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Exergetic Life Cycle Assessment

Exergetic Life Cycle Assessment. Ahmet Ozbilen , Ibrahim Dincer and Marc A. Rosen. July 2-4, 2012 Osmaniye, Turkiye. Outline. Introduction Life Cycle Assessment (LCA) Exergetic LCA (ExLCA) Case study Conclusion. Introduction. Awareness of environmental concerns increases

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Exergetic Life Cycle Assessment

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  1. Exergetic Life Cycle Assessment Ahmet Ozbilen, Ibrahim Dincer and Marc A. Rosen July 2-4, 2012 Osmaniye, Turkiye

  2. Outline • Introduction • Life Cycle Assessment (LCA) • Exergetic LCA (ExLCA) • Case study • Conclusion

  3. Introduction • Awareness of environmental concerns increases • ‘Greener’ products and ‘greener’ processes • Life cycle assessment → Investigates and reduces the environmental impacts of a system or process or product • The concept of exergy in LCA approach • To identify and understand underlying reasons for many environmental impacts • ExLCA identifies exergy utilization and destruction during the life cycle of a system or a product.

  4. Life Cycle Assessment (LCA) • LCA is used to evaluate total environmental impact of a product or process. • LCA is also conducted to decrease overall environmental impact and to identify environmentally critical phases. • Cradle-to-grave analysis (production, transportation, installment, operation, disposal). • Defined by ISO 14000 series.

  5. Life Cycle Assessment (LCA) Goal and scope definition Interpretation Has four phases; • Goal and scope definition: Specifies objectives, boundaries • Life cycle inventory analysis (LCI): Inventory data on energy and material flows • Life cycle impact assessment (LCIA): Evaluates environmental impacts of material and energy flows • Improvement Analysis: Results, conclusions, recommendations and improvements Inventory analysis Impact assessment Improvement analysis Life cycle assessment framework.

  6. Life Cycle Assessment (LCA) • CML 2001 Impact Categories Source: Adapted from (Guineeet al., 2002)

  7. Exergetic LCA • Linkages between exergy analysis and LCA • ExLCA approach and methodology • Applications of Exergy & LCA • Advantages and benefits of ExLCA

  8. Exergetic LCA - Linkages between exergy analysis and LCA • Environmental impacts can often be decreased by reducing exergy reductions • Increase in exergy efficiency • Less resources (exergy) • Reduction in requirements associated with new facilities for the production, transportation and the distribution of the various energy forms

  9. Exergetic LCA – ExLCA Methodology and Approach • Goal and scope definition: Identical with LCA • Inventory Analysis: Mass and energy balances, simplified black box approach (not always) • Impact assessment: Determination of exergies of the flows, and the exergy destructions and efficiencies of the overall processes and its subprocesses. • Improvement analysis: Intended to reduce the life cycle irreversibilities

  10. Exergetic LCA – ExLCA Methodology and Approach Raw material acquisition Inputs for each stage Outputs for each stage Intended products Co-products and energy Emissions Materials Energy EXERGY Manufacturing EXERGY Use/reuse/maintenance Recycling/waste management General flow diagram of ExLCA.

  11. Exergy and LCA – Applications • Daniel and Rosen, 2012 – Fuel cycles for automobiles • Neelis et al., 2002 – Hydrogen production and storage systems for automotive applications • Boyona et al., 2011 – Steam methane reforming process for hydrogen production • Granovskii et al., 2007 – Hydrogen production using renewables • Peiro et al., 2010 – Production of biodiesel from used cooked oil • Beccali et al., 2003 – Plaster materials • Carrado et al., 2006 – High-efficiency power plant for H2 production - (the ZECOTECH cycle). • Dewulf et al., 2001 – Waste treatment plant

  12. Exergetic LCA – Advantages • Not only inputs and emissions, but also consider these quantities from the perspective of exergy. • The depletion of natural resources is measured directly as a loss of exergy. • Improving the efficiency of the systems and processes, so as to decrease their environmental impacts, is often aided more by ExLCA.

  13. Case Study: ExLCA of a hydrogen production process. The five-step Cu-Cl thermochemical cycle for H2 production GaBi 4 model of entire system

  14. Case Study: ExLCA of a hydrogen production process. Exergy diagram of the life cycle of nuclear-based hydrogen production

  15. Results and Discussion Variation of (a) AP and (b) GWP (per 1 MJ exergy of H2) with lifetime of the system

  16. Results and Discussion Variation of GWP and AP with exergy efficiency of hydrogen plant

  17. Concluding Remarks • Thermodynamic analysis throughout the life cycle of a process or system • The main contributor of life cycle irreversibility of nuclear-based hydrogen production is fuel (uranium) processing, for which the exergy efficiency is 26.7%. • The lowest GWP per megajoule exergy of hydrogen is 5.65 g CO2-eq, for a plant capacity of 125,000 kg H2/day. The corresponding GWP for a plant capacity of 62,500 kg H2/day is 5.75 g CO2-eq. • AP can also reduced from an initial value of 0.041 to 0.027 g SO2-eq per megajoule exergy of hydrogen, if the exergy efficiency is increased from 67% to 98%.

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