title: Heat pump integration for total site waste heat recovery

authors: Liew, Peng Yen

abstract: Total Site Heat Integration (TSHI) promotes energy recovery between processes to enhance overall energy efficiency of an industrial complex. Various industrial waste heat utilisation technologies have been studied to improve the energy efficiency of energy system. Vapour compression as an open loop heat pump system has good potential to be used to upgrade the waste heat to useful heat in Total Site systems. Vapour compression systems upgrade low grade waste heat by supplying a low quantity of high pressure steam (thermocompressor) or mechanical work (mechanical-compressor) to generate higher pressure steam, as is common with evaporation systems. The vapour compression system recovers the latent heat content of the industrial waste heat, which reduces cooling demand, decreasing the demand for high quality steam and reducing boiler load. This paper introduces an effective Total Site targeting methodology to integrate open cycle heat pump systems, i.e. vapour compression technologies, into an integrated industrial energy system for enhancing overall site energy efficiency. Industrial waste heat and high quality steam demand are able to be reduced simultaneously though this integration. The energy reduction and cost-benefit of thermo-compressor and mechanical-compressor installations are compared through a literature case study. The case study showed a deficit of heat at the MPS and a surplus of heat the LPS, which was identified as a candidate for compression according to the appropriate placement principle for heat pumps. For the case study, a four-stage mechanical vapour compression system and two-stage thermal vapour compression system resulted in an energy cost reductions of 343,859 USD/y and 168,829 USD/y.

text: Heat pump integration for total site waste heat recovery Total Site Heat Integration (TSHI) promotes energy recovery between processes to enhance overall energy efficiency of an industrial complex. Various industrial waste heat utilisation technologies have been studied to improve the energy efficiency of energy system. Vapour compression as an open loop heat pump system has good potential to be used to upgrade the waste heat to useful heat in Total Site systems. Vapour compression systems upgrade low grade waste heat by supplying a low quantity of high pressure steam (thermocompressor) or mechanical work (mechanical-compressor) to generate higher pressure steam, as is common with evaporation systems. The vapour compression system recovers the latent heat content of the industrial waste heat, which reduces cooling demand, decreasing the demand for high quality steam and reducing boiler load. This paper introduces an effective Total Site targeting methodology to integrate open cycle heat pump systems, i.e. vapour compression technologies, into an integrated industrial energy system for enhancing overall site energy efficiency. Industrial waste heat and high quality steam demand are able to be reduced simultaneously though this integration. The energy reduction and cost-benefit of thermo-compressor and mechanical-compressor installations are compared through a literature case study. The case study showed a deficit of heat at the MPS and a surplus of heat the LPS, which was identified as a candidate for compression according to the appropriate placement principle for heat pumps. For the case study, a four-stage mechanical vapour compression system and two-stage thermal vapour compression system resulted in an energy cost reductions of 343,859 USD/y and 168,829 USD/y.

year: 2016

title: Investigating Macromolecular Rate Theory

authors: Prentice, Erica J.

subjects: MMRT

abstract: Curvature with temperature is a defining characteristic of enzyme catalysed rates.  Historically, curvature has been described by Arrhenius behaviour up to a temperature optimum (Tₒₚₜ), while decreases in rates above Tₒₚₜ have been attributed to protein denaturation.  However, various evidence indicates that denaturation is insufficient to explain the decreases in rates above Tₒₚₜ.  Macromolecular rate theory (MMRT) has been proposed as a description of the temperature dependent curvature of enzyme rates based on the expansion of established thermodynamic principals.  MMRT postulates that it is the unusually large change in heat capacity associated with enzyme catalysis (ΔCǂₚ) that results in curvature of rates with temperature.  This description is commensurate with the classical description of enzyme catalysis which involves the tighter binding of the transition state (TS) to the enzyme.  
Here, the molecular origins of the ΔCǂₚ associated with catalysis are explored through crystallography and molecular dynamics simulations.  Methods are developed which calculate a ΔCǂₚ commensurate with experimental values from in silico data.  Simulations reveal that global rigidification is responsible for reduced heat capacity at the TS, although some protein regions contribute more significantly to differences at the TS.  Exploration of the relationship between enzyme mass and catalytic efficiency implicates the vibrational modes captured in dynamics simulations as a reservoir for energy, some of which is available to drive catalysis.  This provides a theoretical framework for the large size of enzymes and extraordinary rate enhancements enzyme catalysts achieve.      
Curvature with temperature is also a feature of organism growth rates and the fluxes through ecosystems.  Here, an experimental validation of the applicability of MMRT to these multi-enzyme systems is presented based on the characterisation of an enzymatic pathway.  The inherent temperature dependence of an enzyme pathway is found to be an average of the temperature dependence of the constituent enzymes.  This relationship shows the factors influencing the rates of enzymes are relevant at the organism level, providing an intrinsic temperature response upon which regulatory responses act.  This proof gives an experimental justification of the application of MMRT to organism and ecosystem temperature data.

