write only the conclusion for this lab report

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I need to write conclusion about the lab report that attached. it is only one paragraph with details from the objective. it is like from the data analysis, like which fuel cell was the strongest, which is fuel cell 3. and talk about what feature experiment we can do to continue the testing. from the experiment i did FUEL CELL 3 was the strongest and fuel cell 1 and 2 got weak. if we put these fuel cel in forklift after like an hour. more research go to how fast the fuel cell diminish power..

i just attached the lab report that u need to look at and understand it to write the lab report and the rubric that you need to mention in the conclusion. it is only one simple paragraph that explain the main point from the objective. dont try to copy the conclusion in the report. u can look at it and understand it and wtite from what u understand

write only the conclusion for this lab report
Creating​ ​Characteristic​ ​Curves​ ​and​ ​Comparing Performance​ ​and​ ​Max​ ​Power​ ​for​ ​Hydrogen​ ​Fuel​ ​Cells Moayad​ ​Barayan Abdulrahman​ ​Bugubaia Dylan​ ​Kuprienko-Coleman Brendan​ ​Stewart Group​ ​16 Pre-Lab​ ​2 October​ ​23,​ ​2017 Introduction Background Fuel​ ​cells​ ​are​ ​used​ ​in​ ​converting​ ​chemical​ ​energy​ ​in​ ​fuels​ ​into​ ​electrical​ ​energy​ ​with​ ​high efficiency​ ​and​ ​low​ ​environmental​ ​impact.​ ​Fuel​ ​cells​ ​that​ ​use​ ​hydrogen​ ​with​ ​other​ ​oxidizers​ ​to​ ​produce electricity​ ​serve​ ​various​ ​purposes​ ​these​ ​days,​ ​such​ ​as​ ​power​ ​for​ ​vehicles,​ ​backup​ ​power​ ​for telecommunications,​ ​and​ ​power​ ​generation​ ​for​ ​facilities​ ​(​“Early​ ​Market​ ​Applications​ ​for​ ​Fuel​ ​Cell Technologies”)​.​ ​An​ ​additional​ ​source​ ​of​ ​interest​ ​is​ ​storing​ ​energy​ ​in​ ​hydrogen​ ​fuel​ ​cells.​ ​In​ ​the​ ​future, renewable​ ​energy​ ​sources​ ​will​ ​likely​ ​be​ ​used​ ​at​ ​a​ ​higher​ ​rate,​ ​and​ ​a​ ​common​ ​problem​ ​with​ ​these​ ​sources is​ ​their​ ​inability​ ​to​ ​produce​ ​enough​ ​energy​ ​during​ ​peak​ ​energy​ ​usage​ ​hours.​ ​Hydrogen​ ​fuel​ ​cell​ ​storage can​ ​potentially​ ​be​ ​used​ ​by​ ​flowing​ ​an​ ​electrical​ ​current​ ​into​ ​water​ ​during​ ​the​ ​day​ ​when​ ​renewable​ ​energy generation​ ​is​ ​high​ ​and​ ​separating​ ​hydrogen​ ​and​ ​oxygen.​ ​When​ ​energy​ ​is​ ​needed​ ​in​ ​the​ ​evening,​ ​the​ ​fuel cell​ ​can​ ​be​ ​used​ ​to​ ​generate​ ​electricity​ ​and​ ​water​ ​as​ ​a​ ​product.​ ​The​ ​biggest​ ​variable​ ​in​ ​the​ ​development​ ​of these​ ​technologies​ ​is​ ​that​ ​the​ ​efficiency​ ​may​ ​be​ ​too​ ​low​ ​to​ ​use​ ​fuel​ ​cells​ ​as​ ​a​ ​storage​ ​or​ ​energy​ ​generation source.​ ​Over​ ​the​ ​past​ ​twenty​ ​years,​ ​there​ ​has​ ​been​ ​a​ ​huge​ ​improvement​ ​in​ ​some​ ​of​ ​the​ ​fuel​ ​cell,​ ​this resulted​ ​from​ ​improvement​ ​in​ ​the​ ​three-phase​ ​boundary,​ ​reducing​ ​the​ ​thickness​ ​of​ ​the​ ​electrolyte,​ ​and developing​ ​improved​ ​electrode​ ​and​ ​electrolyte​ ​materials.​ ​In​ ​this​ ​lab,​ ​hydrogen​ ​fuel​ ​cell​ ​energy​ ​generation will​ ​be​ ​tested​ ​to​ ​determine​ ​the​ ​efficiencies​ ​of​ ​different​ ​cells​ ​at​ ​various​ ​currents.​ ​A​ ​rheostat​ ​measures​ ​the current​ ​and​ ​voltage​ ​to​ ​produce​ ​a​ ​curve​ ​of​ ​the​ ​two​ ​variables​ ​in​ ​the​ ​Ohmic​ ​Polarization​ ​region,​ ​which​ ​is​ ​the linear​ ​region​ ​of​ ​the​ ​characteristic​ ​curve.​ ​This​ ​will​ ​lead​ ​to​ ​calculating​ ​the​ ​efficiency​ ​of​ ​the​ ​fuel​ ​cells. Objective The​ ​purpose​ ​of​ ​this​ ​experiment​ ​is​ ​to​ ​compare​ ​ohmic​ ​polarization​ ​regions​ ​for​ ​three,​ ​distinct, single-unit,​ ​hydrogen​ ​fuel​ ​cells,​ ​plot​ ​the​ ​characteristic​ ​curves​ ​of​ ​the​ ​fuel​ ​cells,​ ​and​ ​assess​ ​the​ ​maximum power​ ​generated​ ​by​ ​each​ ​cell​ ​as​ ​shown​ ​in​ ​the​ ​curves. Theory Polymer​ ​electrolyte​ ​fuel​ ​cells​ ​work​ ​through​ ​chemical​ ​reactions​ ​that​ ​produce​ ​an​ ​electric​ ​current. Hydrogen​ ​will​ ​enter​ ​the​ ​fuel​ ​cell,​ ​and​ ​the​ ​anode​ ​reaction: H 2 → 2H + + 2e− ​ ​ ​ ​ ​ ​ ​ ​ ​(eq.​ ​1) takes​ ​place​ ​where​ ​the​ ​hydrogen​ ​gas​ ​loses​ ​its​ ​electrons.​ ​The​ ​hydrogen​ ​ion​ ​then​ ​moves​ ​through​ ​the​ ​cell,​ ​and the​ ​electrons​ ​move​ ​across​ ​the​ ​path​ ​of​ ​least​ ​resistance,​ ​the​ ​wire.​ ​The​ ​voltage​ ​is​ ​then​ ​measured​ ​through​ ​this movement​ ​of​ ​electrons​ ​across​ ​the​ ​wire.​ ​At​ ​the​ ​cathode,​ ​oxygen​ ​completes​ ​the​ ​redox​ ​reaction: 1 O2 + 4H + + 4e− →2H 2 O ​ ​ ​ ​ ​ ​(eq.​ ​2) and​ ​produces​ ​the​ ​harmless​ ​byproduct​ ​water. Fuel​ ​cells​ ​can​ ​not​ ​utilize​ ​all​ ​of​ ​the​ ​chemical​ ​energy​ ​within​ ​them​.