Solar

The depletion of fossil fuels and onset of global warming dictate the achievement of efficient technologies for clean and renewable energy sources. The conversion of solar energy into chemical energy plays a vital role both in energy production and environmental protection. A photocatalytic approach for H₂ production and CO₂ reduction has been identified as a promising alternative for clean energy production and CO₂ conversion. In this process, the most critical parameter that controls efficiency is the development of a photocatalyst. Two-dimensional nanomaterials have gained considerable attention due to the unique properties that arise from their morphology. In this paper, examples on the development of different 2D structures as photocatalysts in H₂ production and CO₂ reduction are discussed and a perspective on the challenges and required improvements is given. Full article

Fully printable carbon-based perovskite solar cells (C-PSCs) represent some of the most promising perovskite solar cell (PSC) architectures. Highly scalable, stable, and low in cost—these devices consist of a TiO₂ compact layer (C-TiO₂) and three sequentially screen-printed mesoporous layers of TiO₂, ZrO₂, and carbon, through which perovskite is infiltrated. While there has been remarkable progress in optimizing and scaling up deposition of mesoporous layers and perovskite, few publications have focused on optimizing C-TiO₂. In this work, we investigate the potential for substituting commonly used spray pyrolysis with more easily scaled screen-printing. It was found that when comparing layers of similar thickness, 1 cm² devices fabricated with printed C-TiO₂ exhibited similar power conversion efficiency (PCE) to those fabricated with spray pyrolysis. In contrast, thicker-printed C-TiO₂ led to lower efficiency. The influence of TiCl₄ treatment on the quality of produced compact layers was also examined. This proved beneficial, mostly in the printed films, where a champion PCE of 13.11% was attained using screen-printed, TiCl₄ treated C-TiO₂. This work proves that screen-printing is a viable replacement for spray pyrolysis in C-PSCs fabrication. Full article

We present laser-doped interdigitated back contact (IBC) solar cells with efficiencies of 23% on an area of 244 cm² metallized by a screen-printed silver paste. Local laser doping is especially suited for processing IBC cells where a multitude of pn-junctions and base contacts lay side by side. The one-sided deposition of boron-doped precursor layers by atmospheric pressure chemical vapor deposition (APCVD) is a cost-effective method for the production of IBC cells without masking processes. The properties of the laser-doped silicon strongly depend on the precursor’s purity, thickness, and the total amount of boron dopants. Variations of the precursor in terms of thickness and boron content, and of the laser pulse energy density, can help to tailor the doping and sheet resistance. With saturation-current densities of 70 fA/cm² at sheet resistances of 60 Ohm/sq, we reached maximum efficiencies of 23% with a relatively simple, industrial process for bifacial IBC-cells, with 70% bifaciality measured on the module level. The APCVD-layers were deposited with an inline lab-type system and a metal transport belt and, therefore, may have been slightly contaminated, limiting the efficiencies when compared to thermal-diffused boron doping. The use of an industrial APCVD system with a quartz glass transport system would achieve even higher efficiencies. Full article

Concentrated solar power is an alternative renewable energy technology that converts solar energy into electrical energy by using a solar concentrator and a solar receiver. Computational fluid dynamics have been used to numerically design concentrated solar power. This is a powerful numerical analysis approach that is widely used in energy and environmental engineering applications. In this paper, we review previous work on the applications of computational fluid dynamics in the design of concentrated solar power technology. We performed a bibliometric analysis of journal articles relevant to applications to analyze the current trend of utilization of computational fluid dynamics in these technologies. Then, we conducted a comprehensive analysis focused on the design of solar dish technology using computational fluid dynamics. Furthermore, we reviewed in detail the optical modeling of solar concentrators and solar receivers. Of the 83 retrieved publications from Scopus database, 80 were journal articles, and only three were review papers. Among these 80 journal articles, only 54 were relevant to this study, and 23 were relevant to solar dish technology. The documents were analyzed according to their number of citations, journal sources, and keyword evolution and network map. The information presented in this paper is useful to further recognize the contributions of computational fluid dynamics to the development of concentrated solar power, particularly to solar dish technology. In addition, we also discuss the challenges and future research directions to make solar energy a more sustainable source of renewable energy. Full article

