PhD Thesis - Energy Systems Research Unit - University of Strathclyde

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increases by 10% when it is being run on biodiesel [11,13], due to its reduced lower heating value (LHV), and slightly higher density. This increase, however, is less than would be expected due to the cleaner and more thorough burning of the fuel. Therefore, fuel consumption figures for diesel vehicles may be used directly for biodiesel-fuelled vehicles if they are increased by 10%, and these figures are widely available [8,22]. There are a wide number and range of different types of electric vehicles on the market [8,9,23], which give no emissions at the vehicle (and none overall if renewable electricity generating methods are used). These may be recharged slowly overnight, or at any time, providing an excellent use for off-peak excess electricity. Vehicles may also be recharged quickly (in under 5 minutes), but this should be kept to a minimum to prevent damage to the battery. The travelling range of these vehicles is less than conventionally fuelled vehicles, but is increasing with further research. None of these types of alternatively fuelled vehicles have, as yet, emerged as a clear front-runner to replace traditional vehicles, but it is likely that different countries or areas will favour different fuels, depending on their available natural resources. For example, biodiesel is becoming a popular alternative in many states of the United States of America where large areas can be devoted to soybean growth [24], whereas Iceland is looking towards a hydrogen economy and the use of fuel cell vehicles [4]. The main barriers to the implementation of alternative fuels will be the requirement for a choice of fuel at a national level, the necessity to create a suitable refuelling infrastructure, the length of time it will take to replace or convert existing vehicles, and the need for a strong public incentive to change. 2.2 Combined Heat and Power Production Technologies Various types of engine, turbine and fuel cell may be run on a variety of fuels for combined heat and power (CHP) production, and these technologies are described in this section. Plant types which have slow response times are best suited to base load operation, where they are run at a constant percentage load at 34
set times, producing a constant electricity and heat output. Other types, with faster start-up and response times, are also suitable for load following applications, where they can be used to follow the demand for electricity, heat or both. 2.2.1 Internal Combustion and Diesel Engines Two common load following generation technologies involve the use of diesel in compression ignition engines (diesel engines), and natural gas in internal combustion engines (ICEs). Both of these engine types may also be run on sustainable fuels derived from biomass and waste, with diesel engines running on biodiesel, pyrolysis oil, or vegetable oil, and ICEs running on biogas, ethanol or methanol [25,26], and this requires little or no modification. Diesel engine generating sets with rated outputs from 50 kWe to 10 MWe, and ICE generating sets with rated outputs of between 100 kWe and 2 MWe are available. These engine types are both suited to CHP production as the electrical output of a typical engine generating set is around 40% of the fuel input, the rest being lost as heat, around 50% of which is recoverable. This gives heat to electricity ratios ranging from 1:1 to 2:1, depending on the efficiency of the engine. The efficiency of these engine types decreases (substantially below 60% of rated power), and the heat to electricity ratio increases at lower percentage loads, which further complicates system design. These engines are also subject to a minimum recommended load, generally around 20% of the rated power [25], and constant starting and stopping should be avoided as this increases engine wear. 2.2.2 Stirling Engines A Stirling engine is an external combustion engine, where combustion of the fuel does not take place inside the engine, but in an external boiler. Mechanical work is derived from the pressure changes that result from the cyclic heating and cooling of an enclosed working gas [27]. In fact, heat from any source may be used to run a Stirling engine, including concentrated solar rays, and waste heat, 35
Page 1 and 2: Decision Support for New and Renewa
Page 3 and 4: Abstract The global requirement for
Page 5 and 6: CONTENTS 1 ENERGY SYSTEMS FOR SUSTA
Page 7 and 8: 5.5 Steam Turbine Model 149 5.6 Fue
Page 9 and 10: FIGURES Figure 1.1 Final Energy Con
Page 11 and 12: Figure 7.30 Following Electricity a
Page 13 and 14: on the use of fossil fuels, energy
Page 15 and 16: The general increase in energy cons
Page 17 and 18: supply is reduced or eliminated, lo
Page 19 and 20: Figure 1.3 The Electricity Supply G
Page 21 and 22: on different generation mixes depen
Page 23 and 24: Various studies have been carried o
Page 25 and 26: provision for smaller areas, and he
Page 27 and 28: 1.7 References [1] The Internationa
Page 29 and 30: 2 Options for New and Renewable Ene
Page 31 and 32: the amount of usable heat that is g
Page 33: the conversion of petrol cars; howe
Page 37 and 38: partial load. Fast response and sta
Page 39 and 40: 2.3 The Production and Storage of H
Page 41 and 42: dedicated boiler, which runs contin
Page 43 and 44: Figure 2.3 A Typical Hydrogen Filli
Page 45 and 46: part of the natural carbon cycle (a
Page 47 and 48: Figure 2.4 Layout of a Gasification
Page 49 and 50: met by process integration and the
Page 51 and 52: Figure 2.5 The Inputs and Outputs o
Page 53 and 54: 1. Scale for measuring out lye and
Page 55 and 56: feedstock being used. Sugary feedst
Page 57 and 58: carbon dioxide via steam reforming.
Page 59 and 60: • Where CHP is used, the balance
Page 61 and 62: [22] Vehicle Certification Agency (
Page 63 and 64: [55] M. A. Paisley, J. M. Irving, R
Page 65 and 66: 3 Approaches to Renewable Energy Sy
Page 67 and 68: Because of the intermittent nature
Page 69 and 70: A renewable energy supply evaluatio
Page 71 and 72: the system are kept. The output of
Page 73 and 74: There are various models available
Page 75 and 76: When the use of climate dependant i
Page 77 and 78: 3.5 References [1] M. Muselli, G. N
Page 79 and 80: 4 A Procedure for Demand and Supply
Page 81 and 82: pumped storage and flywheels), a ba
Page 83 and 84: 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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production and energy use profiles
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If it is the last timestep of the p
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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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