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The National Renewable Energy Laboratory (NREL), under the National Laboratory R&D competitive funding opportunity, is developing and demonstrating a novel collector design and low-cost heliostat that will reduce equipment and installation costs while improving or maintaining performance, thereby reaching SunShot Initiative cost and performance targets for concentrating solar power (CSP) collector systems.
The design goals for the project include:
- A structure that maintains less than 4.0 mrad total image error at wind speeds up to 12 m/s (26.8 mph)
- A wireless, locally-powered communication and control system that decreases the cost of these components by at least 20%
- An autonomous, optical calibration technique that provides greater accuracy through the ability to have increased calibration frequency.
This design approach is unique because it uses an optimized structure that not only reduces material costs, but also minimizes loads on the drive system, permitting a reduction in drive costs compared to standard designs. The approach integrates an off-grid, redundant, shared-node, mesh network that mitigates any downtime due to communication errors. The team will also assess an innovative closed-loop feedback control system that integrates into the wireless mesh network to ensure accurate tracking throughout the day.
Specifications of a baseline power plant and field layout used to develop field layouts and specifications for fully wired and shared-node wireless power and data communication systems were completed. Wired system included all power and data communications wiring and hardware needed to track the heliostat field. This system was used to inform the design bases for the shared-node wireless system. Wi-Fi communication with was selected as the most appropriate communication standard for the wireless system. The ZigBee communication standard was selected for increased communication distances. Ultra-battery provides the best performance value for the system. Algorithms to calculate wiring and trenching lengths within shared nodes were developed.
Finally, a probabilistic cost model for the wired and shared-node wireless systems demonstrated their relative installed cost. Given some assumptions, the wired system’s mean cost was $13.35/m2 and the wireless system minimized at $7.77/m2, a reduction of 42%. Two factors impacted the cost differential between fully wired and shared-node wireless systems. The first was the need to convert 48 VAC to 48 VDC at each heliostat pedestal for the fully wired systems. This conversion is not needed in the shared-node system. The second was the cost benefit derived from the PV modules generating their own electricity in the shared-node system. Both factors greatly reduced the cost of the shared-node system relative to the fully wired system. Analysis of 40 m2 and 116 m2 heliostat sizes showed that the minimum cost of the shared-node wireless system in the design space was $5.37/m2 and occurred using 40 m2 heliostats with 60 heliostats per node.
Publications, Patents, and Awards
At this time, this project does not have published articles, patents, or awards.