Concentrating Solar Power
2021 ATB data for concentrating solar power (CSP) are shown above. The Base Year is 2019; thus costs are shown in 2019$. CSP costs in the 2021 ATB are based on cost estimates for CSP components that are available in Version 2020.11.29 of the System Advisor Model (SAM). (Turchi et al., 2019) detail the updates to the SAM cost components Future year projections are informed by the literature, NREL expertise, and technology pathway assessments for reductions in capital expenditures (CAPEX) and operation and maintenance (O&M) costs.
The three scenarios for technology innovation are:
- Conservative Technology Innovation Scenario (Conservative Scenario): no change in CAPEX, O&M, or capacity factor from current estimates (2019 for CSP) to 2050
- Moderate Technology Innovation Scenario (Moderate Scenario): projection based on recently published projections and NREL judgment of potential innovations in the powerblock, receiver, thermal storage, and solar field; it is anticipated that ATB CSP 2019 CAPEX of $6,781/kWe could be reduced to $6,307/kWe in 2021, and from 2019 could drop by approximately 32% to $4,594/kWe by 2030. From 2030 to 2050, CSP CAPEX is projected to fall to approximately $4,213/kWe.
- Advanced Technology Innovation Scenario (Advanced Scenario): projection based on the lower bound of the literature sample, and on the Power to Change report (IRENA, 2016), consistent with innovations in powerblock, receiver, and thermal storage to accommodate higher temperature systems, and modularity in the solar field.
Solar resource is prevalent throughout the United States, but the Southwest is particularly suited to CSP plants. The direct normal irradiance (DNI) resource across the Southwest, which is some of the best in the world, ranges from 6.0 kWh/m2/day to more than 7.5 kWh/m2/day (Roberts, 2018). The raw resource technical potential of seven states (Arizona, California, Colorado, Nevada, New Mexico, Utah, and Texas) exceeds 11,000 GWe, which is almost tenfold the current total U.S. electricity generation capacity; and some regions in these states have an annual average resource greater than 6.0 kWh/m2/day (Mehos et al., 2009).
For illustration in the ATB, a range of capacity factors calculated in SAM Version 2020.11.29 is associated with three resource locations in the contiguous United States for three classes of insolation:
- Class 7: Abilene Regional Airport, Texas: 6.25 kWh/m2/day based on the site's Typical Meteorological Year 3 (TMY3) file; the 2019 Physical Solar Model (PSM) TMY file for a site adjacent to the airport is used, and it was downloaded from the National Solar Radiation Database (NSRDB) Data Viewer.
- Class 3: Phoenix, Arizona: 7.34 kWh/m2/day based on the site TMY3; the TMY file used is available in SAM Version 2029.11.29, titled phoenix_az_33.450495_-111.983688_psmv3_60_tmy.
- Class 2: Daggett, California: 7.67 kWh/m2/day based on the site TMY3 file, the TMY file used is available in SAM Version 2020.11.29, titled daggett_ca_34.865371_-116.783023_psmv3_60_tmy.
The full categorization of DNI resource classes is below.
|CSP Resource Class||DNI (kWh/m2/day)||Available Resource (GW)|
|Class 2||7.50 - 7.75||677|
|Class 3||7.25 - 7.50||1,251|
|Class 4||7.00 - 7.25||1,381|
|Class 5||6.75 - 7.00||1,098|
|Class 6||6.50 - 6.75||1,252|
|Class 7||6.25 - 6.50||1,282|
|Class 8||6.00 - 6.25||1,850|
|Class 9||5.75 - 6.00||1,725|
|Class 10||5.50 - 5.75||1,495|
|Class 11||5.25 - 5.50||1,925|
|Class 12||5.00 - 5.25||2,641|
Source: (Murphy et al., 2019). The 2021 ATB reverses the class numbers such that Class 1 is the best resource.
In the United States, CSP plants can be found in Arizona, California, Florida, and Nevada. And California can be considered the most representative location for new plants in the United States because of the excellent resource there.
CSP research for today's and future advanced technologies is primarily in four main areas: the powerblock, the receiver, the thermal storage, and the solar field. The following table highlights key innovation and research trends for the three ATB technology innovation scenarios.
|Scenario||Powerblock||Receiver||Thermal Storage||Solar Field|
|Conservative Scenario||Technology Description: In the Conservative Scenario, no change is expected if costs stay similar to current costs.||Technology Description: In the Conservative Scenario, no change is expected if costs stay similar to current costs.||Technology Description: In the Conservative Scenario, no change is expected if costs stay similar to current costs.|
Technology Description: In the Moderate Scenario, the supercritical cycle (supercritical carbon dioxide carbon dioxide [sCO2]) operates at 565°C with today's salts.
Justification: The U.S. Department of Energy (DOE) Supercritical Transformational Electric Power program and other countries are researching the use of sCO2 with today's salts (e.g., China).
Technology Description: In the Moderate Scenario, advanced coatings are applied to today's receiver technology.
Justification: Testing of the coatings have founds increased selective absorption and enhanced durability.
Technology Description: In the Moderate Scenario, storage tank designs, pumps, and component configurations are improved.
