PhD Thesis - Energy Systems Research Unit - University of Strathclyde

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5.9 Instantaneous Space and Water Heating System Model Space and water heating systems are provided here to allow the use of remaining fuels and excess electricity to help meet the demands for heat and hot water. Considered here are space heaters, which have an instantaneous action, instantaneous water heaters, and water heaters with some storage, which are capable of providing a full tank of hot water or more within a half hour period, depending on their rated power. Larger hot water storage systems will be considered later in this chapter. This basic type of heating is simple to model, as efficiency of the plant does not vary significantly with partial load, and is not subject to minimum loads. This is due to the way in which a heating system is controlled – when the thermostatic control determines that heating is required, the heater is turned on at its full rated power, and turned off again when the correct temperature is reached. Therefore, the efficiency always remains the efficiency at rated power, and the heat supplied is the heat required. The information required to model instantaneous space or water heater performance is the number of heaters, their rated power and efficiency, and the type of fuel to be used. If a liquid fuel is being used, the lower heating value (kJ/kg) and density (kg/m 3 ) of the fuel are also required. The lower heating value only is required for a solid fuel. An example of the heating system definition window for this type of system can be seen in Appendix 1, Figure A1.49. The maximum heat or hot water that may be supplied is equal to the rated power of the heater multiplied by the number of heaters. If demand is greater than this, there will be a residual demand, and the heaters will run at full load. If demand is less, the heater will supply only the required amount. The amount of fuel required is then calculated using Equations 5.33, 5.35 or 5.36 as appropriate, multiplied by the number of heaters. If there is not enough fuel, the amount of heat that can be supplied with the available fuel is calculated, and the user is alerted that there was not enough fuel to run the heater at the desired capacity. The profile shown on matching is a graph of percentage heater loading with time. Figure 5.22 gives a graphical representation of this procedure for a system 164
following the heat demand. To follow the hot water demand, simply substitute the hot water required for the heat required. Is HeatReq Rated x Num ? Fuel = ( Req x 3610.3 / ( Timesteps x LHV )) Is Fuel > Fuel Supply ? No Yes No Yes Yes No Fuel = 0 Heat = 0 Req = Rated X Num x 100 / Eff Heat = Rated x Num Req = HeatReq x 100 / Eff Heat = HeatReq Is fuel unit = litres ? No 165 HeatReq = Heat Required (kW) Heat = Heat Supplied (kW) Rated = Rated Power (kW) Num = Number of Heaters Fuel = Fuel Required (kWh, litres or kg) Fuel Supply = Fuel Available (kWh, litres or kg) Is fuel unit = kWh ? Yes No Yes Fuel = ( Req x 3610300 / ( Timesteps x LHV x Density )) Issue Warning Fraction = Fuel Supply / Fuel Figure 5.22 Instantaneous Heater Algorithm 5.10 Space Heating Storage Heater Model Yes Fuel = Req / Timesteps Is fuel type electricity ? Fuel = Fuel Supply Heat = Fraction x HeatReq Fuel = Fuel Heat = HeatReq Fuel = Req Storage heaters have a rated capacity (kW), which limits the rate at which electricity may be converted to heat and stored in the bricks, and a maximum storage level (kWh). There is also a limit to the rate at which the heat may be given out from the bricks. This is generally given as a minimum length of time, in hours, for a full discharge of heat from the bricks [29]. A small amount of heat will be lost from the bricks over time, and the amount lost depends on the amount of heat stored. This heat loss may be quoted as the percentage of the heat stored that is lost per hour. Although this heat will be lost into the room, and will therefore serve some useful purpose in offsetting future heat demand, It will be assumed that this heating effect is negligible as it occurs at times when
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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
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
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
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
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: 5.8 Regenerative Fuel Cell Model A
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 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
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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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