text: Investigating Macromolecular Rate Theory Curvature with temperature is a defining characteristic of enzyme catalysed rates.  Historically, curvature has been described by Arrhenius behaviour up to a temperature optimum (Tₒₚₜ), while decreases in rates above Tₒₚₜ have been attributed to protein denaturation.  However, various evidence indicates that denaturation is insufficient to explain the decreases in rates above Tₒₚₜ.  Macromolecular rate theory (MMRT) has been proposed as a description of the temperature dependent curvature of enzyme rates based on the expansion of established thermodynamic principals.  MMRT postulates that it is the unusually large change in heat capacity associated with enzyme catalysis (ΔCǂₚ) that results in curvature of rates with temperature.  This description is commensurate with the classical description of enzyme catalysis which involves the tighter binding of the transition state (TS) to the enzyme.  
Here, the molecular origins of the ΔCǂₚ associated with catalysis are explored through crystallography and molecular dynamics simulations.  Methods are developed which calculate a ΔCǂₚ commensurate with experimental values from in silico data.  Simulations reveal that global rigidification is responsible for reduced heat capacity at the TS, although some protein regions contribute more significantly to differences at the TS.  Exploration of the relationship between enzyme mass and catalytic efficiency implicates the vibrational modes captured in dynamics simulations as a reservoir for energy, some of which is available to drive catalysis.  This provides a theoretical framework for the large size of enzymes and extraordinary rate enhancements enzyme catalysts achieve.      
Curvature with temperature is also a feature of organism growth rates and the fluxes through ecosystems.  Here, an experimental validation of the applicability of MMRT to these multi-enzyme systems is presented based on the characterisation of an enzymatic pathway.  The inherent temperature dependence of an enzyme pathway is found to be an average of the temperature dependence of the constituent enzymes.  This relationship shows the factors influencing the rates of enzymes are relevant at the organism level, providing an intrinsic temperature response upon which regulatory responses act.  This proof gives an experimental justification of the application of MMRT to organism and ecosystem temperature data.

year: 2017

title: Two-step human−environmental impact history for northern New Zealand linked to late-Holocene climate change

authors: Newnham, Rewi M.

subjects: New Zealand

abstract: Following resolution of a long-standing debate over the timing of the initial settlement of New Zealand from Polynesia (late 13th century), a prevailing paradigm has developed that invokes rapid transformation of the landscape, principally by fire, within a few decades of the first arrivals. This model has been constructed from evidence mostly from southern and eastern regions of New Zealand, but a more complicated pattern may apply in the more humid western and northern regions where forests are more resilient to burning. We present a new pollen record from Lake Pupuke, Auckland, northern New Zealand, that charts the changing vegetation cover over the last 1000 years, before and after the arrival of people. Previous results from this site concurred with the rapid transformation model, although sampling resolution, chronology and sediment disturbance make that interpretation equivocal. Our new record is dated principally by tephrochronology together with radiocarbon dating, and includes a cryptotephra deposit identified as Kaharoa tephra, a key marker for first settlement in northern New Zealand. Its discovery and stratigraphic position below two Rangitoto-derived tephras enables a clearer picture of environmental change to be drawn. The new pollen record shows an early phase (step 1) of minor, localised forest clearance around the time of Kaharoa tephra (c. 1314 AD) followed by a later, more extensive deforestation phase (step 2) commencing at around the time of deposition of the Rangitoto tephras (c. 1400‒1450 AD). This pattern, which needs to be corroborated from other well-resolved records from northern New Zealand, concurs with an emerging hypothesis that the ‘Little Ice Age’ had a significant impact on pre-European Māori with the onset of harsher conditions causing a consolidation of populations and later environmental impact in northern New Zealand.

text: Two-step human−environmental impact history for northern New Zealand linked to late-Holocene climate change Following resolution of a long-standing debate over the timing of the initial settlement of New Zealand from Polynesia (late 13th century), a prevailing paradigm has developed that invokes rapid transformation of the landscape, principally by fire, within a few decades of the first arrivals. This model has been constructed from evidence mostly from southern and eastern regions of New Zealand, but a more complicated pattern may apply in the more humid western and northern regions where forests are more resilient to burning. We present a new pollen record from Lake Pupuke, Auckland, northern New Zealand, that charts the changing vegetation cover over the last 1000 years, before and after the arrival of people. Previous results from this site concurred with the rapid transformation model, although sampling resolution, chronology and sediment disturbance make that interpretation equivocal. Our new record is dated principally by tephrochronology together with radiocarbon dating, and includes a cryptotephra deposit identified as Kaharoa tephra, a key marker for first settlement in northern New Zealand. Its discovery and stratigraphic position below two Rangitoto-derived tephras enables a clearer picture of environmental change to be drawn. The new pollen record shows an early phase (step 1) of minor, localised forest clearance around the time of Kaharoa tephra (c. 1314 AD) followed by a later, more extensive deforestation phase (step 2) commencing at around the time of deposition of the Rangitoto tephras (c. 1400‒1450 AD). This pattern, which needs to be corroborated from other well-resolved records from northern New Zealand, concurs with an emerging hypothesis that the ‘Little Ice Age’ had a significant impact on pre-European Māori with the onset of harsher conditions causing a consolidation of populations and later environmental impact in northern New Zealand.

year: 2018