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Some Important Power SourcesCharacteristics of Power Systems for Marine ApplicationsThis LectureSlide Number 4Otto and Diesel CyclesSlide Number 6LM2500 Specifications - QuotedSlide Number 8Battery TechnologiesOverall Discharge Dependence on Current and TemperatureSlide Number 11Comparison of Battery Performance for Mobile ApplicationsFuel CellsSome Fuel Cell IssuesState of the Art 2005ReferencesMassachusetts Institute of Technology 2.019Some Important Power SourcesMassachusetts Institute of Technology 2.019Characteristics of Power Systems for Marine Applications• “Main Supply” of power – energy source must be carried on board; has to last days, months, years.• Weight and volume constraints *may* be significantly reduced compared to terrestrial and esp. aeronautical applications. • Reliability and safety critical due to ocean environment.• Capital cost, operating costs, life cycle analysis, emissions are significant in design, due to large scale.Massachusetts Institute of Technology 2.019This Lecture• Fuel Engines– Characteristics of typical fuels; combustion– Internal combustion engines– Brayton cycle (gas turbine) engines• Batteries and Fuel Cells– Electrochemical processes at work– Canonical battery technologies– Fuel cell characteristics• NOT ADDRESSED: Nuclear power sources, renewable energy, emissions, green manufacturing, primary batteries, generators … !Massachusetts Institute of Technology 2.019Reaction for gasoline:4 C8 H15 + 47 O2  30 H2 O + 32 CO2 + other productsFuelHeat Content MJ/kgGasoline*:C8 H1545Diesel*:C13 H2342Propane:C3 H848Hydrogen:H2130Ethanol:C2 H5 0H28Engines transform chemical energy into heat energy into mechanical or kinetic energy.1 MegaJoule is:1 kN force applied over 1 km;1 Kelvin heating for 1000 kg air;1 Kelvin heating for 240 kg water;10 Amperes flowing for 1000 seconds at 100 Volts*Approx.: complex mixturesPulkrabek, p. 444Massachusetts Institute of Technology 2.019Otto and Diesel Cycles[pressure * volume] = N/m2 * m3/kg = Nm/kg = Energy/mass volumepressurePulkrabek p. 88, 111.IDEALOTTO TypicalOttoTurbochargerCW area enclosed:Specific work!TDCBDC4 & 6-stroke enginesDieselFour-stroke engine: 1: TDC to BDC, bring air into cylinder2: BDC to TDC, compress airADD FUEL and IGNITE!3: TDC to BDC, expand heated air (power stroke)4: BDC to TDC, blow out products of combustionTypical ICE efficiency to BHP: 30%Typical power density: 0.05- 0.4 kW/kgGE LM2500 gas turbine:22kW for marine propulsionMassachusetts Institute of Technology 2.019Photo of the 9H rotor removed due to copyright restrictions.Photo of a LM2500 gas turbine removed due to copyright restrictions.Massachusetts Institute of Technology 2.019LM2500 Specifications - Quoted“ Output: 33,600 shaft horsepower (shp) Specific Fuel Consumption: 0.373 lbs/shp-hr Thermal Efficiency: 37% Heat Rate: 6,860 Btu/shp-hr Exhaust Gas Flow: 155 lbs/sec Exhaust Gas Temperature: 1,051°F Weight: 10,300 lbs Length: 6,52 meters (m) Height: 2.04 m Average performance, 60 hertz, 59°F, sea level, 60% relative humidity, no inlet/exhaust losses, liquid fuel, LHV=18,400 Btu/lb ”http://www.geae.com/aboutgeae/presscenter/marine/marine_200351.htmlMassachusetts Institute of Technology 2.019Brayton cycleSpecific volumePressureCombustionCompressionExpansion through compressor turbine(Expansion through jet nozzle: thrust)Expansion through power turbineGiampaolo, p. 46, 52CompressorCombustorCompressor turbinePower turbine (or nozzle)Working fluid inExhaustsame shaftPressureTypical GT efficiency to SHP: 35%Typical power density (large engines): 5 kW/kg (single spool)Massachusetts Institute of Technology 2.019Battery TechnologiesElectrochemical Cells_electrolyte bath: 35% sulfuric acid solution saturated with PbS04+ ion migration- ion migration+electronsTotal Chemistry of the Lead-Acid battery:Pb + PbO2 + 2 S042- + 4H+ 2 PbSO4 + 2 H2 OLead-acid battery has two electrode reactions (discharge):Releasing electrons at the negative electrode:Pb  Pb2+ + 2e- (oxidized)orPb + S042-  PbSO4 + 2e-Gathering electrons at the positive electrode:Pb4+ + 2e-  Pb2+ (reduced)orPbO2 + SO42- + 4H+ + 2e-  PbSO4 + 2H2 OBerndt, p. 36, 43Theoretical limit of lead-acid energy density: 0.58MJ/kgcathodeanodeMassachusetts Institute of Technology 2.019Overall Discharge Dependence on Current and TemperatureDischarge capacityOsaka & Datta, p. 30, 61, 63100%1C0.2C4C8C100%293K333K273K253KNominal discharge rate C is capacity of battery in Ah, divided byone hour (typical).Some variation of shapes among battery technologies, e.g., lithium lines more sloped. VoltsMassachusetts Institute of Technology 2.019From Rutherford & DoerffelImage removed due to copyright restrictions.Please see Fig. 3 in Rutherford, K., and D. Doerffel."Performance of Lithium-Polymer Cells at High Hydrostatic Pressure."Proceedings of the Symposium on Unmanned Untethered Submersible Technology, 2005.Massachusetts Institute of Technology 2.019Comparison of Battery Performance for Mobile ApplicationsEnergy density, MJ/kg, MJ/lMemory effectMaximum currentRecharge efficiencySelf-discharge, %/month at 293KLead- acid0.14, 0.36 No 20C 0.8-0.94 ??Ni-Cd 0.24, 0.72 Yes 3C 0.7-0.85 25NiMH 0.29, 1.08 Yes 0.6C <20Li-ion 0.43-0.72, 1.03-1.37*No 2C 12All have 300+ cycles if max current is not exceeded.* Lithium primary cells can reach 2.90 MJ/lOsaka & Datta, p. 41, 449; Berndt p. 254Massachusetts Institute of Technology 2.019Fuel Cells• Electrochemical conversion like a battery, but the fuel cell is defined as having a continuous supply of fuel.• At anode, electrons are released: 2H2  4H+ + 4e-• At cathode, electrons are absorbed: O2 + 4e- + 4H+  2H2 0• Proton-exchange membrane (PEM) between electrodes allows H+ to pass, forcing the electrons around outside the battery – the load. PEMFC operates at 300-370K; a low-temperature fuel cell. ~40% efficient.electrolyte or PEMloadO2H2Porous cathodePorous anodee-Larminie & DicksMassachusetts Institute of Technology 2.019Some Fuel Cell Issues• High sensitivity to impurities: e.g., PEMFC is permanently poisoned by 1ppb sulfide.• Weight cost of storage of H2 in metal hydrides is 66:1; as compressed gas: 16:1.• Oxidant storage: as low as 0.25:1• Reformation of H2 from other fuels is complex and weight inefficient: e.g., Genesis 20L Reformer supplies H2 at ~ 0.05 kW/kg• Ability of FC to change load rapidly.• Typical Overall Performance


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MIT 2 017J - Some Important Power Sources

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