Technoeconomic modeling of nuclear hybrid energy systems with heat storage

This work seeks to quantify the technical and economic feasibility of integrating nuclear power plants with renewable energy generation and heat storage. A variety of technoeconomic models were developed for this purpose, including cash-flow based project financing models; capital cost scaling models for heat storage systems; thermodynamic models of heat storage charging, discharging, and standing losses; an electric grid unit commitment and economic dispatch model for modeling prices; and statistical models of load, wind, and solar PV at various locations for Monte Carlo market analyses.

Based on the assumptions of recent market conditions in three major electricity markets in the United States, all systems evaluated would not be economically viable. Average electricity prices varied from around $25/MWh (ERCOT) to $42/MWh (Mid-Columbia) and $54/MWh (PJM). For integrating a new nuclear power plant with wind and hydrogen production, the very high capital costs of the nuclear plant led to multi-decade payback times, and the assumed cost of hydrogen at $2.50/kg was too low to justify the capital investment in the associated chemical plant. For the heat storage systems evaluated, power-related capital costs varied $1,200–2,300/kW, and energy-related capital costs ranged $36–140/kWh. Increasing the size of the power block had significant positive effects on net revenue, while increasing the size of the energy storage reservoir was generally not helpful beyond five hours of storage time. However, when considering the entire cash flow of a system beyond its operating revenue, no heat storage system had enough free cash flow to break even in the markets and scenarios analyzed, with the smallest system having the best overall economic performance.

In contrast to other studies where only a single representative year of load and weather data is used, this work showed that the historical variability of those time series can lead to significant spreads in the distributions of results. Selecting a “lucky” year could yield revenue estimates three times greater than the median. However, the results were more sensitive to the capital cost assumptions than to the weather year.

Integrating renewable energy generation and/or heat storage with nuclear power plants is unlikely to be economically feasible in the near term without significant changes in energy markets, significant decreases in capital costs of power turbines, or significant increases in development or operating subsidies for these system concepts.