* denotes first author publication
Census data is crucial to understanding energy and environmental justice outcomes such as poor air quality which disproportionately impacts people of color in the U.S. With the advent of sophisticated personal datasets and analysis, the Census Bureau is considering adding top-down noise (differential privacy) and post-processing 2020 census data to reduce the risk of identification of individual respondents. Using the 2010 demonstration census and pollution data, I find that compared to the original census, the differentially private (DP) census significantly changes ambient pollution exposure in areas with sparse populations. White Americans have the lowest variability, followed by Latinos, Asians, and Black Americans. DP underestimates pollution disparities for SO2 and PM2.5 while overestimates the pollution disparities for PM10.
Ensuring reliable and affordable access to modern energy services, especially for the poorer and deprived section of the population, is a basic requisite for sustainable development. Given that a majority of the energy-deprived population lives in rural regions of developing countries, effective rural electrification is critical for bridging the rural-urban divide. Microgrid electricity systems, especially with hybrid renewable energy resources, can be a good alternative for centralized electricity grid expansion. In this paper, we report the techno-economic feasibility and sustainability analysis of a hybrid solar-biomass system in India. The system consists of 30-kW solar photovoltaic (PV) and 20-kW biomass gasifier modules. Energy demand and resource availability are estimated with inputs from extensive stakeholder discussions and field surveys, and they account for daily and seasonal variations in both supply and end uses and availability and productive hours. The expected temporal electricity demand is estimated for households, communities, irrigation, and commercial needs. Furthermore, opportunities for the development of productive uses and their expansion through a sustainable business model are explored.
Emissions from electric vehicles depend on when they are charged, and which power plants are meeting the electricity demand. We introduce a new metric, the grid emissions factors (CEFs), as the emissions intensity of electricity that needs to be achieved when charging to ensure electric vehicles achieve lifecycle greenhouse gas emissions parity with some of the most efficient gasoline hybrid vehicles across the US. We use a consequential framework, consider 2018 as our reference year, and account for the effects of temperature and drive cycle on vehicle efficiency to account for regional climate and use conditions. We find that the Nissan Leaf and Chevy Bolt battery electric vehicles reduce lifecycle emissions relative to Toyota Prius and Honda Accord gasoline hybrids in most of the United States. However, in rural counties of the Midwest and the South power grid, marginal emissions reductions of up to 208 gCO2/kWh are still needed for these electric vehicles to have lower lifecycle emissions than gasoline hybrids. Except for the Northeast and Florida, the longer-range Tesla Model S battery-electric luxury sedan has higher emissions than the hybrids across the U.S., and the emissions intensity of the grid would need to decrease by up to 342 gCO2/kWh in some locations for it to achieve carbon parity with hybrid gasoline vehicles. Finally, we conclude that coal retirements and stricter standards on fossil fuel generators are more effective in the medium term at reducing consequential electric vehicle emissions than the expansion of renewable capacity.
Light-duty transportation continues to be a significant source of air pollutants that cause premature mortality and greenhouse gases that lead to climate change. To reduce the damages from air pollution and climate change, the U.S. light-duty fleet will need to transition to more sustainable transportation strategies. Electric vehicles (EVs) are one of the possible strategies. Internal combustion vehicles that comply with the latest emissions standards (currently, Tier 3 emission standard) are another possible alternative, although their emissions increase with age and mileage. While pollution from ICV occurs at ground level and its effects are largely confined to nearby areas, pollution from EVs occurs at the smokestacks of power plants used to charge the EVs which can spread to longer distances. We estimate and compare the health impacts (and disparities of) the current stock of light-duty vehicles across the United States with a large-scale shift to EVs or Tier-3 ICVs. We couple a fine-scale emissions inventory with a reduced complexity air quality model. We find that either strategy reduces premature mortality by 80-93% compared to today’s light-duty vehicle damages. As the grid decarbonizes, EVs would lead to even larger health benefits from reduced air pollution and greenhouse gas emissions (a benefit not present for ICV). The health and climate mitigation benefits of electrification are larger in the West and Northeast. The Midwest and the South have larger mortality reductions when choosing Tier 3 ICV due to present-day high electricity emission intensity; this aspect too may shift as those regions clean their electric grid emissions. We also focus on the 50 most populous metropolitan areas, and find that in almost all cases electrification leads to lower health damages. Pollution from ICV (current LDV and Tier 3) impacts people of color more than White Americans across all states, levels of urbanization, and household income. Consequently, electrification reduces health disparities more than Tier 3 ICV in most states and MSAs, especially in urban parts of the Western United States. EV impacts are on average more equitable by race-ethnicity but damages from them are geographically concentrated in Ohio Valley, New York, and Pennsylvania; retiring or retrofitting with CCS 50 power plants with high SO2 emissions achieves health benefits parity for EVs and new Tier 3 ICVs in all regions.
