conversion

Chapter 8

8.1. DIALYSIS BATTERY

8.1.1 Overview of Technology

Dialysis battery is a technology to generate electricity using salt con-centration (chemical potential) difference across an ion exchange membraneplaced in salt solutions. It is also termed ‘reverse electrodialysis’ and isapplicable at the place where diluted and concentrated salt solutions suchas seawater, river water or spring brine are supplied simultaneously. It is aprimary battery and generates a constant direct current continually. In spite ofthe following assessment research, the process has not been practiced till now(Itoi, 1986).

DOI: 10.1016/S0927-5193(07)12022-2

Concentrated Solution
Diluted Solution Location
Dead Sea
Mediterranean Israel Solar Pond Sea Mexico, Taiwan Sea River USA, Japan etc.
Fundamental study started in 1952 by Manecke (1952). Pattele (1954)generated electric power of 0.015W. Weinstein and Leitz (1976) generated0.33W (m2 pair)1 using an electrodialyzer (232 cm2, 30 pairs). Ohya et al.(1990) supplied concentrated seawater to a battery (200 cm2, 40 pairs) andgenerated maximum 0.5 W of electric power.

8.1.2 Principle of a Dialysis Battery System

Fig. 8.1 shows operating circumstances in a unit cell in a dialysis battery.Here a and C are, respectively, activity coefficient and concentration of elec-trolytes dissolving in solutions. L is molar conductivity of a solution. a isdistance between ion exchange membranes. t and r are, respectively, apparenttransport number and electric resistance of the membrane. E is electricpotential generated between the solutions in contact with both membranesurfaces. Subscripts 1 and 2 refer to, respectively, diluted and concentratedsides. Subscripts K and A refer to, respectively, the cation and anion exchangemembranes.

dx.doi.org/10.1016/S0927-5193(07)12022-2.3d

a1

C1

d1

1

a2

C2

d2

2

a1

C1

d1

1

Dilutingcompartment

Cationexchangemembrane

Concentratingcompartment

Anionexchangemembrane

Dilutingcompartment

a : electrolyte activityC : electrolyte concentration : molar conductivity of a solutiond : distance between membranes

Figure 8.1 Operating circumstances in a dialysis battery.

Ion Exchange Membranes: Fundamentals and Applications506

E is expressed by the following equation (cf. Eq. (2.6) in Fundamentals).

EK ¼ ðtK 1ÞRT

F

ln

a2

a1

EA ¼ ðtA 1ÞRT

F

ln

a2

a1

(8.1)

in which R, T and F are, respectively, the gas constant, absolute temperature andthe Faraday constant.

The dialysis battery is assumed to be formed as an electric circuit as shownin Fig. 8.2, by arranging N unit cells described in Fig. 8.1 and connecting anexternal load rext. rint is internal electric resistance of the battery and I is anelectric current generated by the battery. Voltage produced by the battery V isexpressed by the following equation using Eq. (8.1).

V ¼ NðEK þ EAÞ ¼ 2NðtK þ tA 1ÞRT

F

ln

a2

a1

(8.2)

Relationship between NaCl concentration C (mol dm3) and NaCl activity a isapproximated by the following empirical equations at 251C (Tanaka, 1986).

a2

a1

¼

9:532 103 þ 0:6477C2 1:329 102C22 þ 1:154 102C3

2

9:532 103 þ 0:6477C1 1:329 102C21 þ 1:154 102C3

1

!

(8.3)

rext

rint

I

V

Figure 8.2 Electric circuit in a dialysis battery.

Energy Conversion 507

Internal electric resistance rint is

rint ¼N

SrK þ rA þ

1000d1

L1C1þ

1000d2

L2C2

(8.4)

S is effective membrane area. Relationship between L [(S/cm)/(mol/cm3)] and C

(mol dm3) of a NaCl solution is approximated by the following empiricalequation at 251C (Tanaka, 1986).

L ¼ 126:18 83:98C0:5 þ 82:19C 47:40C1:5 þ 9:202C2 (8.5)

Electric current I and electric power W in Fig. 8.2 are

I ¼V

rint þ rext(8.6)

W ¼ I2rext ¼V 2rext

ðrint þ rextÞ2

(8.7)

W in Eq. (8.7) becomes maximum at

rext ¼ rint (8.8)

Substituting Eq. (8.8) into Eqs. (8.6) and (8.7) leads to the following maximumvalues

Imax ¼V

2rint(8.9)

Wmax ¼V 2

4rint(8.10)

8.1.3 Performance of a Dialysis Battery (Computation)

In this section, we compute electric power generated from a dialysisbattery using the equations described in Section 8.1.2 based on the followingassumptions.