​ ​The​ ​efficiency​ ​of​ ​each​ ​fuel​ ​cell is​ ​given​ ​by: η= (ηideal *V act ) E ideal ​ ​ ​ ​ ​ ​ ​ ​ ​(eq.​ ​3) where​ ​ ηideal ​ ​equals​ ​0.83​​ ​at​ ​standard​ ​conditions,​ ​ E ideal ​ ​equals​ ​1.229​ ​volts​ ​at​ ​standard​ ​conditions​ ​for​ ​a​ ​cell using​ ​oxygen​ ​and​ ​hydrogen,​ ​and​ ​ V act ​ ​equals​ ​the​ ​voltage​ ​passing​ ​through​ ​the​ ​wire​ ​(​EG&G​ ​Technical Services,​ ​Inc).​ ​This​ ​reduces​ ​the​ ​actual​ ​efficiency​ ​to: η = 0.675 * V act ​ ​ ​ ​ ​ ​ ​ ​ ​ ​(eq.​ ​4) where​ ​the​ ​voltage​ ​is​ ​measured​ ​at​ ​any​ ​given​ ​time​ ​through​ ​the​ ​fuel​ ​cell.​ ​ ηideal ​ ​is​ ​derived​ ​through​ ​the​ ​ratio of​ ​free​ ​energy​ ​to​ ​thermal​ ​energy​ ​and​ ​was​ ​tabulated​ ​along​ ​with​ ​ E ideal (​EG&G​ ​Technical​ ​Services,​ ​Inc)​. This​ ​efficiency​ ​relates​ ​the​ ​amount​ ​of​ ​useful​ ​energy​ ​to​ ​the​ ​amount​ ​of​ ​total​ ​energy.​ ​It​ ​determines​ ​the performance​ ​of​ ​the​ ​cell;​ ​a​ ​larger​ ​efficiency​ ​gives​ ​better​ ​performance. The​ ​cell​ ​voltages​ ​will​ ​be​ ​recorded​ ​at​ ​varying​ ​resistances​ ​and​ ​graphed​ ​versus​ ​the​ ​current​ ​density​ ​to produce​ ​a​ ​characteristic​ ​curve​ ​consisting​ ​of​ ​the​ ​three​ ​areas​ ​illustrated​ ​in​ ​Figure​ ​1. Figure​ ​1:​ ​Potential​ ​characteristic​ ​curve​ ​of​ ​a​ ​fuel​ ​cell. The​ ​first​ ​region​ ​is​ ​the​ ​reaction​ ​rate​ ​loss​ ​from​ ​overcoming​ ​activation​ ​energy,​ ​the​ ​second​ ​is​ ​the​ ​linear resistance​ ​loss​ ​region,​ ​and​ ​the​ ​third​ ​is​ ​the​ ​gas​ ​transport​ ​loss​ ​from​ ​slow​ ​gas​ ​transport​ ​rates​ ​(​EG&G Technical​ ​Services,​ ​Inc).​ ​The​ ​losses​ ​represent​ ​the​ ​voltage​ ​loss​ ​from​ ​the​ ​ideal​ ​voltage​ ​as​ ​the​ ​current density​ ​increases.​ ​The​ ​region​ ​of​ ​resistance​ ​loss​ ​will​ ​be​ ​tested​ ​at​ ​a​ ​constant​ ​current​ ​density​ ​to​ ​determine​ ​the performance​ ​of​ ​the​ ​fuel​ ​cells​ ​at​ ​this​ ​region​ ​through​ ​equation​ ​4. 2 Method Apparatus The​ ​three​ ​different​ ​fuel​ ​cells:​ ​Z0001,​ ​Z0002,​ ​and​ ​Z5184​ ​were​ ​connected​ ​to​ ​the​ ​hydrogen​ ​tank​ ​fuel source​ ​in​ ​order​ ​to​ ​measure​ ​their​ ​performance​ ​at​ ​the​ ​same​ ​time​ ​using​ ​the​ ​variable​ ​resistors.​ ​A​ ​rheostat​ ​was attached​ ​to​ ​each​ ​of​ ​the​ ​three​ ​fuel​ ​cells​ ​as​ ​illustrated​ ​in​ ​Figure​ ​2.​ ​Then,​ ​a​ ​connection​ ​using​ ​the​ ​tubing​ ​and clamps​ ​was​ ​made​ ​between​ ​the​ ​three​ ​fuel​ ​cells​ ​and​ ​the​ ​hydrogen​ ​tank.​ ​At​ ​the​ ​top​ ​port​ ​of​ ​each​ ​fuel​ ​cell​ ​a connection​ ​to​ ​the​ ​fuel​ ​line​ ​was​ ​made,​ ​and​ ​the​ ​bottom​ ​port​ ​was​ ​connected​ ​to​ ​a​ ​tubing​ ​to​ ​help​ ​control​ ​the excess​ ​hydrogen​ ​gas.​ ​The​ ​fuel​ ​flow​ ​was​ ​kept​ ​continuous​ ​during​ ​the​ ​whole​ ​experimental​ ​period.​ ​Also, oxygen​ ​was​ ​supplied​ ​to​ ​the​ ​fuel​ ​cells​ ​by​ ​flowing​ ​air​ ​into​ ​the​ ​top​ ​port​ ​on​ ​the​ ​cathode​ ​side​ ​of​ ​the​ ​fuel​ ​cell. Figure​ ​2:​ ​A​ ​fuel​ ​cell​ ​hooked​ ​up​ ​to​ ​an​ ​air​ ​tank,​ ​hydrogen​ ​tank,​ ​and​ ​a​ ​rheostat. 3 Experimental​ ​Design Readings​ ​of​ ​currents​ ​and​ ​voltages​ ​were​ ​taken​ ​using​ ​the​ ​variable​ ​resistors​ ​with​ ​it​ ​set​ ​at​ ​five different​ ​resistances​ ​for​ ​the​ ​fuel​ ​cells​ ​Z0001,​ ​Z0002,​ ​and​ ​Z5184.​ ​The​ ​rheostat​ ​was​ ​moved​ ​in​ ​one​ ​sixth intervals.​ ​The​ ​results​ ​were​ ​recorded​ ​in​ ​a​ ​table.​ ​The​ ​tabulated​ ​results​ ​were​ ​then​ ​used​ ​for​ ​graphical​ ​analysis by​ ​plotting​ ​voltage​ ​against​ ​current​ ​density.​ ​A​ ​curve​ ​that​ ​was​ ​almost​ ​linear​ ​was​ ​obtained.​ ​The​ ​above procedure​ ​was​ ​then​ ​undertaken​ ​for​ ​the​ ​other​ ​two​ ​hydrogen​ ​cells.​ ​The​ ​current​ ​and​ ​voltage​ ​data​ ​were​ ​used to​ ​generate​ ​power​ ​curves​ ​to​ ​compare​ ​maximum​ ​output​ ​of​ ​each​ ​fuel​ ​cell.​ ​All​ ​the​ ​experiments​ ​were conducted​ ​at​ ​room​ ​temperature​ ​and​ ​pressure.​ ​Gas​ ​composition​ ​changes​ ​between​ ​the​ ​inlet​ ​and​ ​outlet​ ​of​ ​a fuel​ ​cell,​ ​caused​ ​by​ ​the​ ​electrochemical​ ​reaction,​ ​lead​ ​to​ ​reduced​ ​cell​ ​voltages.​ ​This​ ​reduction​ ​in​ ​voltage arises​ ​because​ ​the​ ​cell​ ​voltage​ ​adjusts​ ​to​ ​the​ ​potential​ ​of​ ​the​ ​lowest​ ​electrode.​ ​This​ ​phenomenon​ ​is​ ​defined by​ ​the​ ​NERNS​ ​equation​ ​for​ ​various​ ​gas​ ​composition​ ​as​ ​they​ ​exist​ ​anode​ ​and​ ​cathode​ ​chambers​ ​(EG&G Technical​ ​Services,​ ​Inc.).​ ​Electrodes​ ​are​ ​good​ ​electronic​ ​conductors​ ​and​ ​isopotential​ ​surfaces.