In recent years, concentrating solar collectors have been integrated with several district heating systems with the aim of taking advantage of their low heat losses. The present study investigates the Brønderslev combined heat and power plant, which consists of a 16.6 MW parabolic trough collector field, two biomass boilers, and an organic Rankine cycle system. The study focuses on the solar collector field performance and integration with the district heating network. An in situ characterization of the parabolic solar collector field using the quasi-dynamic test method found that the field had a peak efficiency of 72.7%. Furthermore, a control strategy for supplying a constant outlet temperature to the district heating network was presented and implemented in a TRNSYS simulation model of the solar collector field. The developed simulation model was validated by comparison to measurement data. Subsequently, the simulation model was used to conduct a sensitivity analysis of the influence of the collector row spacing and tracking axis orientation. The results showed that the current suboptimal tracking axis rotation, made necessary by the geography of the location, only reduced the annual power output by 1% compared to the optimal configuration. Additionally, there were only minor improvements in the annual heat output when the row spacing was increased past 15 m (ground cover ratio of 0.38). Full article

At present, the purchasing prices for silicon-based photovoltaic modules with 20% efficiency and more are between 20 and 40 EURct/W_p. These numbers correspond to 40 to 80 EUR/m² and are in the same range as the mounting costs (material prices plus salaries) of such modules. Installers and operators of photovoltaic systems carefully balance the module and mounting costs when deciding among modules of different efficiencies. This contribution emulates the installer’s decision via a simple, analytical module mounting decision (Mo²De) model. A priori, the model, and the resulting conclusions are completely independent of the photovoltaically active material inside the modules. De facto, however, based on the present state (cost, efficiency, reliability, bankability, etc.) of modules fabricated from (single) crystalline Si cells, conclusions on other photovoltaic materials might also be drawn: On the one hand, the model suggests that lower-efficiency modules with efficiencies below 20% will be driven out of the market. Keeping in mind their installation costs, installers will ask for large discounts for lower-efficiency modules. Technologies based on organic semiconductors, CdTe, CIGS, and even multicrystalline Si, might not survive in the utility market, or in industrial and residential applications. Moreover, this 20% mark will soon reach 23%, and finally will stop at around 25% for the very best, large-area (square meter sized) commercial modules based on single crystalline silicon only. On the other hand, it also seems difficult for future higher-efficiency modules based on tandem/triple cells to compete with standard Si-based reference modules. Compared to their expected higher efficiency, the production costs of tandem/triple cell modules and, therefore, also their required markup in sales, might be too high. Depending on the mounting cost, the Mo²De-model predicts acceptable markup values of 1 EURct/W_p (for low mounting costs of around 10 EUR/m²) to 11 EURct/W_p (for high mounting costs of 100 EUR/m²) if the module efficiency increases from 23% to 30%. Therefore, a 23% to 24% module efficiency, which is possible with silicon cells alone, might be enough for many terrestrial photovoltaic applications. Full article

Understanding the implications of introducing increasing shares of low-carbon technologies such as heat pumps and electric vehicles on the electricity network demand patterns is essential in today’s fast changing energy mixture. Application of heat pumps for heating and cooling, combined with the rooftop installation of photovoltaic panels, is already considered as a convenient retrofitting strategy towards building electrification. This may further profit from the parallel, rapid electrification of the automotive powertrain, as demonstrated in the present study. Exploitation of the combined battery storage of the house owners’ electric car(s) may help cover, to a significant degree, the building’s and cars’ electricity needs. To this end, an efficient single family house’s energy system with an optimized rooftop PV installation, heat pump heating and cooling, and two high efficiency electric cars is studied by transient simulation. The use of TRNSYS simulation environment makes clear the interaction of the house’s heating, ventilation, and air conditioning (HVAC) system, the house’s and cars’ batteries, and the rooftop PV system in transient operation. The building’s and EV’s energy performance on a daily, monthly, and seasonal level is compared with the respective demand curves and energy sources of the Greek electricity network. The specific design of the house’s energy system makes it a net exporter of electricity to the grid, to an annual amount of 5000 kWh. On the other hand, electricity imports are slightly exceeding 400 kWh and limited to the first two months of the year. In addition to the self-sufficiency of the household, the impact to the electricity grid becomes favorable due to the phase shift of the electricity export towards the late afternoon hours, thus assisting the evening ramp-up and adding to the grid’s stability and resilience. Based on the results of this study, the possibility of combining the financial incentives for the purchase of an EV with those for the installation of rooftop PV in the owners’ house is very promising and worth considering, due to the demonstrated synergy of electrical storage with the rooftop photovoltaic installations. Full article

