Row Of Panels Research Articles

Investigation of the cooling effect of wind on rooftop PV power plants

This study investigates the cooling of PV panels installed on the roof of a 5.9 MW power plant in Bursa, Turkey, under varying wind conditions. Meteorological measurements were conducted during the summer period to analyse the cooling effects. When wind speed differences were below 0.5 m/s, the cooling effect on the PV panels ranged between 2-3°C. However, when the wind speed differences approached 1 m/s, the cooling effect increased up to 7°C. At lower wind speeds, winds blowing from behind the panels provided better cooling, whereas side winds offered improved performance as wind speed increased. Due to the roof slope and the minimal gap between the panels and the roof, winds from behind were less effective, as they could not penetrate the back of the PV panels. Side winds, on the other hand, faced no difficulty in flowing over the panel surfaces but lost their cooling effect as they passed along the long rows of panels. These findings suggest that during the design phase of PV power plants, high wind speed locations should be prioritized, and optimal configurations should be implemented to ensure uniform wind access to all PV arrays.

Quantifying soil moisture and evapotranspiration heterogeneity within a solar farm: Implications for stormwater management

As solar energy becomes a cheap source of renewable energy, the number of major utility-scale ground solar panel installations, often called ‘solar farms,’ are growing. With these solar farms often covering hundreds of acres, there is potential for impacts on natural hydrologic processes, including runoff generation and erosion. There is still limited research in this area, and best management practices to address these impacts are variable and not well understood. To fill this gap, we conducted a field investigation of soil moisture patterns, solar radiation, and vegetation at two solar farms in central Pennsylvania, USA that are representative of the complex terrain in the region (e.g., high or variable slopes). Both solar farms also included engineered infiltration basins or trenches that were investigated. Analysis of soil moisture patterns reveals redistribution of water relative to panels, with dripline soil moisture 19 % higher than the reference, and underpanel moisture 25 % lower than the reference, on average at both solar farms over a year. There are also the greatest periods of saturation and runoff generation at the panel driplines. However, an open interspace between panel rows and existing infiltration basins and trenches are playing a critical role in managing runoff. Micrometeorological monitoring indicates reduced evapotranspiration (ET) under panels, with potential underpanel ET 37–67 % lower in summer, and minimal difference in winter. However, a survey of vegetation revealed almost complete ground coverage under panels, which is critical for supporting infiltration and reducing erosion. As solar farms expand to meet important renewable energy goals, it is essential that care be taken to design the landscape to minimize runoff generation and erosion. This work demonstrates that healthy vegetation and well-draining soils can help manage runoff on solar farms; where necessary on more challenging landscapes, engineered stormwater controls can manage any unmitigated runoff.

Stormwater runoff calculator for evaluation of low impact development practices at ground-mounted solar photovoltaic farms

Estimating runoff at ground-mounted solar photovoltaic (PV) installations is challenging because of the disconnected nature of impervious solar panels and the pervious ground surface underneath and between panel rows. There is a need for improved tools to estimate how low impact development practices at these solar installations affect stormwater runoff. The objective of this study was to develop an innovative spreadsheet-based runoff calculator that rapidly estimates stormwater runoff from ground-mounted solar PV sites. The calculator is built on a 2-D hydrologic model (Hydrus-2D/3D) calibrated and validated using experimental data from five commercial solar farms in Colorado, Georgia, Minnesota, New York, and Oregon. The Hydrus-2D/3D hydrologic model was then used to generate nomographs for stormwater runoff that were incorporated into an easy-to-use Excel-based solar farm runoff calculator. This calculator allows for rapid estimation of NRCS stormwater runoff curve number (CN) values at solar farms by considering several complex factors unique to PV installations including: soil and topographic characteristics, surface cover, disconnected impervious surface factors associated with various solar panel designs, and climatic factors. The solar farm runoff calculator quickly estimates runoff CN for pre- and post-construction scenarios, and can estimate actual depth of runoff based on a user-specified 24-h design storm depth. Factors that have the most significant impact on stormwater runoff include design storm return frequency, soil texture, soil bulk density, and soil depth. Ground surface cover has a moderate impact on stormwater runoff, and factors that have a lesser impact on stormwater runoff include slope and array size, spacing and orientation on the landscape. The runoff calculator allows for accurate estimates of runoff generated by disconnected impervious surfaces and low impact development practices at solar farms as affected by a wide range of site-specific conditions.