Distance between the membranes d1 ¼ d2 ¼ 0.05 cmElectric resistance of ion exchange membrane rK ¼ rA ¼ 2O cm2

Transport number of an ion exchange membrane tK ¼ tA ¼ 0.95Effective membrane area S ¼ 200 dm2

Numbers of membrane pairs integrated in the battery N ¼ 3000 pairsElectrolyte concentration in a diluted side C1 and concentrated side C2

For a River/Sea system: C1 ¼ 0.05M, C2 ¼ 0.5MFor a Sea/Brine system: C1 ¼ 0.5M, C2 ¼ 3.4M

Fig. 8.3 gives electric power W plotted against external resistance rext.If we assume equipment cost of the dialysis battery described here to be

100,000,000 yen per unit, the system cost for unit electric power becomesFor a River/Sea system: 100,000,000/9,752 ¼ 10,250,000 yen per kWFor a Sea/Brine system: 100,000,000/32,881 ¼ 3,040,000 yen per kWThese values are extremely high compared to the system cost for water

power generation 100,000 yen per kW and for pump up generation 250,000 yenper kW.

8.2. REDOX FLOW BATTERY


The term ‘‘redox’’ means reduction and oxidation and it means anoxidation–reduction reaction between two chemical species occurring on inactiveelectrode surfaces in the battery. It is also termed ‘‘redox flow battery’’ becausechemical species stored outside the battery are supplied by pumps to the battery.The redox flow battery is a secondary battery and its performance is characterizedas follows.

(a)
Operating at room temperature (b) Long life (c) No explosion and no ignition (d) Easy to scale up (e) Easy automatic operation (f) Easy to recycle
The basic principle of the technology was established by NASA in 1974(Thaller, 1974) and the iron/chromium (Fe/Cr) system was initially selected(Hagedorn and Thaller, 1980). At nearly the same time, ElectrochemicalLaboratory, the Ministry of International Trade and Industry, Japan initiatedthe development research in the Moon Light project for the Fe/Cr systembattery (Nozaki et al., 1984). However, the system did not lead to practicalapplication because of the following problems in an electrolysis solution and abattery stack. (1) Occurrence of cross contamination of Fe and Cr ions acrossthe ion exchange membrane. (2) Breaking of charge balance between the

0 2 31 4 50

5

10

15

20

25

30

35

W (

kW)

rext (Ω)

Sea/Brine

River/Sea

Wmax = 32.88 kw

Wmax = 9.75 kw

Figure 8.3 Generating power of a dialysis battery.


electrodes due to side reactions. (3) Low electromotive force (1 V) and lowoutput density.

After that, the direction of the development research was converted to avanadium (V2+/V3+ for an anode and V5+/V4+ for a cathode) system. Theadvantages of this system are (1) high electromotive force (1.3 V), (2) high out-put density (several times as much as that for a Fe/Cr system) and (3) noperformance deterioration due to contamination of ions across the membranes.The fundamental research on vanadium system battery was carried out inAustralia (Rychcik and Skyllas-Kazcos, 1988). This system was not investigatedin Japan because of lack of resources; however, the problem was solved bydeveloping the technology to recover vanadium from soot and smoke dis-charged from a thermal power plant (Sato et al., 1998). The following are earlyachievements in a vanadium system in Japan.

1990
1 kW plant, Electrochemical Laboratory, Ebara Corp. 1991 10 kW plant, Mitsui Shipbuilding Co. 1996 450 kW plant, Sumitomo Electric Industry Co., Kansai Electric
Power Co.
1997 200 kW plant, Mitsubishi Chemical Co., Kashima North Electric
Power Corp.


8.2.2 Principle of a Redox Flow Battery System

Electrochemical reaction in the iron/chromiumbattery is presented as follows.

