The impact of photovoltaic (PV) installations on downwind particulate matter concentrations: Results from field observations at a 550-MW_AC utility-scale PV plant

<p>With utility-scale photovoltaic (PV) projects increasingly developed in dry and dust-prone geographies with high solar insolation, there is a critical need to analyze the impacts of PV installations on the resulting particulate matter (PM) concentrations, which have environmental and health impacts. This study is the first to quantify the impact of a utility-scale PV plant on PM concentrations downwind of the project site. Background, construction, and post-construction PM_2.5 and PM₁₀ (PM with aerodynamic diameters <2.5 and <10 μm, respectively) concentration data were collected from four beta attenuation monitor (BAM) stations over 3 yr. Based on these data, the authors evaluate the hypothesis that PM emissions from land occupied by a utility-scale PV installation are reduced after project construction through a wind-shielding effect. The results show that the (1) confidence intervals of the mean PM concentrations during construction overlap with or are lower than background concentrations for three of the four BAM stations; and (2) post-construction PM_2.5 and PM₁₀ concentrations downwind of the PV installation are significantly lower than the background concentrations at three of the four BAM stations. At the fourth BAM station, downwind post-construction PM_2.5 and PM₁₀ concentrations increased marginally by 5.7% and 2.6% of the 24-hr ambient air quality standards defined by the U.S. Environmental Protection Agency, respectively, when compared with background concentrations, with the PM_2.5 increase being statistically insignificant. This increase may be due to vehicular emissions from an access road near the southwest corner of the site or a drainage berm near the south station. The findings demonstrate the overall environmental benefit of downwind PM emission abatement from a utility-scale PV installation in desert conditions due to wind shielding. With PM emission reductions observed within 10 months of completion of construction, post-construction monitoring of downwind PM levels may be reduced to a 1-yr period for other projects with similar soil and weather conditions.</p> <p><i>Implications</i>: This study is the first to analyze impact of a utility photovoltaic (PV) project on downwind particulate matter (PM) concentration in desert conditions. The PM data were collected at four beta attenuation monitor stations over a 3-yr period. The post-construction PM concentrations are lower than background concentrations at three of four stations, therefore supporting the hypothesis of post-construction wind shielding from PV installations. With PM emission reductions observed within 10 months of completion of construction, postconstruction monitoring of downwind PM levels may be reduced to a 1-yr period for other PV projects with similar soil and weather conditions.</p

The impact of photovoltaic (PV) installations on downwind particulate matter concentrations: Results from field observations at a 550-MW_AC utility-scale PV plant

<p>With utility-scale photovoltaic (PV) projects increasingly developed in dry and dust-prone geographies with high solar insolation, there is a critical need to analyze the impacts of PV installations on the resulting particulate matter (PM) concentrations, which have environmental and health impacts. This study is the first to quantify the impact of a utility-scale PV plant on PM concentrations downwind of the project site. Background, construction, and post-construction PM_2.5 and PM₁₀ (PM with aerodynamic diameters <2.5 and <10 μm, respectively) concentration data were collected from four beta attenuation monitor (BAM) stations over 3 yr. Based on these data, the authors evaluate the hypothesis that PM emissions from land occupied by a utility-scale PV installation are reduced after project construction through a wind-shielding effect. The results show that the (1) confidence intervals of the mean PM concentrations during construction overlap with or are lower than background concentrations for three of the four BAM stations; and (2) post-construction PM_2.5 and PM₁₀ concentrations downwind of the PV installation are significantly lower than the background concentrations at three of the four BAM stations. At the fourth BAM station, downwind post-construction PM_2.5 and PM₁₀ concentrations increased marginally by 5.7% and 2.6% of the 24-hr ambient air quality standards defined by the U.S. Environmental Protection Agency, respectively, when compared with background concentrations, with the PM_2.5 increase being statistically insignificant. This increase may be due to vehicular emissions from an access road near the southwest corner of the site or a drainage berm near the south station. The findings demonstrate the overall environmental benefit of downwind PM emission abatement from a utility-scale PV installation in desert conditions due to wind shielding. With PM emission reductions observed within 10 months of completion of construction, post-construction monitoring of downwind PM levels may be reduced to a 1-yr period for other projects with similar soil and weather conditions.</p> <p><i>Implications</i>: This study is the first to analyze impact of a utility photovoltaic (PV) project on downwind particulate matter (PM) concentration in desert conditions. The PM data were collected at four beta attenuation monitor stations over a 3-yr period. The post-construction PM concentrations are lower than background concentrations at three of four stations, therefore supporting the hypothesis of post-construction wind shielding from PV installations. With PM emission reductions observed within 10 months of completion of construction, postconstruction monitoring of downwind PM levels may be reduced to a 1-yr period for other PV projects with similar soil and weather conditions.</p

Novel Method of Sensitivity Analysis Improves the Prioritization of Research in Anticipatory Life Cycle Assessment of Emerging Technologies

It is now common practice in environmental life cycle assessment (LCA) to conduct sensitivity analyses to identify critical parameters and prioritize further research. Typical approaches include variation of input parameters one at a time to determine the corresponding variation in characterized midpoints or normalized and weighted end points. Generally, those input parameters that cause the greatest variations in output criteria are accepted as the most important subjects of further investigation. However, in comparative LCA of emerging technologies, the typical approach to sensitivity analysis may misdirect research and development (R&D) toward addressing uncertainties that are inconsequential or counterproductive. This paper presents a novel method of sensitivity analysis for a decision-driven, anticipatory LCA of three emerging photovoltaic (PV) technologies: amorphous-Si (a-Si), CdTe and ribbon-Si. Although traditional approaches identify metal depletion as critical, a hypothetical reduction of uncertainty in metal depletion fails to improve confidence in the environmental comparison. By contrast, the novel approach directs attention toward marine eutrophication, where uncertainty reduction significantly improves decision confidence in the choice between a-Si and CdTe. The implication is that the novel method will result in better recommendations on the choice of the environmentally preferable emerging technology alternative for commercialization