Carabid beetles in solar parks: assemblages under solar panels are severely impoverished compared to gaps between panel rows and edge areas

Renewable energies are a major tool to reduce greenhouse gas emissions and combat climate change. Among renewables, solar parks are a key technology and their expansion will strongly increase in the future. Hence, there is a great need for research regarding their impact on biodiversity. In this study, we investigated the importance of three solar parks in northern Germany as habitat for carabid beetles. More specifically, we determined how habitat characteristics (temperature, vegetation structure), species richness, activity densities and carabid beetle assemblages vary between different locations within solar parks: areas under solar panels “UNDR”, gaps between panel rows “BTW” and areas at the edge of solar parks “EDGE”. We found that UNDR strongly differed from BTW/EDGE in terms of habitat conditions, species richness and activity densities of carabid beetles. UNDR mainly provided habitat for a species- and individual-poor subset of species already present in BTW/EDGE and made only a small contribution to the total species richness of the investigated solar parks. BTW and EDGE, on the other hand, differed only slightly. Thus, the narrow gaps between the panel rows were of similar importance as a habitat for carabid beetles as the edge areas. Overall, the investigated solar parks—and thus also the more species-rich areas EDGE and BTW—almost exclusively provided habitat for widespread and common non-threatened generalists, while species of conservation concern were extremely rare.Implications for insect conservationThe low importance of UNDR for carabid beetles should be considered when assessing the biodiversity value of solar parks, since a large proportion of these facilities is covered with solar panels. Between panel rows and at the edge of solar parks, larger areas should be kept free from construction with solar panels in order to provide habitats for carabid beetles and other species groups. More research should be conducted on how to further improve solar parks for carabid beetles and overall biodiversity.

Challenges in the Planning, Construction and Farming Practices in Agrivoltaic Systems With Vertically Mounted Panels

Several challenges in planning, construction, and farming practices hinder the optimization of agrivoltaic systems (AS) and the achievement of optimal crop production. This paper identifies and addresses these issues while presenting initial solutions. One specific type of AS involves vertically mounted panels on arable or grassland sites. The installation of panel rows divides large fields into narrow units, restricting the use of farming implements with different working widths. Implement widths must align with the spacing between panel rows, which often results in residual strips or overlapping issues when field operations are carried out. Furthermore, boundary effects in AS are more pronounced, impacting yield along field borders. The presence of panel rows also complicates driving operations, requiring reduced speeds and posing collision risks between implements and panels. Soil compaction during AS construction, microclimate variations, and panel contamination by dust, or spray drift deposits further affect plant growth and solar system performance. Initial solutions are proposed to address these challenges. These include careful planning of row spacing based on the working widths of critical implements such as combines, adoption of field sprayers with foldable booms, consideration of pneumatic fertilizer spreaders, and integration of precision farming techniques to manage variability within AS. Additionally, the use of construction machinery with low soil pressure, employment of steering technologies based on global navigation satellite systems, and research on panel cleaning devices are suggested. Overall, this paper highlights the need for further research and development to overcome farming challenges in agrivoltaic systems with vertically mounted panels.

Polarized Light Pollution of Fixed-Tilt Photovoltaic Solar Panels Measured by Drone-Polarimetry and Its Visual-Ecological Importance

Specific polarized light pollution (PLP) means the adverse influences of strongly and horizontally polarized light reflected from smooth and dark artificial surfaces on polarotactic water-seeking aquatic insects. Typical PLP sources are photovoltaic panels. Using drone-based imaging polarimetry, in a solar panel farm, we measured the reflection-polarization patterns of fixed-tilt photovoltaic panels from the viewpoint of flying polarotactic aquatic insects, which are the most endangered targets and potential victims of such panels. We found that the temporal changes in PLP were complementary for the two orthogonal viewing directions relative to the panel rows. The estimated magnitude plp of the polarized light pollution of solar panels viewed parallel to the panel rows was the highest (primary peak plp = 49–58% after sunrise and secondary peak plp = 35–48% prior to sunset) at low solar elevations, after sunrise and at or prior to sunset, when many aquatic insect species fly and seek water bodies. On the other hand, the PLP of solar panels viewed perpendicular to the panel rows was the highest (plp = 29–35%) at the largest solar elevations, near noon, when numerous flying aquatic insect species also seek water. Solar panel farms near wetlands can, therefore, be dangerous for these insects.