At a cathode : Fe3þ þ e !discharge

chargeFe2þ (8.11)

At an anode : Cr2þ !discharge

chargeCr3þ þ e (8.12)

Standard electrode potential difference E0 is +0.77V for Fe3+/Fe2+ and 0.42Vfor Cr3+/Cr2+, so that the theoretical electromotive force E0 for Eqs. (3.11) and(3.12) is computed as

E0 ¼ 0:77 ð0:42Þ ¼ 1:19V (8.13)

Electrochemical reaction in the vanadium battery is

At a cathode : V5þ þ e !discharge

chargeV4þ (8.14)

At an anode : V2þ !discharge

chargeV3þ þ e (8.15)

From standard electrode potential difference E0¼+1.14V for V5+/V4+ and

E0¼ 0.26V for V2+/V3+, the theoretical electromotive force E0 is computed as

E0 ¼ 1:14 ð0:26Þ ¼ 1:4 V (8.16)

Structure of a redox flow battery is an array of a unit battery cell consisting ofcathodes, anodes and cation exchangemembranes with bipolar plates and terminalelectrodes as illustrated in Fig. 8.4 for a vanadium battery in discharging operation.Electrolysis solutions dissolving active vanadium ions into sulfuric acid solutionsare placed in a cathode solution tank and an anode solution tank, and are supplied,respectively, to cathode cells and anode cells. A direct current is generated throughthe electrochemical reactions in Eqs. (8.14) and (8.15). In this process, cation ex-change membranes pass only H+ ions and do not pass vanadium ions, so thatvanadium ions dissolving in each solution do not mix with each other. Directelectric current output is converted to an alternating current through an inverterand supplied to loads. In charging operation, an electric current generated by apower plant is supplied to the battery through the inverter, and stored in the batterydue to the reverse electrochemical reactions.

8.2.3 Practice

8.2.3.1 Parts of the Redox Flow Battery System

The battery system is composed of the following parts (Shigematsu, 2002).

(a) Battery Cell

The battery cell illustrated in Fig. 8.4 must be designed to make theoxidation–reduction reaction efficiency as high as possible and internal electric

Load

+−A/D Inverter

K BP K BP K BP K

V2+ V5+

V2+/V3+

A Tank H+ V5+/V4+

C TankV3+ V4+

T A C A C A C A CT

C: Cathode BP: Bipolar plateA: Anode C Tank: Cathode solution tankK: Cation exchange membrane A Tank: Anode solution tankT: Terminal electrode

Figure 8.4 Discharging process in a vanadium redox flow battery. Reverse reactionoccurs in a charging process.


resistance as low as possible. The surface of the material in contact with the feedingelectrolysis solutions must be anti-acidic because the solutions include sulfuric acid.

Electrodes are prepared using woven or non-woven carbon fibers. Theelectrodes only offer the place at which the oxidation–reduction reactions occurand they do not react with themselves. Accordingly, it is necessary to offerlargest area and solution penetrability. The fiber material should have affinitywith the solution. Further, it is necessary to have largest hydrogen over potentialand oxygen over potential for preventing side reactions due to water splitting.

(b) Ion Exchange Membrane

Cation exchange membranes are incorporated with the vanadium redoxflow battery. The function of the cation exchange membranes in this situation isto accelerate H+ ion transport and reject vanadium ion transport across themembranes for preventing vanadium ion mixing between cathode cells andanode cells. At the same time, electric resistance of the membrane is desired to beas low as possible. The above requirements are in the trade-off relationship witheach other, so it is necessary to design to minimize total energy loss.


(c) Bipolar Plate

Many battery cells are arranged in series through bipolar plates as seen inan electrolyzer. The function of the bipolar plate is first to connect a cathodewith an anode and second to prevent the mixing of each solution. The bipolarplate is prepared with carbon resins (plastic carbon).

(d) Flame

The above-mentioned parts are arranged in the flame, which is preparedfrom polyvinyl chloride, polyethylene etc.

8.2.3.2 Plant Operation of a Redox Flow Plant

Fig. 8.5 exemplifies the performance of a charge/discharge cycle operationcarried out by Kashima North Electric Power Corp. using a 10 kW battery. Thespecifications of a 200 kW battery are as follows (Sato et al., 1998).

Basic specifications:Output: 200 kW, 4 hCurrent density: 80–100mA cm2

Electric power efficiency: 80%

Figure 8.5 Charge/discharge operation of a 10 kW redox flow battery. Current density,80mA/cm2; charge/discharge time, each 2.5 h (Sato et al., 1998).


