Questions on Engineering Essay

Submitted By DeadEnd1
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Life Cycle Greenhouse Gas Emissions from Concentrating Solar Power
Over the last thirty years, more than 100 life cycle assessments (LCAs) have been conducted and published for a variety of utility-scale concentrating solar power (CSP) systems. These LCAs have yielded wide-ranging results. Variation could be attributed to differences in technologies evaluated (i.e., differing system designs, commercial versus conceptual systems, system operating assumptions, technology improvements over time), and LCA methods and assumptions. The National Renewable Energy Laboratory (NREL) recently led the Life Cycle Assessment (LCA) Harmonization Project, a study that makes great strides in clarifying inconsistent and conflicting GHG emission estimates in the published literature while providing more precise estimates of GHG emissions from utility-scale CSP systems. Analysts developed and applied a systematic approach to review LCA literature, identify primary sources of variability and, where possible, reduce variability in GHG emissions estimates through a process called “harmonization.”

LCA is a standardized technique that tracks all material, energy, and pollutant flows of a system—from raw material extraction, manufacturing, transport, and construction to operation and endof-life disposal. LCA can help determine environmental burdens from “cradle to grave” and facilitate fair comparisons of energy technologies. Comparing life cycle stages and proportions of GHG emissions from each stage for CSP and coal shows that, for coalfired power plants, fuel combustion during operation emits the vast majority of GHGs (see figure below). It also demonstrates that for CSP plants, the majority of GHG emissions are upstream of operation. Published results from 125 studies of CSP systems were reviewed and screened. Ten studies on parabolic trough and power tower passed the screening (providing 19 and 17 estimates of life cycle GHG emissions, respectively) and were included in this analysis. Results based on the six estimates for parabolic dish technologies are reported in our journal publication (Burkhardt…