Financial analysis of solar cooling systems in Australia Dan Wu, Lu Aye, Priyan Mendis & Tuan Ngo Presenter: Dan Wu Renewable Energy and Energy Efficiency Group Melbourne School of Engineering, The University of Melbourne 1 Overview Introduction Solar cooling technologies investigated - Solar electric cooling - Solar thermal cooling (thermo-chemical & thermo-mechanical cooling) Simulations of the cooling systems - System descriptions - System sizing Financial analysis - Cost assumptions - Financial parameters: annualised life cycle cost (ALCC) and unit cooling cost (UCC) Conclusions Dan Wu Australian Solar Cooling 2013 Conference, Sydney, 12 April 2 of 18 2
Introduction In Australia, heating, ventilation and air-conditioning (HVAC) of commercial buildings account for 40-50% of electricity consumption and 80% of electricity is generated from fossil fuels (Fong et al. 2010). Cooling demand in Australia has high sensitivity to global warming (Wang, Chen & Ren 2010). SOLAR COOLING Dan Wu Australian Solar Cooling 2013 Conference, Sydney, 12 April 3 of 18 3 Introduction Market share Solar cooling << Conventional cooling Dan Wu Australian Solar Cooling 2013 Conference, Sydney, 12 April 4 of 18 4
Solar cooling technologies Aim: To investigate the life cycle costs of solar cooling systems which can be designed and assembled with commercially available system components. Solar electric cooling system Solar thermo chemical cooling system VS Conventional cooling system Solar thermo mechanical cooling system Dan Wu Australian Solar Cooling 2013 Conference, Sydney, 12 April 5 of 18 5 Solar electric cooling system PV panels + scroll chiller Dan Wu Australian Solar Cooling 2013 Conference, Sydney, 12 April 6 of 18 6
Solar thermo chemical system PTC + absorption chiller PTC: Parabolic Trough Collector Dan Wu Australian Solar Cooling 2013 Conference, Sydney, 12 April 7 of 18 7 Solar thermo mechanical system ETSC + ORC + scroll chiller ETSC: Evacuated Tube Solar Collector ORC: Organic Rankine Cycle Dan Wu Australian Solar Cooling 2013 Conference, Sydney, 12 April 8 of 18 8
Simulations Simulation tools: TRNSYS, STEC library, TMY data files (Morrison & Litvak 1999) Locations: Darwin, Brisbane, Perth, Sydney, Adelaide, Canberra and Melbourne Building characteristics: - 2 storeys office building with 3000 m 2 floor area and 2.7 m ceiling height - East and west walls: 33% double-glazing windows - North and South walls: 60% double-glazing windows Target solar fraction: ~75% Location Darwin Brisbane Perth Sydney Adelaide Canberra Melbourne Cooling season Jul - Jun Aug - Jun Sep - May Sep - Apr Oct - Apr Nov - Mar Oct - Apr Latitude (deg S) 12.42 27.42 31.93 33.93 34.97 35.32 37.83 Tilt angle (deg) 16 10 16 14 12 4 18 Max. cooling load (kw r ) 135 113 151 139 159 91 118 Total cooling (kwh r ) 269 096 106 901 102 947 71 432 59 883 28 083 35 681 Dan Wu Australian Solar Cooling 2013 Conference, Sydney, 12 April 9 of 18 9 Simulations Specifications for main components Component Parameter Value Module area of PV panel (m 2 ) 1.61 PV panel Maximum output (W) 250 Maximum voltage (V) 30.4 Module efficiency (%) 15.55 AC output voltage (V) 400/230 Inverter DC input voltage (V) 300~450 Efficiency (%) 98 Cell voltage (V) 2 Battery bank Depth of discharge (%) 65 Charging efficiency (%) 92 Absorber area (m 2 ) 24 Demand outlet temperature (Celsius degree) 150 PTC Heat loss coefficient A 70 Heat loss coefficient B -0.0042 Heat loss coefficient C -7.44 Heat loss coefficient D -0.0958 Absorber area (m 2 ) 1.938 ETSC Intercept efficiency based on gross area 0.498 Negative of first order efficiency coefficient (WK -1 m -2 ) 1.610 Negative of second order efficiency coefficient (WK -1 m -2 ) 0.0027 Dan Wu Australian Solar Cooling 2013 Conference, Sydney, 12 April 10 of 18 10