​ ​Due​ ​to​ ​this fact​ ​the​ ​cell​ ​voltage​ ​cannot​ ​fall​ ​to​ ​a​ ​value​ ​below​ ​the​ ​NERNS​ ​potential​ ​in​ ​a​ ​system​ ​designed​ ​for​ ​co-flow. Method​ ​of​ ​Analysis Current​ ​density​ ​and​ ​voltage​ ​values​ ​were​ ​recorded​ ​and​ ​plotted​ ​to​ ​form​ ​a​ ​curve​ ​that​ ​ensures​ ​a​ ​linear Ohmic​ ​Polarization​ ​region​ ​occurred​ ​for​ ​each​ ​cell.​ ​Linear​ ​regression​ ​analysis​ ​was​ ​performed​ ​for​ ​the​ ​part​ ​of the​ ​curves​ ​that​ ​appeared​ ​linear.​ ​Equation​ ​4​ ​was​ ​used​ ​to​ ​obtain​ ​the​ ​efficiencies​ ​at​ ​the​ ​different​ ​current densities.​ ​Five​ ​voltage​ ​values​ ​were​ ​recorded​ ​from​ ​each​ ​fuel​ ​cell​ ​for​ ​a​ ​specified​ ​resistance.​ ​These​ ​data values​ ​were​ ​compared​ ​in​ ​equal​ ​variance​ ​t-tests​ ​between​ ​the​ ​three​ ​fuel​ ​cells​ ​to​ ​determine​ ​if​ ​there​ ​were statistically​ ​significant​ ​differences​ ​between​ ​the​ ​efficiencies​ ​and​ ​power​ ​outputs​ ​of​ ​the​ ​cells​ ​at​ ​the​ ​specified resistance. Safety Safety​ ​glasses,​ ​closed-toed​ ​shoes,​ ​and​ ​long​ ​pants​ ​were​ ​worn​ ​at​ ​all​ ​times​ ​when​ ​in​ ​the​ ​lab.​ ​To safeguard​ ​against​ ​the​ ​highly​ ​flammable​ ​hydrogen​ ​gas,​ ​unused​ ​tubing​ ​was​ ​clamped​ ​off​ ​to​ ​minimize​ ​risks of​ ​gas​ ​leaks.​ ​Routine​ ​checks​ ​were​ ​also​ ​carried​ ​out​ ​throughout​ ​the​ ​experiment​ ​to​ ​make​ ​sure​ ​the​ ​hydrogen gas​ ​was​ ​not​ ​leaking.​ ​A​ ​limited​ ​time​ ​of​ ​two​ ​seconds​ ​was​ ​kept​ ​for​ ​the​ ​purges​ ​on​ ​the​ ​hydrogen​ ​side​ ​of​ ​the fuel​ ​cell.​ ​It​ ​is​ ​important​ ​to​ ​look​ ​for​ ​any​ ​leaks;​ ​any​ ​leaks​ ​should​ ​be​ ​reported​ ​to​ ​the​ ​supervisors.​ ​Some hydrogen​ ​diffused​ ​through​ ​the​ ​tubing​ ​hence​ ​extreme​ ​caution​ ​was​ ​maintained​ ​throughout​ ​the​ ​experiment. Obviously,​ ​no​ ​flames​ ​or​ ​sparks​ ​were​ ​present​ ​around​ ​the​ ​hydrogen​ ​gas.​ ​The​ ​location​ ​of​ ​the​ ​fire​ ​hydrant 4 was​ ​located​ ​next​ ​to​ ​the​ ​far​ ​exit​ ​door​ ​in​ ​case​ ​of​ ​any​ ​emergencies.​ ​Since​ ​the​ ​experiment​ ​was​ ​an​ ​electrical one,​ ​water​ ​and​ ​metal​ ​were​ ​kept​ ​away​ ​from​ ​the​ ​cells​ ​and​ ​rheostat. Anticipated​ ​Results The​ ​voltages​ ​of​ ​each​ ​fuel​ ​cell​ ​were​ ​taken​ ​at​ ​five​ ​different​ ​resistances​ ​on​ ​the​ ​rheostat.​ ​This​ ​data can​ ​be​ ​seen​ ​in​ ​Table​ ​1​ ​for​ ​the​ ​Z0001​ ​fuel​ ​cell.​ ​Characteristic​ ​curves​ ​were​ ​created​ ​for​ ​all​ ​three​ ​fuel​ ​cells and​ ​can​ ​be​ ​seen​ ​in​ ​Figure​ ​3. Figure​ ​3:​ ​Characteristic​ ​curves​ ​comparing​ ​the​ ​relationship​ ​of​ ​current​ ​and​ ​voltage​ ​for​ ​Z0001​ ​(●),​ ​Z0002 (▲),​ ​and​ ​Z5184​ ​(■)​​ ​fuel​ ​cells. The​ ​Z0001​ ​fuel​ ​cell​ ​preformed​ ​the​ ​best​ ​in​ ​terms​ ​of​ ​both​ ​power​ ​and​ ​efficiency.​ ​It​ ​consistently produced​ ​more​ ​power​ ​for​ ​the​ ​given​ ​current​ ​and​ ​also​ ​ran​ ​more​ ​efficiently​ ​at​ ​each​ ​current.​ ​This​ ​data​ ​can​ ​be seen​ ​in​ ​Table​ ​2​ ​and​ ​Table​ ​3​ ​which​ ​compare​ ​the​ ​efficiencies​ ​and​ ​the​ ​power​ ​outputs​ ​of​ ​each​ ​of​ ​the​ ​cells respectively.​ ​The​ ​Z5184​ ​fuel​ ​cell​ ​was​ ​found​ ​to​ ​consistently​ ​perform​ ​more​ ​efficiently​ ​and​ ​produce​ ​more power​ ​than​ ​the​ ​Z0002​ ​fuel​ ​cell. 5 Table​ ​1:​ ​Raw​ ​and​ ​calculated​ ​data​ ​obtained​ ​for​ ​fuel​ ​cell​ ​Z0001. Fuel​ ​Cell​ ​ID:​​ ​Z0001 Wire​ ​Diameter​ ​(cm):​​ ​0.2 Wire​ ​Cross​ ​Sectional​ ​Area​ ​( cm2 ):​​ ​0.126 Temperature​ ​(K):​​ ​298 Pressure​ ​(atm):​ ​1 Voltage Efficiency Resistance​ ​(Ω) (V) Current​ ​Density​ ​(mA/ cm2 ) (ɳ) 0.095454545 1.05 11 0.70875 0.0259375 0.83 32 0.56025 0.015 0.75 50 0.50625 0.008695652 0.6 69 0.405 0.00483871 0.45 93 0.30375 Average​ ​Efficiency​ ​(ɳ): 0.4968 There​ ​was​ ​no​ ​overlap​ ​between​ ​the​ ​efficiencies​ ​or​ ​the​ ​power​ ​outputs​ ​of​ ​each​ ​of​ ​the​ ​fuel​ ​cells suggesting​ ​that​ ​at​ ​any​ ​given​ ​current​ ​the​ ​Z0001​ ​fuel​ ​cell​ ​would​ ​perform​ ​best,​ ​the​ ​Z5184​ ​fuel​ ​cell’s performance​ ​would​ ​fall​ ​in​ ​the​ ​middle,​ ​and​ ​the​ ​Z0002​ ​fuel​ ​cell​ ​would​ ​perform​ ​the​ ​worst​ ​in​ ​terms​ ​of​ ​their power​ ​outputs​ ​and​ ​efficiencies. 6 Table​ ​2:​ ​The​ ​efficiencies​ ​of​ ​the​ ​three​ ​fuel​ ​cells​ ​tested​ ​at​ ​varying​ ​currents​ ​specified​ ​by​ ​adjusting​ ​the resistance​ ​on​ ​the​ ​rheostat. Efficiencies​ ​(ɳ) Current (mA) Z0001 Z0002 Z5184 11 0.70875 0.62775 0.6615 32 0.56025 0.4995 0.54675 50 0.50625 0.4185 0.4455 69 0.405 0.31725 0.35775 93 0.30375 0.20925 0.243 Two​ ​null​ ​hypotheses​ ​were​ ​formed​ ​stating​ ​that​ ​there​ ​were​ ​no​ ​differences​ ​between​ ​the​ ​efficiencies or​ ​the​ ​power​ ​outputs​ ​of​ ​the​ ​different​ ​fuel​ ​cells​ ​at​ ​a​ ​specified​ ​resistance.