As renewable electricity prices continue to decline, interest grows in alternative routes for the synthesis of sustainable fuels and chemicals, including ammonia. Considering demand for fertilizers, as well as its future potential as a dispatchable energy vector, sustainable synthesis of ammonia is being explored as an alternative to the capital- and carbon-intensive fossil-fuel-driven Haber–Bosch process. Here we assess stages along a transition to the sustainable synthesis of ammonia, looking at economic feasibility and climate impacts compared to the incumbent Haber–Bosch without and with CO2 capture. This analysis enables us to suggest technological thresholds for sustainable synthesis of ammonia to become economically and environmentally favourable. When driven by renewable energy sources, the water electrolyzer (near $400 per kW) coupled Haber–Bosch process will reach cost parity near 2.5 cents per kWh electricity. In the case of direct electrochemical ammonia synthesis, achieving cost-parity using the same 2.5 cents per kWh electricity will rely on achieving major advances in performance: an electrolysis full-cell energy efficiency exceeding 40% at a current density of 0.5 A cm−2. Once this operating performance is reached, electrically-powered ammonia synthesis will bring climate benefits when coupled with low-carbon electricity (<180 gCO2e per kWh), achievable when over half of today's U.S. electricity generation is supplied by renewable energy sources. We conclude with a forward-looking perspective on the key challenges and opportunities for sustainable ammonia synthesis routes to be competitive with the incumbent Haber–Bosch process in the future.

Can sustainable ammonia synthesis pathways compete with fossil-fuel based Haber–Bosch processes?

The purpose of this paper is to review the recent literature regarding the effects of low temperatures on Lithium ion (Li-ion) batteries for electric vehicle, plug-in hybrid electric vehicle, and hybrid electric vehicle applications. Special consideration is given to nine major effects that directly or indirectly impact the battery use at low temperatures and it is presented that they are correlated to each other. The main discussions in this paper are capacity loss, power loss, life degradation, safety hazard, unbalanced capacity, charging difficulty, thermal management system complexity, battery model and state estimation method complexity, and incremental cost. The effects correlations and possible solutions are explained to provide a detailed, yet broader understanding of the Li-ion batteries low-temperature operating scenarios.

xEV Li-Ion Battery Low-Temperature Effects—Review

Unbalanced economic benefits and the electricity-related carbon emissions embodied in China's interprovincial trade.

The climate change impacts of the anticipated growth in shared autonomous vehicles (SAVs) are highly uncertain due to competing mechanisms whose magnitudes are difficult to estimate. On the one hand, SAVs could reduce greenhouse gas emissions by driving more efficiently, avoiding traffic congestion, accelerating adoption of alternative fuel vehicles, and charging in alignment with renewable electricity generation. On the other hand, SAVs could induce more vehicle miles traveled (VMT) by lowering the time cost of travel and allowing non-drivers to travel more by car. In this study, we develop an energy system optimization model that integrates the electricity and transport sectors, computes endogenous technology adoption, and distinguishes SAVs from privately owned vehicles (POVs) to explore the contributions of SAVs to climate change mitigation. Our results show that widespread SAV adoption lowers costs and emissions, and that these desirable outcomes remain true even if SAVs induce double the VMT of the POVs they replace. SAVs dramatically accelerate the market penetration of electric vehicles. The environmental and economic benefits of this electrification trend are larger if electric SAV charging can be optimally aligned with renewable electricity generation. Especially in the short to medium term, SAV adoption can be a more impactful lever than a carbon tax for decarbonizing vehicle travel.

Contributions of shared autonomous vehicles to climate change mitigation

Urban carbon emissions associated with electricity consumption in Beijing and the driving factors

Understanding electricity consumption and production patterns is a necessary first step toward reducing the health and climate impacts of associated emissions. In this work, the economic input–output model is adapted to track emissions flows through electric grids and quantify the pollution embodied in electricity production, exchanges, and, ultimately, consumption for the 66 continental US Balancing Authorities (BAs). The hourly and BA-level dataset we generate and release leverages multiple publicly available datasets for the year 2016. Our analysis demonstrates the importance of considering location and temporal effects as well as electricity exchanges in estimating emissions footprints. While increasing electricity exchanges makes the integration of renewable electricity easier, importing electricity may also run counter to climate-change goals, and citizens in regions exporting electricity from high-emission-generating sources bear a disproportionate air-pollution burden. For example, 40% of the carbon emissions related to electricity consumption in California’s main BA were produced in a different region. From 30 to 50% of the sulfur dioxide and nitrogen oxides released in some of the coal-heavy Rocky Mountain regions were related to electricity produced that was then exported. Whether for policymakers designing energy efficiency and renewable programs, regulators enforcing emissions standards, or large electricity consumers greening their supply, greater resolution is needed for electric-sector emissions indices to evaluate progress against current and future goals.

https://www.pnas.org/content/pnas/116/51/25497.full.pdf

Tracking emissions in the US electricity system.

Electric vehicles offer a means of substantially reducing emissions in the short run, and reaching near-zero levels with complementary power sector policies over the longer-term. However, to date, consumer adoption has been limited by range anxiety and lack of familiarity with the technology. Understanding the effects of ambient temperature on electric vehicle efficiency is relevant for improving vehicle performance, enabling widespread consumer adoption and ensuring beneficial environmental outcomes. Using real-world fleet data from the Tesla Model S, vehicle efficiency is observed across a range of trip characteristics, regional climates, and ambient temperatures. The data suggest that low-temperature penalties to vehicle efficiency are mostly confined to short-distance drives, limiting the impacts on useful range experienced by the driver. Drivers are also able to adapt behaviors in response to anticipated range needs. Lastly, average efficiency impacts of climate are moderate (10% or less), as very low temperature conditions strongly affect only a small subset of trips.

John Taggart

Papers

Tracking emissions in the US electricity system.

Ambient temperature impacts on real-world electric vehicle efficiency & range

On the climate policy implications of substitutability and flexibility in the economy: An in-depth integrated assessment model diagnostic