Simulations Part load performance of scroll chiller and absorption chiller Rated compressor COP for scroll chiller: 4.0 Rated COP for absorption chiller: 1.2 Dan Wu Australian Solar Cooling 2013 Conference, Sydney, 12 April 11 of 18 11 Simulations Assumptions: Quasi steady state Peak cooling load = Design capacity of chiller All solar collectors and PV panels are placed facing north Two-days energy storage (electricity and heat) for all solar cooling systems Location Darwin Brisbane Perth Sydney Adelaide Canberra Melbourne PV area (m 2 ) 188 105 97 84 71 53 64 Battery capacity (kwh e ) 585 328 360 273 264 198 210 PTC area (m 2 ) 144 120 96 96 72 48 72 PTC tank volume (m 3 ) 54 36 39 28 30 18 23 ETSC area (m 2 ) 416 273 260 247 195 130 189 ETSC tank volume (m 3 ) 207 136 155 126 119 75 94 Location Darwin Brisbane Perth Sydney Adelaide Canberra Melbourne Conventional, electricity (kwh e ) 64 900 26 419 24 270 17 019 14 468 7 534 9 387 PV + VCC, electricity (kwh e ) 17 072 6 389 6 449 4 306 3 530 1 874 2 489 PTC + Absorption, gas (MJ h ) 190 170 72 696 80 865 68 220 61 011 27 655 38 074 PTC + Absorption, electricity (kwh e ) 8 294 6 386 5 321 4 643 3 776 2 445 2 909 ETSC +ORC + VCC, gas (MJ h ) 495 145 213 097 214 370 144 985 133 060 58 900 78 976 ETSC + ORC + VCC, electricity (kwh e ) 8 313 6 393 5 336 4 655 3 799 3 453 2 926 Dan Wu Australian Solar Cooling 2013 Conference, Sydney, 12 April 12 of 18 12
Life cycle cost (LCC) Annualised life cycle cost (ALCC) Unit cooling cost (UCC) LCC ALCC = Pa ALCC ($/year) UCC = Cooling supplied (kwh r/year) t n t 1+ i 1 LCC = C + Cr = C + Cr = + n n 1 1 D n= 1 ( 1+ d ) t 1 1 1 Pa = 1 1 1+ d 1+ d 1+ d C = Initial cost of the system ($) Cr = Single future cost ($) D = Nominal discount rate d = Real discount rate i = Real inflation rate t = Project life time Pa = Present worth factor Dan Wu Australian Solar Cooling 2013 Conference, Sydney, 12 April 13 of 18 13 Financial parameter used Project life time: 20 years Land costs were not included Social and environment benefits & costs were not considered Loss of efficiency in PV system over time was neglected Parameter Value Real discounted rate 8 % Electricity cost ($/kwh) 0.26 [1] Real escalation rate of electricity price 3 % Natural gas cost ($/MJ) 0.02 [1] Real escalation rate of natural gas price 2 % [1] Office of the Tasmanian Economic Regulator Comparison of 2012 Australian Standing Offer Energy Prices, pp.1-31, 2012. Dan Wu Australian Solar Cooling 2013 Conference, Sydney, 12 April 14 of 18 14
Results Item System Darwin Brisbane Perth Sydney Adelaide Canberra Melbourne Initial cost ($) Conventional 103 275 86 445 115 515 106 335 121 635 69 615 90 270 PV + VCC 362 645 226 385 253 655 214 345 216 095 144 255 171 410 PTC + Absorption 363 510 285 450 312 390 277 790 283 830 169 470 226 780 ETSC +ORC + VCC 702 084 487 566 562 424 486 969 477 014 293 049 380 438 Conventional 765 765 765 765 765 765 765 Specific cost PV + VCC 2 686 2 003 1 680 1 542 1 359 1 585 1 453 ($/kw r ) PTC + Absorption 2 693 2 526 2 069 1 998 1 785 1 862 1 922 ETSC +ORC + VCC 5 201 4 315 3 725 3 503 3 000 3 220 3 224 Conventional 31 805 29 467 33 506 32 230 34 356 27 129 29 999 ALCC PV + VCC 68 324 43 732 48 843 41 084 41 476 29 639 33 642 ($/year) PTC + Absorption 44 511 36 302 39 492 35 827 36 677 24 231 30 385 ETSC +ORC + VCC 88 716 65 985 75 133 66 967 66 755 45 291 55 274 UCC ($/kwh r ) UCC ($/kwh r ) w/o storage Conventional 0.118 0.276 0.325 0.451 0.574 0.966 0.841 PV + VCC 0.254 0.409 0.474 0.575 0.693 1.055 0.943 PTC + Absorption 0.165 0.340 0.384 0.502 0.612 0.863 0.852 ETSC +ORC + VCC 0.330 0.617 0.730 0.937 1.115 1.613 1.549 PV + VCC 0.109 0.204 0.241 0.320 0.398 0.585 0.550 PTC + Absorption 0.125 0.271 0.306 0.422 0.510 0.732 0.720 ETSC +ORC + VCC 0.173 0.358 0.423 0.578 0.710 1.069 1.012 Dan Wu Australian Solar Cooling 2013 Conference, Sydney, 12 April 15 of 18 15 Conclusions Under current technical and financial conditions, solar cooling systems investigated are less competitive compared to conventional cooling system. Among the solar cooling systems with storage components the solar absorption system has the lowest life cycle cost. If the storage components are not included in the system, the PV solar electric system would have the lowest life cycle cost. Initial estimations showed that the UCCs for all solar cooling systems investigated in this study become closer to that of conventional systems. Dan Wu Australian Solar Cooling 2013 Conference, Sydney, 12 April 16 of 18 16
Acknowledgement The authors would like to acknowledge and extend their gratitude to the followings: Anonymous reviewers for providing feedbacks; Permasteelisa Group and Australian Research Council (ARC) for supporting the research; The University of Melbourne for providing a scholarship to Dan Wu. Dan Wu Australian Solar Cooling 2013 Conference, Sydney, 12 April 17 of 18 17 Dan Wu Australian Solar Cooling 2013 Conference, Sydney, 12 April 18 of 18 18