PhD Thesis - Energy Systems Research Unit - University of Strathclyde

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used in vehicles, for the production of heat, and, when necessary, turned back into electricity via fuel cells. Currently, communities of this type typically use diesel generators for electricity generation (for which diesel must be imported) and many small local electricity distribution networks already exist. It would, therefore, be prudent to assess the feasibility of the local production of biodiesel from dedicated crops for use in the existing plant. As diesel generators produce a substantial amount of waste heat, the use of CHP in a district-heating scheme should also be considered. Although the importation of methanol would still be required to allow biodiesel manufacture, this would be roughly one tenth of the amount of diesel that would otherwise need to be imported. Also, the glycerine produced by the transesterification process is a valuable by-product, which may be exported or used on the island to produce toiletries and cosmetics that may be exported or sold alongside the local craftwork. As biodiesel and diesel can be mixed in an engine with no ill effects, diesel may still be imported and used in the same plant if a shortage should occur. Another option for the production of a multi-purpose fuel from an energy crop would be the fermentation of an extension to the currently grown grain crops to produce ethanol. A by-product of this process would be a nutrient rich animal feed that could be used on the farm, reducing the need to import feed. Such energy crops could be grown on the 10% to 15% of the farmer’s land that is required to be set-aside under European Union legislation, but can be used for non-food production. To reduce the amount of biodiesel or ethanol required, and therefore the amount of land required, electricity and heat production from either of these fuels could be supplemented by electricity from the intermittent sources outlined earlier. As the heat demand is substantially larger than the electricity demand, some electricity would be required to produce heat, and this supplementary electrical heating could be used, in conjunction with heat storage, to help achieve a desirable heat to electricity ratio, and allow the CHP plant to operate as efficiently as possible. The use of multiple engine sets may also be appropriate 254
to allow for efficient operation during different seasons and times of the day. The use of biodiesel, electric and hydrogen-powered vehicles should also be considered, along with the other supplementary supply and storage methods mentioned earlier. The amount of waste available on the island should also be considered as a potential source of fuel for heat, electricity and transportation. Unfortunately, due to the small population, the amount of household waste produced would not be enough to make burning it for heat and/or electricity production a viable option both practically and ecomonically. However, household organic, garden and agricultural wastes could be put into an anaerobic digester, along with the main feedstock (the manure produced by 100 dairy cows on the farm), in order to produce biogas. The small amount of human sewage produced on the island could also be treated in this way in order to solve a disposal problem. The biogas produced could be used in gas engines for CHP production, and as a transportation fuel, and the fertiliser produced could be used on the farm, reducing the need for import. The potential amount of biogas available throughout the year is shown in Figure 8.3, with less being available during the summer as the animals go out to pasture for some of the time, making collection more difficult. The anaerobic digestion process requires heat and electricity inputs, but these have been removed from this graph for clarity. Figure 8.3: Potential Biogas Supply 255
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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
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5.7 Electrolyser Model An electroly
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original calculation of the amount
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5.8 Regenerative Fuel Cell Model A
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following the heat demand. To follo
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C:\ My Documents\ Nic\ Thesis\ Old\
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As 1 kWh = 3610.3 kJ, and using lit
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Add Heat to Water Storage Tank Usin
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Use Stored Hot Water to Supply Heat
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information is given about the over
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[23] K. Foger, B. Godfrey, “Syste
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the gasification and pyrolysis defi
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eing used each day for a continuous
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Where Biogas = Biogas production ra
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6.1.3 Use of Biogas Various options
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The amount of hydrogen that can be
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direct proportion, and the weight o
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produce in total (Nm 3 per tonne fe
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Electricity (kW) = Elec x Feed (6.1
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3. Make hydrogen via steam reformin
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Where Methane = Methane Production
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(continued) Keep as medium heating
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Yes Feed1 = Yield1 x Land1 / No. of
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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 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: Figure 8.2: Overall Yearly Heat Dem
Page 257 and 258: would be incurred, and the scale of
Page 259 and 260: Figure 8.5: Electricity Supply and
Page 261 and 262: heat demand or both, or run at cons
Page 263 and 264: ut with 30% less land being require
Page 265 and 266: 9 Conclusions and Recommendations T
Page 267 and 268: through these, technically viable p
Page 269 and 270: considered. The introduction of coo
Page 271 and 272: When considering larger geographica
Page 273 and 274: Appendix 1: Program Windows Figure
Page 275 and 276: Figure A1.5 CreateClimate.exe Figur
Page 277 and 278: Figure A1.9: Demand Profile Designe
Page 279 and 280: Figure A1.13: Derived Fuel Supply W
Page 281 and 282: Figure A1.17: Fermentation System D
Page 283 and 284: Figure A1.21: PV Electrolysis Syste
Page 285 and 286: Figure A1.25: Fuel Supply Profile D
Page 287 and 288: Figure A1.29: Auxilliary Supply Def
Page 289 and 290: Figure A1.33: Stirling Engine Syste
Page 291 and 292: Figure A1.37: Fuel Cell System Defi
Page 293 and 294: Figure A1.41: Electric Vehicle Syst
Page 295 and 296: Figure A1.45: Vehicle Conversion Fa
Page 297 and 298: Figure A1.49: Heating System Defini
Page 299 and 300: Figure A1.53: Pumped Hydro System D
Page 301: Figure A1.57: Auto Search Evaluatio
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PhD Thesis - Energy Systems Research Unit - University of Strathclyde

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