Battery module:Module: 8 stacksStack: 3 substacksSubstack: 21 cellsElectrode area: 4000 cm2

Stack output: 25 kWElectrolyte solution:

Volume: 22m3

Concentration: 1.8M.

System cost for a 50MW plant (eight hours output) is estimated to beless than 200,000 yen per kW as follows, which is less than that of a newlyestablished thermal power plant (200,000–250,000 yen per kW) (Sato et al.,1998).

Ion exchange membrane
26,000 Carbon resin electrode 19,000 Stack material 12,000 Electrolysis solution 36,000 Pipe, rack, tank 37,000 Meter, electrical system 9,000 Total 139,000 yen per kW
8.2.3.3 Application of Redox Flow Batteries

Redox flow batteries are now operating in the following instances.

(a)
Effective electric power utilization:In factories or buildings, batteries are charged in night time and
discharged in day time, thus electricity charges are reduced by availingnight charges.

(b)
Measures against an interruption or an instantaneous lowering of powersupply:
It is available to avoid inferior semi-finished good production.
(c) Combination with natural energy utilization:
Output of natural energy utilization unit such as solar generators,wind-driven generators is not stable. The output becomes stable with theaid of the redox flow battery operation.

(d)
Electric load leveling:It is available in adjustment of electric supply and demand in an
electricity undertaking.
(e) Emergency uninterruptible power supply:
Emergency lightning, hospital equipment, etc.


8.3. FUEL CELL


The fuel cell is a primary battery and was invented by Lord Glove inEngland in 1839. However, it was not popular until General Electric Co.started its investigation in the later half of 1950s and a 1 kW battery wasloaded in Gemini No. 5 in 1965. During the day time, a space station gen-erates electric power from solar energy and electrolyzes water using the elec-tricity to obtain hydrogen and oxygen. During the night time, the stationcreates water from hydrogen and oxygen using the fuel cell. Such a generationsystem came to be widely applied in NASA space development projectsbecause it does not discharge wastes, is light weight and its generation efficiencyis high.

Ion exchange membranes incorporated in the fuel cell at first were inferiorin chemical durability because they were based on polystyrene. However,perfluorinated Nafion membranes developed by Du Pont Co. exhibited excellentdurability and were applied for the fuel cell in Biosatellite in 1969. On the otherhand, ion exchange membrane technology in Japan was developed with sea-water concentration for sodium chloride production and sodium chloride elec-trolysis for chlor-alkali production. In the course of development research,Asahi Glass Co. and Asahi Chemical Co. produced, respectively, perfluorinatedFlemion membranes and Aciplex membranes having excellent endurance inalkaline atmosphere.

Fuel cell technology investigation in Japan was started in 1981 in MoonLight project carried out by Agency of International Science and Technology,Ministry of International Trade and Industry, Japan. The development researchwas advanced extensively in cooperation with many research organizations.

In the middle of the 21st century, the fuel cells are estimated to be widelyapplied to electric traction for industrial tracks, delivery vehicles and passengercars; to cogeneration systems for households and buildings and to portabletelephone power sources, etc.

8.3.2 Principle of a Fuel Cell System

The fuel cells are classified into phosphoric acid fuel cell (PAFC), moltencarbonate fuel cell (MCFC), solid oxide fuel cell (SOFC) and polymer electro-lyte fuel cell (PEFC). We discuss only the PEFC in this section because onlyPEFC includes an ion exchange membrane (polymer electrolyte). The greatestmerit of the PEFC is that it can be operated at less than 1001C. It consists of afuel electrode, an air electrode and an ion exchange membrane as illustrated inFig. 8.6. In this system, water molecules are obtained from hydrogen gas andoxygen gas by the following chemical reaction.

H2 þO2! H2O (8.17)

H2 → 2H+ + 2e−

e−

Fuel electrode (Anode)

Ion exchangemembrane

IAir electrode (Cathode)

2H+ + 2e− + 1/2O2 → H2O

H+

O2 (Air)

H2

Figure 8.6 Polymer electrode fuel cell.


The relationship between the enthalpy change DH and Gibbs’ free energychange DG in the reaction (8.17) is

DG ¼ DH TDS (8.18)

in which T is the absolute temperature and DS entropy change. DH and DG areevaluated as DH ¼ 285.83kJ mol1 and DG ¼ 237.13kJ mol1. Accordingly,the theoretical maximum efficiency of the PEFC Z is calculated as

Z ¼DGDH 100 ¼

237:13

285:83 100 ¼ 82:9% (8.19)

The efficiency calculated above far exceeds the theoretical efficiency of a heatengine given by the Carnot’s cycle.