Modelling the Impact of Array Wiring on Electrical Output of Vertical Bifacial Agrivoltaic Installations

We present a model and study investigating the potential power output of vertical bifacial solar panels on New Jersey farms. The simulation calculates instantaneous brightness and shading based on the position of the sun and adjacent rows of panels, and uses that to calculate current and voltage values. We explore different strategies to improve the power output further. Double-high modules, which use two panels stacked together, offer significant gains per acre with only a modest increase of inter-row shading. When bypass diodes and improved inverter wiring are also used, much of the losses due to shading are avoided, and the total power output per acre is nearly doubled. In a double high configuration it is advantageous to have the top and bottom modules on separate inverter strings.

The Capstone Design of Solar Farm for Alternative Energy

The capstone design integrates advanced technologies to optimize energy capture, storage, and transmission, addressing key challenges in traditional solar farm configurations. The study delves into the conceptualization, engineering, and performance evaluation of the proposed solar farm, emphasizing its potential for enhanced efficiency and sustainability. Additionally, the article discusses the environmental impact and economic viability of the free space solar farm, highlighting its role in advancing the transition to a more sustainable and resilient energy infrastructure. The results of this design use polycrystal type solar panels with a panel length of 1995mm and a width of 990mm which will be installed on empty land that has been provided with a land area of 80m x 40m, 50 rows of solar panels are obtained and the total energy produced before being converted into KWP with a total of 50 rows of panels is obtained 325 WP and multiplied by the total existing panels, namely 36 solar panels, the result is 11,700 WP, then converted to KWP and the result is 585 KWP for 1 day. The findings contribute valuable insights to the field of renewable energy engineering, offering a comprehensive understanding of the practical application of free space for solar energy generation.

Ecovoltaics: Maintaining Native Plants and Wash Connectivity inside a Mojave Desert Solar Facility Leads to Favorable Growing Conditions

The installation of solar facilities is increasing rapidly in the Mojave Desert USA, with the largest facility in North America (3227 ha) currently being built 30 km north of Las Vegas, NV. At the state level, Nevada (USA) has developed an energy plan to diversify its energy portfolio by 2030 with green energy representing 50% of the energy produced. Although solar is considered a clean energy, it does require significant amounts of land and as such may have negative consequences at the habitat and ecosystem levels. A multi-year study was conducted to assess the impact a photovoltaic facility in the Mojave Desert had on the growth and physiological response of two native shrubs (Ambrosia dumosa and Larrea tridentata) growing inside and outside the facility. These species were selected because they were the dominant species at the site and are representative of desert scrub communities throughout the Mojave Desert. At the time of construction, native plants and washes were left intact inside the solar facility. The solar panel arrays were separated at either 8 m or 10 m. Plants were selected for monitoring on the basis of location: at the panel drip line, below the panels, or midway between panel rows. Abiotic factors, including PAR, reference evapotranspiration, precipitation, soil water in storage, and infiltration, were monitored bi-monthly. The growth and physiological status of the plants were assessed by monitoring leaf water potential, chlorophyll index, canopy temperatures, non-structural carbohydrates in the roots and stems, leaf tissue ion concentrations, stem elongation, and seed production. Plants at the bottom edges of the panels received more precipitation due to runoff from the panels, which led to increased soil moisture in the long spacing but not the short spacing. The lower soil water in storage in the short spacing was related to greater growth and higher soil water extraction. Although the area under the panels provided shade in the summer and warmer temperatures in the winter, the incoming PAR was reduced by as much as 85%, causing plants growing under the panels to be spindly with lower canopy volume (L. tridentata, p = 0.03) and seed yield (A. dumosa, p = 0.05). Ambrosia plants remained green in color year-round (not going into winter dormancy) inside the facility and had elevated levels of starch in their roots and stems compared with plants growing at the outside control sites (p < 0.001). Larrea growing outside the facility had lower xylem water potentials compared with those inside the facility (p < 0.001), lower chlorophyll index (p < 0.001, Ambrosia as well), and lower stem elongation (p < 0.001), supporting the conclusion that both Larrea and Ambrosia performed better inside the facility. Shifts in δ13 C suggested greater water-use efficiency at the locations with the least amount of soil water in storage. Our results support the installation of solar facilities that minimize the impact on native plants and wash connectivity (ecovoltaics), which should translate into a reduced negative impact at the habitat and ecosystem levels. Basedon our results, energy companies that embrace ecovoltaic systems that take an engineering and biological approach should provide acceptable environments for desert fauna. However, corridors (buffers) will need to be maintained between solar facilities, and fences will need to have openings that allow for the continuous flow of animals and resources.

