Position Of Sun Research Articles

Made-to-measure modelling of observed galaxy dynamics

Among dynamical modeling techniques, the made-to-measure (M2M) method for modeling steady-state systems is among the most flexible, allowing non-parametric distribution functions in complex gravitational potentials to be modeled efficiently using N-body particles. Here we propose and test various improvements to the standard M2M method for modeling observed data, illustrated using the simple setup of a one-dimensional harmonic oscillator. We demonstrate that nuisance parameters describing the modeled system's orientation with respect to the observer---e.g., an external galaxy's inclination or the Sun's position in the Milky Way---as well as the parameters of an external gravitational field can be optimized simultaneously with the particle weights. We develop a method for sampling from the high-dimensional uncertainty distribution of the particle weights. We combine this in a Gibbs sampler with samplers for the nuisance and potential parameters to explore the uncertainty distribution of the full set of parameters. We illustrate our M2M improvements by modeling the vertical density and kinematics of F-type stars in Gaia DR1. The novel M2M method proposed here allows full probabilistic modeling of steady-state dynamical systems, allowing uncertainties on the non-parametric distribution function and on nuisance parameters to be taken into account when constraining the dark and baryonic masses of stellar systems.

Accuracy of the hypothetical sky-polarimetric Viking navigation versus sky conditions: revealing solar elevations and cloudinesses favourable for this navigationmethod.

According to Thorkild Ramskou's theory proposed in 1967, under overcast and foggy skies, Viking seafarers might have used skylight polarization analysed with special crystals called sunstones to determine the position of the invisible Sun. After finding the occluded Sun with sunstones, its elevation angle had to be measured and its shadow had to be projected onto the horizontal surface of a sun compass. According to Ramskou's theory, these sunstones might have been birefringent calcite or dichroic cordierite or tourmaline crystals working as polarizers. It has frequently been claimed that this method might have been suitable for navigation even in cloudy weather. This hypothesis has been accepted and frequently cited for decades without any experimental support. In this work, we determined the accuracy of this hypothetical sky-polarimetric Viking navigation for 1080 different sky situations characterized by solar elevation θ and cloudiness ρ, the sky polarization patterns of which were measured by full-sky imaging polarimetry. We used the earlier measured uncertainty functions of the navigation steps 1, 2 and 3 for calcite, cordierite and tourmaline sunstone crystals, respectively, and the newly measured uncertainty function of step 4 presented here. As a result, we revealed the meteorological conditions under which Vikings could have used this hypothetical navigation method. We determined the solar elevations at which the navigation uncertainties are minimal at summer solstice and spring equinox for all three sunstone types. On average, calcite sunstone ensures a more accurate sky-polarimetric navigation than tourmaline and cordierite. However, in some special cases (generally at 35° ≤ θ ≤ 40°, 1 okta ≤ ρ ≤ 6 oktas for summer solstice, and at 20° ≤ θ ≤ 25°, 0 okta ≤ ρ ≤ 4 oktas for spring equinox), the use of tourmaline and cordierite results in smaller navigation uncertainties than that of calcite. Generally, under clear or less cloudy skies, the sky-polarimetric navigation is more accurate, but at low solar elevations its accuracy remains relatively large even at high cloudiness. For a given ρ, the absolute value of averaged peak North uncertainties dramatically decreases with increasing θ until the sign (±) change of these uncertainties. For a given θ, this absolute value can either decrease or increase with increasing ρ. The most advantageous sky situations for this navigation method are at summer solstice when the solar elevation and cloudiness are 35° ≤ θ ≤ 40° and 2 oktas ≤ ρ ≤ 3 oktas.

Energetic analysis of simplified 2-position and 3-position North-South horizontal single-axis sun tracking concepts

