Carbon Emissions Pinch Analysis (CEPA) and Energy Return On Energy Investment (ERoEI) analysis are combined to investigate the feasibility of New Zealand reaching and maintaining a renewables electricity target of above 80% by 2025 and 2050, while also increasing electricity generation at an annual rate of 1.5%, and with an increase of electricity generation in the distant future to accommodate a 50% switch to electric vehicle transportation. To meet New Zealand’s growing electricity demand up to 2025 the largest growth in renewable generation is expected to come from geothermal generation (four-fold increase) followed by wind and hydro. To meet expected demand up to 2050 and beyond, including electric vehicle transportation, geothermal generation will expand to 17% of total generation, wind to 16%, and other renewables, such as marine and biomass, will make up about 4%. Including hydro, the total renewable generation in 2050 is expected to reach 82%
Progress on California’s Renewable Portfolio Standard (RPS), which requires 33% of all retail electricity sales to be served by renewable energy sources by 2020, excluding large hydro, is reported in this paper. The emerging renewable electricity mix in California (CA) and surrounding states which form the Western Electricity Coordination Council (WECC) is analysed using the Carbon Emission Pinch Analysis (CEPA) and Energy Return on Energy Invested (EROI) methodologies. The reduction in emissions with increased renewables is illustrated and the challenge of maintaining high EROI levels for renewable generation is examined for low and high electricity demand growth. The role of the California government in facilitating progress towards a more sustainable renewable electricity future is also highlighted. The investigation shows that wind and solar PV collectively form an integral part of California reaching the 33% renewables target (excluding large hydro) by 2020. Government intervention of tax rebates and subsidies, net electricity metering and a four tiered electricity price has accelerated the uptake of renewable wind and solar PV. Residential uptake of solar PV is also reducing overall California electricity grid demand. Emphasis on new renewable generation is stimulating development of affordable wind and solar technology in California which has the added benefit of enhancing social sustainability through improved employment opportunities at a variety of technical levels
Dairy processing is critical to New Zealand’s (NZ) economy producing NZ13billioninexportsfor2012whileconsuming32PJoffossilfuelsforprocessheat.ThreequartersofNZdairyexportsaremilkpowders.ThisthesispresentsmethodstoreduceprocessheatuseinMilkPowderPlants(MPP)throughimprovedheatintegrationandaddresseskeytechnicalchallengespreventingindustrialimplementation.Myoriginalcontributionstoliteratureinclude:(1)anoveldesignmethodcalledtheCostDerivateMethod(CDM)thatcostoptimallyallocatesareaindirectheatexchangenetworks,(2)anewdesignmethodologyforintegrationofsemi−continuousprocessclustersusingaHeatRecoveryLoop(HRL)withaVariableTemperatureStorage(VTS)systemforimprovedheatrecovery,(3)anexperimentallyvalidateddepositionmodelforpredictingcriticalairconditionsthatcausemilkpowderfouling,and(4)athermo−economicassessmenttoolfortheoptimisationofindustrialspraydryerexhaustheatrecoveryprojectsviaaLiquidCoupledLoopHeatExchanger(LCHE)system.ByapplyingPinchAnalysistoanindustrialMMP,thisworkconfirmsthatheatmustberecoveredfromthemilkspraydryerexhaustair(75°C)toachievemaximumheatintegrationinMPPs.Forstand−aloneMPPsexhaustheatisbestusedtoindirectlypreheattheinletdryerairreducingsteamuseby12.7AkeybarrierpreventingexhaustheatrecoveryimplementationinNZMPPsisthepossibilityofmilkpowderfouling.Dryerexhaustaircontainsalowconcentrationofpowderthatwhenexposedtolowtemperaturesathighhumiditybecomessticky.Foraheatexchangerfaceairvelocityof4m/s,experimentaldatafrommilkpowderfoulingtestsofflatplates,tubesandfinsindicatesparticulatefoulingbecomesseverewhentheexhaustairtemperaturereaches55°C.Higherfacevelocitiesareshowntolowerthiscriticalexhausttemperatureforavoidingseverefouling,whichgivespotentialforincreasedheatrecoverybutforincreasedpressuredrop.Lowerfacevelocitiesshowtheoppositeeffect.Designingexhaustheatrecoverysystemsentailanacutetrade−offbetweenheattransfer,pressuredropandfouling.Twoimportantdesignparametersarethenumberoftuberowsintheexhaustheatexchangerandthefacevelocity.Theoutputsofathermo−economicspreadsheettoolsuggestLCHEsystemsforadryerproducing23.5t/hiseconomic.Withafacevelocityof4m/sand14rowsoffinnedroundtube,theprojecthadanestimatedpaybackof1.6years,anetpresentvalueofNZ3 million and internal rate of return of 71 %. This tool will empower industry with greater confidence to uptake exhaust heat recovery technology as a vital method for improving the heat integration of MPPs in NZ
N-heterocyclic carbenes (NHCs) have played a dominant role in organometallic chemistry for decades and revolutionized the field of homogenous catalysis. NHCs have been thoroughly studied, both experimentally and theoretically, and have shown unique reactivity towards transition metals, chalcogens, azides and pnictogens.
