PhD Thesis - Energy Systems Research Unit - University of Strathclyde

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If four, three or two fuel cells are specified, the procedure outlined above is followed, checking first if the factor is greater than four, three or two respectively, rather than five. In this way, the percentage load, the number of fuel cells running, and their efficiency at this load, may be determined, to provide the optimum use of the total fuel available. No No Is Num = 5 ? No Is Num = 4 ? No Is Num = 3 ? No Is Num = 2 ? No Is Fuel Unit = kWh ? Is Fuel Unit = litres ? Fuel Unit = kg Yes Yes Yes Yes No No No No No Yes Yes Is Factor > 5 ? Is Factor = 5 ? Is Factor > 4 ? No Is Factor = 4 ? Is Factor > 3 ? No Is Factor = 3 ? Is Factor > 2 ? No Is Factor = 2 ? Is Factor > 1? No Is Factor = 1 ? No No No BestFC = BestPL x Rated / ( BestEff x Timesteps ) BestFC = BestPL x Rated x 3610300 / ( BestEff LHV x Density x Timesteps ) BestFC = BestPL x Rated x 3610.3 / ( BestEff x LHV x Timesteps ) Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Is Fuel Available < FC1 ? Is FC1 < Fuel Available < FC2 ? Is FC2 < Fuel Available < FC3 ? Factor = Fuel Available / BestFC Fuel Cells 1,2,3,4,5 ON Fuel = Fuel Avialable / 5 PL = BestPL Fuel Cells 1,2,3,4,5 ON Fuel Cells 1,2,3,4,5 ON Fuel = Fuel Avialable / 5 PL = BestPL Fuel Cells 1,2,3,4 ON Fuel Cells 1,2,3,4,5 ON Fuel = Fuel Avialable / 5 PL = BestPL Fuel Cells 1 ,2,3 ON Fuel Cells 1,2,3,4,5 ON Fuel = Fuel Avialable / 5 PL = BestPL Fuel Cells 1 ,2 ON Fuel Cells 1,2,3,4,5 ON Fuel = Fuel Avialable / 5 PL = BestPL Fuel Cells 1 ON No Yes Yes Yes 158 Is BestPL < PC1 ? No Is BestPL < PC2 ? No Is BestPL < PC3 ? No PL = ((( FC1 - Fuel Available ) / FC1 ) x ( PC1 - PC2 )) + PC1 Yes No No PL = ((( Fuel Available- FC1 ) / ( FC2 - FC1 )) x ( PC2 - PC1 )) + PC1 PL = ((( Fuel Available - FC2 ) / ( FC3 - FC2 )) x ( PC3 - PC2 )) + PC2 PL = ((( Fuel Available - FC3 ) / ( FC4 - FC3 )) x ( PC4 - PC3 )) + PC3 Figure 5.20 Possible Load Determination for a Fuel Cell Is Fuel < FC1 ? PL = ((( FC1 - Fuel ) / FC1 ) x ( PC1 - PC2 )) + PC1 No Is FC1 < Fuel < FC2 ? PL = ((( Fuel - FC1 ) / ( FC2 - FC1 )) x ( PC2 - PC1 )) + PC1 Is FC2 < Fuel < FC3 ? PL = ((( Fuel - FC2 ) / ( FC3 - FC2 )) x ( PC3 - PC2 )) + PC2 PL = ((( Fuel - FC3 ) / ( FC4 - FC3 )) x ( PC4 - PC3 )) + PC3 Yes Yes Yes
5.7 Electrolyser Model An electrolyser uses excess electricity to create pure hydrogen from water, which may then be used for transport, for the production of heat or electricity, or stored for later use. It is, effectively, a fuel cell operating in reverse, and shows the same increase in efficiency at lower running levels. Again, complex models such as TRNSYS and SIMELINT do exist to predict the output of specific electrolysers [25,26], but these require large amounts of data specific to each electrolyser, and give more detail than is required here. Therefore, easily available manufacturers’ data will again be used to provide a sufficient approximation of the performance of a range of electrolysers. The performance of an electrolyser is defined by its electricity consumption (kWh/Nm 3 ), which varies at partial loads, and may be quoted at a range of percentage loads, and by its maximum hydrogen production rate (Nm 3 /hour). The unit Nm 3 represents one normal cubic metre of hydrogen (measured at 0°C and 1 bar), which is equivalent to 3 kWh. The amount of water required is around one litre/Nm 3 , and there is usually a minimum acceptable percentage load of around 25%. If the hydrogen produced is to be compressed or liquefied for storage, the energy required to do this must be taken into consideration, and this is also given in kWh/Nm 3 . The performance of an electrolyser is not significantly affected by ambient temperature or altitude, and as it operates at ambient temperature, it does not require to run on standby. Little waste heat is produced, and this is not enough to be of use for CHP [27,28]. An example of the electrolyser definition window can be seen in Appendix 1, Figure A1.50. 5.7.1 Electrolyser Performance Algorithm To determine the amount of hydrogen that may be produced, the amount of electricity available for use over each timestep must be known. Therefore, the rate at which electricity is available (kW) must be divided by the number of timesteps per hour to give the total amount of electricity available for use (kWh). The maximum amount of hydrogen that may be made over the timestep (Nm 3 ) must also be determined by dividing the maximum production rate by the 159
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Decision Support for New and Renewa
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Abstract The global requirement for
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CONTENTS 1 ENERGY SYSTEMS FOR SUSTA
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5.5 Steam Turbine Model 149 5.6 Fue
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FIGURES Figure 1.1 Final Energy Con
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Figure 7.30 Following Electricity a
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on the use of fossil fuels, energy
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The general increase in energy cons
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supply is reduced or eliminated, lo
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Figure 1.3 The Electricity Supply G