The state of California has ambitious climate and public health targets, including reaching a net-zero emissions economy by 2045. In this work we explore pathways to achieve zero emissions in California’s light-duty transportation sector, responsible for 28% of the state’s emissions. We establish a business-as-usual trajectory and focus on fleet turnover dynamics under different policy scenarios. Specifically, we consider the following policies and their combination: (i) a zero-emissions vehicles (ZEV) sales mandate and (ii) accelerated retirement of internal combustion vehicles (ICV). We simulate scenarios with varying ZEV mandate onset, retirement year, and retirement age to find cumulative CO2 and PM2.5 emissions, premature mortality, and environmental justice impacts. We discuss the implications of delaying the start of these policies as well as benefits and costs associated with accelerated retirement by monetizing climate and health benefits and using second-hand vehicle prices as a proxy for costs. We find that 20% of the 2019 ICV fleet will remain on the road in 2045 even if California achieves 100% ZEV sales by 2035. Given the status quo, retiring vehicles above the age of 10 starting in 2040 have positive net benefits. These scenarios reduce GHG emissions by 35% and premature mortality by 23% compared to BAU. Retirements of vehicles 10 years and above starting in 2025 yield net benefits if the social cost of carbon is doubled. These scenarios reduce cumulative emissions and mortality by 50%. Retiring vehicles of age 5 and above isn’t cost-effective in almost all scenarios.
As the world’s 5th largest economy, California contributes to roughly ¾ of a percent of global greenhouse gas emissions (GHGs) and has ambitious climate targets including a goal of reaching economy-wide net zero GHGs by 2045. To achieve this goal, all sectors of the economy will need to rapidly decrease their emissions. Nearly 8% of the state’s GHG emissions are caused by the heavy-duty transportation sector. We simulate different decarbonization strategies for the heavy-duty fleet using a detailed fleet turnover model paired with an air quality model to track the evolution of the vehicle fleet and the associated greenhouse gas emissions, criteria air pollutant emissions, and air quality and health impacts of each scenario. We find that even a ZEV policy instrument mandating that 100% of heavy-duty vehicles (HDVs) sold are zero-emission vehicles beginning in 2025 would not achieve zero emissions from heavy-duty trucks by 2045 given the slow fleet turnover. In combination with a ZEV sales mandate in 2035, the retirement of vehicles aged 10 years or older beginning in 2040 or earlier would result in zero GHG emissions by 2045. Beginning retirements sooner or retiring younger vehicles as well results in lower cumulative emissions and reduced air quality impacts and health damages.
Rooftop solar and storage (distributed electricity generation, DER) can play an important role in enabling decarbonization and improving reliability. Households can consume, store, or send the electricity produced by DER back to the grid. Under net-energy metering policies, households with DER are compensated for the surplus electricity produced at the retail electricity rate. Retail rates typically charge residential users a volumetric rate that covers the bulk of energy, transmission, and distribution costs. The resulting price, charged per unit of electricity, neither reflects the marginal costs of producing the electricity nor does it vary by space and time. Non-time-varying volumetric electricity rates also don’t accurately reflect the true benefits that DERs provide to the electricity grid and have led to interest among policymakers to modernize the electricity rates. Significant concerns about cross-subsidies have also been raised. By realizing significant bill savings under net-energy metering, adopters of DERs effectively shift part of their obligation for the grid operation costs to non-adopters. Hence, the challenge to modernize the electricity rate entails aligning prices to the true cost of generation of electricity; pricing benefits to the true benefits DERs provide; and ensuring that non-adopters, often low-income and/or renters, don’t bear the burdens of cost-shift. In this work, we propose an electricity pricing and household electricity consumption model that tests different electricity rates to enable efficiency and equity for adopters and non-adopters. California, which has one of the highest electricity rates and penetration of DERs in the United States, is used as a case study for demonstration.
California has taken great strides in modernizing and decarbonizing its electricity system. The state has one of the least carbon-intensive electricity and has the largest adoption of grid-scale storage (3,136 MW), residential rooftop solar (13,064 MW), and zero emissions vehicles (18% of total sales) in the country. At the same time, electricity is expensive in California. Customers in three investor-owned utilities pay 45-100% more than the national average per kilowatt hour. This primer parses out reasons for California's high electricity prices using data on revenue requirements, rate of return, trends in electricity generation, network, and wildfire mitigation costs, and distribution upgrades.
The design of residential electricity rates varies across the United States. Some utilities charge a fixed charge as well as a volumetric rate, whereas others include only a volumetric rate which can change depending on the time of the day and total electricity consumption. The average values of electricity rates per kWh consumed range from 12.7 to 47.7 cents across the U.S. Other differences across states include subsidies for low-income, real-time prices, time-of-use prices, and special retail rates for distributed energy resources and electric vehicle charging. Despite the varying designs in electricity rates, there are commonalities in the goals of electricity service provision by utilities, such as reliably providing electricity, while recovering generation, transmission, and distribution costs of electricity. In regions where constant volumetric rates are used, these costs are lumped together often failing to reflect the true social marginal costs of electricity. In most regions, utility revenue requirements will likely continue to increase as end-uses electrify and electricity decarbonizes. Progress in rate reform and utility innovation has been slow, with less than 1% of Americans facing an electricity price that varies with time, and the implications of different designs of electricity rate designs for consumers are poorly understood. In this perspective, we discuss the challenges and progress in designing an efficient and equitable retail rate for a decarbonizing grid. Specifically, we delve into two aspects of retail rate design: one, how do we make efficient retail rates – i.e., rates that reflect the varying social marginal cost of electricity, recoup required costs, and enable proper utilization of the grid infrastructure, and second, are current and new retail rates designs equitable, particularly with bill impacts across income and race gradients. Given California’s high and increasing retail rates, high distributed energy generation and EV penetration, and rising utility-related wildfire risk, we also discuss the case of California, using it as a case study with potentially generalizable results across the country