Intertemporal Cumulative Radiative Forcing Effects of Photovoltaic Deployments

Current policies accelerating photovoltaics (PV) deployments are motivated by environmental goals, including reducing greenhouse gas (GHG) emissions by displacing electricity generated from fossil-fuels. Existing practice assesses environmental benefits on a net life-cycle basis, where displaced GHG emissions offset those generated during PV production. However, this approach does not consider that the environmental costs of GHG release during production are incurred early, while environmental benefits accrue later. Thus, where policy targets suggest meeting GHG reduction goals established by a certain date, rapid PV deployment may have counterintuitive, albeit temporary, undesired consequences. On a cumulative radiative forcing (CRF) basis, the environmental improvements attributable to PV might be realized much later than is currently understood, particularly when PV manufacturing utilizes GHG-intensive energy sources (e.g., coal), but deployment occurs in areas with less GHG-intensive electricity sources (e.g., hydroelectric). This paper details a dynamic CRF model to examine the intertemporal warming impacts of PV deployments in California and Wyoming. CRF payback times are longer than GHG payback times by 6–12 years in California and 6–11 years in Wyoming depending on the PV technology mix and deployment strategy. For the same PV capacity being deployed, early installations yield greater CRF benefits (calculated over 10 and 25 years) than installations occurring later in time. Further, CRF benefits are maximized when PV technologies with the lowest manufacturing GHG footprint (cadmium telluride) are deployed in locations with the most GHG-intensive grids (i.e., Wyoming)

Sensitivity to weighting in life cycle impact assessment (LCIA)

Purpose: Weighting in life cycle assessment (LCA) incorporates stakeholder preferences in the decision-making process of comparative LCAs. Research efforts on this topic are concerned with deriving weights according to different principles, but few studies have evaluated the relationship between normalization and weights and their effect on single scores. We evaluate the sensitivity of aggregation methods to weights in different life cycle impact assessment (LCIA) methods to provide insight on the receptiveness of single score results to value systems. Methods: Sensitivity to weights in two LCIA methods is assessed by exploring weight spaces stochastically and evaluating the rank of alternatives via the Rank Acceptability Index (RAI). We assess two aggregation methods: a weighted sum based on externally normalized scores and a method of internal normalization based on outranking across CML-IA and ReCipE midpoint impact assessment. The RAI represents the likelihood that an alternative occupies a certain rank given all possible weight spaces, and it can be used to compare the sensitivity of final ranks to weight values in each aggregation method and LCIA. Evaluation is based on a case study of a comparative LCA of five PV technologies whose inventory is readily available in Ecoinvent. Results and discussion: Influence of weights in single scores depend on the scaling/normalization step more than the value of the weight itself. In each LCIA, aggregated results from a weighted sum with external normalization references show a higher weight insensitivity in RAI than outranking-based aggregation because in the former, results are driven by a few dominant impact categories due to the normalization procedure. Differences in sensitivity are caused by the notable variety (up two orders of magnitude) in the scales of normalized values for the weighted sum with external normalization and intrinsic properties of the methods including compensation and a lack of accounting for mutual differences. Conclusions: Contrary to the belief that the choice of weights is decisive in aggregation of LCIA results, in this case study, it is shown that the normalization step has the greatest influence in the results. This point holds for EU and World references in ReCiPe and CML-IA alike. Aggregation consisting of outranking generates rank orderings with a more balanced contribution of impact categories and sensitivity to weights’ values as opposed to weighted sum approaches that rely on external normalization references. Recommendations: Practitioners aiming to include stakeholder values in single scores for LCIA should be aware of how the weights are treated in the aggregation method as to ensure proper representation of values

Photovoltaic Capacity Additions: The Optimal Rate of Deployment with Sensitivity to Time-Based GHG Emissions

<p>Environmental impact assessments of photovoltaic (PV) deployments are based on the assumption that the environmental benefits can be allocated at the time of installation. However, benefits do not accrue immediately after installation but accrue over the entire life cycle of the PV module. There is an inter-temporal trade-off which depends on the magnitude of upfront PV manufacturing GHG emissions and the year-on-year GHGs avoided when PV electricity displaces electricity generated from fossil fuels. Moreover, environmental impact assessments of PV systems precludes temporally sensitive technology factors which impact the environmental benefits allocated to a PV depending on the year of installation. These factors include: the varying rates of technology improvements for different PV technologies, electricity mixes of the deployment location and location where PV systems are manufactured. By not incorporating inter-temporal trade-off analysis and temporally sensitive technology factors that influence net environmental impacts of PV deployments, PV capacity additions can inadvertently become counter-productive by increasing net GHG emissions over the short term.<br>This project designs and implements an optimization model to minimize the short term environmental impacts of PV system deployments by incorporating the inter-temporal trade-offs involved. When integrated with PV LCAs this model can help policy makers to minimize short term impacts along with fulfilling long term renewable energy policy goals. The results show that the optimal PV deployment strategy for the three states - California, Wyoming and Arizona - varies depending on the electricity mixes of these states. The optimal PV deployment strategy is sensitive to the state of technology and the choice of PV technology to fulfill the targets. Also, adopting an sub-optimal PV deployment strategy to meet California's PV policy targets by<br>importing Silicon PV modules from China will increase the CO2 emissions over the short term.</p

The Need for and Path to Harmonized Life Cycle Assessment and Techno-Economic Assessment for Carbon Dioxide Capture and Utilization

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/163553/2/ente201901034_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/163553/1/ente201901034.pd