Heliostat-based concentrating solar-thermal power (CSP) systems can offer immense potential to provide low-cost, dispatchable renewable thermal and electrical energy to help achieve 100% decarbonized energy infrastructure in the United States. Heliostats are a major determinant of both capital cost and performance of state-of-the-art commercial molten salt towers and Generation 3 CSP systems. In 2021, the U.S. Department of Energy (DOE) Solar Energy Technologies Office (SETO) launched the Heliostat Consortium (HelioCon), a five-year initiative to advance heliostat technologies. The HelioCon mission is threefold: (1) establish strategic core testing and modeling capabilities and infrastructure at national labs; (2) support heliostat technology development in relevant industries; and (3) serve as a central repository to integrate industry, academia, and other stakeholders for heliostat technology research, development, validation, and deployment. In the past years, HelioCon has conducted a roadmapping study on advancing heliostat technologies, intended as a central reference for the entire CSP community; also a RFP process to issue a number of projects to engage a wider RD community.

NREL is presenting an indoor optical measurement system for large heliostat mirrors. This is a target-based deflectometry system, which uses a thin printed patterned targets and a moving camera to scan large mirrors, measuring the surface slope. This system is compared to existing fringe deflectometry and photogrammetry measurement systems, and the computer vision techniques that make it possible are described. While it cannot achieve the resolution of a fringe deflectometry system, the simplicity and low cost of setup make it well suited for the CSP industry.

Heliostats with active adjustment of surface shape and provision for highly accurate orientation are being prototyped for use with receivers with secondary reflectors, to focus sunlight at concentrations as high as 4,000 suns and at high power, > 1 MW. One application is making green hydrogen from water. Heliostats in a field will each form a disc image of the sun, all centered on a compound paraboloidal concentrator (CPC). A mechanical linkage to the cross axis drive of target-axis mount drive continuously adjusts the shape of each reflector through the day, as needed for the changing angle of incidence.

This presentation outlines the Non-Intrusive Optical (NIO) technology for optical measurement of in-situ, operational heliostat mirrors in concentrating solar power tower plants. NIO is a photogrammetric process that uses a camera mounted to an uncrewed aircraft system (UAS). We first capture the edge of the central tower reflected in the heliostat. By extracting heliostat features using deep learning object detection and computer-vision techniques, we can precisely determine camera positions, detect the reference in the image, and use this data to describe errors in the mirror. NIO is rapid, inexpensive, and does not interfere with plant operations. It requires only an off-the-shelf UAS with an appropriate camera to use.

Heliostat calibration is crucial for efficient solar tower power plant operation. Geometry-based models are reliable but yield moderate accuracy, while neural networks promise higher accuracy but need high amounts of data. We introduce a hybrid model that combines a reliable geometric model with a neural network disturbance model over a regularization sweep. Using real measurement data from the Jülich solar tower, we achieve higher accuracies than rigid body models starting from the first measurement, with a top performance below 0.7 milliradians. Our approach reduces data requirements of deep learning models, making them promising for heliostat calibration in solar tower power plants.

The development of renewable energy sources is of vital importance, not only in the fight against climate change but also in securing the energy supply. In this context, solar technologies are already playing an essential role in the shift towards carbon-neutral economies, while ensuring a reliable and competitive energy supply. The durability and performance of solar components are crucial to increase the reliability and output of solar power plants and ultimately reducing the cost of electricity. Both the glass used as the front cover of photovoltaic modules and the absorber tubes of parabolic trough collectors currently include anti-reflective (AR) coatings; however, these coatings have not yet convincingly demonstrated their durability in the field, and there are reasonable doubts about their resistance against abrasion. Also, coatings with anti-soiling (AS) functionality are now being explored and laboratory-scale developments are being carried out on coatings with passive cooling functionality that bring higher efficiency and longer service lifetime to PV modules by reducing their operating temperature. Unfortunately, these developments are still far from demonstrating relevant improvements and even further away from demonstrating the required durability. In this work, this issue has been addressed through an innovative approach, developing a process that is not a conventional coating at all, but is based on a combination of micro and nano-structuring of the glass surface itself, which provides the three functionalities mentioned above, far exceeding the characteristics of any of the current solutions: anti-reflective (AR) with an improvement of more than 2.3%, anti-soiling (AS) with a reduction in the rate of soiling of 48% and passive cooling, with cooling peaks of up to 2.5 ºC. In addition to these significant improvements over the current state of the art, the most relevant aspect of the development is the quantitative improvement in its durability, thanks to the innovative technique of structuring the glass surface itself, which does not involve any added material and maintains the mechanical properties of the surface. Thus, this structured glass applied to solar technology will result in a reduction of the LCOE, favouring the transition towards a sustainable energy model and displacing the use of fossil fuels.

Thermochemical hydrogen production via redox reactions with the input of concentrated solar thermal energy has been well recognized as an advanced green hydrogen generation technology. Creating a high enough temperature in the solar receiver relies on very high solar concentration ratio. Through the development of special heliostats and solar concentration technology, high heat flux of over 3000 suns could be achieved. Each specially designed heliostat creates a solar disc image of small area, and overlapping images make possible temperatures of up to 1500 oC in the solar receiver. In this work, special solar receiving chambers are configured to accommodate reduction reaction and oxidation reaction reciprocally to satisfy the demand of temperatures and gas environments for the different reactions. Analysis of the redox material temperature variation in transient processes of reaction is carried out to understand the dynamics of temperature control for thermochemical reactions.

Concentrated solar power with a field of heliostats has the potential to reach temperatures as high as 1500C, as required for industrial processes. We plan to accomplish this using heliostats on target-oriented mounts, with a mirror surfaces whose toroidal shape is changed throughout the day to maintain a focused disc images of the sun on a receiver. We have built a simple mechanism that deforms a rectangular mirror without the expense of dedicated motors or computer control. The heliostat’s slewbearing has a dual function of orienting the reflector to direct sunlight to the tower and also twisting the mirror shape.