Enhancing the Efficiency of Bi-Facial Photovoltaic Panels: An Integration Approach

This work presents a novel approach to increasing the efficiency of photovoltaic (PV) panels by integrating them with a cooling tower (CT). An infusion of water cools the hot, dry ambient air at the top of the CT. Due to gravity, the cooled air drops toward the base of the CT, where it interacts with a turbine placed at the bottom of the CT to produce electricity. The air then exits the CT base, creating a cooled air jet stream. The PV panels were placed at the base of the CT, right at the stream’s exit. As the cooled air passes underneath the PV panels, it exchanges energy with the PV, reducing the panels’ temperature. The results showed that the maximum annual efficiency improvement (6.831%) was observed using two rows of PV panels. The efficiency declined incrementally from 6.831% to 4.652% when the number of rows of PV panels was increased from two to twelve. The results also showed a significant improvement in the temperature of the PV panels. The best results were obtained at noon (maximum ambient temperature), where the solar panel temperature was lowered to 25 °C from 55 °C. Furthermore, the annual electrical energy generated with two rows of panels was 39,207.4 kWh without the CT, compared to 41,768.2 kWh with the CT. In addition, the results showed that with a 10 m diameter and 200 m height CT, the maximum number of PV rows that can be effectively cooled is 24. Future work will investigate integrating additional techniques to improve the system’s efficiency further.

Can Grasslands in Photovoltaic Parks Play a Role in Conserving Soil Arthropod Biodiversity?

Under the increasing global energy demand, the new European Union Biodiversity Strategy for 2030 encourages combinations of energy production systems compatible with biodiversity conservation; however, in photovoltaic parks, panels shadowing the effects on soil health and biodiversity are still unknown. This study (location: Northern Italy) aimed to evaluate the effect of ground-mounted photovoltaic (GMPV) systems on soil arthropod biodiversity, considering two parks with different vegetation management: site 1-grassland mowed with tractor; site 2-grassland managed with sheep and donkeys. Three conditions were identified in each park: under photovoltaic panel (row), between the panel rows (inter-row), and around the photovoltaic plant (control). The soil pH and organic matter (SOM), soil arthropod community, biodiversity, and soil quality index (e.g., QBS-ar index) were characterised. Differences between the two GMPVs were mainly driven by the SOM content (higher values where grazing animals were present). No differences were observed in site 1, even if a high heterogeneity of results was observed for the soil biodiversity parameters under the panels. In site 2, SOM and pH, as well as arthropods biodiversity and QBS-ar, showed low values in the row. Soil fauna assemblages were also affected by ground-mounted panels, where Acarina, Collembola, Hymenoptera, and Hemiptera showed the lowest density in the row. This study suggests that ground-mounted solar panels had significant effects on below-ground soil fauna, and was more marked depending on the system management. Furthermore, the results obtained for the inter-row were similar to the control, suggesting that the area between the panel rows could be considered a good hotspot for soil biodiversity.

Economical sizing and multi-azimuth layout optimization of grid-connected rooftop photovoltaic systems using Mixed-Integer Programming

Solar energy is expected to be a significant contributor to meet the increasing global energy demand. Rooftop photovoltaic (PV) systems account for a substantial portion of the global solar energy potential. However, optimizing the size and layout of these systems remains challenging. Existing approaches either focus on maximizing energy generation, heavily restrict the space of potential layouts, ignore inverter-type implications, or neglect practical aspects, such as minimizing self-shading. This paper presents a mixed-integer programming (MIP) model to address these limitations for PV systems installed on flat rooftops. The proposed model optimizes the net present value (NPV) and can produce multi-azimuth layouts while accounting for practical considerations, including mitigating self-shading, and ensuring rooftop walkability. The proposed model is adapted for systems that utilize micro-inverters or string-inverters. Two case studies are conducted to evaluate the performance of the proposed model. In one case study, the model is applied to a residential area. It is numerically shown that in some instances of capital costs and billing policies, the use of multi-azimuth layouts could significantly improve the NPV compared to the use of single-azimuth layouts with parallel rows of panels. The proposed model solutions are compared to an existing optimized installation in the second case study. The proposed model multi-azimuth layout solution improves the NPV by 10.17%. When restricted to single-azimuth layouts, the proposed model produces the same design as that of the existing installation in only a few seconds.

