PhD Thesis - Energy Systems Research Unit - University of Strathclyde

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As electricity costs increase (relative to the LPG price) the financial advantage of theproject increases. The higher the electricity tariff considered, the higher is the PW ofthe project. The rationale for this stems from the fact that the financial value of thecogenerated electricity used to satisfy the electrical demand of the households andhence offset imported electricity, is equivalent to the value of the imported electricitywhich has been offset. The higher the cost to import electricity, the more valuable isthe cogenerated electricity used to satisfy the building’s own energy demand.Comparing the PW plots for the scenarios in the 3 household building with those inthe 6 household building it can be observed how increasing the thermal demand (byincreasing occupancy or connecting the micro-trigeneration system to a largerbuilding), significantly increases the value of the project. At electricity tariffs lowerthan the current tariffs (approx. at a value of 0.95 times the current electricity tariff),the energy demand in the 3 household building results in a negative PW whichrenders the system financially unfeasible. The higher energy demand in the 6household building, on the other hand, renders the scenarios feasible even at lowelectricity tariffs.Comparing the scenarios for the different buildings also highlights the fact that thedifference between the PW for the two sets of scenarios is sensitive to the electricitytariff. The difference between the two sets increases with increasing electricity tariffs.Any measure aimed at reducing the energy demand of the building results in adecrease in the PW of the trigeneration system. Improving the electrical efficiency ofappliances, hence reducing the electrical demand, results in a decrease in theproject’s PW. For both the 3 and the 6 household building scenarios it can beobserved that the difference between the PW of the different appliances’ electricalefficiency scenarios (current and high) increases substantially with increasingelectricity tariffs, whilst the difference in PW between the different building fabricscenarios (low and high), stays reasonably constant throughout the entire range ofelectricity tariffs.210
Given the different energy quantities of the two sets of scenarios for the 3 and 6household buildings involved and the cost of the energy products, it can be observedthat in the 3 household building scenarios the overall difference in PW is highest forthe difference in fabric efficiency (for the same appliances’ electrical efficiency),whilst in the 6 household building scenarios the overall difference in PW is highestfor the difference in appliances’ electrical efficiency (for the same building fabric).An explanation as to why this occurs necessarily has to take into consideration thecash flow (CF) of each scenario. Recall equation (4.16) in Chapter 4 describing howto calculate the cash flow for each individual scenario:Excluding the net exports term (E Net Export x FIT), the annual maintenance cost term([E Net Export + E Net Demand μTRIGEN ]MC) and the annual fuel costs term ([Fuel μTRIGEN –Fuel SEPERATE ]Cost of Fuel), which are constant and independent of the electricitytariff, the other two terms, the total invoiced electricity without trigeneration term(E Total x Tariff) and the total invoiced electricity with trigeneration term (E Net Import xTariff), are variable and dependent on the electricity tariff. In this context, Figure5.12 shows the value of the individual terms making up the CF for the 6 householdbuilding with low efficiency fabric and current appliances’ electrical efficiency(Scenario 2 Low/Current efficiency ).It can be observed that the shape and magnitude of the resulting cash flow (solidblack line) partly relies on terms which are dependent on the electricity tariff (i) andpartly on terms which are independent of the electricity tariff (ii):i. In the former case although the energy quantities calculated for E Total and E NetImport, are constant for a particular scenario, the varying electricity tariffdictates the magnitude and shape of the total invoiced electricity withouttrigeneration term and the total invoiced electricity with trigeneration term.211
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University of StrathclydeDepartment
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ACKNOWLEDGEMENTSIt has been a long
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ABSTRACTThe domestic sector account
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TABLE OF CONTENTSACKNOWLEDGEMENTSAB
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2.4.3.3 Aggregated loads frequency
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4.1.1.1 Factoring for electricity g
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5.5.1.2 Present worth assuming a va
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LIST OF FIGURESFig. 1.1 Separate ge
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Fig. 2.38 Aggregated DHW draw profi
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Fig. 5.23 PP for Scenarios 1 and 2
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uilding 95Table 3.5 Control scheme
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ACRONYMS & ABBREVATIONSBMS Building
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CHAPTER 1INTRODUCTIONChapter overvi
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uildings, and Directive 2006/32/EC
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Micro-cogeneration can make use of
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offer reasonable and adequate retur
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system in a residential building, i
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conditions have on the performance
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effective manner. The research in t
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investigate how a residential micro
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Table 1.1 also includes additional
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1.7 Chapter References[1] DG for En
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[18] Pehnt, M., Cames, M., Fischer,
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[39] Cardona, E. and Piacentino, A.
