Alfonso Gago-Calderón

The accurate characterization of photovoltaic devices under diverse spectral conditions is essential for optimizing solar energy systems beyond standardized test environments. This work presents the development and application of a monochromatic LED‐based system to assess the spectral efficiency of monocrystalline silicon photovoltaic devices. Eleven custom‐built luminaires, emitting from 410 to 730 nm, were developed, and their emission spectra were determined. These luminaires were used to illuminate two types of reference devices: 6 × 6 cm ² individual solar cells and 6 × 5.5 cm ² small‐encapsulated photovoltaic panels, enabling controlled I–V and P–V measurements. The maximum power output under each wavelength was recorded, and relative efficiencies were calculated. Second‐order polynomial regression models were fitted to the efficiency data as a function of wavelength for both reference devices. Subsequently, the normalized spectral functions obtained for both devices were averaged to define a representative relative spectral function. This empirical function was then scaled using a factor based on the manufacturer′s nominal average efficiency, allowing the construction of a surface model capable of estimating the spectral efficiency of monocrystalline silicon photovoltaic devices as a function of wavelength and nominal efficiency. The results confirm the expected spectral response trend of silicon‐based devices, with higher efficiency in the orange‐red to near‐infrared region, and provide a practical tool for estimating energy yield under variable illumination conditions. The method facilitates system sizing and performance prediction in scenarios affected by optical filters, nonstandard solar spectra, or specific environmental conditions. The proposed methodology may also be applied to other photovoltaic technologies, provided that their corresponding spectral response is experimentally characterized.

Sustainability and energy prices make the use of energy obtained from renewable sources on an urban scale and for isolated local facilities necessary for municipal authorities. Moreover, when the demand of energy is at night, as for street lighting installations, the use of accumulative systems is necessary, which means a major drawback due to a short lifetime expectancy and high cost. The use of batteries can require more than 70% of the budget of these lighting systems and has a critical impact in the project. The problem to solve is finding different renewable energy sources that can produce energy throughout the day, especially during the night, at the same time at which it is consumed. As one of the competences of municipal authorities is water supply networks, this paper analyzes the use of energy recovery turbines within these installations as an alternative to photovoltaic generators. To study the viability and effectiveness of this alternative, the water flows available in the network of a medium-size municipality were monitored and analyzed in depth to assess the amount of recoverable energy. In addition, an energy recovery turbine (ERT) station was set up, installing a bypass around one of the pressure-reducing valves (PRV) of the installation where energy is dissipated without practical use. The results obtained imply that the system proposed has economical and technical viability, is reliable and guarantees full service in all the seasons’ conditions. Moreover, the needs of the energy storage capacity are much lower (~8%) than with solar panels.

In the last decades, lighting installations in plant tissue culture have generally been renewed or designed based on LED technology. Thanks to this, many different light quality advances are available but, with their massive implementation, the same issue is occurring as in the 1960s with the appearance of the Grolux (Sylvania) fluorescent tubes: there is a lack of a methodological standardization of lighting. This review analyzes the main parameters and variables that must be taken into account in the design of LED-based systems, and how these need to be described and quantified in order to homogenize and standardize the experimental conditions to obtain reproducible and comparable results and conclusions. We have designed an experimental system in which the values of the physical environment and microenvironment conditions and the behavior of plant tissue cultures maintained in cabins illuminated with two lighting designs can be compared. Grolux tubes are compared with a combination of monochromatic LED lamps calibrated to provide a spectral emission, and light irradiance values similar to those generated by the previous discharge lamps, achieving in both cases wide uniformity of radiation conditions on the shelves of the culture cabins. This study can help to understand whether it is possible to use LEDs as one standard lighting source in plant tissue culture without affecting the development of the cultures maintained with the previously regulated protocols in the different laboratories. Finally, the results presented from this caparison indicate how temperature is one of the main factors that is affected by the chosen light source.

This paper analyzes the technical and economic viability and sustainability of urban street lighting installation projects using equipment powered by photovoltaic (PV) energy. First, a description of the state-of-the-art of the technology is performed, studying the components involved in solar LED luminaires for street lighting application and examples of autonomous PV systems installed in different countries. Later, a case study a based on a renovation project of the street lighting installation at a 5000-inhabitant municipality in Lanzarote (Spain) is presented. Two alternatives are analyzed: underground channeling of the previous aerial electrical grid and the installation of LED luminaires, and, on the other hand, the installation of autonomous LED solar luminaires. Simulations concluded that a PV lighting installation proposal guarantees the existing M3 lighting requirements (EN 13201-2:2015) and represents a saving in the material execution budget of 43.78% with respect to the channeled power grid option. Finally, a statistical study has been carried out to assess the social acceptance of Spanish citizens of this autonomous PV technology in urban environments. This considers strengths and weakness of the technology: sustainability, robustness, visual impact, or risk of vandalism. In general, most subjects of all age segments are aware of the problem that means having aerial wiring running at facades (95%) and considers the use of PV in urban lighting sustainable (88%). However, 47% of those surveyed consider that shutdowns due to lack of energy harvesting is problematic and 17% consider this very problematic. This major drawback (visual impact of PV equipment is mostly evaluated as neutral) gives rise to social reluctance, especially in people younger than 50 who remarked this as more problematic than senior segments. Thus, guaranteed operational service is fundamental to have social agreement for PV technology implementation.

