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1. Estimating the impacts of natural gas power generation growth on solar electricity development: PJM's evolving resource mix and ramping capability

   https://doi.org/10.1002/wene.454  

   Nyangon, Joseph ; Byrne, John ( July 2022 , WIREs Energy and Environment)

   Expansion of distributed solar photovoltaic (PV) and natural gas‐fired generation capacity in the United States has put a renewed spotlight on methods and tools for power system planning and grid modernization. This article investigates the impact of increasing natural gas‐fired electricity generation assets on installed distributed solar PV systems in the Pennsylvania–New Jersey–Maryland (PJM) Interconnection in the United States over the period 2008–2018. We developed an empirical dynamic panel data model using the system‐generalized method of moments (system‐GMM) estimation approach. The model accounts for the impact of past and current technical, market and policy changes over time, forecasting errors, and business cycles by controlling for PJM jurisdictions‐level effects and year fixed effects. Using an instrumental variable to control for endogeneity, we concluded that natural gas does not crowd out renewables like solar PV in the PJM capacity market; however, we also found considerable heterogeneity. Such heterogeneity was displayed in the relationship between solar PV systems and electricity prices. More interestingly, we found no evidence suggesting any relationship between distributed solar PV development and nuclear, coal, hydro, or electricity consumption. In addition, considering policy effects of state renewable portfolio standards, net energy metering, differences in the PJM market structure, and other demand and cost‐related factors proved important in assessing their impacts on solar PV generation capacity, including energy storage as a non‐wire alternative policy technique.

   This article is categorized under:

   Photovoltaics > Economics and Policy

   Fossil Fuels > Climate and Environment

   Energy Systems Economics > Economics and Policy

    

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2. Quantification of the water-use reduction associated with the transition from coal to natural gas in the US electricity sector

   https://doi.org/10.1088/1748-9326/ab4d71  

   Kondash, Andrew J. ; Patino-Echeverri, Dalia ; Vengosh, Avner ( December 2019 , Environmental Research Letters)

   The transition from coal to natural gas and renewables in the electricity sector and the rise of unconventional shale gas extraction are likely to affect water usage throughout the US. While new natural-gas power plants use less water than coal-fired power plants, shale gas extraction through hydraulic fracturing has increased water utilization and intensity. We integrated water and energy use data to quantify the intensity of water use in the US throughout the electricity’s lifecycle. We show that in spite of the rise of water use for hydraulic fracturing, during 2013–2016 the overall annual water withdrawal (8.74 × 10¹⁰m³) and consumption (1.75 × 10⁹m³) for coal were larger than those of natural gas (4.55 × 10¹⁰m³, and 1.07 × 10⁹m³, respectively). We find that during this period, for every MWh of electricity that has been generated with natural gas instead of coal, there has been a reduction of ∼1 m³in water consumption and ∼40 m³in water withdrawal. Examining plant locations spatially, we find that only a small proportion of net electricity generation takes place in water stressed areas, while a large proportion of both coal (37%) and natural gas (50%) are extracted in water stressed areas. We also show that the growing contribution of renewable energy technologies such as wind and solar will reduce water consumption at an even greater magnitude than the transition from coal to natural gas, eliminating much of water withdrawals and consumption for electricity generation in the US.

    

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3. Differences in leaf gas exchange strategies explain Quercus rubra and Liriodendron tulipifera intrinsic water use efficiency responses to air pollution and climate change

   https://doi.org/10.1111/gcb.16673  

   Mathias, Justin M. ; Smith, Kenneth R. ; Lantz, Kristin E. ; Allen, Keanan T. ; Wright, Marvin J. ; Sabet, Afsoon ; Anderson‐Teixeira, Kristina J. ; Thomas, Richard B. ( March 2023 , Global Change Biology)

   Trees continuously regulate leaf physiology to acquire CO₂while simultaneously avoiding excessive water loss. The balance between these two processes, or water use efficiency (WUE), is fundamentally important to understanding changes in carbon uptake and transpiration from the leaf to the globe under environmental change. While increasing atmospheric CO₂(iCO₂) is known to increase tree intrinsic water use efficiency (iWUE), less clear are the additional impacts of climate and acidic air pollution and how they vary by tree species. Here, we couple annually resolved long‐term records of tree‐ring carbon isotope signatures with leaf physiological measurements ofQuercus rubra(Quru) andLiriodendron tulipifera(Litu) at four study locations spanning nearly 100 km in the eastern United States to reconstruct historical iWUE, net photosynthesis (A_net), and stomatal conductance to water (g_s) since 1940. We first show 16%–25% increases in tree iWUE since the mid‐20th century, primarily driven by iCO₂, but also document the individual and interactive effects of nitrogen (NO_x) and sulfur (SO₂) air pollution overwhelming climate. We find evidence forQuruleaf gas exchange being less tightly regulated thanLituthrough an analysis of isotope‐derived leaf internal CO₂(C_i), particularly in wetter, recent years. Modeled estimates of seasonally integratedA_netandg_srevealed a 43%–50% stimulation ofA_netwas responsible for increasing iWUE in both tree species throughout 79%–86% of the chronologies with reductions ing_sattributable to the remaining 14%–21%, building upon a growing body of literature documenting stimulatedA_netoverwhelming reductions ing_sas a primary mechanism of increasing iWUE of trees. Finally, our results underscore the importance of considering air pollution, which remains a major environmental issue in many areas of the world, alongside climate in the interpretation of leaf physiology derived from tree rings.