In this work, the method for calculation of uncertainty of pyrheliometers’ responsivity during their outdoor calibration process in the laboratory is exposed. It is applied first for calibration of standard pyrheliometers by comparison to cavity radiometers, and after for calibration of an end-user pyrheliometer against that standard pyrheliometer. The dissemination of the WRR irradiance scale is illustrated in practice and the increasing uncertainty in the traceability chain is quantified. The way of getting traceability to both WRR scale and to SI units in the current situation, where the shift between these radiometric scales is pending to be solved, is also explained. However, the impact of this gap between scales seems to be more important for calibrations of reference Class A pyrheliometers than in the final determination of DNI irradiance, because in this case, the cumulative uncertainty is large enough as to not significantly be affected for the difference. The way to take into account different correction terms in the measurement model function, and how to compute the corresponding uncertainty, is explained too. The influence of temperature of some pyrheliometers during calibration process and the potential impact on the DNI irradiance calculated with these instruments is exemplified. Full article

Aminophosphonate diethylenetriamine penta(methylenephosphonic acid) (DTPMP) is a scale inhibitor commonly used in several industries. DTPMP is suspected to cause anthropogenic pollution through discharge into the aquatic environment. DTPMP is assumed to be degraded by sunlight radiation. We recently predicted a preliminary degradation pathway of DTPMP applying UV treatment. Currently, we have not yet evidenced that DTPMP shows the same degradation pattern with natural sunlight. One major reason leads to the fact that the light spectrum emitted by UV lamps does not completely represent the natural sunlight spectrum, and the emitted UVB and UVA irradiation flux is much higher than for solar light. For that reason, the degradation pattern and kinetics might be different between artificial UV treatment and natural sunlight treatment. Here, we investigated whether DTPMP is degradable under natural sunlight radiation, and whether the degradation mechanisms determined through UV treatment are transferable to sunlight. We investigated five different treatment conditions, i.e., DTPMP degradation in direct or diffuse sunlight, in diffuse sunlight with addition of Ca²⁺ or Mg²⁺, and in diffuse sunlight with local TW. Our experiment was carried out from March 2021 to October 2021. We performed LC/MS analyses and measured the release of o-PO₄³⁻. DTPMP was degraded with all five treatment conditions. The fastest DTPMP degradation occurred in direct and diffuse sunlight without addition of bivalent cations. The addition of Ca²⁺ and Mg²⁺ resulted in inhibited degradation. Similar effects occurred for sunlight treatment with local TW. We evidenced different degradation mechanisms for DTPMP depending on the presence of alkaline earth metals as we previously proposed for UV-treated DTPMP. However, both degradation mechanisms of DTPMP belong to the same degradation pathway determined with UV treatment. Therefore, we conclude that DTPMP undergoes a similar degradation pathway in sunlight as compared to UV light. Full article

There is a large gap between the vast solar resources and the magnitude of solar energy deployment in Argentina. In the case of photovoltaics, the country only reached the 1000 GWh electricity generated yearly landmark in 2020. Solar thermal technology is even less developed, in part due to the low natural gas prices resulting from political strategies that aim to soften the impact of an unstable economy on family budgets. This review describes this gap by summarizing the current state of Argentine solar energy. We summarize the fundamental legal and strategic tools which are available for solar energy deployment, survey the penetration of solar energy into the country’s energy landscape, identify national contributions to the local value chain, and review past and present research and development achievements. Both photovoltaic and solar thermal technologies show a historical fluctuation between local technology development and imported technology and know-how. Finally, a discussion on the main ingredients required to abridge Argentina’s solar gap indicates that stronger, consistent long-term strategies are required in Argentina in order to take advantage of the present window of opportunity, and to play a considerable role in the global energy transition. Full article

Wind and solar renewable energy in the United States is projected to triple by 2050 to nearly 30% of total electric energy generation. The upper Midwest region (Iowa, Minnesota, and North and South Dakota in particular) is considered wind energy country and not historically known for solar energy development. In this work, Value of Solar (VOS) is developed as a photovoltaic (PV) optimization measure and analysis tool using a northwest Iowa municipality as a representative case study. By applying a top-down load duration curve system analysis, VOS is used to optimize PV orientation and compare electric rate structures for increasing levels of total PV energy contribution. VOS of a fixed south-southwest orientation exceeds the levelized annual costs of installation with a larger net benefit than a one-axis-tracking solar system. Production-data modeled VOS is up to 12% higher than Typical Meteorological Year (TMY) predictions, indicating significant correlation between PV generation and peak municipal demand. Compared to alternative time-of-use rates, a demand/energy rate structure better matches VOS economic value and optimal orientation. This VOS methodology is an easy-to-use yet meaningful tool for municipalities and smaller utilities to evaluate strategic installation of and investment in PV for their local community. Full article