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on different generation mixes depen
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Various studies have been carried o
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provision for smaller areas, and he
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1.7 References [1] The Internationa
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2 Options for New and Renewable Ene
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the amount of usable heat that is g
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the conversion of petrol cars; howe
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set times, producing a constant ele
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partial load. Fast response and sta
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2.3 The Production and Storage of H
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dedicated boiler, which runs contin
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Figure 2.3 A Typical Hydrogen Filli
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part of the natural carbon cycle (a
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Figure 2.4 Layout of a Gasification
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met by process integration and the
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Figure 2.5 The Inputs and Outputs o
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1. Scale for measuring out lye and
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feedstock being used. Sugary feedst
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carbon dioxide via steam reforming.
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• Where CHP is used, the balance
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[22] Vehicle Certification Agency (
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[55] M. A. Paisley, J. M. Irving, R
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3 Approaches to Renewable Energy Sy
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Because of the intermittent nature
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A renewable energy supply evaluatio
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the system are kept. The output of
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There are various models available
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When the use of climate dependant i
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3.5 References [1] M. Muselli, G. N
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4 A Procedure for Demand and Supply
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pumped storage and flywheels), a ba
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for the agricultural vehicle use re
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Figure 4.4 Combining Demands to Tak
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ates for vehicles, engines and othe
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Figure 4.5 Derived Fuel Production
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together if desired, and taken forw
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profiles are output from this part
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dividing the production rate at eac
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As it would be too confusing to sho
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Figure 4.12 Output of the Matching
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However, when more than one transpo
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considered, this amount is added to
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users are alerted if there is not e
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Page 109 and 110: vehicles if they are increased by 1
Page 111 and 112: If biogas is being considered, the
Page 113 and 114: The number of timesteps per hour wi
Page 115 and 116: After the algorithm has been follow
Page 117 and 118: • Float Charge - once the battery
Page 119 and 120: Discharge No tank = tank fuel used
Page 121 and 122: equired (kW) = maxkWh x bulk% (5.16
Page 123 and 124: An example of the output graph prod
Page 125 and 126: 5.2.1 Required Power Specifically d
Page 127 and 128: 5.2.3 Engine Performance in the Con
Page 129 and 130: used for gas powered ICEs, but the
Page 131 and 132: and five times, depending on the nu
Page 133 and 134: Is PL < Min ? No Is PL = 0 ? No Is
Page 135 and 136: where Max = maximum energy availabl
Page 137 and 138: where Ratiopart = heat to electrici
Page 139 and 140: (including following heat demand wh
Page 141 and 142: where SFC = specific fuel consumpti
Page 143 and 144: engines running respectively). If t
Page 145 and 146: (continued) Is Fuel Available > (4
Page 147 and 148: of the definition window for a Stir
Page 149 and 150: and continuous operation. Again, mu
Page 151 and 152: The performance of a fuel cell is n
Page 153 and 154: percentage loading, rather than usi
Page 155 and 156: Is Min = 0 ? No Is Min = PC1 ? No I
Page 157: 5.6.4 If Fuel Availability is Less
Page 161 and 162: original calculation of the amount
Page 163 and 164: 5.8 Regenerative Fuel Cell Model A
Page 165 and 166: following the heat demand. To follo
Page 167 and 168: C:\ My Documents\ Nic\ Thesis\ Old\
