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Description:
This project is developing a closed loop controls and wireless communications test bed, which will parallel a DOE SETO heliostat field refurbishment effort. This experimental test system comprising 218 heliostats will be flexible to bring in python closed-loop controls architectures to demonstrate on-sun with an approximate 200 ft. tall solar tower. This system would also enable testing of wireless controls communications such as WiFi, Mesh and radio platforms. This work is being conducted in a phased approach with a laboratory closed-loop controls test bed, prior to real-time closed loop control with 4, 16 and the subsequent 218 heliostats, where feedback is tested from one or more measurements of direct optical metrology.

Project Lead:
Ken Armijo (Sandia)

Team: Ansel Blumenthal, Haden Harper, Zachary Bernius, Luis Garcia-Maldonado 

Objectives: 

• Closed loop controls test bed with highly-flexible software and hardware controls, communication and optical sensors which will be communicating with both wired and wireless protocols. 
• Software architectures utilized to determine optimal pointing of each heliostat, accounting for unique metrology considerations.
• Goal to decrease commissioning and O&M cost, while increasing plant performance for varying solar market flux requirements.  

Approach: 

• Closed-loop systems possess beam characterization system, provides feedback based on heliostat’s receiver aiming. 
• Closed-loop control enables automatic calibration as part of commissioning and fine calibration on a daily or even more frequent basis. 
• Hardware to enable closed-loop heliostat control capable of feedback for plant-level control.  
• Provided Python software integrated within control room architecture, setup to decide which heliostats aim at receiver to maximize flux and desired pointing strategy distribution.  

Status:

• Controls and real-time processing architecture being completed with validation work underway.


• Completion of Wifi communications setup with mesh communications development on-going.

Description:
The components and controls FY24 subtask is focused on laminating and testing coupon sandwich mirror facets with 96% reflectivity mirrors. Improving reflectivity from 93% to 96% results in significant field performance gains that offer more than a one-to-one reduction in CSP LCOE. 96% reflectivity is achieved with 1-2 mm glass mirrors as opposed to the standard 3-4 mm glass. Such thin glass is not structurally robust and therefore requires additional support. Testing with coupons provide the opportunity to learn which adhesive materials and support structures provide the most protection to the silver layer as well as robustness to hail and other damage mechanisms.

Project Lead:
Matthew Muller, NREL

Team: Matthew Muller, Stephanie Meyen, Christa Schreiber 

Objectives: 

• Test multiple adhesive materials including 3M adhesive tape, Ethylene Vinyl Acetate (EVA), and Polyolefin Elastomers (POE) with other stack materials including Aramid honeycomb, Pop Foam (foam from recycled plastic bottles, mirror back paint, and aluminum. 
•  Laminate stacks with multiple support structures and subject the samples to accelerated environmental testing and hail testing. 
• Demonstrate robustness to hail and corrosion of the silver layer.  

Approach: 

•  Conduct peel testing for bond strength between the 3 adhesives and the 4 adjoining surfaces 
•  Measure the performance of thin mirrors from 2 sources 
•  Complete accelerated damp heat, thermal cycling with humidity, UV plus humidity, and condensation testing on 10 cm samples. 
•  Conduct hail testing on 24-inch samples  

Status:

• Peel testing is complete resulting in EVA providing the highest bond strength


• Mirror performance characterization is complete.


• 10 cm samples have been laminated with both 1- and 3-mm glass. 3 mm glass is indoor glass and was included because it does not have outdoor protective paint. This provides the opportunity to determine if adhesive layers and an edge are sufficiently hermetically sealed to protect the silver layer.
• Samples are currently undergoing damp heat, UV plus humidity and thermal cycling with humidity.

The Reflected Target Non-intrusive Assessment (ReTNA) tool measures mirror surface slope and facet canting error for heliostat qualification, R&D, and quality assurance on the heliostat assembly line. It is designed to adopt simple, low-cost equipment such as modular, lightweight printed targets and off-the-shelf cameras.