This thesis is aimed at utilizing the unique reactivity of N-heterocyclic carbenes to develop novel, robust catalysts to mediate organic transformations. The multi-faceted work within this thesis explores the use of NHCs as ancillary ligands on early and late transition metals as potential catalysts for olefin polymerization and ring-closing metathesis, respectively. This work also includes exploring the synthesis and coordination of ancillary ligands derived from the unique reactivity of NHCs towards azides, chalcogens and pnictinidenes.
The reactivity of a novel aryl-substituted acyclic imino-N-heterocyclic carbene to early transition metals, cyclooctasulfur and Grubbs-type ruthenium benzylidene complexes was explored. The reactivity of imidazol-2-imide towards Grubbs-type ruthenium benzylidene complexes and the synthesis and coordination of a novel group of ligands bearing an imidazol-2-imine scaffold were also explored. Lastly, this work will include the reactivity of IMes=PPh to Grubbs-type ruthenium benzylidene complexes
Solar is a renewable energy that can be used to provide process heat to industrial sites. Solar is extremely variable and to use it reliably thermal storage is necessary. Heat recovery loops (HRL) are an indirect method for transferring heat from one process to another using an intermediate fluid (e.g. water, oil). With HRL’s thermal storage is also necessary to effectively meet the stop/start time dependent nature of the multiple source and sink streams. Combining solar heating with HRL’s makes sense as a means of reducing costs by sharing common storage infrastructure and pipe transport systems and by lowering nonrenewable hot utility demand. To maximise the value of solar in a HRL, the means of controlling the HRL needs to be considered. In this paper, the HRL example and design method of Walmsley et al. (2013) is employed to demonstrate the potential benefits of applying solar heating using the HRL variable temperature storage (VTS) approach and the conventional HRL constant temperature storage (CTS) approach. Results show the VTS approach is superior to the CTS approach for both the non-solar and solar integration cases. When the pinch is around the hot storage temperature the CST approach is constrained and the addition of solar heating to the HRL decreases hot utility at the expenses of increased cold utility. For the VTS approach the hot storage pinch shifts to a cold storage pinch and increased heat recovery is possible for the same exchanger area without solar. With solar the VTS approach can maintain the same heat recovery while also reducing hot utility still further due to the presence of solar, but only with additional area. When the pinch is located around the cold storage temperature, solar heating can be treated as an additional heat source and the benefits of CTS and VTS are comparable
Inter-plant integration via a heat recovery loop (HRL) is an economic method for increasing total site process energy efficiency of semi-continuous processes. Results show that both the constant storage temperature approach and variable storage temperature approach have merit. Depending on the mix of source and sink streams attached, it may be advantageous to change the operation of an existing HRL from a constant temperature storage to a variable temperature storage. To realise the full benefits of this change in operation, a redistribution of the existing heat exchanger area may be needed