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SkyFuel, under the Baseload CSP FOA, developed an advanced, low-cost CSP collector using higher-concentration, higher-temperature, parabolic trough technology to substantially reduce the cost of baseload utility-scale solar power generation.

Approach

SkyFuel worked toward two anticipated outcomes:

• A baseload parabolic trough collector that is optimized for high-temperature service with a maximum temperature of 100°C above prior state-of-the-art systems (up to 500°C or more). High-temperature design points demand larger apertures and concentration ratios (40%–90% greater than the prior state-of-the-art) with associated improvements in optical accuracy (30%–75% over the prior state-of-the-art).
• A baseload trough that realizes significant reductions in cost because of the larger aperture, while incorporating additional advancements that substantially lower installed solar field costs. For example, the reflective film surfaces are being upgraded to improve reflectance and specularity. A surface coat is being developed to provide anti-soiling and abrasion resistance.

Innovation

SkyFuel demonstrated the SkyTrough DSP - a novel parabolic trough with a 25% increase in concentration ratio, a 40% increase in aperture width, and a 50% increase in length compared to today's troughs. The increased concentration ratio coupled with an operating temperature 100°C higher than the current state-of-the-art trough designs supports higher efficiency power cycles and substantially reduced thermal storage costs.

Conclusion

The SkyTrough DSP will advance the state-of-the-art in parabolic troughs for utility applications, with a larger aperture, higher operating temperature, and lower cost.

The result of Phase I optimization was a trough design of larger aperture and operating temperature than has been fielded in large, utility scale parabolic trough applications: 7.6m width x 150m SCA length (1,118m² aperture), with four 90mm diameter x 4.7m receivers per mirror module and an operating temperature of 500°C. The results from physical modeling in the System Advisory Model indicate that, for a capacity factor of 75% the levelized cost of energy (LCOE) will be 8.87¢/kWhe.

SkyFuel examined the design of almost every parabolic trough component from a perspective of load and performance at aperture areas from 500 to 2,900m². Aperture-dependent design was combined with fixed quotations for similar parts from the commercialized SkyTrough product, and established an installed cost of $130/m² in 2020.

Phase II resulted in the erection of a full-scale module at SkyFuel’s hilltop facility with testing at ambient conditions. The optical efficiency was demonstrated to be 76% (±4.8%) with a 95% confidence interval. With the optical efficiency measured, it became key to demonstrate that a new trough heat transfer fluid, molten salt, could operate in the receiver piping. A test loop was constructed, which proved successful with a nitrate based molten salt. No damage was observed in the equipment. These successful tests open the possibility of increasing the maximum operating temperature of a trough based CSP plant, thereby increasing the overall plant efficiency and reducing the LCOE. 

Final Report

Schuknecht, Nate, David White, and Graeme Hoste. High-Concentration, Low-Cost Parabolic Trough System for Baseload CSP. No. DE- EE0003584. SkyFuel, 2014. DOI:  10.2172/1155057 

Publications, Patents, and Awards

At this time, this project does not have published articles, patents, or awards.

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