Electrochemical reactions on the electrodes in Fig. 8.6 are

Anode ðFuel electrodeÞ : H2! 2Hþ þ 2e (8.20)

Cathode ðAir electrodeÞ : 12O2 þ 2Hþ ! H2O ðLiquidÞ (8.21)

Gibb’s free energy change in the above reactions is

DG ¼ nFE0 (8.22)

in which F is the Faraday constant (96,485C mol1). Theoretical electromotiveforce of the PEFC E0 is

E0 ¼ DGnF¼

237:13 1000

2 96; 485¼ 1:229 V (8.23)

Under an applied electric current, unit cell voltage in the PEFC is decreasedas shown in Fig. 8.7 because of energy loss generated in the cell. This

-

E = 1.481 V

A

Theoretical voltage

E0 =1.229V

Voltage

BV

I − V curveC

Electric current I

A: Energy which can not be converted into electric power (Heat generation)B: Energy loss due to internal cell resistance (Heat generation)C: Electric energy which can be taken out to the external circuit

T ∆S = 48.7 kJ/mol

-

Diffusion polarization

Resistance polarization

Activation polarization−∆ ∆ H = 285.53 kJ/mol

∆G = 237.13 kJ/mol

Figure 8.7 Performance and energy consumption in a fuel cell (New Sunshine Program, 1999, p. 14).

IonExchangeMem

branes:

FundamentalsandApplica

tions

516


phenomenon is caused by the following (New Sunshine Program PromotionCenter, 1999).

(1)
Diffusion polarization:Electrochemical reaction in Eqs. (8.20) and (8.21) brings about diffu-
sion due to the occurrence of concentration difference (concentrationpolarization) of each component. A part of electromotive force of thePEFC is consumed by the concentration polarization.

(2)
Resistance polarization:Electric resistance of the ion exchange membrane, electrode, separator
and the interface between the membrane and electrode consumes theelectromotive force (IR loss).

(3)
Activation polarization:Oxidation–reduction reaction in Eqs. (8.20) and (8.21) proceeds via the
peak of activation energy. The reaction is accelerated by the potentialshift (over voltage) established in the reaction system. A part of electro-motive force in the PEFC is consumed to generate the over voltage.

8.3.3 Practice

8.3.3.1 Parts of PEFC (Poly Electrolyte Fuel Cell)

(a)
Membrane electrode assembly (MEA) and cell stack:MEA is composed of an ion exchange membrane, a cathode catalyst
layer, anode catalyst layer and gas diffusion layers placed between ananode separator and a cathode separator as illustrated in Fig. 8.8. Pas-sways are provided in the anode and cathode separator for feeding,respectively, fuel gas and air into the electrodes. Passway in the waterseparator is provided for cooling the assembly.

The cell stack is an array of MEA between terminal electrodes (cur-rent collectors) placed on both outsides of the array as shown in Fig. 8.9.The cell stack is unified by fastening plates attached on both outsides ofthe terminal electrodes.

(b)
Ion exchange membrane:Perfluorinated ion exchange membranes, such as Nafion membrane
(Du Pont Co.), Flemion membrane (Asahi Glass Co.), Aciplex mem-brane (Asahi Chemical Co.) or Dow membrane (Dow Chemical Co.),are applied to the PEFC system (Yoshitake, 1999). The membranecharacteristics are generally, the thickness: 30–175 mm and ion exchangecapacity: 0.91–1.1meq g1. The functions of the ion exchange mem-brane are (1) to carry H+ ions generated at the fuel electrode toward theair electrode, (2) to prevent the direct contact between H2 and O2 and(3) to prevent the formation of a short circuit between both electrodes(Fuel Cell Generation System Technology Investigative Committee, 2002).

Figure 8.8 Unit cell arrangement in a PEFC. MEA, Membrane electrode assembly;IEM, ion exchange membrane; GDL, gas diffusion layer AC: anode catalyst layer; CC,cathode catalyst layer; AS, anode separator; CS, cathode separator; WS, water separator(Fuel Cell Generation System Technology Investigative Committee, 2002, p. 57).

