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.
SHORT is a patented (PCT/ES2016/070681 – WO 2017/055663) automatic heliostat calibration system based on lowcost artificial vision systems mounted on each heliostat which is used to observe a number of targets with known positions distributed throughout the solar field. During the calibration, the heliostat is moved to sequentially capture such targets with the camera. Once sufficient observations are made, the parameters of a detailed kinematic model of the heliostat are adjusted through an iterative optimization process. This model allows predicting the precise position and orientation of the heliostat for any given axis’s angles and, by means of inverse kinematic, calculating the angles required to move the heliostat into a specific desired orientation. SHORT has been thoroughly validated at the Plataforma Solar de Almeria with a heliostat equipped with a low-cost camera observing artificial infrared light sources – targets – distributed throughout the solar field with accurately measured positions. The experimental error in movement prediction resulted below 0.25 mrad (RMS). To successfully implement SHORT in commercial Solar Towers and face the challenge of applying the system in large heliostat fields (thousands of heliostats) a dedicated methodology to find a minimum set of suitable infrared lights distribution has been developed. Results show that no more than 6-8 targets surrounding the field are enough to reach the aimed accuracy. In addition, a techno-economic analysis of Solar Tower plants according to the solar field optical error has been performed to estimate the impact of SHORT implementation in LCOE reduction with a promising result of 5% cost savings.
Heliostat’s reflected beam quality has been estimated using the target-camera method for years due to being the only method that can be realistically implemented in a commercial plant. But this methodology is prone to errors such as those derived from target surface flaws and its limited size, and the sensitivity and dynamic range of the camera. To reach a high quality characterization, thus reducing required security margins and boosting plant profitability, a novel system and methodology have been developed. This is a scanner-based methodology in which the spot reflected by a static heliostat, no matter how far it is from the measurement system, is captured simultaneously by two subsystems, a vertical array of detectors and a group of cameras, in order to produce a high quality representation of the reflected beam and a precise characterization of the normal vectors along the whole heliostat reflective surface. The use of optoelectronic detectors allows capturing the solar beam with reduced optical and electronical noise and wider dynamic range with respect to the state-of-the-art methodology. At once, the camera subsystem is used as a scanner to perform an accurate normal vector estimation of the heliostat surface. The combination of both approaches lead to the most precise heliostat characterization to date. This system can be implemented at low cost in any commercial plant, planned, under construction or under exploitation with any size of heliostat field and any number and typology of heliostats.
Solar radiation attenuation in the path from the heliostats to the receiver is one of the main contributions to production estimation uncertainty in the operation of central-receiver concentrated solar plants (CSP). Few systems are commercially available to monitor this phenomenon and those available have high uncertainties due to the non-uniform attenuation pattern across the wavelength range of the useful solar radiation. In this work, we report the results from a 6-month measurement campaign carried out in a commercial CSP tower plant using a prototype system to measure the spectrally-resolved solar radiation attenuation. The system measures the differential spectrum between two pairs of high-resolution spectrometers (VIS and IR) separated approximately 800 meters and each coupled to a telescope system. Both systems are pointed at a white Lambertian target and regularly take a baseline measurement pointing at a black target to eliminate contributions from the diffuse light present in the solar field. The system is calibrated to <1% uncertainty using the reference of a portable spectrometer at both locations. Full-spectrum measurements were taken every 5 minutes. Spectral characteristics of different atmospheric conditions (suspended dust, fog, humidity) and their intra-day and seasonal evolutions are observed and analyzed.
Conference Committee Involvement (1)
Advances in Solar Energy: Heliostat Systems Design, Implementation, and Operation II
3 August 2025 | San Diego, California, United States
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