Concentrating Solar Power

Representative Technology

In the 2020 ATB, concentrating solar power (CSP) technology is assumed to be molten-salt power towers. Thermal energy storage (TES) is accomplished by storing molten salt in a two-tank system that includes a hot-salt tank and a cold-salt tank. Stored hot salt can be dispatched to the power block as needed, regardless of solar conditions, to continue power generation and allow for electricity generation after sunset. CSP technology in the 2020 ATB is represented as 100-MW_e molten-salt power towers, which use today's sodium and potassium nitrate salts, with 10 hours of TES using a two-tank molten salt system. This configuration is similar to the Crescent Dunes CSP plant in Nevada, is representative of new global CSP development, and has the potential for further cost reductions relative to other configurations, such as parabolic trough.

In 2019, parabolic trough projects made up approximately 1 GW of the CSP projects under construction, followed closely by power towers at 0.8 GW of plants under construction. Molten-salt power tower plants are being built in Chile (e.g. Cerro Dominador) and Dubai (NREL, "Concentrating Solar Power Projects"). The largest CSP plant being constructed in the world is the 700-MW combined parabolic trough and power tower system in Dubai, United Arab Emirates (UAE). This Dubai Electricity and Water Authority (DEWA) 700-MW complex is comprised of 600 MW of parabolic troughs (i.e., 3 x 200-MW trough plants) and a 100-MW power tower site, with each plant having 12–15 hours of TES (SolarPACES 2019; Lilliestam and Pitz-Paal 2018).

Most new global capacity of CSP plants in development is from molten-salt power towers; for example, 3.7 GWe of molten-salt power towers and 1.3 GWe of parabolic are in development (IRENA 2018). Current indications are that molten-salt power towers have the greatest cost reduction potential, in terms of both CAPEX and LCOE ((IRENA 2016), (Mehos et al. 2017)). These are part of the DOE Generation 3 (Gen3) road map for the next generation of commercial CSP plants (Mehos et al. 2017).

Crescent Dunes (110 MWe with 10 hours of storage) was the first large molten-salt power tower plant in the United States. It was commissioned in 2015 with a reported installed CAPEX of $8.96/W_AC ((Danko 2015), (Taylor 2016)). Despite the emergence of power tower systems, the CSP landscape is still dominated by parabolic trough systems. The United States is home to:

• 3 operational power tower plants totaling 392 MW_e (i.e., the Ivanpah project) (SolarPACES 2020)
• 14 operating parabolic trough projects totaling 1,746 MW_e (NREL, "Concentrating Solar Power Projects in the United States").

The CSP technologies highlighted in the 2020 ATB are assumed to be power towers but with different power cycles and operating conditions as time passes, as shown in the following table:

Though an advanced molten salt projection is used for the Advanced Scenario, lower costs for baseload CSP are being investigated via different technology options (e.g., solid particle and gas phase towers) and as defined by the DOE Gen3 program ((Mehos et al. 2017); DOE EERE, "Goals of the Solar Energy Technologies Office").