Figure 8.9 Cell stack arrangement in a PEFC. MEA, Membrane electrode assembly;AS, anode separator; CS, cathode separator; WS, water separator; Se, seal; TE, terminalelectrode; FP, fastening plate (Fuel Cell Generation System Technology InvestigativeCommittee, 2002, p. 58).


Ion conductivity of the membrane is enhanced by water in the mem-brane, so it is necessary to increase water content of the membrane byinjecting moisture into the feeding fuel and air. In order to keep thewater content to suitable values, it is important to control the following

Figure 8Research


water transport in the assembly. Namely, moisture is injected intothe fuel gas transporting from the anode toward the cathode across themembrane with H+ ions generated by Eq. (8.20) (electro-osmosis). TheH+ ions are converted to H2O by Eq. (8.21) at the cathode, and the H2Ogenerated at the cathode diffuses from the cathode toward the anode(back diffusion) (Yasuda, 2000). If the feeding water or generated waterin the assembly fills the fine pores in the electrodes, energy and voltage isdecreased by the increase of cell resistance. Accordingly, it becomesnecessary to control water supply to the system.

(c)
Catalyst:Catalysts reduce the energy consumption of the cell by decreasing the
activation energy peak of the electrode reactions (Eqs. (8.20) and (8.21)).Platinum/ruthenium catalyst is used for the fuel electrode to avoid theperformance deterioration caused by carbon monoxide. Platinum cat-alyst is used for the air electrode. The catalyst layers are formed on theelectrodes as follows (NEDO Research and Development Report, 1999).(1) The catalyst is applied to a base plate (carbon plate) of both electrodes.Then they are pasted with the membrane (Fig. 8.10(a)). (2) Catalyst layersare formed on both surfaces of the membrane. Then the membrane ispasted with the carbon plates (Fig. 8.10(b)).

8.3.3.2 Performance of a Fuel Cell System

Cell voltage change of a unit cell PEFC system (membrane area: 225 cm2)being supplied by pure hydrogen is exemplified in Fig. 8.11 (Mitsuta et al.,1997). Current density and operating pressure in this operation are, respectively,250mA cm2 and 1 ata. Decreasing rate of cell voltage was 4mV per 1000h.

.10 Formation of catalyst layers in a membrane electrode cell assembly (NEDOand Development Report, 1999).

Figure 8.11 Cell voltage change of a unit cell PEFC system with time (Mitsuta et al.,1997).


Fig. 8.12 gives the performance of a 20-cell unit operated at 367mA cm2 and6 ata (Washington, 2000). Cell voltage decreasing rate in this unit was 2.2mV per1000h. Cell voltage decrease during the operation is caused by (1) decrease ofeffective reaction area of the catalyst due to the increase of catalysis particlediameter or the increase of moisture in the catalysis layer, (2) fouling of themembrane and (3) an excessive or an insufficient moisture injection to the elec-trodes (Fuel Cell Generation System Technology Investigative Committee, 2002).

8.3.3.3 Application of Fuel Cells

(a)
Electrically powered car:Fig. 8.13 exemplifies an electrically powered car system in which
hydrogen and air are supplied to the PEFC and a motor is derived fromelectric power generation. Ultra-capacitor is applied for recoveringbraking energy and increasing driving force.

In 1993, Ballad Power Systems Inc. in Canada developed an electricallypowered car (electric output; 120 kW, motor output; 80kW, mileage;160km) by supplying compressed hydrogen and air to the PEFC. In 1997,DaimlerChrysler developed the NECAR 3 passenger car (electric output;50kW, mileage; 400km) refueling methanol. In 1998, fuel cell bus serviceseated 62 passengers stated between Vancouver and Chicago refuelingcompressed hydrogen.

A fuel cell car developed by Adam Opel Gmbh in Germany supplyingliquid hydrogen was applied for leading marathon runners in SydneyOlympic in 2000. Highway test driving was started in California

Compressedhydrogen

tank

Drivingmotor

Moistureinjector

orSecondary

battery

Airfeeder

Ultracapacitor

Cellstack

Moistureinjector

Coolingsystem

Figure 8.13 Polymer fuel cell system in an electrically powered car (Fuel Cell Gener-ation System Technology Investigative Committee, 2002, p. 78).

Figure 8.12 Performance of a 20-cell PEFC unit (Washington, 2000).


