PhD Thesis - Energy Systems Research Unit - University of Strathclyde

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The length of time required for one batch is translated into the equivalent number of timesteps necessary using Number of Timesteps = Time x Timesteps (6.26) Where Time = Length of batch (hours) If the process is continuous throughout the day, the process will start at the first timestep where sufficient oil is available. If more oil is available than the maximum oil input, the process will run at full load. If the oil 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 oil used (litres) is removed from the store at this timestep, and a timestep count is initiated to chart progress through the batch. The ethanol or methanol demand is also attributed to this timestep, if desired, and is translated into a production rate (litres/hr) by multiplying by the number of timesteps per hour. For the subsequent timesteps, if the count is greater than or equal to zero, and less than the timestep equivalent of the heating time, then the energy required for this is applied for that timestep (directly in kW). This may be kept as a heat demand, or made directly into an electricity demand if a 100% efficient electric heater is used. The partial production factor is applied as necessary, as the amount of energy required is in direct proportion to the amount of oil being heated. If the timestep count is greater than or equal to the timestep equivalent of the heating time (which may be zero), and less than the timestep equivalent of the time required for mixing, then the electricity required is applied for that timestep (directly in kW). If the timestep count is greater than or equal to the timestep equivalent of the batch length minus the timestep equivalent of the time required for biodiesel cleaning (which may be zero), and less than the timestep equivalent of the batch length, then the electricity required is applied for that timestep (directly in kW). The partial production factor is not applied to either of these electricity demands, as they would be independent of the amount of oil used. 204
If it is the last timestep of the process, the amount of biodiesel made is added to the production profile for that timestep. The partial production factor is applied as necessary, and the amount of biodiesel 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 provided there is enough oil available. If a number of batches per day with a starting time have been specified, the batch can only be started after a given time each day, if no batch production is currently in progress, and if the maximum number of batches allowed each day has not been exceeded. Otherwise, the procedure outlined above is followed. The outputs of the batch process simulation are the same as for the continuous process described in Section 6.3.2. 6.3.4 Use of Crop Residue If energy crops are used, a certain amount of crop residue, left over after oil extraction, will be available. This may 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 amount of residue made is calculated using Equation 6.3, with the yield being the crop residue (kg/ha), and this is made available at the last timestep of every day during the harvest season. If the crop residue 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 the anaerobic digestion or gasification process is to be used, the feedstock availability for these processes is defined by the production of the crop residue, which is made available at the last timestep of each day. This feedstock is used immediately for the digestion process, or may be added to a store, for use at any time, for the gasification process. This can be done because the type of residue suitable for gasification will be much drier than that suitable for anaerobic digestion, and therefore will not suffer from the problem of degradation if stored properly. 205
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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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Page 155 and 156: Is Min = 0 ? No Is Min = PC1 ? No I
Page 157 and 158: 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
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: production and energy use profiles
Page 207 and 208: For each process, the process chara
Page 209 and 210: At the end of the simulation, graph
Page 211 and 212: As the time required for one batch
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
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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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