The timely detection of photovoltaic (PV) system failures is important for maintaining optimal performance and lifetime reliability. A main challenge remains the lack of a unified health-state architecture for the uninterrupted monitoring and predictive performance of PV systems. To this end, existing failure detection models are strongly dependent on the availability and quality of site-specific historic data. The scope of this work is to address these fundamental challenges by presenting a health-state architecture for advanced PV system monitoring. The proposed architecture comprises of a machine learning model for PV performance modeling and accurate failure diagnosis. The predictive model is optimally trained on low amounts of on-site data using minimal features and coupled to functional routines for data quality verification, whereas the classifier is trained under an enhanced supervised learning regime. The results demonstrated high accuracies for the implemented predictive model, exhibiting normalized root mean square errors lower than 3.40% even when trained with low data shares. The classification results provided evidence that fault conditions can be detected with a sensitivity of 83.91% for synthetic power-loss events (power reduction of 5%) and of 97.99% for field-emulated failures in the test-bench PV system. Finally, this work provides insights on how to construct an accurate PV system with predictive and classification models for the timely detection of faults and uninterrupted monitoring of PV systems, regardless of historic data availability and quality. Such guidelines and insights on the development of accurate health-state architectures for PV plants can have positive implications in operation and maintenance and monitoring strategies, thus improving the system’s performance. Full article

This paper presents a measurement-based stability analysis of commercially available single-phase inverters in public low-voltage networks. In practice, manufacturers typically do not disclose the parameters of the inverter design, although interactions with the low-voltage network need to be assessed and predicted. State-of-the-art modeling methods require knowledge about the internal parameters. The method proposed in the paper is based on measurements in the laboratory and does not require detailed knowledge about the specific inverter design for the identification of the black-box linear time-periodic representation. The gained information is used for the black-box stability analysis in the frequency range up to 2 kHz, which covers the bandwidth of the control of the inverters. The method is validated for a commercially available photovoltaic inverter in the laboratory. An instability that leads to a shutdown of the inverter is demonstrated, while the critical frequency range is predicted accurately. Full article

The significance of Distributed Generators (DGs) in the technical and economic operations of electric power distribution systems cannot be overemphasized in recent times. This is essential as a result of the incessant increase in electrical energy demand, which is becoming considerably difficult to meet with the conventional means of energy supply. Thus, DGs offer better alternatives for providing a quality supply of energy near the site of consumption. This type of energy supply is cleaner and cheaper most of the time due to the lessened transmission losses, which consequently reduced the cost of operation at the transmission and distribution levels of the power system. In this work, an approach for placement and sizing of solar PV DGs into radial distribution networks (RDN) based on the solar PV capacity factor of the site was analyzed using particle swarm optimization. The aim of this study is to analyze the effect of the approach on the real and reactive power losses within the network as well as the bus voltage profile. Constraints on credible system operation parameters, which includes bus voltage limits, power balance, and power flow limits, are considered in the formulation of the optimization problem. In order to verify the viability of the deployed approach, steady-state performance analyses were executed on IEEE 33-bus RDN; and the results obtained were compared with the results from other approaches reported in the literature. Full article

In the last few years, renewable energies became more socially and economically relevant, and among them, photovoltaic systems stand out. Residential self-consumption of electricity is a field with great potential, and implementation of grid-connected photovoltaic systems (GCPS) is in full rise. The installation of distributed generation systems in residential environments could alter the performance of low-voltage distribution networks, since these are designed for unidirectional power flow and adding these generators means fluctuations in power-flows. For these reasons, a study of the fundamental magnitudes of three low-voltage distribution networks located in Madrid was made for various photovoltaic penetration rates, making use of simulations via the software OpenDSS and subsequent analysis of results. The research concludes that, among other aspects, GCPS produce load flow variations that are dependent on: the penetration rates; the distance from the point of interest and the distribution transformer, increasing the voltage variation between the most productive hours and the night hours with that distance; and on the rate between consumption and generation, so that when it diminishes, the self-sufficiency of the system increases, and with it the voltage of all the buses that tend to the rated voltage. Moreover, there are wide seasonal fluctuations: specifically, in summer months, generation profiles override consumption fluctuations, while in winter months consumption guides voltage and power profiles. Both the code implemented and the results of the analysis were published in an open source website using a free software license. Full article

