PhD Thesis - Energy Systems Research Unit - University of Strathclyde

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• Heat and/or electricity for by-product preparation (kW). Each of these stages is given a number of minutes or hours duration (which may be zero), and these are translated into the equivalent timestep values using Equation 6.25 or 6.26. The process will start at the start time for each day provided sufficient feedstock and equipment are available. If more feedstock is available than the maximum oil input, the process will run at full load. If the feedstock available is between the maximum and minimum input amounts, a partial production factor is calculated using Equation 6.6, and is applied to all inputs. The feedstock used (kg) is removed from the store at this timestep, and a timestep count is initiated to chart progress through the batch. A separate count is initiated, and partial production factor calculated (as appropriate), for each fermenter being used, up to a maximum of five fermenters. The energy demands are applied to the relevant timesteps throughout the batch process in a similar manner to that described in Section 6.3.3. The partial production factor is only applied to the heat demands, and there is the option to translate these heat demands directly into electricity demands (if electric heaters are being used). Distillation and by-product preparation take place after the end of the fermentation process, allowing the equipment to be used for the next batch. A separate count is, therefore, initiated for these stages, for each fermenter. Some of these processes may specify a time, but not an energy demand, if residues are being used to provide some of the process requirements. If it is the last timestep of the fermentation process, the amount of ethanol made is added to the production profile for that timestep. The partial production factor is applied as necessary, and the amount of ethanol produced, in litres, is translated into a production rate (litres/hr) by multiplying it by the number of timesteps per hour. The process is then free to start again, for that particular fermenter, at the next start time, provided there is enough feedstock available. 210
As the time required for one batch is generally between two and four days, the batch process will run through a number of days longer than the batch length before starting to record data, when a continuous feedstock supply is being used. This allows the batches to start working through so that the ethanol production and energy requirements will start from the beginning, for the different batches running simultaneously. This is also done in the transesterification process if the batch length is longer than 24 hours, but this is not generally the case. The outputs of the batch process simulation are the same as for the continuous process described in Section 6.4.2. This process is also shown in Figure 6.7. 6.4.4 Use of Residues If energy crops are used, a certain amount of crop residue may be available. This may, again, be used as cattle feed, sent to an anaerobic digester or gasifier, or burned directly to produce heat and/or electricity, depending on the residue type, and other system requirements. The processes for dealing with this type of residue are as described in Section 6.3.4. If these crop residues are used to meet some or all of the process energy needs, the input energy requirements and amount of residue produced are reduced accordingly. If a dry animal feed is produced, this can be used or processed in the same way as the energy crop residues. Determining the feedstock availability for this residue, however, is more difficult than for the crop residues, as it is produced more erratically. This is not a problem when gasification is being considered, as the feedstock is put into a store when available, and used from that store when possible. The gasification process characteristics are defined, and the outputs and energy use are calculated, in the same manner as described in Section 6.1, and the various options for processing the resulting gas are also available. If the dry animal feed is to be made available for use in boilers, engines or turbines, a temporal production rate graph for a specified “other” category of fuel is produced. If a wet animal feed is produced, this may be sent, if desired, to an anaerobic digester. This is also an option for the dry animal feed. The erratic nature of 211
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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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at the matching stage, along with t
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vehicles if they are increased by 1
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If biogas is being considered, the
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The number of timesteps per hour wi
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After the algorithm has been follow
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• Float Charge - once the battery
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Discharge No tank = tank fuel used
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equired (kW) = maxkWh x bulk% (5.16
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An example of the output graph prod
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5.2.1 Required Power Specifically d
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5.2.3 Engine Performance in the Con
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used for gas powered ICEs, but the
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and five times, depending on the nu
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Is PL < Min ? No Is PL = 0 ? No Is
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where Max = maximum energy availabl
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where Ratiopart = heat to electrici
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(including following heat demand wh
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where SFC = specific fuel consumpti
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engines running respectively). If t
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(continued) Is Fuel Available > (4
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of the definition window for a Stir
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and continuous operation. Again, mu
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The performance of a fuel cell is n
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percentage loading, rather than usi
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Is Min = 0 ? No Is Min = PC1 ? No I
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5.6.4 If Fuel Availability is Less
Page 159 and 160: 5.7 Electrolyser Model An electroly
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
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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
Page 209: At the end of the simulation, graph
Page 213 and 214: Ethanol = Factor1 x Eth x Timesteps
Page 215 and 216: 6.5 Electrolysis As it is sometimes
Page 217 and 218: 6.7 Landfill Gas Processing As the
Page 219 and 220: Demand Profile Design & Profile Dat
Page 221 and 222: Figure 7.2 Degree-Days Versus Month
Page 223 and 224: Stage 1 - Sustainable Fuel Supply S
Page 225 and 226: The different profile of use graphs
Page 227 and 228: Figure 7.3 Fermentation System Inpu
Page 229 and 230: Figure 7.7 Fermentation System Info
Page 231 and 232: Figure 7.10 Fermentation System Out
Page 233 and 234: The output obtained when a second h
Page 235 and 236: Figure 7.16 Anaerobic Digestion Par
Page 237 and 238: Figure 7.19 Fermentation System Inp
Page 239 and 240: clarity. A constant supply rate of
Page 241 and 242: Figure 7.25 Heat Demand Profile Fig
Page 243 and 244: Figure 7.28 Effect of Minimum Load
Page 245 and 246: esidual heat demand as this would r
Page 247 and 248: Figure 7.35 Second Engine: Followin
Page 249 and 250: This chapter described how the over
Page 251 and 252: heat and electricity during the tou
Page 253 and 254: Figure 8.2: Overall Yearly Heat Dem
Page 255 and 256: to allow for efficient operation du
Page 257 and 258: would be incurred, and the scale of
Page 259 and 260: 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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