PhD Thesis - Energy Systems Research Unit - University of Strathclyde

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These studies are, however, only concerned with electricity supply. The important issues of energy demand for transportation, hot water and heat have not been addressed, and any full analysis of the energy needs of an area must also consider these. 1.5 Decision Support Framework Although various studies have been carried out to find the best supply mix for given areas, results from specific studies cannot be easily applied to other situations due to area-specific resources and energy-use profiles. This is because the ideal way to organise an energy supply system, with a large percentage of renewable resources, will vary substantially with the size and type of area (rural, urban), climate, location, typical demand profiles, and available renewable resource mix. Therefore, a decision support framework is required in order to aid the design of future renewable energy supply systems (both large and small), effectively manage transitional periods, and encourage and advance state-of-the-art deployment as systems become more economically desirable. This system model will concentrate on the technical feasibility of possible renewable energy supply systems, although the ultimate decision will also be affected by wider economic and political issues. The proposed decision support framework will allow possible supply scenarios to be quickly and easily tried, to see how well the demands for electricity, heat and transport for any given area can be matched with the outputs of a wide variety of possible generation methods. These generation methods will include the generation of electricity from intermittent sources, the production of fuels derived from waste and biomass and their use in CHP, heating and energy limited plant, and the use of electricity and derived fuels for transportation. The framework will allow the appropriate type and sizing of spinning reserve, fuel production and energy storage to be ascertained, and will support the analysis of supplies and demands for an area of any type and geographical location, to allow potential renewable energy provision on the small to medium scale (from an individual building to a medium sized community) to be analysed. This system will aid the making of informed decisions about suitable overall energy 24
provision for smaller areas, and help guide the transition towards higher percentage sustainable energy provision in larger areas. This work considers the various ways in which the total energy needs of an area may be met in a sustainable manner, the problems and benefits associated with these, and the ways in which they may be used together to form reliable and efficient energy supply systems. Consideration is given to the type of decision support framework that is required, and the proposed system is described in detail. The applicability and relevance of the decision support framework are shown through the use of a case study, which highlights the complex nature of sustainable energy supply system design. 1.6 Outline of Thesis Demands for electricity, heat, hot water and transportation fuel may be met, in a sustainable manner, using a number of different processes. These may use climate related sources, biomass or waste fuels, or fuels derived from biomass or waste. Chapter 2 discusses currently available supply technologies for these demand types, methods for producing fuel from biomass and waste, storage technologies and possible overall supply scenarios. Chapter 3 looks at existing methods for aiding the design of renewable energy systems, and discusses what is required from this type of system. Chapter 4 describes the requirements for a demand and supply matching tool that will allow possible sustainable energy system designs to be evaluated, and shows how this can be achieved by enhancing an existing software package. Chapter 5 details the algorithms used to describe the behaviour of the supply systems that may be used to follow the demand for all energy types. These include the use of electricity and a variety of fuels derived from biomass and waste in vehicles, engines, turbines and fuel cells, with possible CHP generation. An electrolyser model is included to allow the use of excess electricity for the manufacture of hydrogen, which may then be used in any of the plant described. Also considered are different types of heating system, and 25
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: Various studies have been carried o
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 and 34: the conversion of petrol cars; howe
Page 35 and 36: set times, producing a constant ele
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
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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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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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