The Impact of Selected Parameters on the efficiency of PV Installations - Simulation Test of the 1 MW PV Farm in the PVSyst Program

Abstract Nowadays, more and more solar farms are being created in Poland. This is due to the development of PV technology, the appearance of more efficient systems on the market, but also the need for Poland to achieve a 50% share of energy production from zero-emission sources. In designing PV farms, an important issue is the selection of the right angle, but also the distance between individual rows of panels. The article shows the work analysis of the 1 MW PV farm consisting of 2000 units of 500 Wp panels with dimensions of 2220 mm x 1108 mm x 40 mm and a weight of 28.60 kg and 8 inverters SUN2000-105KTL-H1. The panels are arranged in 10 rows in two directions: south and south-west. The analysis was performed for the angles of 10°, 20°, 25° and 30°. The investigation was carried out in order to evaluate the effect of changing the angle of the panels and the distance between the rows on the PV farm efficiency.

Floating photovoltaics performance simulation approach

Floating photovoltaics (FPVs) provide various benefits especially where land is scarce (e.g., reducing land occupancy, water evaporation and environment control…), or when they are combined with hydropower plants (enhanced capacity factor and green energy generation). Software such as PV∗SOL, SAM and PVSyst® are commonly used for the design and simulation of land-based photovoltaic (PV) systems. However, when it comes to the simulation of photovoltaics installed on water surface, such software does not offer the option to directly simulate FPV systems.In this work, a new approach combining MATLAB and Rhino/Grasshopper environments is proposed for the assessment of FPV systems performance. The approach is divided into various steps considering major influencing parameters such as temperature, irradiance, albedo, PV modelling, panel rows spacing, tilt angle, as well as the benefits of including a tracking mechanism. The proposed approach was validated against PV∗SOL simulations for land-based PV systems with a small deviation of less than 2.4%. FPVs simulations considering climatic conditions of Štěchovice, Czechia, showed an increase of the performance in the range of 3% compared to terrestrial PVs. This result is in accordance with some published studies based on real FPVs installations. Finally, the developed approach was applied in the simulations of two large-scale FPV systems with different designs (fixed and with a tracking mechanism) including economical aspects.

Minimizing environmental impacts of solar farms: a review of current science on landscape hydrology and guidance on stormwater management

Abstract As solar energy becomes an increasingly cheap source of renewable energy, major utility-scale ground solar panel installations, often called ‘solar farms’, are rapidly growing. With these solar farms often covering hundreds of acres, there is the potential for impacts on natural hydrologic processes, including runoff generation and erosion. Here we review the current state of scientific research on the hydrology and water quality impacts of solar farms, as well as management recommendations for minimizing any impacts. The limited field measurements indicate the redistribution of soil moisture around solar farms, but the net impacts on runoff and erosion are less clear. Research focused on coupling solar farms with agriculture as ‘agrivoltaics’ demonstrates reduced evaporative water losses and associated crop stress, particularly in more arid regions. With regards to land and the stormwater management associated with solar farms, most US states currently do not have solar farm-specific recommendations and instead defer to standard stormwater management permits and guidance. In states with solar farm-specific guidance, typical recommendations include minimizing construction-related compaction, ensuring a high cover of perennial vegetation with minimal maintenance, and designing with pervious space between solar panel rows to promote infiltration of any runoff; in some cases, structural stormwater management like infiltration basins may be required. In general, solar farms can be designed to minimize the impact on landscape ecohydrological processes, but more research is needed to determine whether current recommendations are adequate. In particular, there is a need for more field research on less ideal sites such as those with higher slopes.

Effects of wind loads on the solar panel array of a floating photovoltaic system – Experimental study and economic analysis

Floating photovoltaic systems have been installed around the world as solar energy is powerful renewable energy source, but they can sink or overturn depending on harsh environmental conditions. Analyzing the wind load on a solar panel array is important for designing an appropriate supporting structure for floating photovoltaic systems. In this study, the local pressure distributions on a solar panel array were experimentally measured and economic analysis was conducted for reduced manufacturing cost. The results showed that the first and last rows of panels had the highest drag and lift coefficients because they were the first to encounter the wind. The drag and lift coefficients gradually decreased in subsequent rows because of the sheltering effect. When the wind flowed from the side, the leftmost and rightmost columns provided a sheltering effect, which reduced the drag and lift coefficients for the center of the solar panel array by 45%–86%. From these results, the middle regions of floating bodies could be changed to the lower-cost materials which showed the 19% reduced manufacturing costs for 2.5 MW system (20 × 30). If the size of the floating PV system increases further, many floating bodies could be changed to lower-cost materials which will be more economical.