Recently, reactive dyes have attracted a lot of attention for dye-sensitized solar cell applications. This study endeavors to design dye sensitizers with enhanced efficiency for photovoltaic cells by modifying the reactive blue 5 (RB 5) and reactive brown 10 (RB 10) dyes. Three different strategies were used to design the sensitizers, and their efficiency was compared using the density functional theory (DFT). The optimized geometry, bang gap values, the density of states, electrostatic potential surface analysis, and theoretical FT-IR absorption spectra of the sensitizers were obtained. In the first strategy, functional groups (electron-donating (C₂H₅), electron-withdrawing (–NO₂) groups) were anchored onto dye molecules, and their effect on the charge transport properties was evaluated using the DFT analysis. The latter two designs were based on a donor-π-acceptor strategy. The second design consisted of intramolecular donor-acceptor regions separated by a benzodithiophene-based π-spacer. In the third strategy, an external acceptor unit was attached to the dye molecules through the benzodithiophene-based π-spacer. The electron-donating strengths of donor moieties in the donor-π-acceptor systems were studied using B3LYP/6-31G level DFT calculations. The quantum chemical analysis of the three designs revealed that the anchoring of functional groups (–NO₂ and C₂H₅) on the dye molecules showed no impact on the charge transport properties. The introduction of a benzodithiophene-based π-spacer improved the conjugation of the dye sensitizers, which enhanced the electron transport properties. The electron transport properties further improved when an external acceptor unit was attached to the dye molecule containing a π-spacer. It was thus concluded that attaching an external acceptor unit to the donor dye molecule containing a π-spacer produced desired results for both of the dyes. Full article

Renewable energy sources such as photovoltaic (PV) technologies are considered to be key drivers towards climate neutrality. Thin-film PVs, and particularly copper indium gallium selenide (CIGS) technologies, will play a crucial role in the turnaround in energy policy due to their high efficiencies, high product flexibility, light weight, easy installation, lower labour-intensiveness, and lower carbon footprint when compared to silicon solar cells. Nonetheless, challenges regarding the CIGS fabrication process such as moderate reproducibility and process tolerance are still hindering a broad market penetration. Therefore, cost-efficient and easily implementable in-line process control methods are demanded that allow for identification and elimination of non-conformal cells at an early production step. As part of this work, a practical approach towards industrial in-line photoluminescence (PL) imaging as a contact-free quality inspection tool is presented. Performance parameters of 10 CIGS samples with 32 individually contacted cells each were correlated with results from PL imaging using green and red excitation light sources. The data analysis was fully automated using Python-based image processing, object detection, and non-linear regression modelling. Using the red excitation light source, the presented PL imaging and data processing approach allows for a quantitative assessment of the cell performance. Full article

In this study, recorded empirical data were applied with a practical approach to investigate the optimal tilt angle of the flat plate collectors facing south for a long period in Tehran, Iran. The data included 20 years of recorded average total radiation on the horizontal plane in Tehran’s meteorological station. Based on the previous studies, the annual optimum tilt angle for Tehran was estimated at 33 degrees annually; however, this estimation does not focus on the energy absorption and effectiveness of changing the tilt angle monthly, seasonally, and bi-annually via measured data. This paper aims to explain this distinction between various radiation receptions with different tilt angle adjustments. This study shows that annual solar cumulative radiation energy gained via a monthly tilt angle can be approximately 7% higher than that achieved with an annual tilt angle setup. Additionally, the seasonal and bi-annual tilt angles have about 6% more annual cumulative radiation absorption than the annual tilt angle setup. Moreover, with consideration of similar monthly received radiation, the results illustrate that the radiation gained with a monthly tilt angle set up was 20% greater in the summer months than an annual tilt angle adjustment. Full article

Doped ZnO are among the most attractive transparent conductive oxides for solar cells because they are relatively cheap, can be textured for light trapping, and readily produced for large-scale coatings. Here, we focus on the development of alternative Na and K-doped ZnO prepared by an easy low-cost spray pyrolysis method for conducting oxide application. To enhance the electrical properties of zinc oxide, alkali-doped Zn_1−x M_xO (x = 0.03) solid solutions were investigated. The resulting layers crystallize in a single hexagonal phase of wurtzite structure with preferred c-axis orientation along a (002) crystal plane. Dense, well attached to the substrate, homogeneous and highly transparent layers were obtained with great optical transmittance higher than 80%. The optical energy band gap of doped ZnO films increase from 3.27 to 3.29 eV by doping with Na and K, respectively. The electrical resistivity of the undoped ZnO could be decreased from 1.03 × 10⁻¹ Ω.cm to 5.64 × 10⁻² Ω.cm (K-doped) and 3.18 × 10⁻² (Na-doped), respectively. Lastly, the carrier concentrations increased from 5.17 × 10¹⁷ (undoped ZnO) to 1 × 10¹⁸ (doped ZnO). Full article