PhD Thesis - Energy Systems Research Unit - University of Strathclyde

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LHV = Lower heating value of specified gas (kJ/Nm 3 ) GasDensity = Density of biogas (kg/Nm 3 ) Elec = Electricity to compress or liquefy biogas (kWh/Nm 3 ) The total amounts of hydrogen and methane produced throughout the simulation period are given along with the final production rate graphs. Any excess energy requirements arising from the separation process may be added to the overall process energy requirements considered in section 6.1.2. 3. Make hydrogen, from the methane component, via steam reforming Hydrogen may be made, via the steam reforming of methane, according to the following chemical equation: - 2CH4 + 3H20 CO + CO2 + 7H2 64 kg CH4 + 108 kg H20 56 kg CO + 88 kg CO2 + 28 kg H2 By considering the molecular weights of each component, it can be determined that 64 kg of methane are required to produce 28 kg of hydrogen. In practice, however, this reaction will not go to completion, so a completion percentage must be applied [3]. To determine the total amount of hydrogen that is made, the rates of production by weight (in kg/hr) of hydrogen and methane are calculated using Equation 6.10, and the partial production factor is applied as necessary. Specified Gas = Biogas x Percentage x Density (6.10) Production Rate (kg/hr) GasDensity x 100 Where Biogas = Biogas production rate (kg/hr) Percentage = Percentage of specified gas in mixture (by volume) Density = Density of specified gas (kg/Nm 3 ) GasDensity = Density of biogas (kg/Nm 3 ) 186
The amount of hydrogen that can be produced from this weight of methane is calculated by direct proportion, using the weights given in the above chemical equation, and the completion percentage is applied to find the weight actually produced. This is then added to the weight of hydrogen already in the biogas mixture to determine the total hydrogen production rate in kg/hr. If desired, the weight of methane remaining can also be calculated by direct proportion, in the same manner as for hydrogen, and the percentage applied should be 100 minus the completion percentage. The production rate of hydrogen and methane (in kW) is calculated using Equation 6.11, and the electricity required to put either or both gases into storage is calculated using Equation 6.12. Specified Gas = Gas x LHV (6.11) Production Rate (kW) Density x 3610.3 Electricity Required (kW) = Gas x Elec (6.12) Density Where Gas = Specified gas production rate (kg/hr) LHV = Lower heating value of specified gas (kJ/Nm 3 ) Density = Density of specified gas (kg/Nm 3 ) Elec = Electricity to compress or liquefy specified gas (kWh/Nm 3 ) Again, the total amount of hydrogen, and methane if desired, produced throughout the simulation period is given along with the final production rate graphs. The heat required to raise the steam necessary for this process may be added to the overall process energy requirements considered in section 6.1.2. 4. Make methanol, via catalytic conversion As the biogas mixture produced will typically contain a mixture of hydrogen, carbon dioxide and carbon monoxide, this allows the production of methanol, via catalytic conversion, according to the following chemical equations [3]: - 187
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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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Page 137 and 138: where Ratiopart = heat to electrici
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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
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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
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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: 6.1.3 Use of Biogas Various options
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 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
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Page 235 and 236: 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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