Figure 8.14 Household cogeneration system (Fuel Cell Generation System TechnologyInvestigative Committee, 2002, p. 85).


participated by NECAR 4a (DaimlerChrysler, compressed tank), Focus(Ford, compressed hydrogen), FCX-3V (Honda, compressed tank) etc.in November 2000.

Upper cost limit of an electrically powered fuel car is assumed to be5–15% more than traditional cars, and the system cost is estimated to be5,000–10,000 yen per kW.

(b)
Household cogeneration:Fig. 8.14 shows a household cogeneration system, which consists of
(1) fuel treating unit, (2) blower, (3) PEFC cell stack, (4) heat recoveringunit and (5) inverter.

In the fuel treating unit, town gas is converted to hydrogen includingcarbon dioxide and a very small quantity of carbon monoxide. In thePEFC cell stack CS, a direct current and heat are generated from H2 andO2 being supplied, respectively, from the fuel treating unit FTU and theblower Blw. In the inverter Inv, the direct current is converted to analternating current, which is consumed in the household for lighting,heating etc. In the heat recovering unit HRU, heat discharged fromPEFC cell stack and fuel treating unit is converted to warm water oftemperature higher than 601C, which is also consumed in the household.

The household cogeneration apparatuses are developed and commer-cialized by many electrical product firms and gas companies.

REFERENCES

Fuel Cell Generation System Technology Investigative Committee, 2002, Society ofElectricity, Japan, 2002, Fuel cell technology, Ohm Co., Tokyo, pp. 55–98.

Hagedorn, N. H., Thaller, L. H., 1980, Redox storage systems for solar application,NASA TM-81464, NASA, U.S. Department of Energy.


Itoi, S., 1986, Dialysis battery technology development project. Paper presented at themeeting of Research group of dialysis battery, March 1986, Tokyo.

Manecke, G., 1952, Membranak kumulator, Z. Phys. Chem., 201, 1–15.Mitsuta, K. et al., 1997, Development of an exterior manifold type PEFC module, The

4th FCDIC symposium, pp. 265–268.NEDO Research and Development Report, 1999, Development of polymer electrolyte

fuel cell – Development of a high current density 10kW mobile power source system.New Sunshine Program Promotion Center, Agency of Industrial Science and Technology,

1999, Ministry of International Trade and Industry, Japan, Polymer Electrolyte FuelCell, pp. 13–14.

Nozaki, K., Kaneko, H., Negishi, A., Ozawa, T., 1984, Proceedings of the Symposiumon Advances in Battery Materials Vol. 84-4, Electrochemical Society, Inc., Princeton,NJ, p. 143.

Ohya, H., Watanabe, S., Hiroishi, K., Negishi, Y., 1990, Scale-up of multi-compartmentdialytic battery with ion-exchange membranes, Bull. Soc. Sea Water Sci. Jpn., 44,361–364.

Pattele, R. E., 1954, Production of electric power by mixing fresh and salt water in thehydro-electric pile, Nature, 174, 660.

Rychcik, M., Skyllas-Kazcos, M., 1988, Characteristics of a new all-vanadium redox flowbattery, J. Power Sources, 22, 59–67.

Sato, K., Sawahama, M., Miyahayashi, M., Kageyama, Y., Nakajima, M., 1998,Development of new fuel and electric power storage battery, Soda Chlorine, 49(4),149–158.

Shigematsu, T., 2002, Redox flow battery for electric power storage in practically avail-able stage, Material Stage, 1(10), 40–43.

Tanaka, Y., 1986, Performance of a dialysis battery. Paper presented at the meeting ofresearch group of dialysis battery, September 1986, Tokyo.

Thaller, L. H., 1974, Proceedings of the 9th Inter-Society Energy Conversion EngineeringConference, American Society of Mechanical Engineering, p. 924.

Washington, K., 2000, Development of a 250kW class polymer electrolyte fuel cell. Paperpresented at the Stack, Fuel Cell Seminar, pp. 468–472.

Weinstein, J. N., Leitz, F. B., 1976, Electric power from differences in salinity:The dialytic battery, Science, 191, 557–559.

Yasuda, K., 2000, Development and application of polymer electrolyte fuel cells, Lecture2, Material development in PEFC, NTS Co., Tokyo.

Yoshitake, Y., 1999, Development of ion exchange membranes for PEFC, Text book inFCDIC lecture meeting, pp. 22–33.

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