Justification: Engineering studies to improve designs are ongoing.
Technology Description: In the Moderate Scenario, improvements in heliostat installations lead to decreases in cost as a result of increased deployment and learning.
Justification: The pipeline of projects is significant, and projects are currently being constructed.
|Advanced Scenario||Technology Description: In the Advanced Scenario, an elevated-temperature (>700°C) sCO2 powerblock is used.||Technology Description: In the Advanced Scenario, a high-temperature receiver consistent with >700°C power cycle is used.||Technology Description: In the Advanced Scenario, advanced storage media compatible with >700°C delivery is used.||Technology Description: In the Advanced Scenario, very low-cost, modular solar fields with increased solar field efficiency are deployed.|
Projections of future utility-scale CSP plant CAPEX and O&M are based on the three technology innovation scenarios developed for scenario modeling as bounding levels. In general, differences among the scenarios reflect different levels of adoption of innovations. Reductions in technology costs reflect the cost reduction opportunities that are listed below.
- Power tower improvements
- Better and longer-lasting selective surface coatings improve receiver efficiency and reduce O&M costs.
- Advanced heat transfer fluids allow for higher operating temperatures and lower-cost thermal energy storage.
- Development of the power cycle running at approximately 700° C and 55% gross efficiency improves cycle efficiency, reduces powerblock cost, and reduces O&M costs.
- Lower-cost heliostats are developed as a result of design changes and automated and high-volume manufacturing.
- General and soft costs improvements
- Expansion of world market leads to greater and more-efficient supply chains, and reduction of supply chain margins (e.g., profit and overhead charged by suppliers, manufacturer, distributors, and retailers).
- Expansion of access to a range of innovative financing approaches and business models
- Greater deployment volume and learning is assumed for 2021 and onward based on current state of industry (IRENA, 2016); (Lilliestam et al., 2017).
These improvements are reflected in the following tables.
Concentrating solar power (CSP) technologies capture the heat of the sun to drive a thermoelectric power cycle. The most widely deployed CSP technology uses parabolic trough collectors. As of 2020, of the 6,128 megawatts (MW) of installed CSP capacity, more than 4,000 MW of operational parabolic trough CSP were present ((SolarPACES, 2020); (Turchi et al., 2017)). In the 2021 ATB, CSP technology is assumed to be molten-salt power towers. Molten-salt power towers are chosen as the representative technology for the ATB, as indications are that molten-salt power towers have the greatest cost reduction potential.
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 2021 ATB is represented as 104 net-MWe 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, and they were followed closely by power towers at 0.8 GW of plants under construction (REN21, 2019). 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. This Dubai Electricity and Water Authority 700-MW complex, which is under construction, is composed 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).
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/WAC ( (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:
- Three operational power tower plants totaling 392 MWe (e.g., the Ivanpah project) (SolarPACES, 2020)
- Fourteen operating parabolic trough projects totaling 1,746 MWe (NREL, "Concentrating Solar Power Projects in the United States").
The CSP technologies highlighted in the 2021 ATB are assumed to be power towers but with different power cycles and operating conditions as time passes, as shown in the following table.
|2019||A molten-salt (sodium nitrate/potassium nitrate; aka, solar salt) power tower with direct two-tank TES combined with a steam-Rankine power cycle running at 574°C and 41.2% gross efficiency|
|2021||Design similar to that of 2019 with identified near-term reductions in heliostat and power system costs|
|2030 Moderate Scenario||Longer-term cost reductions (e.g., in the heliostats and power system)|
|2030 Advanced Scenario||Low projection based on molten-salt power tower with direct two-tank TES combined with a power cycle running at 700°C and 55% gross efficiency.|
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, "Goals of the Solar Energy Technologies Office").
This section describes the methodology to develop assumptions for CAPEX, O&M, and capacity factor. For standardized assumptions, see labor cost, regional cost variation, materials cost index, scale of industry, policies and regulations, and inflation.
For the 2021 ATB, various factors are used to demonstrate the range of LCOE and performance across the United States. These include that:
- CAPEX is determined using manufacturing cost models and is benchmarked with industry data. CSP performance and cost are based on the molten-salt power tower technology with dry-cooling to reduce water consumption.
- O&M cost is benchmarked against industry data.
- Capacity factor varies with inclusion of TES and solar irradiance. The listed resource classes assume power towers with 10 hours of TES at three types of locations.
CSP costs in the 2021 ATB are based on cost estimates for CSP components that are available in Version 2020.11.29 of the System Advisor Model (SAM). (Turchi et al., 2019) detail the updates to the SAM cost components. DOE’s Solar Energy Technologies Office uses more-conservative financial terms, resulting in higher LCOE values than are obtained using the ATB methodology.
Future year projections are informed by the literature, NREL expertise, and technology pathway assessments for CAPEX and O&M cost reductions. Three projections are developed for scenario modeling as bounding levels:
- Conservative Scenario: no change in CAPEX, O&M, or capacity factor from current estimates (2019 for CSP) to 2050
- Moderate Scenario: based on recently published projections and NREL judgment of U.S. costs for future CAPEX at 2025, 2030, 2040, and 2050 ( (IRENA, 2016), (Breyer et al., 2017), (Feldman et al., 2016), (World Bank, 2014)). From analysis of these sources, it is anticipated that the 2019 CAPEX of $6,781/kWe could reduce to $6,307/kWe in 2021, and from 2019 could drop by approximately 32% to $4,594/kWe by 2030. From 2030 to 2050, CAPEX is projected to fall to approximately $4,213/kWe.
- Advanced Scenario: based on the lower bound of the literature sample and on the Power to Change report (IRENA, 2016).
Capital Expenditures (CAPEX)
Definition: For plants whose construction duration exceeds one year, CAPEX costs represent technology costs that lag current-year estimates by at least one year. For CSP plants, the construction period is typically three years.
In the 2021 ATB, CAPEX does not vary with resource.
Base Year: The CAPEX estimate (with a Base Year of 2019) is approximately $6,781 kWe in 2019$. It is for a representative power tower with 10 hours of storage and a solar multiple (SM) of 2.4. Based on recent assessment of the industry in 2017 and updated CSP systems costs reflected from SAM 2020.11.29 (Turchi et al., 2019), the CAPEX estimate for 2021 is $6,450/kWe in 2019$.
Note, the CAPEX for the representative CSP plant in the downloadable ATB Data in Solar-CSP is estimated in the Base Year with three main portions (the Turbine CC, Storage CC and Field CC), where CC is Capital Cost. The Turbine CC includes the Power Cycle, Balance of Plant (BOP) and Indirect and Direct Contingencies. The Storage CC includes the Hot and Cold Tanks, Molten Salt Inventory, Heat Exchangers for the storage system, and the Indirect and Direct Contingencies. The Field CC includes the Heliostat Installed Cost, Site Improvements, Tower, Receiver, and the Indirect and Direct Contingencies.
Future Years: Three cost projections are developed for CSP technologies:
- Conservative Scenario: no change in CAPEX, O&M, or capacity factor from current estimates (2021 for CSP) to 2050; consistent across all renewable energy technologies in the 2020 ATB.
- Moderate Scenario: based on recently published projections and NREL judgment of U.S. costs for future CAPEX at 2025, 2030, 2040 and 2050 ( (IRENA, 2016); (Breyer et al., 2017); (Murphy et al., 2019); (Feldman et al., 2016); (World Bank, 2014)). From analysis of these sources, it is anticipated that the 2019 CAPEX of $6,781/kWe could reduce to $6,307/kWe in 2021, and from 2019 could drop by approximately 32% to $4,594/kWe by 2030. From 2030 to 2050, CAPEX is projected to fall to approximately $4,213/kWe.
- Advanced Scenario: based on the lower bound of the literature sample, and on the Power to Change report (IRENA, 2016).
Considering currently reported CAPEX for plants either announced or in construction, $6,307/kWe in the ATB in 2021 and $4,594/kWe in 2030 is possible. For example, the Noor III CSP power station in Morocco—a 150-MWe molten salt power tower with 7.5 hours of storage that became operational in 2018—has an estimated CAPEX of $6,500/kWe in 2018$ (Kistner, 2016). And the Dubai project mentioned above has an estimated bundled CAPEX of $5,500/kWe in 2018$ ( (Shemer, 2018), (Turchi et al., 2019)).
A range of literature projections is shown in the chart below to illustrate the comparison with the 2021 ATB. When comparing the 2021 ATB projections with other projections, note that there are major differences in technology assumptions, radiation conditions, field sizes, storage configurations, and other factors. As shown in the chart, the 2021 ATB CSP Moderate Scenario projection is in-line with other recently analyzed projections from other organizations. The Advanced Scenario ATB projection is based on the lower bound of the literature sample, and on the Power to Change report (IRENA, 2016).
Use the following tables to view the components of CAPEX, and how they change with the scenarios:
Operation and Maintenance (O&M) Costs
Definition: Operation and maintenance (O&M) costs represent the annual expenditures required to operate and maintain a CSP plant over its lifetime, including items noted on the definitions page.
Base Year: Fixed O&M (FOM) is assumed to be $66/kW-yr until 2021. Variable O&M is approximately $3.50/MWh until 2021 and $2.90/MWh after that (Kurup and Turchi, 2015).
Future Years: Future FOM is assumed to decline to $50/kW-yr by 2030 in the Moderate Scenario (i.e., approximately a 25% drop) and approximately $39/kW-yr by 2050 in the Conservative Scenario based on DOE investments that are likely to help lower costs (DOE, 2012).
Use the following table to view the components of operating expenditures.
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 2021 ATB capacity factors are generated from plant simulations using SAM Version 2020.11.29 at the resource locations identified below, with 10 hours of storage, and corroborated by operational data:
- Class 7: Abilene, Texas: leads to a 50% capacity factor
- Class 3: Phoenix, Arizona: leads to a 61% capacity factor
- Class 2: Daggett, California: leads to a 64% capacity factor.
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 CSP capacity deployments of up to 5 gigawatts electrical (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 2021 ATB estimates of capacity factor or LCOE.
Estimates of capacity factors for CSP in the 2021 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.