​ ​T-tests​ ​were​ ​performed​ ​to compare​ ​the​ ​efficiencies​ ​and​ ​power​ ​outputs​ ​of​ ​each​ ​of​ ​the​ ​fuel​ ​cells​ ​at​ ​the​ ​specified​ ​resistance.​ ​It​ ​was determined​ ​that,​ ​at​ ​the​ ​95%​ ​confidence​ ​level,​ ​there​ ​were​ ​statistically​ ​significant​ ​differences​ ​between​ ​the efficiencies​ ​and​ ​the​ ​power​ ​outputs​ ​of​ ​Z0001​ ​and​ ​Z0002​ ​and​ ​also​ ​between​ ​the​ ​efficiencies​ ​and​ ​power outputs​ ​of​ ​Z0001​ ​and​ ​Z5184.​ ​Therefore​ ​the​ ​null​ ​hypotheses​ ​were​ ​rejected​ ​for​ ​those​ ​comparisons.​ ​For​ ​the comparison​ ​of​ ​the​ ​Z0002​ ​and​ ​the​ ​Z5184​ ​fuel​ ​cells,​ ​it​ ​was​ ​determined​ ​that,​ ​at​ ​the​ ​95%​ ​confidence​ ​level, there​ ​were​ ​not​ ​statistically​ ​significant​ ​differences​ ​between​ ​their​ ​efficiencies​ ​and​ ​power​ ​outputs.​ ​See​ ​the appendix​ ​for​ ​the​ ​T-tests:​ ​Tables​ ​A1-A6. 7 Table​ ​3:​ ​Power​ ​output​ ​of​ ​each​ ​cell​ ​at​ ​different​ ​currents​ ​calculated​ ​by​ ​multiplying​ ​the​ ​voltage​ ​by​ ​the current. Power​ ​(mW) Current (mA) Z0001 Z0002 Z5184 11 11.55 10.23 10.78 32 26.56 23.68 25.92 50 37.5 31 33 69 41.4 32.43 36.57 93 41.85 28.83 33.48 Averages 31.772 25.234 27.95 8 References “Early​ ​Market​ ​Applications​ ​for​ ​Fuel​ ​Cell​ ​Technologies”.​ ​Department​ ​of​ ​Energy​, energy.gov/eere/fuelcells/early-market-applications-fuel-cell-technologies. EG&G​ ​Technical​ ​Services,​ ​Inc.​ ​“Fuel​ ​Cell​ ​Handbook​ ​(Seventh​ ​Edition).”​ ​Ecat.montana.edu,​ ​2004, ecat.montana.edu/d2l/le/content/461714/viewContent/3060263/View. 9 Appendix Appendix​ ​A:​ ​Raw​ ​Data Table​ ​A1:​ ​T-test​ ​comparing​ ​the​ ​efficiencies​ ​of​ ​the​ ​Z0001​ ​and​ ​Z0002​ ​fuel​ ​cells. t-Test:​ ​Two-Sample​ ​Assuming​ ​Equal​ ​Variances Z0001​ ​vs​ ​Z0002​ ​Efficiencies Mean Variance Observations Pooled​ ​Variance Hypothesized​ ​Mean Difference df t​ ​Stat P(T<=t)​ ​one-tail t​ ​Critical​ ​one-tail P(T<=t)​ ​two-tail t​ ​Critical​ ​two-tail 0.5075 0.41 0.000758333 0.000466667 4 4 0.0006125 0 6 5.571428571 0.000708861 1.943180281 0.001417722 2.446911851 10 Table​ ​A2:​ ​T-test​ ​comparing​ ​the​ ​efficiencies​ ​of​ ​the​ ​Z0001​ ​and​ ​Z5184​ ​fuel​ ​cells. t-Test:​ ​Two-Sample​ ​Assuming​ ​Equal​ ​Variances Z0001​ ​vs​ ​Z5184​ ​Efficiencies Mean Variance Observations Pooled​ ​Variance Hypothesized​ ​Mean Difference df t​ ​Stat P(T<=t)​ ​one-tail t​ ​Critical​ ​one-tail P(T<=t)​ ​two-tail t​ ​Critical​ ​two-tail 0.5075 0.44 0.000758333 0.0006 4 4 0.000679167 0 6 3.662946616 0.005271193 1.943180281 0.010542387 2.446911851 11 Table​ ​A3:​ ​T-test​ ​comparing​ ​the​ ​efficiencies​ ​of​ ​the​ ​Z0002​ ​and​ ​Z5184​ ​fuel​ ​cells. t-Test:​ ​Two-Sample​ ​Assuming​ ​Equal​ ​Variances Z0002​ ​vs​ ​Z5184​ ​Efficiencies Mean Variance Observations Pooled​ ​Variance Hypothesized​ ​Mean Difference df t​ ​Stat P(T<=t)​ ​one-tail t​ ​Critical​ ​one-tail P(T<=t)​ ​two-tail t​ ​Critical​ ​two-tail 0.41 0.44 0.000466667 0.0006 4 4 0.000533333 0 6 -1.837117307 0.05792 1.943180281 0.11584 2.446911851 12 Table​ ​A4:​ ​T-test​ ​comparing​ ​the​ ​power​ ​outputs​ ​of​ ​the​ ​Z0001​ ​and​ ​Z0002​ ​fuel​ ​cells. t-Test:​ ​Two-Sample​ ​Assuming​ ​Equal​ ​Variances Z0001​ ​vs​ ​Z0002​ ​Power​ ​Output Mean Variance Observations Pooled​ ​Variance Hypothesized​ ​Mean Difference df t​ ​Stat P(T<=t)​ ​one-tail t​ ​Critical​ ​one-tail P(T<=t)​ ​two-tail t​ ​Critical​ ​two-tail 37.25 30.5 2.916666667 5.666666667 4 4 4.291666667 0 6 4.607929004 0.001830704 1.943180281 0.003661408 2.446911851 13 Table​ ​A5:​ ​T-test​ ​comparing​ ​the​ ​power​ ​outputs​ ​of​ ​the​ ​Z0001​ ​and​ ​Z5184​ ​fuel​ ​cells. t-Test:​ ​Two-Sample​ ​Assuming​ ​Equal​ ​Variances Z0001​ ​vs​ ​Z5184​ ​Power​ ​Output Mean Variance Observations Pooled​ ​Variance Hypothesized​ ​Mean Difference df t​ ​Stat P(T<=t)​ ​one-tail t​ ​Critical​ ​one-tail P(T<=t)​ ​two-tail t​ ​Critical​ ​two-tail 37.25 33.25 2.916666667 6.25 4 4 4.583333333 0 6 2.642313036 0.019210702 1.943180281 0.038421405 2.446911851 14 Table​ ​A6:​ ​T-test​ ​comparing​ ​the​ ​power​ ​outputs​ ​of​ ​the​ ​Z0002​ ​and​ ​Z5184​ ​fuel​ ​cells. t-Test:​ ​Two-Sample​ ​Assuming​ ​Equal​ ​Variances Z0002​ ​vs​ ​Z5184​ ​Power​ ​Outputs Mean Variance Observations Pooled​ ​Variance Hypothesized​ ​Mean Difference df t​ ​Stat P(T<=t)​ ​one-tail t​ ​Critical​ ​one-tail P(T<=t)​ ​two-tail t​ ​Critical​ ​two-tail 30.5 33.25 5.666666667 6.25 4 4 5.958333333 0 6 -1.593255014 0.081105601 1.943180281 0.162211203 2.446911851 15 Table​ ​A7:​ ​Blank​ ​Data​ ​Sheets Fuel​ ​Cell​ ​ID: Wire​ ​Diameter: Wire​ ​Cross​ ​Sectional​ ​Area: Temperature: Pressure: Resistance​ ​(Ω) Voltage​ ​(V) Current​ ​Density​ ​(mA/ cm2 ) Efficiency​ ​(ɳ) Average​ ​Efficiency​ ​(ɳ): Fuel​ ​Cell​ ​ID: Wire​ ​Diameter: Wire​ ​Cross​ ​Sectional​ ​Area: Temperature: Pressure: Resistance​ ​(Ω) Voltage​ ​(V) Current​ ​Density​ ​(mA/ cm2 ) Efficiency​ ​(ɳ) Average​ ​Efficiency​ ​(ɳ): 16 Fuel​ ​Cell​ ​ID: Wire​ ​Diameter: Wire​ ​Cross​ ​Sectional​ ​Area: Temperature: Pressure: Resistance​ ​(Ω) Current​ ​Density​ ​(mA/ cm2 ) Voltage​ ​(V) Efficiency​ ​(ɳ) Average​ ​Efficiency​ ​(ɳ): Voltages​ ​measured​ ​at​ ​specified​ ​resistance​ ​(V) Resistance​ ​(Ω): Z0001 Z0002 Z5184 17 Appendix​ ​B:​ ​Pre-Lab​ ​Method​ ​Section Experimental​ ​Protocol 1. Connect​ ​the​ ​hydrogen​ ​tank​ ​to​ ​the​ ​three​ ​fuel​ ​cells​ ​via​ ​a​ ​rubber​ ​tubing 2. Connect​ ​each​ ​fuel​ ​cell​ ​to​ ​a​ ​rheostat​ ​using​ ​the​ ​copper​ ​cables.​ ​Copper​ ​cables​ ​used​ ​are​ ​red​ ​and​ ​black in​ ​color.​ ​The​ ​black​ ​wire​ ​is​ ​connected​ ​the​ ​black​ ​input​ ​on​ ​the​ ​cell​ ​and​ ​the​ ​red​ ​is​ ​connected​ ​to​ ​the red. 3. To​ ​obtain​ ​the​ ​current​ ​densities,​ ​the​ ​areas​ ​of​ ​electrodes​ ​were​ ​recorded​ ​by​ ​measuring​ ​the​ ​diameter of​ ​the​ ​wire. 4. Regulators​ ​on​ ​the​ ​fuel​ ​tanks​ ​were​ ​set​ ​to​ ​3​ ​psi. 5. A​ ​10​ ​min​ ​window​ ​was​ ​given​ ​to​ ​the​ ​fuel​ ​cells​ ​to​ ​get​ ​into​ ​a​ ​condition​ ​of​ ​equilibrium. 6. Resistance​​ ​was​​ ​adjusted​​ ​by​​ ​about​ ​a​ ​sixth​​ ​of​​ ​a​ ​rotation​​ ​and​​ ​then​​ ​allowed​​ ​to​​ ​stabilize​​ ​for​​ ​at​ ​least​​ ​10​ ​min.​ ​After​​ ​the​​ ​system​​ ​had​​ ​stabilized,​ ​voltage​​ ​and​​ ​current​​ ​values​​ ​were​ ​recorded. 7. By​ ​sliding​ ​the​ ​rheostat​ ​to​ ​different​ ​points,​ ​the​ ​resistance​ ​was​ ​varied.​ ​This​ ​was​ ​done​ ​four​ ​more times​ ​and​ ​each​ ​time​ ​it​ ​was​ ​varied​ ​by​ ​a​ ​sixth​ ​of​ ​a​ ​rotation. 8. On​ ​the​ ​third​ ​rotation,​ ​the​ ​voltage​ ​was​ ​recorded​ ​5​ ​times​ ​with​ ​an​ ​interval​ ​of​ ​30​ ​sec​ ​between​ ​each voltage​ ​value​ ​recorded. Appendix​ ​C:​ ​Sample​ ​Calculation​ ​for​ ​determining​ ​the​ ​efficiencies. Equation​ ​3​:​ ​ η = (ηideal *V act ) E ideal = 0.675 * V act =​ ​0.675​ ​ V −1 *​ ​(1​ ​ V )​ ​=​ ​0.675 18 19
Performance Analysis of Polymer Electrolyte Membrane Fuel Cells Mohammed Alghamdi Rashed Alghamdi Saleh Almansour Nicholas Billette Will Steffe Group #3 October 15, 2018 Abstract - New (Do Last) Introduction Fuel cells are used to convert chemical energy in reactions into electrical energy at a high efficiency and low environmental impact. Fuel is converted to electricity through an electrochemical reaction that uses hydrogen with oxygen or other oxidizing agents. A single fuel cell consists of an anode, a cathode, and a polymer electrolyte membrane (PEM). The pure hydrogen gas flows into the anode, where the hydrogen is separated into protons and electrons. The negatively-charged electron flow generates electricity. The membrane only allows the protons to flow toward the cathode. The oxygen (from ambient air) flows into the cathode where it reacts with the protons to form water and heat. The amount of power, water and heat produced depends on many factors such as the fuel cell size, reaction used, and operating conditions. (“Early Market Applications for Fuel Cell Technologies”). This experiment used three fuel cells as a sample to test the quality in production of TB12 Fuel Cells for use in P3’s forklifts. The power output in both normal use and limited oxygen use was measured at multiple current levels and used to find maximum power output to construct a t-test between the fuel cells. A characteristic curve was also created for each fuel cell, to provide a visual comparison to determine differences. This provides an insight to the differences in the catalytic reactions and possibly a reason for further testing to understand why these differences exist. Objectives The objective of this lab was to determine how three fuel cells performed in the linear Ohmic Polarization region of a characteristic curve. Voltages produces at a maximum power were tested for significance with an equal variance t-test to determine if there was a difference in performance. A parallel objective was to use an equal t-test to analyze how the oxygen concentration affected the position of the characteristic curve and the voltage by varying the flow of oxygen into a fuel cell. Theory An electric current is produced when polymer electrolyte fuel cells do work through a chemical reaction. During this reaction, hydrogen gas enters the fuel cell at the anode, and participates in an oxidation reaction. The free electrons are forced through a wire to the cathode, driving the current. The reaction proceeds as: 𝐻2 → 2𝐻 + + 2𝑒 − (𝐸𝑞. 1) The rate of hydrogen oxidation determines the rate of flow of the electrons, which determines the current of the fuel cell. Hydrogen migrates through the fuel cell membrane. Meanwhile, oxygen present in air drives the reaction by being reduced by the electrons, and forms water with the hydrogen ions at the cathode. The reaction proceeds as: 1 𝑂 + 2𝐻 + + 2𝑒 − → 𝐻2 𝑂 2 2 (𝐸𝑞. 2) The internal resistance of the system is the slope of the linear region in the characteristic curve. The relationship is expressed as: Δ𝑉𝑖𝑛𝑡𝑒𝑟𝑛𝑎𝑙 = 𝐼 ∗ 𝑅𝑖𝑛𝑡𝑒𝑟𝑛𝑎𝑙 (𝐸𝑞. 3) Where 𝑉 is voltage (Volts), 𝐼 is current (amps), and 𝑅 is internal resistance (ohms). As the current increases, the voltage loss increases as a result of the constant internal resistance, resulting in a decrease in the measured cell potential. The power of the system is the product of voltage and current: 𝑃 =𝑉∗𝐼 (𝐸𝑞. 4) Where P is power in Watts. This is the metric by which the fuel cells were compared. Figure 1 shows the general characteristic curve of a fuel cell. The nonlinear regions are a result of overpowering activation energy and hyper-concentration losses due to slow gas transport, respectively. (EG&G Technical Services, Inc.). The middle region is the linear Ohmic Polarization region, where voltage drop is due to internal resistance only. This is the region that will be used for all analysis of the fuel cells. Figure 1: General characteristic curve for a fuel cell, where increasing current decreases the voltage due to internal resistance. (EG&G Technical Services) Methods Tubing and splitters were distributed so that the valve controlling the hydrogen feed stream was connected to all three fuel cells. Similarly, all three fuel cells were attached with an inlet air stream running from a wall pump. Hydrogen entered through a connection at the top of the fuel cell and the exited tubing at the bottom of the cell was clamped off. On the alternate side, air entered the fuel cell and the lower exit stream released air and water to the environment. Each fuel cell was connected to a rheostat with the red and black wire being connected to the positive and negative end of the unit respectively. All the equipment and materials used were provided by the Chemical Engineering department at Montana State University. This experiment required three fuel cells containing cathodes, anodes and membranes to accomplish the oxidation reaction. Three rheostats were required to record voltage, current, and to change resistance metrics. Three sets of positive and negative wires connected the rheostats to the fuel cells. A pressurized hydrogen cylinder, plastic tubing, tube clamps, and an air pump were also needed. Figure 2 details the setup. Figure 2: Hydrogen and oxygen from air are fed and reacted in the fuel cell, releasing air and water, with no hydrogen released to the surroundings. Resistance is controlled through the attached Rheostat. Equipment was created and provided by Montana State University. Experimental Design After turning the hydrogen tank’s valve stem 90 degrees and setting the pressure regulator to three psi, the tanks regulator was turned 90 degrees to allow hydrogen to enter the fuel cell. The air pump was turned so that an audible hiss could be heard as air exited the fuel cells after being pulled from the environment and through the fuel cell. Once both feed streams were running, the rheostat was used to adjust the resistance on the fuel cell. Resistance was initially set to the point where it began to show a change in current and voltage response (Activation Polarization region). Once at steady state (voltage and current measurements were no longer fluctuating) current and voltage were recorded. Resistance was was changed by on tick mark until the rheostat reached its minimum resistance. This process was done for each fuel cell and resulting data sets were used to construct the unit’s characteristic curve. Next, the rheostat was adjusted to a resistance that correlated with the maximum power found in the characteristic curve trials. Once at steady state, current and voltage were recorded every 30 seconds for five minutes. This process was used for all three fuel cells. The final set of trials involved fuel cell performance under oxygen depletion. The rheostat was reattached to the fuel cell with the most power and was adjusted to a resistance that correlated with the maximum power found in the characteristic curve trials. After two minutes at steady state, the voltage and current were recorded. Once recorded, the air inlet stream and exit stream were tapped off, ceasing the oxygen flow into the system. Every 15 seconds following that action, the current and voltage were recorded. This