Sun trackers allow the energy yield of photovoltaic systems to be increased. Among the different types of sun tracking strategies, North-South horizontal single-axis sun trackers are of big interest nowadays, especially for their implementation in utility-scale photovoltaic plants. It is important to find concepts which simplify as much as possible these sun trackers. In this paper, an energetic analysis of two very simple tracking strategies, based on a 2-position or 3-position rotatory movement for the North-South horizontal single-axis tracker, is carried out for latitudes up to 50°. The tracker positions (morning/afternoon for 2-positions, or morning/noon/afternoon for 3-positions) change at pre-defined daily schedules and the tilt angle at the morning and afternoon periods is fixed. However, both the daily schedules and the tilt angles can be adjusted in the installation process, to maximize the annual irradiation capture in a given location. Such simple tracking concepts can be implemented without the need of illumination sensors, complex sun position calculations or continuous control of the motion. The energetic analysis was carried out over a set of 22 locations worldwide and the captured irradiation was compared to that of equator-pointed optimally tilted fixed systems and to that of the best energetically efficient North-South horizontal single-axis tracker, i.e. the continuous sun tracker. Results indicate that, depending on the analysed location, the 2-position tracker can provide between 41% and 74%, and the 3-position tracker can provide between 68% and 87% of the annual irradiation gains that the North-South horizontal single-axis continuous sun tracker achieves with respect to an optimally tilted fixed system. Therefore, these types of simplified tracking concepts, especially the 3-position tracker, can be seen asalternatives to existing North-South horizontal single-axis continuous sun trackers, providing significant energy gains with respect to fixed photovoltaic systems.

Direction indicator and magnetic compass-aided tracking of the sun by flamingos?

Abstract. Animals use to align their body axis with respect to different cues (e.g. sun position, wind direction, magnetic field lines) and signals (informing about source of interest) in diverse behavioural contexts. Existence of alignment indicates ability to sense such cues or signals and its study can enlighten the mechanism of their sensing. Global cues (sun position, magnetic field) might provide a directional reference (direction/heading indicator) for organization of the mental map and/or for coordinated take-off. The existence of a common direction indicator may be of importance especially in birds living in large colonies and having impeded maneuverability. We measured the direction of the body axis (alignment) in flamingos of four species at 18 localities in zoological gardens and in the wild in altogether eight countries during different seasons of the year and at different times of the day. The measurements were taken from photographs in a blinded way. Flamingos in Europe showed a significant...

A Solar Position Sensor Based on Image Vision.

Solar collector technologies operate with better performance when the Sun beam direction is normal to the capturing surface, and for that to happen despite the relative movement of the Sun, solar tracking systems are used, therefore, there are rules and standards that need minimum accuracy for these tracking systems to be used in solar collectors’ evaluation. Obtaining accuracy is not an easy job, hence in this document the design, construction and characterization of a sensor based on a visual system that finds the relative azimuth error and height of the solar surface of interest, is presented. With these characteristics, the sensor can be used as a reference in control systems and their evaluation. The proposed sensor is based on a microcontroller with a real-time clock, inertial measurement sensors, geolocation and a vision sensor, that obtains the angle of incidence from the sunrays’ direction as well as the tilt and sensor position. The sensor’s characterization proved how a measurement of a focus error or a Sun position can be made, with an accuracy of 0.0426° and an uncertainty of 0.986%, which can be modified to reach an accuracy under 0.01°. The validation of this sensor was determined showing the focus error on one of the best commercial solar tracking systems, a Kipp & Zonen SOLYS 2. To conclude, the solar tracking sensor based on a vision system meets the Sun detection requirements and components that meet the accuracy conditions to be used in solar tracking systems and their evaluation or, as a tracking and orientation tool, on photovoltaic installations and solar collectors.

Optimal fixed reconfiguration scheme for PV arrays power enhancement under mutual shading conditions

Mutual shading (MS) in photovoltaic (PV) plants occurs when a collector is shadowed by the front row of collectors. The prevention of MS is considered in designing of the PV plants (PVPs). Perforce, this can be ignored in places with low maximum Sun elevation angle during some days and rows spacing limitations. In MS conditions, the reduction in energy and increase in the payback time of PV systems occur. In this study, a new optimal fixed reconfiguration scheme is presented for minimising of the MS effects. In this scheme, the physical locations of modules in a total cross-tied (TCT) PV array are rearranged without altering the electrical interconnections. The presented scheme is able to minimise the MS effects independently from all shading parameters such as Sun position in the sky, latitude of PVP, and PV installation features. For this purpose, the MS pattern is initially determined and its features are explained. Then, an optimal physical arrangement is determined based on the aforementioned pattern. Minimisation of the resistance losses is also considered in the presented reconfiguration. Finally, the comparison of the optimal arrangement with the simple TCT and Sudoku arrangements is given in different conditions.

