PhD Thesis - Energy Systems Research Unit - University of Strathclyde

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5 Load Following Supply Algorithms This chapter presents the algorithms used to describe the behaviour of a variety of load following supplies. In each case, the residual demands, supplies and fuel availabilities are sent to each model at the matching stage, in the order in which they were chosen, for each consecutive half-hourly timestep, and this information is amended appropriately and returned. Each technology also gives a relevant output graph, showing plant use or storage characteristics, and information about overall fuel consumption or energy taken in and given out, as appropriate. These models have been designed to be generic to a particular plant type group (e.g. gas turbines or fuel cells), and require only readily available manufacturers’ data in order to predict performance. The main issues that affect the performance of a particular type group are considered, and the performance analysis is based on these. This allows a wide variety of sizes and types of plant to be considered without having to run extensive tests to find specific data for each single engine, turbine or fuel cell, which would be time-consuming, much of the required information may be proprietary, and would quickly be out of date. This level of performance modelling is appropriate for the initial suitability assessment through demand and supply matching that is being considered here. 5.1 Vehicle Performance Algorithm The input to this part of the procedure, at the demand and supply matching stage, is a transport demand profile (km/h versus time) and the appropriate fuel availability profile. From these, the ability to meet the transport demand, and half hourly fuel use, must be derived. To do this, the specific fuel consumption of the chosen vehicle, the amount of fuel that can be stored on board, and the refuelling requirements are defined when choosing the load following supplies, and examples of the vehicle definition windows for the different fuel types can be seen in Appendix 1 (Figures A1.40 to A1.44). This information is then used 106
at the matching stage, along with the fuel availability, to determine what demand may be met, to determine the necessary refuelling times and amounts, and to reduce the available fuel accordingly. The procedure for this is described in this section. 5.1.1 Fuel consumption A number of factors affect the fuel consumption of a vehicle, including personal driving style, driving speeds, and the number of stops and starts. To allow comparison, international standard test conditions have been set to determine fuel consumption figures for different vehicles for three typical types of driving condition - urban, extra-urban and combined driving [1], and these typical figures are used in this program in order to calculate vehicle fuel use. The fuel consumption units used by the program depend on the fuel type, as discussed below, but all are quoted as an amount of fuel per 100km. As the transport demand is in km/h, all consumption figures are converted to the amount of fuel required per km by dividing by 100, to allow the actual fuel requirement to be calculated in the correct units (kWh for gases and electricity, and litres for liquid fuels). This calculated specific fuel consumption (kWh/km or litres/km) is then input into the algorithm defined later. Biogas vehicle fuel consumption is quoted in petrol equivalent litres per 100km, with one petrol equivalent litre being the quantity of biogas that has the same energy content as one litre of petrol. This is because there are various different storage mediums being used in vehicles, so the use of a measure of the energy content saves confusion and provides a standard. By quoting in petrol equivalent litres rather than kWh, it allows comparisons to be made with petrol driven engines, as this is generally better understood. As the transport demand is in km/h and the biogas fuel use is in kWh, this consumption figure is converted to kWh/km using Equation 5.1. FU = 8.827 x FC (5.1) 100 107
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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
Page 55 and 56: feedstock being used. Sugary feedst
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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
Page 85 and 86: Figure 4.4 Combining Demands to Tak
Page 87 and 88: ates for vehicles, engines and othe
Page 89 and 90: Figure 4.5 Derived Fuel Production
Page 91 and 92: together if desired, and taken forw
Page 93 and 94: profiles are output from this part
Page 95 and 96: dividing the production rate at eac
Page 97 and 98: As it would be too confusing to sho
Page 99 and 100: Figure 4.12 Output of the Matching
Page 101 and 102: However, when more than one transpo
Page 103 and 104: considered, this amount is added to
Page 105: users are alerted if there is not e
Page 109 and 110: vehicles if they are increased by 1
Page 111 and 112: If biogas is being considered, the
Page 113 and 114: The number of timesteps per hour wi
Page 115 and 116: After the algorithm has been follow
Page 117 and 118: • Float Charge - once the battery
Page 119 and 120: Discharge No tank = tank fuel used
Page 121 and 122: equired (kW) = maxkWh x bulk% (5.16
Page 123 and 124: An example of the output graph prod
Page 125 and 126: 5.2.1 Required Power Specifically d
Page 127 and 128: 5.2.3 Engine Performance in the Con
Page 129 and 130: used for gas powered ICEs, but the
Page 131 and 132: and five times, depending on the nu
Page 133 and 134: Is PL < Min ? No Is PL = 0 ? No Is
Page 135 and 136: where Max = maximum energy availabl
Page 137 and 138: where Ratiopart = heat to electrici
Page 139 and 140: (including following heat demand wh
Page 141 and 142: where SFC = specific fuel consumpti
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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
Page 151 and 152: The performance of a fuel cell is n
Page 153 and 154: percentage loading, rather than usi
Page 155 and 156: 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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