process was repeated two times. Other fuel cells were not tested under oxygen depletion because at this point in the experiment, they were already running at deprived states and resulting data would not have been indicative of normal operating conditions. After collecting measurements on voltage and current for each fuel cell, the data was used to construct a characteristic curve for each fuel cell. Figure 3 shows the characteristic curve for fuel cell 1. The trendline was plotted over the linear Ohmic Voltage (mV) Results/Discussion 700 600 500 400 300 200 100 0 y = -12.348x + 569.34 0 10 20 30 40 Current (mA) Figure 3: The characteristic curve for fuel cell 1. The trendline lies in the Ohmic Polarization region, and shows an internal resistance of 12.348 Ω. Polarization region, where current and voltage are inversely proportional (Equation 3). They are related through the Ohmic resistance losses, due to the internal resistances of the device. These losses can be used to compare the efficiency of the devices. As the slope decreases, the losses in voltage due to resistance as the current rises also decreases. This correlates to a device that is comparatively more efficient. Conversely, a steeper slope corresponds to a greater Ohmic loss with increased current. The figures for the other fuel cells can be found in the appendix. 0.008 0.007 of the fuel cells can be calculated for 0.006 each measurement. The maximum power produced could then be found by creating a current vs. Power (W) Using Equation 4, the power 0.005 0.004 0.003 0.002 0.001 power graph (Figure 4) for use in the 0 0 next tests. The other power figures 5 10 15 20 25 30 35 Current (mA) can be found in the appendix. A statistical analysis between the average power of each fuel cell yielded a comparison that is a function of both voltage and current. It is the relationship between voltage Figure 4: Maximum power for fuel cell 1 was found to be at the 14th data point, corresponding to a current of around 19.9 mA. This was used to set the resistance for the constant resistance analysis. Table 1: Fuel cells 1 and 3 are statistically different while the combinations of fuel cells 1 and 2 and fuel cells 2 and 3 are not. and current that contributes to efficiency of the fuel cells. Table 1 shows the statistical analysis between Fuel Cell Average P (W) T-Test P value Outcome 1 0.00337 ± 0.0016 1 vs. 2 0.0053 P<α 2 0.00190 ± 0.00073 1 vs. 3 0.0061 P>α 3 0.00588 ± 0.0048 2 vs. 3 0.07 P<α the maximum power of each fuel cell from and unequal variance t-test. It was determined that fuel cells 1 and 3 were not statistically different, while fuel cell 1 and fuel cell 2 were statistically different, as well as fuel cell 2 and fuel cell 3. The power produced by fuel cell 3 was also significantly higher than either 1 or 2, and the rheostat used could not register the maximum power that it was able to produce. Fuel cell 3 was deemed the most efficient in terms of maximum power ability. When the resistance of the rheostat is held constant by keeping the voltage and current constant, the variability in the data collected is reduced. The resulting power was expected to be constant. After 10 measurements were taken in 30 second intervals for each fuel cell, the power was again calculated at each point. It was at the beginning of this test that two of the fuel cells began displaying a limiting behavior. The intention was to set the current to result in a maximum power output for each cell (found from the power curve, Figure 4) for the data Table 2: All three fuel cells perform statistically differently from each other at their maximum power output. collection. However, the maximum power that could be produced by both fuel cells 2 and 3 was significantly lower than expected. This was determined to be a “sickening” of the catalytic sites inside the fuel cells, contributing to Fuel Cell 1 2 3 Average Max Power (W) 7.67E-03 ± 1.15E-05 1.64E-05 ± 3.27E-6 9.84E-06 ± 2.74E-6 T-Test P value Outcome 1 vs. 2 2.13E-29 P<α 1 vs. 3 1.89E-29 P<α 2 vs. 3 0.00015 P<α a decrease in the reaction rates. After comparison through an unequal variance t-test, it can be seen in Table 2 that all three fuel cells were deemed statistically different from each other, rejecting the null hypothesis. demonstrated how the fuel cell reacted to limiting the oxygen availability. Assuming oxygen was the limiting reactant, as it goes to 0, the voltage and current should also go to 0 in a proportional manner. Fuel cell 1 was the only cell used in this test, as fuel cells 2 and 3 were unable to perform with useable results. The voltage and current were measured every 10 seconds over the course of 100 seconds, and repeated 3 times from 600 550 y = 26.224x 500 450 400 350 300cell 1 is consistent in its loss of power as the Table 3: Fuel 250 oxygen in the system is depleted. 