Evaluating models of shortwave radiation below Eucalyptus canopies in SE Australia

In this study we examine the performance of four models that simulate radiation under forest canopies. The models are different in terms of how transmittance of radiation is conceptualised and the data sources used to obtain parameters. Two models (PAIMS and PAINC models) use plant area index (PAI) to represent transmission. A third model (PL model) represents transmission as a function of the path length (L) of a directional beam as it crosses the canopy. The fourth model (LPI model) is based on a light penetration index obtained directly from lidar. The PAIMS and PL models were calibrated using 6 months of radiation data at 4 independent sites. The LPI and PAINC models are uncalibrated. Performance was assessed using sub-daily and daily radiation measurements during summer (December–March) at 10 sites in forests ranging from open dry forests (PAI=1.6) to tall temperate forests (PAI=4.6). Mean annual precipitation ranged from 760 to 1750mm across the domain. The PL model with a calibrated extinction coefficient (k2=0.033) was the most accurate model within sites (R-square=0.32–0.89 for sub-daily radiation) and across all sites (R-square=0.82 for daily and sub-daily radiation). The LPI model performed well at most sites, but displayed some systematic bias in dense forests resulting in lower performance (R-square=0.61 across all sites) while PAINC was negatively biased and a poor predictor across all sites (overall R-square=0). The PAIMS model, with a calibrated extinction coefficient (k1=0.48), produced good results, but inspection of sub-daily radiation patterns show that the model tends to underestimate (overestimate) sub-canopy radiation during times of high (low) radiation. This is because transmittance is highest when the sun elevation is high (i.e. short path length), resulting in sub-canopy radiation that varies non-linearly with the intensity of above canopy radiation. Models that explicitly include path length in the transmission term therefore provide more flexibility for capturing sub-daily, seasonal and latitudinal variation due to sun position and vegetation structure. Other advantages of the path length approach include i) simple parameterisation using tree height as input and ii) explicit representation of diffuse and direct radiation, which can be important when accounting for terrain-effects on energy balance at the forest floor. We therefore recommend path length based modelling approaches for investigating hydrological processes below the canopy in temperate Eucalyptus forests.

Daylight And Seating Preference In Open-Plan Library Spaces

Daylight factor has long been the predominant metric to evaluate daylight performance. Recently, the profession has moved toward annual dynamic daylight metrics such as useful daylight illuminance and daylight autonomy, which are based on absolute values of time varying daylight illuminance for a period of full year. As opposed to static daylight metrics that only concentrate on individual sky conditions, such as the widely used daylight factor, these metrics provide a more comprehensive way to measure illuminance for a wide range of sun positions and sky conditions. Although there is a growing consensus assigning importance to dynamic daylight metrics, there is no common understanding of how to integrate the preference and behaviour of building occupants in assessing the applicability of these metrics. In fact, it is when these occupancy observations and quantitative measurements are taken together that the importance of daylight performance metrics is fully realized. This study seeks to investigate the extent to which the influence of daylight on behaviour can be predicted, and for this the behaviour investigated is seating preferences of occupants in open plan, hot-desking spaces in two university libraries in Sheffield: Western Bank Library and the Information Commons. The results suggest that the association between daylight and seat choice may not be strong, and that any effect is better associated with daylight factor than with useful daylight illuminance or daylight autonomy.

Design of novel hybrid control solar tracking system

This paper describes a hybrid control solar tracking system consisted of sunlight gathering platform, mechanical structure and MCU controller system which is mainly based on time and light dependent resistors module. An adaptive calibration and operating algorithm are proposed to solve accumulated error for inaccuracy sun position model and servo system error of single axis solar tracking system, which can make the focused sunlight matching the solar evacuated tube well. The proposed system and algorithm effectively will improve the utilization of solar energy.

THE UTILIZATION OF LANDSAT 8 FOR MAPPING THE SURFACE WATERS TEMPERATURE OF GRUPUK BAY - WEST NUSA TENGGARA: WITH IMPLICATIONS FOR SEAWEEDS CULTIVATION