Page 169 and 170: As 1 kWh = 3610.3 kJ, and using lit
Page 171 and 172: Add Heat to Water Storage Tank Usin
Page 173 and 174: Use Stored Hot Water to Supply Heat
Page 175 and 176: information is given about the over
Page 177 and 178: [23] K. Foger, B. Godfrey, “Syste
Page 179 and 180: the gasification and pyrolysis defi
Page 181 and 182: eing used each day for a continuous
Page 183 and 184: Where Biogas = Biogas production ra
Page 185 and 186: 6.1.3 Use of Biogas Various options
Page 187 and 188: The amount of hydrogen that can be
Page 189 and 190: direct proportion, and the weight o
Page 191 and 192: produce in total (Nm 3 per tonne fe
Page 193 and 194: Electricity (kW) = Elec x Feed (6.1
Page 195 and 196: 3. Make hydrogen via steam reformin
Page 197 and 198: Where Methane = Methane Production
Page 199 and 200: (continued) Keep as medium heating
Page 201 and 202: Yes Feed1 = Yield1 x Land1 / No. of
Page 203 and 204: production and energy use profiles
Page 205 and 206: If it is the last timestep of the p
Page 207 and 208: For each process, the process chara
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At the end of the simulation, graph
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As the time required for one batch
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Ethanol = Factor1 x Eth x Timesteps
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6.5 Electrolysis As it is sometimes
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6.7 Landfill Gas Processing As the
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Demand Profile Design & Profile Dat
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Figure 7.2 Degree-Days Versus Month
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Stage 1 - Sustainable Fuel Supply S
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The different profile of use graphs
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Figure 7.3 Fermentation System Inpu
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Figure 7.7 Fermentation System Info
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Figure 7.10 Fermentation System Out
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The output obtained when a second h
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Figure 7.16 Anaerobic Digestion Par
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Figure 7.19 Fermentation System Inp
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clarity. A constant supply rate of
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Figure 7.25 Heat Demand Profile Fig
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Figure 7.28 Effect of Minimum Load
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esidual heat demand as this would r
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Figure 7.35 Second Engine: Followin
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This chapter described how the over
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heat and electricity during the tou
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Figure 8.2: Overall Yearly Heat Dem
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to allow for efficient operation du
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would be incurred, and the scale of
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Figure 8.5: Electricity Supply and
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heat demand or both, or run at cons
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ut with 30% less land being require
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9 Conclusions and Recommendations T
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through these, technically viable p
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considered. The introduction of coo
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When considering larger geographica
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Appendix 1: Program Windows Figure
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Figure A1.5 CreateClimate.exe Figur
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Figure A1.9: Demand Profile Designe
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Figure A1.13: Derived Fuel Supply W
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Figure A1.17: Fermentation System D
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Figure A1.21: PV Electrolysis Syste
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Figure A1.25: Fuel Supply Profile D
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Figure A1.29: Auxilliary Supply Def
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Figure A1.33: Stirling Engine Syste
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Figure A1.37: Fuel Cell System Defi
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Figure A1.41: Electric Vehicle Syst
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Figure A1.45: Vehicle Conversion Fa
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Figure A1.49: Heating System Defini
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Figure A1.53: Pumped Hydro System D
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Figure A1.57: Auto Search Evaluatio
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PhD Thesis - Energy Systems Research Unit - University of Strathclyde

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