The sensitivity of the human eye varies with the different lighting conditions to which it is exposed. The cone photoreceptors perceive the color and work for illuminance conditions greater than 3.00 cd/m² (photopic vision). Below 0.01 cd/m², the rods are the cells that assume this function (scotopic vision). Both types of photoreceptors work coordinately in the interval between these values (mesopic vision). Each mechanism generates a different spectral sensibility. In this work, the emission spectra of common sources in present public lighting installations are analyzed and their normative photopic values translated to the corresponding mesopic condition, which more faithfully represents the vision mechanism of our eyes in these conditions. Based on a common street urban configuration (ME6), we generated a large set of simulations to determine the ideal light point setup configuration (luminance and light point height vs. poles distance ratio) for each case of spectrum source. Finally, we analyze the derived energy variation from each design possibility. The results obtained may contribute to improving the criterion of light source selection and adapting the required regulatory values to the human eye vision process under normalized artificial street lighting condition, reaching an average energy saving of 15% and a reduction of 8% in terms of points of light required. They also offer a statistical range of energy requirements for lighting installation that can be used to generate accurate electrical designs or estimations without the necessity of defining the exact lighting configuration, which is 77.5% lower than conventional design criteria.

Sustainability and energy prices make the energy production from renewable sources necessary and photovoltaic energy is ideal on an urban scale and on isolated facilities. However, when the demand for energy is at night, as in lighting installation, the use of accumulative systems is necessary. The use of batteries can account for more than 70% of the budget of these systems and have a critical impact in the project. This problem increases when the installation’s location moves away from the equator, as the variation between the duration of days and nights increases. This implies that the system must be oversized to almost triple its generation and storage capacity to guarantee operation. This paper proposes the use of a robust and affordable electronic centralized management system that can regulate the consumption based on the energy available in the batteries. To test this system, a real case of outdoor lighting nanogrid has been used. The facility has been powered by a grouped photovoltaic battery system dimensioned for the average year solar conditions with and without consumption management. When used without regulation, in winter or cloudy days, there have been repetitive crashes of the system. On the other hand, with the use of the electronic control proposed, the shutdowns have been avoided, regulating the lighting level when necessary. Thus, more efficient and economically affordable systems can be designed which can help to spread the installation of isolated photovoltaic lighting.

Nowadays, LED lighting technology reaches a higher Value of Energy Efficiency in Installations (VEEI) (W/m2*100 lux) than current luminaire lighting due to the number of lumens per watt that these are able to generate, as well as the directional nature of their emissions together with the adjustment capability through concentrator lenses with beam graduations that reach 5º. This achieves energy savings of up to 80%. Furthermore, also considering the substantial decrease in flickers, and that it noticeably improves usage of ultra-slow-motion cameras and the fading of switching-on or rearm times upon failure, LED technology stands out as the main solution for illumination of professional sports facilities. This article describes the evolution of regulatory requirements that are being imposed by the governing institutions of sports (FIFA, UEFA, FIBA, etc.) and professional leagues (LaLiga, Euroliga, etc.) in order to guarantee their competence as high-quality television products. In addition, the trends in requirements and specifications regarding lighting equipment and its installation, which are intended to convert stadiums into optimized centers for the celebration and dissemination of mass events, are analyzed (settings, photometry, etc.), particularly those concerning horizontal, vertical, and camera illuminance, average and extreme uniformities, glare, reduction of intrusive light in bleachers, flickers, color rendering index (CRI), correlated color temperature (CCT), and start-up times.

Photodynamic therapy is taking importance as a non‐intrusive treatment for nail onychomycosis. Knowledge of true transmittance values across nails could lead to qualitative and quantitative improvements in light‐based treatments. We have characterized the spectral transmittance of healthy and fungally infected human finger nails and toenails according to nail thickness and we propose a surface transmittance model for the small‐scale optimization of light‐based treatments. Transmittance of finger nails and toe nails was analyzed by means of spectroradiometric measurements under solar simulated visible light radiation (400 nm to 750 nm). The nail thickness was measured by means of microscope measurement. Transmittance was highest at longer wavelengths and decreased gradually as the wavelengths became shorter but with a significant nail transmittance of around 20% in the blue region of the spectrum. In the case of nails affected by onychomycosis, transmittance fell to under 10% because of the thickness of the nails, with no changes in spectral characteristics of transmitted light. Nail thickness is the main variable controlling exponentially light transmission in the visible spectrum and not only red radiation is effective for nail onychomycosis PDT. Blue light, the spectral band more effective for PPIX absorption is also effectively transmitted.