Locating a suitable site is the key to success in cultivating seaweed, as it is becomes one of the coastal and marine prospects for improving the national economy. Numerous factors such as water movement, substratum, depth, salinity, light intensity, surface water temperature, influence the growth of this aquatic plant, and should be considered while choosing a farming area. One of key parameters on studying sea water conditions is surface temperature distribution, as changes on temperature effecting physical, chemical, and biological condition of the sea water. Surface waters temperature is affected by radiation, and sun position, geographic, seasons, overcast, interaction process between air and waters, evaporation level, and wind blowing. It's rarely easy job to measure surface waters temperature, because often, researcher has to deal with strong winds and high waves. The objectives of this research is to do surface waters temperature mapping of Grupuk Bay – West Nusa Tenggara, using thermal infrared channel of Landsat8 data, which is supported by field observation data. Surface temperature measurement is conducted through field survey in conjunction with Landsat 8 orbit. Surface temperature calculation is carried out by using certain method issued by United States Geological Survey (USGS, 2013). Calculation result on Grupuk Bay's water surface temperature shows that it ranges from 28.00 to 30.00oC, while field survey result shows that it ranges from 28.27 to 29.69oC. This research shows that sea surface temperature measurement result based on Landsat8 data has nearly identical range with field survey result.

Mathematical study of the movement of solar tracking systems based on rational models

This paper presents the analytical deduction of generic and unified equations of the movement of solar tracking systems. These equations reproduce published equations, which only consider the sun position, or the equations of the astronomical movement. As a novelty, these equations are more generic, thus allowing the optimization of the positioning of PV installations where diffuse and reflected irradiance are usable. The analysis of the results obtained criticizes the axiomatic idea – widely considered by numerous authors – establishing that the ideal tracking system in PV installations is that tracker providing the best possible alignment with direct sunbeams.

Static concentrator photovoltaics for automotive applications

This research investigated the benefits of utilizing solar power as an energy source for future passenger vehicles and an innovative static concentrator photovoltaic module for practical automotive applications. Due to strict emissions standards, alternative energy sources must be found for vehicles in the future. It was estimated that replacing all passenger vehicles with hybrid vehicles (HVs) equipped with an 800W rated-power solar module that generates an average output of 1.8kWh/day would reduce CO2 emissions by 63% in Japan. To confirm the validity of this estimation, a test vehicle was created by installing a 6.8m2 solar module onto a commercially available plug-in HV. An average power generation of 2.1kWh/day was obtained by this solar module over 100days under real-world conditions, which was larger than the power required to achieve the estimated CO2 emissions reduction. In addition, an innovative static low-concentrator with III–V cells was studied to help reduce the installation area of the solar module on the vehicles, which is essential for practical passenger vehicles. A new concentrator design method was proposed that can be easily integrated into a standard vehicle design procedure by utilizing numerical optimization in a CAD-friendly environment. Both design equations and a design example are discussed in this paper. The proposed lens design (asymmetric-aspheric type) can expand the acceptance incident angle of solar light and increase the annual energy yield of a solar panel, while maintaining the essential thin structure for automotive applications. In spite of the wide range of sun positions, this asymmetric-aspherical lens can maintaining stable illumination on the cell while suppressing the maximum spot intensity to 20×.

Design and Analysis of Steady State Thermal Physical Model for Communication Base Station

This article theory is based on steady-state heat transfer. According to the positional relationship between Communications base stations and the position of sun, it is calculated by solar radiation intensity and its integrated temperature generated design. Also, Communications base on stations steady-state thermal physical model. The measured data independent Communications base stations building envelope, the internal temperature of the base station communications equipment and other total heat input model, we can simulate the temperature data communication within the base station. The model established for communication base station enclosure structure optimization design, simulation and prediction, performance evaluation and base station auxiliary energy saving equipment research provides convenient and practical and reliable simulation platform.

Spontaneous magnetic alignment behaviour in free-living lizards.

Several species of vertebrates exhibit spontaneous longitudinal body axis alignment relative to the Earth's magnetic field (i.e., magnetic alignment) while they are performing different behavioural tasks. Since magnetoreception is still not fully understood, studying magnetic alignment provides evidence for magnetoreception and broadens current knowledge of magnetic sense in animals. Furthermore, magnetic alignment widens the roles of magnetic sensitivity in animals and may contribute to shed new light on magnetoreception. In this context, spontaneous alignment in two species of lacertid lizards (Podarcis muralis and Podarcis lilfordi) during basking periods was monitored. Alignments in 255 P. muralis and 456 P. lilfordi were measured over a 5-year period. The possible influence of the sun's position (i.e., altitude and azimuth) and geomagnetic field values corresponding to the moment in which a particular lizard was observed on lizards' body axis orientation was evaluated. Both species exhibited a highly significant bimodal orientation along the north-northeast and south-southwest magnetic axis. The evidence from this study suggests that free-living lacertid lizards exhibit magnetic alignment behaviour, since their body alignments cannot be explained by an effect of the sun's position. On the contrary, lizard orientations were significantly correlated with geomagnetic field values at the time of each observation. We suggest that this behaviour might provide lizards with a constant directional reference while they are sun basking. This directional reference might improve their mental map of space to accomplish efficient escape behaviour. This study is the first to provide spontaneous magnetic alignment behaviour in free-living reptiles.