    

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4. Predicting the spatial variation in cost-efficiency for agricultural greenhouse gas mitigation programs in the U.S.

   https://doi.org/10.1186/s13021-024-00252-6  

   Cameron-Harp, Micah V. ; Hendricks, Nathan P. ; Potter, Nicholas A. ( February 2024 , Carbon Balance and Management)

   Two major factors that determine the efficiency of programs designed to mitigate greenhouse gases by encouraging voluntary changes in U.S. agricultural land management are the effect of land use changes on producers’ profitability and the net sequestration those changes create. In this work, we investigate how the interaction of these factors produces spatial heterogeneity in the cost-efficiency of voluntary programs incentivizing tillage reduction and cover-cropping practices. We map county-level predicted rates of adoption for each practice with the greenhouse gas mitigation or carbon sequestration benefits expected from their use. Then, we use these bivariate maps to describe how the cost efficiency of agricultural mitigation efforts is likely to vary spatially in the United States.

   Our results suggest the combination of high adoption rates and large reductions in net emissions make reduced tillage programs most cost efficient in the Chesapeake Bay watershed or the Upper Mississippi and Lower Missouri sub-basins of the Mississippi River. For programs aiming to reduce net emissions by incentivizing cover-cropping, we expect cost-efficiency to be greatest in the areas near the main stem of the Mississippi River within its Middle and Lower sections.

   Many voluntary agricultural conservation programs offer the same incentives across the United States. Yet spatial variation in profitability and efficacy of conservation practices suggest that these uniform approaches are not cost-effective. Spatial targeting of voluntary agricultural conservation programs has the potential to increase the cost-efficiency of these programs due to regional heterogeneity in the profitability and greenhouse gas mitigation benefits of agricultural land management practices across the continental United States. We illustrate how predicted rates of adoption and greenhouse gas sequestration might be used to target regions where efforts to incentivize cover-cropping and reductions in tillage are most likely to be cost -effective.

    

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5. Green ammonia from air, water, and renewable electricity: Energy costs using natural gas reforming, solid oxide electrolysis, liquid water electrolysis, chemical looping, or a Haber–Bosch loop

   https://doi.org/10.1063/5.0101709  

   Pfromm, Peter H. ; Aframehr, Wrya ( September 2022 , Journal of Renewable and Sustainable Energy)

   The purpose of this work is to quantitatively compare the energy cost of design alternatives for a process to produce ammonia (NH 3 ) from air, water, and renewable electricity. It is assumed that a Haber–Bosch (H–B) synthesis loop is available to produce 1000 metric tons (tonnes) of renewable NH 3 per day. The overall energy costs per tonne of NH 3 will then be estimated at U.S.$195, 197, 158, and 179 per tonne of NH 3 when H 2 is supplied by (i) natural gas reforming (reference), (ii) liquid phase electrolysis, (iii) solid oxide electrolysis (SOE) of water only, and (iv) simultaneous SOE of water and air. A renewable electricity price of U.S.$0.02 per kWh electric , and U.S.$6 per 10 6 BTU for natural gas is assumed. SOE provides some energy cost advantage but incurs the inherent risk of an emerging process. The last consideration is replacement of the H–B loop with atmospheric pressure chemical looping for ammonia synthesis (CLAS) combined with SOE for water electrolysis, and separately oxygen removal from air to provide N 2 , with energy costs of U.S.$153 per tonne of NH 3 . Overall, the most significant findings are (i) the energy costs are not substantially different for the alternatives investigated here and (ii) the direct SOE of a mixture of steam and air, followed by a H.–B. synthesis loop, or SOE to provide H 2 and N 2 separately, followed by CLAS may be attractive for small scale production, modular systems, remote locations, or stranded electricity resources with the primary motivation being process simplification rather than significantly lower energy cost. 

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