Project Lead: Devon Kesseli (NREL)

Team: Guangdong Zhu (NREL), Kyle Kattke (Solar Dynamics)

Objectives:

• To develop and validate laboratory optical measurement technology. 
•  To offer the industry a lightweight, low cost, and portable system capable of fast setup and automated measurement. 
•  To enable accurate measurement of slope and facet canting error:
           o  For For heliostats of various geometries
           o  At varied heliostat orientations
           o  With varied loading applied to the heliostat

Approach:

• Using target deflection techniques to accurately measure mirror shape. 
•  Using photogrammetry to reduce the required precision of the setup. 
•  Leveraging advancements in image-processing and computer vision to automate measurement.

Status:

• Completed concept-proof stage, and repeated ReTNA testing on a commercial heliostat. 
•  Built initial ReTNA prototype at NREL, working on second generation system prototype. 
•  In next year, complete further rigorous validation campaigns with research and industry partners and collaborate with industrial partners to demonstrate commercial ReTNA layouts.

OpenCSP is an open-source platform including source code, applications, and data to enable collaborative development for the CSP community, supporting industry, research, and education. 

• OpenCSP_Code – Both foundation classes for building new programs and ready-to-run applications, including Sandia’s SOFAST 2.0 code, all in Python.
  
  
• OpenCSP_Data – Large data sets for research, optical targets for metrology ground truth tests, and test data for OpenCSP_Code.
  
  
• OpenCSP_Mechanical – Includes an interactive CAD tool for designing deflectometry layouts, plus a gallery of CAD models to support collaborative CSP research.
  
  
• OpenCSP_Tools – Non-code tools to aid CSP analysis and understanding.
  
  
• OpenCSP_Documents – Documents supporting OpenCSP and related topics. 

All are provided with an open-source license allowing unlimited use, requiring acknowledgement.

Project Lead: Randy Brost, Ph.D. (Sandia)

Objectives:

• Accelerate transfer of state-of-the-art CSP metrology and analysis tools to industry. 
• Provide a resource for businesses seeking to support CSP development. 
• Enable the code and data to contribute to education. 
• Provide a community collaborative development environment to enable teams to build new advanced CSP applications more quickly, and to speed their deployment.

Approach:

• Establish a strong collaborative code development environment set up to support effective team code development, including automatic testing, document generation, and issue tracking. 
• Provide a large corpus of difficult-to-produce CSP research data. 
• OpenCSP welcomes all to use its resources and contribute to make it even better!

Status:

• As of July 2024, both code and non-code OpenCSP repositories have been operational for months, used by the OpenCSP team. We plan to announce the public opening of OpenCSP at SolarPACES in October 2024. Presentation: “OpenCSP: Collaborative Code and Data For CSP.” 
• OpenCSP web portal is under construction; send inquiries to OpenCSP@sandia.gov.
   
  

Description: The drone-based Non-Intrusive Optical (NIO) Technology developed at NREL allows for in-situ characterization of heliostat optical errors at commercial-scale power tower CSP plants. The method will be validated using data collected from commercial solar fields, including Cerro Dominador and Crescent Dunes and compared against Beam Characterization System (BCS) measurements of tracking error at NREL’s Flatirons campus. Project Lead: Rebecca Mitchell

Project Lead: Rebecca Mitchell

Objectives:

• Update the NIO software so that it is fully automated and reliably produces optical error estimates at high volume 
• Validate the reliability and accuracy of estimates of slope, tracking, and canting error produced by the NIO algorithm through repeatability testing and comparison with BCS data. 
• Perform and comparison test of NIO and BCS measurements at the Flatirons campus

Approach:

• Test and refine the algorithm performance by processing drone image data collected at Crescent Dunes and Cerro Dominador. 
• Install a solar collector and BCS target at NREL’s Flatirons campus. 
•  Perform a comparison study of NIO and BCS measurements of tracking error at the Flatirons campus.  

Status:

• Made significant advancements towards commercialization of the NIO software through streamlining the data architecture and improving the reliability of the automated post-processing of data through testing of collected Cerro Dominador and Crescent Dunes data. 
•  A BCS has been deployed at Flatirons campus and two types of heliostats have been identified for installation at the site. 9 Heliogen heliostats have been delivered on campus and a purchased Heliuss heliostat prototype is being fabricated. 
• An IF1200A hexacopter UAS has been acquired for NIO data collection and test flights were conducted at Flatirons campus.