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Content displaying: Capacity Factor

Concentrating Solar Power

Capacity Factor

Definition: Capacity factors are influenced by power block technology, storage technology and capacity, the solar resource, expected downtime, and energy losses. The solar multiple is a design choice that influences the capacity factor.

Base Year: The 2020 ATB capacity factors are generated from plant simulations using SAM Version 2018.11.11 at the resource locations identified, with 10 hours of storage, and corroborated by operational data:

  • Class 1, Fair Resource: Abilene, Texas: leads to a 50% capacity factor
  • Class 3, Good Resource: Phoenix, Arizona: leads to a 61% capacity factor
  • Class 5, Excellent Resource: Daggett, California: leads to a 64% capacity factor.

Operational data from the first and longest-operating molten salt power tower in the world (i.e., the 20-MW Gemasolar plant that includes 15 hours of molten salt TES in Spain, where DNI resource can be considered Class 1, Fair to Class 3, Good) shows a reported capacity factor of 55% (Torresol Energy 2018). Given the higher Good and Excellent DNI resource areas in the United States, a well operating molten salt power tower with 10 hours of TES could reach capacity factors of 60%–64% (SAM Version 2018.11.11).

A key finding of (Murphy et al. 2019) is that if future costs of CSP decrease sufficiently, CSP could be deployed across a greater range of the United States and DNI resources. For example, with aggressive cost decreases and given regional market constraints, southeastern states with lower DNI resources (e.g., Florida and South Carolina) could see increased CSP capacity deployments of up to 5 GWe.

Future Years: The future projections for the Conservative, Moderate, and Advanced technology innovation scenarios are unchanged from the Base Year. Technology improvements are focused on CAPEX and O&M cost elements.

Over time, CSP plant output may decline. Capacity factor degradation that is due to degradation of mirrors and other components is not accounted for in the 2020 ATB estimates of capacity factor or LCOE.

Estimates of capacity factors for CSP in the 2020 ATB represent typical operation. The dispatch characteristics of these systems are valuable to the electric system to manage changes in net electricity demand. Actual capacity factors will likely be influenced by the degree to which system operators call on CSP plants to manage grid services.


The following references are specific to this page; for all references in this ATB, see References.

Murphy, Caitlin, Sun, Yinong, Cole, Wesley, Maclaurin, Galen, Turchi, Craig, & Mehos, Mark. (2019). The Potential Role of Concentrating Solar Power Within the Context of DOE's 2030 Solar Cost Targets. (No. NREL/TP-6A20-71912). National Renewable Energy Laboratory.

Torresol Energy (2018). Torresol Energy: 2008 to 2018. Torresol Energy.

Developed with funding from the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy.