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10-Megawatt Supercritical Carbon Dioxide Turbine Test—Thermodynamic Cycle to Revolutionize CSP Systems

Advancing concentrating solar power (CSP) systems to the target cost of $0.06 per kilowatt-hour, set by the U.S. Department of Energy (DOE) SunShot Initiative, will require revolutionary power conversion systems with higher efficiency and lower installed cost than conventional steam power blocks.

With funding from a competitive DOE CSP SunShot Research and Development Award, NREL and its partners will demonstrate a multi-megawatt (MW) power cycle that uses supercritical carbon dioxide (s-CO2) instead of steam to produce higher power-cycle efficiency and more compact components.

Research Motivation

During the past decade, researchers have modeled the basic thermodynamics of the supercritical CO2 Brayton cycle and used small test rigs to explore the behavior of s-CO2 turbomachinery. However, to determine its true potential, this power cycle must be validated by operating a larger-scale prototype at temperatures relevant to CSP systems.

Innovative Approach

Column chart showing the levelized cost of energy (with no investment tax credit) of the current CSP power tow er technology compared with the cost of supercritical carbon dioxide powered CSP technology. The supercritical carbon dioxide is nearly three times lower in cost than the current CSP technology.

Cost-breakdown comparison of a (left) current steam-cycle power tower and (right) successful s-CO2 power-cycle tower—with an estimated $0.06/kWh levelized cost of energy, no investment tax credit, and other SunShot technology and financial assumptions.

Cut-away illustration showing the inside components of a supercritical carbon dioxide turbine.

Illustration of the proposed axial-flow s-CO2 turbine. (from Dresser-Rand)

In this project, the research team intends to showcase the turbomachinery for a new cycle for CSP application—the s-CO2 Brayton cycle. The proposed s-CO2 system uses no water, which is significant because CSP plants are typically located in hot, dry climates where water is scarce. The goals of this project are to:

  • Design, fabricate, and validate a closed-loop, s-CO2 power cycle of nominally 10 MW (electric) that can operate at up to 700°C and under dry-cooling conditions.
  • Validate the turbomachinery and control strategies for a power cycle that can fundamentally transform the CSP industry.

The NREL team brings together Echogen Power Systems, Dresser-Rand, Abengoa Solar, Sandia National Laboratories, the University of Wisconsin, Barber-Nichols Inc., and the Electric Power Research Institute to contribute their unique qualifications to support the development and commercialization of s-CO2 power systems.

Significant Impact

This project will provide a foundation for solar applications that exceed SunShot's CSP goal of 50% net thermal-to-electric conversion efficiency. The 10-MW s-CO2 turbine test provides the necessary next step to transition the s-CO2 Brayton power cycle from laboratory experiment to commercial deployment.

The project offers higher efficiency at lower cost to meet the goal of DOE's SunShot Initiative to make installed large-scale solar energy systems cost-competitive with other energy sources by 2020.

Learn about other DOE competitive awards for concentrating solar power research that are in progress.