EPA’s COMET Tool Blazes a Path Towards Planning Cleaner Cities

Published December 14, 2021

City planners are taking action to combat climate change by implementing cost-effective, clean energy solutions, improving building energy efficiency, and changing consumption patterns to reduce carbon emissions and other harmful pollution within their cities. One challenge city planners face is that major cities may rely on a supply of electricity and fuels outside their jurisdiction. If a city is receiving electricity from a grid that relies heavily on fossil fuels and does not have the governing capability to decarbonize and transform the grid, what else can be done to greatly reduce the carbon and other air pollutants that threaten human health and the environment within the jurisdiction?

Energy, environment, urban planning, and living standards are all common elements city planners must consider when building sustainable and smarter cities of the future. To equip local officials with the tools they need to find integrated solutions, EPA researchers designed the City-based Optimization Model for Energy Technologies (COMET). COMET allows users to examine the next 40-50 years of energy technology evolution, based on their planning criteria. The model provides practical and applicable energy policy solutions for cleaner energy, especially for cities that aim to achieve air pollution emissions reduction targets. The tool can reveal how the energy system can be balanced at the city level under a different set of scenario assumptions, and how system costs and resulting emissions change with respect to those scenarios.

The first application of COMET was recently piloted in New York City (COMET-NYC), which has a goal to reach 80 percent greenhouse gas reduction relative to 2005 levels by 2050. In pursuit of this goal, the city implemented benchmarking laws that require large commercial buildings to report their energy consumption. Along with one of the largest subway systems in the world, New York City has an extensive fleet of cars, trucks, busses, and other forms of public transportation, so the city can directly track fuel consumption and resulting emissions from its own public fleets. The city also analyzes data to account for the emissions from private transportation and other sources, such as buildings and waste, that it does not track directly.

An energy systems model like COMET needs generous amounts of data to provide an accurate analysis of future scenarios, so data-driven New York City was the perfect case study for the COMET developers to pioneer the first test of the tool. After populating the model with the energy consumption and emissions data provided from NYC^[1], along with technology portfolios for buildings and transportation technologies, EPA researchers conducted a scenario analysis to explore different pathways to reduce carbon emissions. The analysis highlighted the importance of fuel efficiency, early fleet turnover to high efficiency vehicles, and increasing the use of clean fuel and electric powered vehicles, which resulted in significant reduction of carbon and other air pollution.

Recognizing uncertainty about the future, the researchers examined another scenario where the regional grid did not meet New York State’s clean energy standard of obtaining 50 percent renewable generation by 2050. They found that even in this scenario that relies on a more carbon-intensive grid, New York City’s emission reduction goal could still be met cost-effectively if the city’s transportation sector is electrified earlier. The researchers also found that this scenario provided additional reductions of the air pollutants nitrogen oxide (NO_x) and particulate matter 10 micrometers or smaller (PM₁₀), which are emitted by motor vehicles and industrial sources.

“Many countries, cities, and regions have committed to net-zero emissions targets by 2050 or 2060,” says EPA researcher Dr. Ozge Kaplan, an energy systems modeler who is leading COMET’s development.  “Electric vehicle sales have grown world-wide and charging stations have become increasingly commonplace on streets and roads. Additionally, renewable energy production costs have dropped much faster than many expected,’’ she notes.

Ozge continues: “Energy systems tools such as COMET can help decision makers identify near-term and long-term cost-effective strategies to meet their clean energy targets while quantifying multi-pollutant trade-offs that can improve or worsen public health impacts from air pollution. The tool can focus in on which sectors should be prioritized in order to get the most bang for their buck.”

COMET characterizes and assists with planning the energy system at the city level and is one part of EPA’s broader energy research portfolio that examines the environmental aspects of energy system evolutions at different spatial and temporal scales. To help guide decision-makers who are considering sustainable energy  solutions  beyond the city level, EPA has additional tools. These include  EPAUS9rT, which is a regional database developed by EPA researchers that provides information that represents energy supply, technology, and demand throughout the major sectors of the U.S. energy system. GLIMPSE is another decision support modeling tool being developed by EPA that will assist states with energy and environmental planning through the year 2050.

The recent COMET-NYC pilot study highlights the importance of energy system level planning at the city level and proactive efforts by cities to reduce harmful pollution levels and to mitigate the causes of climate change. EPA’s energy research continues to improve the ability of the nation to evaluate the potential costs, benefits, and risks associated with production and use of existing and emerging energy resources. The tools and information are empowering regional, state, and local governments as they adopt policies and incentivize technologies to address the challenge of climate change and meet environmental and sustainable energy goals to protect public health and our life-giving Earth.