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[56] Shin, Y., Seo, J.A., Cho, H.C,
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2.1 Modelling residential demand -
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minute resolution data. The researc
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2.3.1 Example: specifying the build
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Table 2.1 - Dimensions of the model
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In this second enlarged building, t
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Table 2.3 - Main characteristics of
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Table 2.4 - Main characteristics of
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esolution demand data for individua
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the original data (see equation 2.1
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the course of a year. The end resul
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specific appliance at a particular
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consumption during this period is e
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awarded on a random basis following
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Table 2.7 - Scaling factors for the
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NVF values for washing machines, el
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Table 2.10 - Annual electrical ener
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2.4.4 Creating the profiles used in
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Fig. 2.16 - Electrical demand profi
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Fig. 2.19 - High efficiency electri
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2.4.4.3 6 Household buildingAs ment
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2.29 and Figure 2.30 show the resul
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period [11].In order to improve on
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(as discussed by Richardson et al.
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similar fashion to the modelling of
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observed measurements from a number
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Fig. 2.37 - Total internal heat gai
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comparing water consumption related
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various aspects which make up the h
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natural Resources" - (LN 238 of 200
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in Domestic Appliances and Lighting
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[49] DEFRA (2010). "Dishwashers Gov
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CHAPTER 3MODELLINGMICRO-TRIGENERATI
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the same research also suggests tha
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cooling device in conjunction with
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simulation tool ESP-r by explaining
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Fig 3.2 - Basic micro-trigeneration
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3.2.3 Control strategies for the pl
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or decrease the flow rate of the co
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efrigerant, which in this case is w
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arbitrary cycle configuration, usin
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coefficients for the future and pre
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Applying basic energy and mass cons
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CH Power , the chiller’s refriger
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general form of equation (3.16) [33
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functions of hot water circuit inle
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circuit were obtained and how the p
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the internal high and low pressures
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the imaginary boundary constituting
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the model was then compared to a se
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Fig. 3.9 - Modelled chilled water c
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standard deviation was calculated t
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The selected tank size is based on
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3.5 Summary of Chapter 3This chapte
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Conservation in Buildings and Commu
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uilding simulation." Doctoral Thesi
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CHAPTER 4SIMULATIONMETHODOLOGYANDAN
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Table 4.1 - Scenarios investigatedS
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The building fabric, building size
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analysis in the case of the interme
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micro-trigeneration system are thos
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profile for that same time period (
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4.2.1.3 Calculating the fuel consum
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cogeneration technologies [16].- (4
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the present 1.088 kgCO 2 per kWh de
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Table 4.4 - Explanation of the cash
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FIT and considering the cost involv
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Page 188 and 189: CHAPTER 5RESULTSANDDISCUSSIONThis c
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Page 200 and 201: In the table, the low and high effi
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Page 204 and 205: Comparing Figure 5.3 and 5.4, respe
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Page 214 and 215: Table 5.10 - Micro-trigeneration sy
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Page 218 and 219: Table 5.11 - Micro-trigeneration pr
Page 220 and 221: The PES obtained for the different
Page 222 and 223: Difference inprimary energybetween
Page 224 and 225: Similar results are obtained for al
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Page 228 and 229: Fig. 5.8 - Sensitivity of Emissions
Page 230 and 231: Similarly to the effect on PE SEPAR
Page 232 and 233: 5.5 Micro-trigeneration system econ
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Page 240 and 241: Multiple of current electricity tar
Page 242 and 243: of the system diminishes with incre
Page 244 and 245: Fig. 5.17 - CF and CF component ter
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Page 252 and 253: Similarly to the PW and the IRR, it
Page 254 and 255: Table 5.13 - Summary of micro-trige
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Page 262 and 263: CHAPTER 6CONCLUSION:OUTCOMESANDFUTU
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Page 266 and 267: circuits associated with the absorp
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Page 270 and 271: plant models using the building sim
Page 272 and 273: APPENDIX AEquation factors for sele
Page 274 and 275: Factors for use in equation (2.1) f
Page 282 and 283: APPENDIX BElectrical demand profile
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Fig. B4 - Current efficiency electr
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Fig. B10 - High efficiency electric
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Fig. B16 - Current efficiency elect
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Component ESP-r Database: Annex 42
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0.0000 #88 Performance map: Thermal
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99.999 #1 Evaporator Total Mass (Fl
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100.00 #13 Boiling temperature of f
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One way to solve a partial differen
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The ‘self coupling term’ is def
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C ******************** CMP73C *****
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&COMMON/PCOND/CONVAR(MPCON,MCONVR),
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C and the inlet point into the solu
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IF(CSVF(INOD1,1).LE.BDATA(IPCOMP,17
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C Calculate T1 (DegC): T1 = ((T16-T
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XST=4010 DST=-(9.133128) + (0.94396
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& + 2500.559)*1000C Refrigerating p
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End IfC Calculate h3 (J/kg): h3=h2+
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&&ElseEnd IfActPow=0ActPow = PCONDR
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C Node 1, thermal mass effected by
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WRITE(ITU,*) ' Connection(s) ',ICON
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Fig. F.1 - IRR for scenarios with d
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Fig. F.5 - PP for scenarios with di
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PhD Thesis - Energy Systems Research Unit - University of Strathclyde

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