Theme: 2. Mitigation

Topic Area: 2a. Market Mechanisms (Technology & Process) for Carbon Neutrality

Background/Objectives:

The power sector is the largest emitter of greenhouse gas (GHG) emissions globally, and within it, coal-fired power plants represent the largest source of emissions. GHG emitters face challenges from climate policy and international treaties like the Paris Climate Agreement. By comparison, nuclear fission is a zero-emissions clean energy source of power and is the second largest source of clean electricity globally. The results of climate transition models constructed by various organizations, such as the Intergovernmental Panel on Climate Change, International Energy Agency, the Nuclear Energy Agency of the Organization for Economic Co-operation and Development, and the World Nuclear Association, show nuclear capacity doubling or tripling by 2050. In fact, in December 2023 the US signed a declaration with more than 20 other countries to triple nuclear energy capacity by 2050, recognizing the key role of nuclear energy in reaching net zero. In addition, recent work by the US Department of Energy, Electric Power Research Institute, and others suggests that constructing new nuclear reactors at existing coal power plant sites may offer cost and schedule savings when compared to construction at a greenfield site.

While new coal plants are still being built in other parts of the world, none of the capacity lost to retiring coal plants is expected to be replaced by new coal plants in the US. According to Energy Information Administration models, some US coal capacity replacement is expected to come from converting coal plants to a natural gas burning technology, or by the construction of new gas or diesel plants; but most capacity replacement is expected in the form of additional variable renewable generation (mainly solar) and diurnal energy storage. However, other alternatives such as nuclear could, and should, be considered. For example, replacement of coal power plants with nuclear plants such as small modular reactors could reduce emissions while maintaining firm, dispatchable capacity, since there are no CO₂ emissions associated with the nuclear energy production process.

Approach/Activities:

Due to plant retirements, committed emissions (the cumulative emissions an asset would emit over its lifetime under normal economic conditions) remaining from US coal power are already expected to decrease from 2024 to 2034. In India, the country with the most similar installed coal generation capacity to the US, the average unit age is lower than in US and less capacity is expected to retire over this timeframe. The extent to which committed emissions would be impacted by coal-to-nuclear conversion remains relatively unknown, a question which we consider in this presentation. Most emissions reductions in the US are a result of planned plant retirements, but additional reductions are available.

To pursue this question, we calculate committed emissions for two national fleets using publicly available operational and retirement data from existing coal power plants based on a standardized project timeline for plant conversion. Our calculations consider plant capacity, heat rate, emission factor, capacity factor, and remaining plant lifetime.

Results/Lessons Learned:

A range of unit lifetimes and number of plants converted to nuclear power are incorporated in our calculations. The longer a plant operates, the more emissions are generated. We use 50 years as the base case for coal unit lifetime and perform analysis over a range of 30 to 70 years. Considering a 10-year project timeline and market constraints requiring a phased approach to nuclear construction, conversion of coal power plants to nuclear has the potential to reduce 2024 annual and remaining committed emissions in the US and India. Results from our model show that while the percent reduction in remaining committed emissions from converting the first 46 plants to nuclear is similar for both countries, the number of conversions and total committed emissions reductions available is influenced by fleet composition, primarily the age of the units in the fleet.

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Thomas Bradley