title: Total site heat integration: Utility selection and optimisation using cost and exergy derivative analysis

authors: Tarighaleslami, Amir Hossein

subjects: Total site heat integration

abstract: This paper presents a new Total Site Heat Integration utility temperature selection and optimisation method that can optimise both non-isothermal (e.g. hot water) and isothermal (e.g. steam) utilities. None of the existing methods addresses both non-isothermal and isothermal utility selection and optimisation incorporated in a single procedure. The optimisation affects heat recovery, the number of heat exchangers in Total Site Heat Exchanger Network, heat transfer area, exergy destruction (ED), Utility Cost (UC), Annualised Capital Cost (CC), and Total Annualised Cost (TC). Three optimisation parameters, UC, ED, and TC have been incorporated into a derivative based optimisation procedure where derivatives are minimised sequentially and iteratively based on the specified approach. The new optimisation procedure has been carried out for three different approaches as the combinations of optimisation parameters based on the created derivative map. The merits of the new method have been illustrated using three case studies. These case studies represent a diverse range of processing types and temperatures. Results for the case studies suggest the best derivative optimisation approach is to first optimise UC in combination with ED and then optimise TC. For this approach, TC reductions between 0.6 to 4.6 % for different case studies and scenarios are achieved.

text: Total site heat integration: Utility selection and optimisation using cost and exergy derivative analysis This paper presents a new Total Site Heat Integration utility temperature selection and optimisation method that can optimise both non-isothermal (e.g. hot water) and isothermal (e.g. steam) utilities. None of the existing methods addresses both non-isothermal and isothermal utility selection and optimisation incorporated in a single procedure. The optimisation affects heat recovery, the number of heat exchangers in Total Site Heat Exchanger Network, heat transfer area, exergy destruction (ED), Utility Cost (UC), Annualised Capital Cost (CC), and Total Annualised Cost (TC). Three optimisation parameters, UC, ED, and TC have been incorporated into a derivative based optimisation procedure where derivatives are minimised sequentially and iteratively based on the specified approach. The new optimisation procedure has been carried out for three different approaches as the combinations of optimisation parameters based on the created derivative map. The merits of the new method have been illustrated using three case studies. These case studies represent a diverse range of processing types and temperatures. Results for the case studies suggest the best derivative optimisation approach is to first optimise UC in combination with ED and then optimise TC. For this approach, TC reductions between 0.6 to 4.6 % for different case studies and scenarios are achieved.

year: 2017

title: Diet selectivity in a terrestrial forest invertebrate, the Auckland tree wētā, across three habitat zones.

authors: Brown, Matthew

subjects: feeding behaviour

abstract: Insects are important but overlooked components of forest ecosystems of New Zealand. For many invertebrate species, information on foraging patterns and trophic relationships is lacking. We examined diet composition and selectivity in a large bodied invertebrate, the Auckland tree wētā, in three habitat zones in a lowland New Zealand forest. We asked if Hemideina thoracica selectively forage from available plant food sources, and if these choices were lipid-rich compared to non-preferred available plants. We also identified the proportion of invertebrates in their frass as a proxy for omnivory. From reconnaissance plot sampling, together with faecal fragment analysis, we report that more than 93% of individual wētā had eaten other invertebrates before capture. Wētā in the highest elevation hillslope habitat consumed significantly fewer plants on average than wētā on either the low elevation terrace or mid-slope habitat. Hillslope wētā also had the highest average number of invertebrate fragments in their frass, significantly more than wētā in the low elevation terrace habitat. Wētā showed high variability in the consumption of fruit and seeds across all habitats. Generally, we did not observe diet differences between the sexes (although it appears that male wētā in the mid hillslope habitat ate fruits and seeds more voraciously than females), suggesting that the sexes have similar niche breadths and display similar degrees of omnivorous behaviour. Extraction of leaf lipids demonstrated a range of lipid content values in available plants, and Ivlev’s electivity index indicated that plant species which demonstrated high electivity, tended to have higher concentrations of lipids in their leaves. Our findings indicate that H. thoracica forage omnivorously and selectively, and hence play multiple roles in native ecosystems and food webs.

text: Diet selectivity in a terrestrial forest invertebrate, the Auckland tree wētā, across three habitat zones. Insects are important but overlooked components of forest ecosystems of New Zealand. For many invertebrate species, information on foraging patterns and trophic relationships is lacking. We examined diet composition and selectivity in a large bodied invertebrate, the Auckland tree wētā, in three habitat zones in a lowland New Zealand forest. We asked if Hemideina thoracica selectively forage from available plant food sources, and if these choices were lipid-rich compared to non-preferred available plants. We also identified the proportion of invertebrates in their frass as a proxy for omnivory. From reconnaissance plot sampling, together with faecal fragment analysis, we report that more than 93% of individual wētā had eaten other invertebrates before capture. Wētā in the highest elevation hillslope habitat consumed significantly fewer plants on average than wētā on either the low elevation terrace or mid-slope habitat. Hillslope wētā also had the highest average number of invertebrate fragments in their frass, significantly more than wētā in the low elevation terrace habitat. Wētā showed high variability in the consumption of fruit and seeds across all habitats. Generally, we did not observe diet differences between the sexes (although it appears that male wētā in the mid hillslope habitat ate fruits and seeds more voraciously than females), suggesting that the sexes have similar niche breadths and display similar degrees of omnivorous behaviour. Extraction of leaf lipids demonstrated a range of lipid content values in available plants, and Ivlev’s electivity index indicated that plant species which demonstrated high electivity, tended to have higher concentrations of lipids in their leaves. Our findings indicate that H. thoracica forage omnivorously and selectively, and hence play multiple roles in native ecosystems and food webs.

year: 2018

title: Estimated catchment loads of nitrogen and phosphorus to the Rotorua Te Arawa Lakes

authors: McBride, Chris G.

abstract: The Rotorua Te Arawa Lakes are central to the identity of their region, of immense historical and cultural importance, and provide ecosystem services that underpin biodiversity, conservation and socioeconomic aspirations of the community. The diversity of water quality in the lakes reflects their catchments, which are diverse in topography, hydrogeology and intensity of land use, ranging from the largely undeveloped land around lakes Tikitapu and Okataina, to highly developed forestry and pastoral land around lakes Rerewhakaaitu, Rotorua and Okaro. Lake water quality is strongly linked to nutrients received by each lake from surface flows and groundwater springs. It therefore follows that management of lake water quality requires a good understanding of nutrient loads derived from the landscape, as does the assessment or prediction of the in-lake effects of catchment-based management initiatives aimed at improving lake water quality.

text: Estimated catchment loads of nitrogen and phosphorus to the Rotorua Te Arawa Lakes The Rotorua Te Arawa Lakes are central to the identity of their region, of immense historical and cultural importance, and provide ecosystem services that underpin biodiversity, conservation and socioeconomic aspirations of the community. The diversity of water quality in the lakes reflects their catchments, which are diverse in topography, hydrogeology and intensity of land use, ranging from the largely undeveloped land around lakes Tikitapu and Okataina, to highly developed forestry and pastoral land around lakes Rerewhakaaitu, Rotorua and Okaro. Lake water quality is strongly linked to nutrients received by each lake from surface flows and groundwater springs. It therefore follows that management of lake water quality requires a good understanding of nutrient loads derived from the landscape, as does the assessment or prediction of the in-lake effects of catchment-based management initiatives aimed at improving lake water quality.

year: 2021