A Context-Aware Method for Authentically Simulating Outdoors Shadows for Mobile Augmented Reality.

Visual coherence between virtual and real objects is a major issue in creating convincing augmented reality (AR) applications. To achieve this seamless integration, actual light conditions must be determined in real time to ensure that virtual objects are correctly illuminated and cast consistent shadows. In this paper, we propose a novel method to estimate daylight illumination and use this information in outdoor AR applications to render virtual objects with coherent shadows. The illumination parameters are acquired in real time from context-aware live sensor data. The method works under unprepared natural conditions. We also present a novel and rapid implementation of a state-of-the-art skylight model, from which the illumination parameters are derived. The Sun's position is calculated based on the user location and time of day, with the relative rotational differences estimated from a gyroscope, compass and accelerometer. The results illustrated that our method can generate visually credible AR scenes with consistent shadows rendered from recovered illumination.

Constraining the thin disc initial mass function using Galactic classical Cepheids

Context: The Initial Mass Function (IMF) plays a crucial role on galaxy evolution and its implications on star formation theory make it a milestone for the next decade. It is in the intermediate and high mass ranges where the uncertainties of the IMF are larger. This is a major subject of debate and analysis both for Galactic and extragalactic science. Aims: Our goal is to constrain the IMF of the Galactic thin disc population using both Galactic Classical Cepheids and Tycho-2 data. Methods: For the first time the Besan\c{c}on Galaxy Model (BGM) has been used to characterise the Galactic population of the Classical Cepheids. We have modified the age configuration in the youngest populations of the BGM thin disc model to avoid artificial discontinuities in the age distribution of the simulated Cepheids. Three statistical methods, optimized for different mass ranges, have been developed and applied to search for the best IMF that fits the observations. This strategy allows us to quantify variations in the Star Formation History (SFH), the stellar density at Sun position and the thin disc radial scale length. A rigorous treatment of unresolved multiple stellar systems has been undertaken adopting a spatial resolution according to the catalogues used. Results: For intermediate masses, our study favours a composite field-star IMF slope of $\alpha=3.2$ for the local thin disc, excluding flatter values such as the Salpeter IMF ($\alpha=2.35$). Moreover, a constant Star Formation History is definitively excluded, the three statistical methods considered here show that it is inconsistent with the observational data. Conclusions: Using field stars and Galactic Classical Cepheids, we have found, above $1M_\odot$, an IMF steeper than the canonical stellar IMF of associations and young clusters. This result is consistent with the predictions of the Integrated Galactic IMF.

Proposal and analysis of different methodologies for the shading and blocking efficiency in central receivers systems

Nowadays, there are many simulation codes aimed at the simulation of the solar field performance and the optimization of the layout of central receivers systems. These codes should obtain fast and accurately the different efficiency factors of the solar field at different sun positions (representative of the yearly operation). Among these factors, the shading and blocking efficiency is maybe the most demanding one regarding the computational effort.In this paper four non-conventional methodologies are presented for the calculation of the shading and blocking efficiency. The codes have been developed with the ambition of decreasing the computational time without a significant accuracy drop. For that reason, they are suitable for optimization tools. Additionally, a new methodology for the determination of the subset of heliostats with potential for shading or blocking is presented.The performance of the methodologies is evaluated by means of a study of the errors and computational times, which are compared to those reached by a conventional Monte-Carlo ray tracing reference simulation. Results indicate that the proposed methodologies, particularly two of them, present good accuracy and a significant decrease of the computational time. The causes of the main errors of each methodology are also discussed.

Celestial polarization patterns sufficient for Viking navigation with the naked eye: detectability of Haidinger's brushes on the sky versus meteorological conditions.

