Interpreting Global Energy Scenarios for Emissions Planning at the Utility Scale
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Science has established that carbon emissions from fossil fuel burning, along with other factors, are changing the climate of the Earth. Here in Wisconsin, we are already seeing the consequences of climate change, with southern and western Wisconsin having 3-7 inches more precipitation per year by the early 2000s relative to 1950 and winter temperatures increasing about 2.5oF across the state. These changes will be more extreme in the future [Wisconsin Initiative on Climate Change Impacts, 2011]. An international effort called the Intergovernmental Panel on Climate Change (IPCC) recognized the need to pursue efforts to limit the temperature increase to 1.5oC above pre-industrial levels to significantly reduce the risks and most adverse impacts of climate change. To date, the Earth has warmed about 1oC (1.8oF) on average. To achieve this recommendation, “bold and transformative steps .. are urgently needed,” according to the United Nations [Allen et al., 2018]. Multiple research groups around the world have developed computer models to assess what combination of energy and land-use changes are consistent with the 1.5oC analysis. Many organizations are using these science-based assessments as a component in decision-making, as these model results present multiple options for achieving a global environmental goal. Our group at the University of Wisconsin—Madison was asked by Madison Gas and Electric Company (MGE) to evaluate the IPCC scenarios relevant to its operation. Here we present the results of this analysis. Major findings include: The strength of the IPCC scenarios is in terms of qualitative guidance on the direction and magnitude of emissions changes. Electricity production differs dramatically across the U.S. and around the world. In 2016, 48% of MGE’s electricity generation was coal, and coal is the main source of electricity across the state. Even within the U.S., states vary in whether coal, natural gas, hydropower, or nuclear comprise the largest source of electricity generation. This heterogeneity is even greater across industrial nations. The IPCC scenarios do not account for these differences across countries and states. Rather, the industrial countries are grouped together and treated uniformly in the IPCC scenarios. As a result, it would be unwise to treat these model simulations as prescriptive for any individual sub-region, much less a single utility. Rather, the pathways are useful to identify the general magnitude and timeline of emissions consistent with a 1.5oC outcome. All scenarios require electricity generation in industrialized countries to be at or near net-zero carbon by 2050, suggesting that a 2050 net-zero carbon target is consistent with the current scientific recommendations. Of these pathways, some “overshoot” the target (temporarily exceed the temperature goal but ultimately fall below the temperature threshold by 2100) and others include “negative emissions” (actively removing CO2 from the air). For the purposes of informing a trajectory for a single utility over the coming decades, we limited the scenarios to omit those with “high overshoot” (i.e., temporarily exceeding the temperature goal by 0.1oC to 0.4oC—an exceedance of this magnitude can have detrimental effects even if temporary) and to omit “net-negative emissions” (i.e., not assuming that MGE would remove more CO2 from the atmosphere than it emits). Relative to these scenarios, MGE’s goal is more aggressive than any of the modeled pathways for the electricity sector in industrialized countries. The analysis of the IPCC scenarios of a low-carbon future highlights that electricity demand and carbon intensity of generation affect carbon emissions. In Madison, factors including increasing population, increasing average household income, and increasing electric vehicle (EV) adoption point toward a possible increase in electricity demand. Energy efficiency and/or conservation efforts can help modulate the projected increase in demand. To decrease carbon emissions in an environment of increasing demand requires a lower-carbon intensity generation mix. MGE has been transitioning to lower-carbon sources since 2005, including discontinuing coal use at its Blount Generating Station and adding significant investment in renewable energy resources. To meet the net-zero carbon by 2050 goal, a continued switch away from fossil fuels and toward non-emitting energy sources will be required. Consistent with the qualitative patterns expected for Madison, the IPCC scenarios show electricity consumption is going up, even as total carbon emissions go down. MGE will continue to evaluate how demand (including from EVs), energy efficiency measures, and the transitioning of the generation mix are best combined to support MGE’s goal of net-zero carbon by 2050. By 2050, the carbon intensity of MGE electricity generation will need to decrease to net- zero. Although increasing electricity demand increases total carbon emissions, it is possible that an increase in demand can facilitate the transition to a low-carbon-intensity generation mix. Consistent with MGE’s stated goals of strategies for deep decarbonization, new facilities built to meet new demand should move MGE toward low-carbon-intensity generation. The evolution of electricity generation and use in Madison depend on a wide range of factors specific to our community. Examining these opportunities and trade-offs would be a valuable direction for future research.
climate, emissions, IPCC, scenario, energy
Report Prepared for Madison Gas and Electric Company