200 10 20 Average P lost 15 Voltage (mV) The final test, oxygen depletion, 25 Current (mA) per interval T-Test P value Outcome (W) 5.4E-04 on fuel cell 1Figure 5: The effect of oxygen 1 vs.depletion 2 0.189 P >1,αtrial 2. ± 1.01E-3 The voltage and current decrease proportionally. 6.29E-05 2 1 vs. 3 0.74 P>α ± 3.69E-04 2.00E-04 3 2 vs. 3 0.517 P>α ± 1.25E-3 Fuel Cell around the maximum power. The differences in the power outputs between each measurement interval can be used as a metric to determine if the difference is significant. As shown in Table 3, a statistical analysis with an unequal variance t-test determined that none of the performances under limiting oxygen were statistically different. This is as expected considering only one fuel cell was used. Figure 5 shows the effect of limiting oxygen conditions over the course of 100 seconds for the second trial. As expected, the current and voltage and current drop proportionally to the depletion of oxygen in the air. The slope corresponds to the loss of maximum power capability over the change in oxygen concentration, so a steeper slope will correspond to a larger impact of oxygen loss on the system. The figures for the other fuel cells can be found in the appendix. Conclusion The performance of a fuel cell can be determined through its comparable power production. This experiment explored performance differences by analyzing the linear Ohmic Polarization region of the characteristic curve. The power production was tested under three conditions, with two tests concluding that fuel cell 3 is statistically different in its performance. From the data collected in the constant-resistance test, the average power production of fuel cell 3 is lower, and from decreasing oxygen availability, it also responds more dramatically to depletion of oxygen. The characterization of this efficiency is indisputable. If the supply of oxygen is invariable, and the external resistance is constant, the power produced by fuel cell 3 is less efficient than fuel cells 1 and 2. If the oxygen supply does vary, the power produced by fuel cell 3 decays faster than either fuel cell 1 or 2, and the fuel cells is shown again to be less efficient. The variation in performance of these fuel cells indicates some production issues. To explore the potential impacts of decreased efficiency and further describe the magnitude, another test could be done using the reversible fuel cell and measuring the rate of electrolysis compared to the rate of formation of water and determining if the rates are equal and opposite, as they should be. This would be helpful in deciding if the inefficiency is on the hydrogen catalyst side, the oxygen catalyst side, or in the transfer of electrons. Between this and an oxygen limiting experiment, the limiting reactant can be identified and if a difference exists in the forward and reverse reaction, the transfer of electrons through the fuel cell is perhaps the reason. References Department of Energy. (2017). ENERGY.GOV. Retrieved August 29, 2018, from Energy Efficency : https://www.energy.gov/science-innovation/energy-efficiency EG&G Technical Services. (2004). Fuel Cell Handbook, Seventh Edition. Morgantown, West Virginia: U.S Department of Energy, Office of Fossil Energy, National Energy Technology Laboratory. US Department of Energy. (2015, November ). Energy Efficency & Renewable Energy. Retrieved September 30th, 2018, from Fuel Cell Technologies : https://www.energy.gov/sites/prod/files/2015/11/f27/fcto_fuel_cells_fact_sheet.pdf Wetttein, S. W. (2018, September). ECHM/EBIO Info Pack. Retrieved September 2018, from file:///Users/willsteffe/Downloads/20180928%20FAVRE%20Employee%20handbook.pdf Appendices - New

Tutor Answer

School: Boston College


The experiment was successful in giving us a comparable difference between the three fuel cells.
The current and Voltage curve gave the Ohmic polarization region which is a linear region
showing the output level for different resistance. There exist an inverse proportionality in the
relationship between current and voltage. The relationship contributes to the efficiency of the
fuel cell. From each measurement, a current power curve plotted shows a difference between the
three fuel cells. Fuel 3 cell showed a higher output as compared to the other fuel cel...

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Wow this is really good.... didn't expect it. Sweet!!!!

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