By Shao-Hua Wu, Michelle L. Povinelli
We use a coupled thermal-optical approach to model the operating temperature rise in GaAs nanowire solar cells. We find that despite more highly concentrated light absorption and lower thermal conductivity, the overall temperature rise in a nanowire structure is no higher than in a planar structure. Moreover, coating the nanowires with a transparent polymer can increase the radiative cooling power by 2.2 times, lowering the operating temperature by nearly 7 K.
By Jonathan Eyer
Resource and Energy Economics, 53
Large firms are becoming increasingly dominant in the natural gas production industry. At the same time, regulators and environmental groups are concerned about potential environmental damage associated with hydraulic fracturing. However, small firms are protected from the full extent of their damages, while large firms must internalize a greater portion of their social costs. This paper examines the effect of firm size and liability on environmental safety in the context of hydraulic fracturing in Pennsylvania’s Marcellus Shale across three dimensions of size. Impacts of firm size on safety are found across legal, regulatory, and brand dimensions of size with the largest effects being driven by changes in regulatory liability. These safety gains are sizable as violation rates would be approximately twice as high if firms at remained at 2008 sizes.
By Antonio M. Bento, Teevrat Garg, Daniel Kaffine
Journal of Environmental Economics and Management
Renewable portfolio standards (RPS) are commonly promoted as a policy tool to reduce emissions associated with fossil generation, while also stimulating development of local renewable resource endowments. We develop a general equilibrium model of an RPS policy that captures key features such as a fixed factor renewable endowment, substitution across sectors of the economy, and endogenous price responses. We analytically decompose the effects of an RPS into a) a substitution effect, b) an output-tax effect, and c) an output effect. We show that an increase in the RPS can either deliver large resource booms or large emissions savings but not both. Our framework can translate different renewable resource endowments and pre-existing standards across states into economic and environmental impacts to inform current renewable energy and climate policies.
By Antonio M. Bento, Richard Klotz
Environmental Science & Technology
Lifecycle analysis (LCA) metrics of greenhouse gas emissions are increasingly being used to select technologies supported by climate policy. However, LCAs typically evaluate the emissions associated with a technology or product, not the impacts of policies. Here, we show that policies supporting the same technology can lead to dramatically different emissions impacts per unit of technology added, due to multimarket responses to the policy. Using a policy-based consequential LCA, we find that the lifecycle emissions impacts of four US biofuel policies range from a reduction of 16.1 gCO2e to an increase of 24.0 gCO2e per MJ corn ethanol added by the policy. The differences between these results and representative technology-based LCA measures, which do not account for the policy instrument driving the expansion in the technology, illustrate the need for policy-based LCA measures when informing policy decision making.
By Iraj Ershaghi, Donald L. Paul, Saran Kaba
Society of Petroleum Engineers
In this paper we discuss our studies conducted on two California offshore fields that may be abandoned in near future. The purpose of the study was to examine the feasibility of re-purposing these fields to suitable offshore gas storage by utilizing the reservoir voidage and by using the existing pipeline facilities. These storage sites could offer a significant alternative to the current onshore sites located in highly populated urban areas of California.
By Behrokh Khoshnevis, Mahdi Yoozbashizadeh, Iraj Ershaghi
Society of Petroleum Engineers
In this paper we describe a novel method for water unloading of natural gas wells in mature reservoirs experiencing low reservoir pressures. Current methods for water unloading from gas wells have at least one of the drawbacks of restricting gas production, requiring external energy, using consumable surfactants, or being labor intensive. The proposed design offers a new approach to water unloading that does not restrict or interrupt gas production. It can operate without external energy, and uses no consumables. Virtual and physical simulators have been developed and the full-scale version of the concept has been studied in test wells to demonstrate the feasibility and performance of the new water-unloading concept. An industrial-grade preproduction prototype was tested successfully in a test gas well to validate this study.
By Yonghong Yi, John S. Kimball, Richard H. Chen, Mahta Moghaddam, Rolf H. Reichle, Umakant Mishra, Donatella Zona, Walter C. Oechel
An important feature of the Arctic is large spatial heterogeneity in active layer conditions, which is generally poorly represented by global models and can lead to large uncertainties in predicting regional ecosystem responses and climate feedbacks. In this study, we developed a spatially integrated modeling and analysis framework combining field observations, local-scale ( ∼ 50m resolution) active layer thickness (ALT) and soil moisture maps derived from low-frequency (L+P-band) airborne radar measurements, and global satellite environmental observations to investigate the ALT sensitivity to recent climate trends and landscape heterogeneity in Alaska. Modeled ALT results show good correspondence with in situ measurements in higher-permafrost-probability (PP ≥ 70%) areas (n = 33; R = 0.60; mean bias = 1.58cm; RMSE = 20.32cm), but with larger uncertainty in sporadic and discontinuous permafrost areas. The model results also reveal widespread ALT deepening since 2001, with smaller ALT increases in northern Alaska (mean trend = 0.32±1.18cmyr−1) and much larger increases (> 3cmyr−1) across interior and southern Alaska. The positive ALT trend coincides with regional warming and a longer snow-free season (R = 0.60±0.32). A spatially integrated analysis of the radar retrievals and model sensitivity simulations demonstrated that uncertainty in the spatial and vertical distribution of soil organic carbon (SOC) was the largest factor affecting modeled ALT accuracy, while soil moisture played a secondary role. Potential improvements in characterizing SOC heterogeneity, including better spatial sampling of soil conditions and advances in remote sensing of SOC and soil moisture, will enable more accurate predictions of active layer conditions and refinement of the modeling framework across a larger domain.
By Seyed Hamed Alemohammad, Alexandra G. Konings, Thomas Jagdhuber, Mahta Moghaddam, Dara Entekhabi
Remote Sensing of Environment
Understanding the scattering mechanisms from the ground surface in the presence of different vegetation densities is necessary for the interpretation of P-band Synthetic Aperture Radar (SAR) observations and for the design of geophysical retrieval algorithms. In this study, a quantitative analysis of vegetation and soil scattering mechanisms estimated from the observations of an airborne P-band SAR instrument across nine different biomes in North America is presented. The goal is to apply a hybrid (model- and eigen-based) three component decomposition approach to separate the contributions of surface, double-bounce and vegetation volume scattering across a wide range of biome conditions. The decomposition makes no prior assumptions about vegetation structure. We characterize the dynamics of the decomposition across different North American biomes and assess their characteristic range. Impacts of vegetation coverseasonality and soil surface roughness on the contributions of each scattering mechanism are also investigated. Observations used here are part of the NASA Airborne Microwave Observatory of Subcanopy and Subsurface (AirMOSS) mission and data have been collected between 2013 and 2015.