A Study on a Floating Solar Energy System Applied in an Intertidal Zone

This study was aimed at investigating a floating solar photovoltaic (FPV) system by numerical and experimental simulations under wave and wind loads to analyze the motion characteristics of the platform, the tension of the mooring line, and the pressure and uplift coefficient of panels at 2.5 m/5 m water depth conditions. The floating platform was installed with four rows of solar panels, each row with five panels, attached with four catenary types of mooring lines at the corner of the platform. The numerical model was based on ANSYS AQWA and ANSYS FLUENT (ANSYS Inc., Canonsburg, PA, USA). The experiment model was a scaled FPV platform with four rows of panels scaled in the 1:4 scale ratio. The results obtained from the experiment and numerical simulation achieved a good agreement. The results show that under normal sea conditions, the FPV system may resonate in a high frequency of wave condition, and a larger lift force occurred at the windward surface. Under extreme sea conditions, the pitch motion of the floating platform changed about ±6° without overturning; however, the wind will cause a large drift of the floating platform and the vortex area formed, which will cause damage to the solar panel.

Određivanje optimalnih nagibnih uglova fotonaponskih panela uz uvažavanje smanjenja direktne komponente iradijacije usled efekata senki u fotonaponskim sistemima

This paper considers the influence of the tilt angle of photovoltaic (PV) panels on the total amount of insolation on the surface of these panels on a monthly and annual basis, with and without consideration of shading effect. Based on the obtained results, optimal tilt angles of the PV panels in order to achieve maximum insolation, are determined, as well as the optimal tilt angles for achieving maximum generated electrical energy, taking into account the temperature of the panel. Special attention in the paper is paid to the shading effect created by the panel rows within the PV system and its influence on the reduction of direct component of irradiation and optimal tilt angles for different distances between PV panel rows. In the paper two different models for solar insolation calculation were considered and described in detail, clear day model and real cloud condition model. In order to obtain the average daily solar irradiation on the inclined surface, in addition to appropriate extraterrestrial irradiations, available measurements of the irradiation on the horizontal surface during one year period were used.

Spatial-Temporal Shading Under Mobile & Fixed Tilt Bifacial Agrivoltaic Panels & Implications for the Cropping Practices

Spatial and temporal behavior of the incident sunlight can have important implications for agrivoltaic (AV) crop yield. We explore the daily and monthly variations of the photosynthetically active radiation (PAR) under various tracking and fixed-tilt agrivoltaic solar panels and propose strategies to minimize the shade-induced crop yield loss. Vertically installed solar panels facing East/West provide the best spatial homogeneity and a higher intensity of net daily incident PAR, while North/South faced fixed tilt panels result in a high spatial contrast, i.e., a significantly lower PAR underneath the panels as compared to the spacing between the adjacent panel rows. The shading behavior for the horizontal single axis tracking panels shows a seasonal dependence, a higher shading below the panels during winters and vice versa for summers. The spatial variation in the crop yield correlates well with that of the net daily PAR pattern in the case of the shade sensitive crops (e.g., tomato) while the spatial yield for the shade tolerant crops (e.g., lettuce) is less affected by PAR variations. We propose an intercropping approach using crops with high and low shade sensitivity to minimize the biomass loss related to PAR heterogeneity and present lettuce/tomato intercropping schemes under various agrivoltaic configurations

Author Correction: Tuning of catalytic sites in Pt/TiO2 catalysts for the chemoselective hydrogenation of 3-nitrostyrene

Correction to: Nature Catalysis https://doi.org/10.1038/s41929-019-0334-3, published online 16 September 2019. In the version of this Article originally published, the Fig. 3 panels were mislabelled and the mean particle size in Fig. 3e, which is now labelled Fig. 3b, was incorrectly given as ‘1.2 nm’. From left to right, the top row of panels should have been labelled a, c, e and g and the bottom row of panels should have been labelled b, d, f and h. The mean particle size in Fig. 3b should have been ‘1.0 nm’. This has been corrected in the online versions of this Article.