If a human looks at the clear blue sky from which light with high enough degree of polarization d originates, an 8-shaped bowtie-like figure, the yellow Haidinger's brush can be perceived, the long axis of which points towards the sun. A band of high d arcs across the sky at 90° from the sun. A person can pick two points on that band, observe the yellow brushes and triangulate the position of the sun based on the orientation of the two observed brushes. This method has been suggested to have been used on the open sea by Viking navigators to determine the position of the invisible sun occluded by cloud or fog. Furthermore, Haidinger's brushes can also be used to locate the sun when it is below the horizon or occluded by objects on the horizon. To determine the position of the sun using the celestial polarization pattern, the d of the portion of the sky used must be greater than the viewer's degree of polarization threshold d* for perception of Haidinger's brushes. We studied under which sky conditions the prerequisite d > d* is satisfied. Using full-sky imaging polarimetry, we measured the d-pattern of skylight in the blue (450 nm) spectral range for 1296 different meteorological conditions with different solar elevation angles θ and per cent cloud cover ρ. From the measured d-patterns of a given sky we determined the proportion P of the sky for which d > d*. We obtained that P is the largest at low solar elevations θ ≈ 0° and under totally or nearly clear skies with cloud coverage ρ = 0%, when the sun's position is already easily determined. If the sun is below the horizon (−5° ≤ θ < 0°) during twilight, P = 76.17 ± 4.18% for under clear sky conditions. Consequently, the sky-polarimetric Viking navigation based on Haidinger's brushes is most useful after sunset and prior to sunrise, when the sun is not visible and large sky regions are bright, clear and polarized enough for perception of Haidinger's brushes.

Effects of wind, ambient temperature and sun position on damselfly flight activity and perch orientation

Many animals rely on movement for survival and reproduction. Directed movements incur metabolic costs, however, and animals adjust their behaviour to optimize energy expenditures in different abiotic conditions. Physical flows and solar radiation vary over time and space and influence animal behaviour at multiple spatiotemporal scales. Here, I quantify the effects of wind speed, wind direction, ambient temperature and sun position on the fine-scale movement ecology and perch orientation of a widespread damselfly, Enallagma doubledayi. Through field observations, I found that damselflies fly, forage and engage competitors in territorial interactions more often in calm rather than windy conditions. Furthermore, perched damselflies exhibit rheotaxis, in which individuals typically face into the wind, presumably to minimize biomechanical costs associated with drag and possibly to detect inbound prey on the water surface and in the air column. In contrast, ambient temperature and the position of the sun were largely unassociated with activity levels and damselfly orientation. At higher ambient temperatures, however, perched odonates faced the sun with increasing consistency, perhaps to thermoregulate by minimizing exposure to solar radiation. Taken together, these findings suggest that damselflies preferentially fly when the ratio of animal speed to wind speed is high and adjust their perch orientation to minimize energy loss. These findings strengthen conceptual links between activity budgets and perch orientation strategies among animals in variable abiotic conditions.

Solar photoreactor design by the photon path length and optimization of the radiant field in a TiO2-based CPC reactor

The photon path length inside the radiant field of a photocatalytic solar reactor (with a compound parabolic collector (CPC)) crossing a slurry fluid with suspended particles of TiO2 was studied. The modeling included three sub-models: a ray-tracing algorithm to determine the boundary conditions in the absorber wall, a boundary layer to calculate the path length of the photon before its extinction and finally, the six-flux scattering-absorption model (SFM) to estimate the absorbed energy profiles. A simple expression for the average of the local volumetric rate of photon absorption (LVRPA) in terms of a reference state was proposed.The recent concept of a radiant boundary layer was extended to CPC reactors, and a new calculation of the photon path length is proposed. We found that a catalyst load higher than the optimum value leads to a shorter photon path length causing a dark zone within the absorber where the catalyst activation does not occur. Optimal conditions for six different commercial TiO2 catalysts were determined. The best catalysts are the Fluka and Fischer catalysts, with 20% of radiant energy absorption over the total irradiated energy. The efficiency is independent of the diameter if the optimal catalyst load is guaranteed. The load-diameter optimal pairs share an absorber optical thickness (τa,opt=13.18 for the Degussa catalyst), which can be used to scale-up the reactor. The path length at maximum photon absorption was 3/4 of the absorber diameter. Reactor diameters of 1–5 cm had optimum catalyst loads of 230–46mg/l. The turbulent regime favors 〈LVRPA〉. The angle between the normal axis to the reactor surface and the sun position may vary up to 10° with minor losses of up to 0.5%.