Session: 18-02 HelioCon Windload

Paper Number: 138261

138261 - Tracking Error at an Operational Concentrating Solar Power Plant 

Abstract: 

Concentrating solar power (CSP) provides firm and dispatchable electricity due to its thermal storage and hybridization capabilities, which supports the decarbonization of our energy supply. Of the various CSP technologies, parabolic trough collectors compose the majority of CSP energy production in the United States. The optical performance of parabolic trough systems is sensitive to tracking error, which is defined as the angular offset of a collector away from the sun position in the transversal plane. Tracking error commonly occurs due to non-continuous adjustment of the trough angle to point toward the sun, but other factors such as gravity, heating, wind loading, and installation misalignment can also contribute to tracking error. Additional errors in the measurement and controls feedback loop can compound and lead to misalignment of the troughs. Although the effects of tracking error on optical performance are well-studied, realistic tracking error in operation has not been characterized. Our work presents the first assessment of long-term tracking error at an operational CSP plant. 

 

To fully characterize tracking error of parabolic troughs, we conducted a long-term field measurement campaign at the Nevada Solar One CSP plant located in Boulder City, NV, which has a nominal capacity of 72 MW and 0.5 hours of full-load storage. As a part of this campaign, we installed load measurements on four outermost trough rows and include support structure bending moments, drive torque moments, dynamic accelerations of the spaceframe, mirror displacement and tilt angles. Using these tilt measurements, acquired at 1 Hz frequency, we calculate the deviation between the sun position and the measured trough angle based on measurements at three rows at the western edge of the CSP plant. Thus, we can characterize the tracking error throughout the diurnal cycle and over several months at various spatial locations within the CSP plant.  

 

Preliminary findings indicate that tracking error exceeds conventional industry assumptions, as the three measured troughs are completely misaligned during 42% of the seven-month measurement period. Additionally, tracking error is found to vary by spatial location in the plant as well as over time. The team is also planning a measurement campaign to study heliostat performance under wind driven loads at the Crescent Dunes CSP power plant. Analysis of tracking error measured during this campaign will also be presented. Overall, this first of a kind study will provide important guidance for future solar collector designs and inform advanced control strategies in an effort to reduce tracking error.

Presenting Author: Brooke J. Stanislawski National Renewable Energy Laboratory (NREL)

Presenting Author Biography: Brooke Stanislawski is a Research Scientist at the National Renewable Energy Laboratory in Computational Sciences. She studies wind energy, solar energy, and hybrids (wind and solar) using numerical simulations, specifically focusing on wind loading, turbulence, fluid mechanics, optics, convective heat transfer, and atmospheric boundary layer flow. After working as a design engineer at Siemens Energy, she earned her Ph.D. at University of Utah where she developed expertise in flow modeling of the physical interactions between large solar photovoltaic plants and atmospheric flow.

Authors:

Brooke J. Stanislawski National Renewable Energy Laboratory (NREL)
Ulrike Egerer National Renewable Energy Laboratory
Scott Dana National Renewable Energy Laboratory
Shashank Yellapantula National Renewable Energy Laboratory