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Sustainable choices for residential water supply in Auckland

Sustainable choices for residential water supply in Auckland. Nalanie Mithraratne & Robert Vale Centre for Urban Ecosystem Sustainability Landcare Research. Outline. Mains supply vs. rain tanks Impact of settlement patterns Water system in average house Conclusions. LCA of mains supply.

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Sustainable choices for residential water supply in Auckland

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  1. Sustainable choices for residential water supply in Auckland Nalanie Mithraratne & Robert Vale Centre for Urban Ecosystem Sustainability Landcare Research

  2. Outline • Mains supply vs. rain tanks • Impact of settlement patterns • Water system in average house • Conclusions

  3. LCA of mains supply • System boundary • Initial construction • Maintenance/ replacements - 1% of the total length of pipes/year replaced • Operational requirements • Analysis period – 100 years

  4. Bulk supply system - constructionLIFE CYCLE ENERGY

  5. Bulk supply system LCE LCCO2

  6. Local supply network - 2005 • CLS - cement lined steel • CI - cast iron • PE - polyethylene • AC - asbestos cement

  7. Mains supply performance • Energy intensity = 2.11MJ/m3(Range 2.08 - 2.27MJ/m3) • CO2 emissions factor = 0.128kgCO2/m3(Range 0.126 – 0.146kgCO2/m3) Mains water supply contribution, • Life cycle energy = 86GJ/house • CO2 emissions = 4.9 tonnes CO2/house

  8. Impact of Settlement Pattern Roberton site • Residential density 14units/ha • Parallelogram bounded by roads

  9. Impact of Settlement Pattern Sandringham site • Residential density 17units/ha • Road across the site

  10. Impact of Settlement Pattern Freeman’s Bay site • Residential density 23units/ha • Trapezoid, open spaces within

  11. Impact of Settlement Pattern Ponsonby site • Residential density 24units/ha • Rectangle bounded by roads

  12. Life Cycle Energy and LCCO2 (actual)

  13. Life Cycle Energy composition

  14. Life Cycle CO2 composition

  15. Mains supply vs. Rain tanks • Wastewater and stormwater • Mains - more, rain tanks - reduced • Water quality • Mains - Grade A, rain tanks – untreated • Water supply volume • Mains - 370m3, rain tanks - varies

  16. House size and rain water volume

  17. Rain harvesting system [Source: Marley 2005]

  18. Water supply systems - LCELIFE CYCLE ENERGY (GJ)

  19. Water supply systems – LCCO2LIFE CYCLE CO2 (kg)

  20. Water supply systems – LCCLIFE CYCLE COST (NZ$)

  21. Building Industry Advisory Council House (BIAC) Plan [Source: Baird and Chan (1983)]

  22. Building Industry Advisory Council House (BIAC) Section & Front Elevation [Source: Baird and Chan (1983)]

  23. ASSUMPTIONS • Useful life of NZ houses is 100 years. • Living room faces north. • Space heating: Whole house, temp 18oC, 2 schedules • Water heating: varies with water volume.

  24. Life cycle energy by end use

  25. Life cycle CO2 by end use

  26. Life cycle cost by end use

  27. Conclusions • Consumption significantly impacts the system choice. • Use of mains supply in smaller houses (>150m2) and rain harvesting in larger houses is better for the environment. • Mains supply is cheaper initially but costly in life cycle terms. • Water supply is negligible in terms of total environmental performance of house.

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