Optimizing reflector orientation for a solar panel at various latitudes

Contributors[edit | edit source]

S. Novia Berriel Anup Nair

Intro[edit | edit source]

The angle of incidence of solar rays is different at different latitudes. Therefore, using the same angle of inclination for concentrators will not help in acquiring best solar energy capture. What we aim to do in this project is obtain the optimal positioning of concentrators for 6 cases of latitude ranging from 10-60 degrees with an increment of 10 degrees. For each of the latitude cases, we will consider 9 inclination angles of the PV panels ranging from 0-90 degrees with an increment of 15 degrees and test the position of concentrators aiming to obtain best energy yield. We will simulate 6 angles for the concentrators ranging from 10-60 degrees with 10 degrees increment to find the optimal solution. We ultimately want to generate a thumb of rule from this experiment.

Searches[edit | edit source]

Google Scholar:

• low concentration solar reflectors
• pv reflector for shaded panels
• planar reflector for shaded solar panel
• booster reflector

Web of Science:

• (pv OR solar) AND planar AND reflector

IEEE Xplore:

• (pv OR solar) AND reflector

Literature Review[edit | edit source]

The papers reviewed for the completion of this project have been listed below in chronological order of publication. Included are brief summaries of each.

Enhanced solar energy collection using reflector-solar thermal collector combinations - 1975^[1][edit | edit source]

Abstract - The amount of direct light gathered by a combination of reflector plus flat-plate collector has been analyzed. The calculations were done allowing variable reflector and collector orientation angles, variables latitude, and arbitrary sun hour angle away from solar noon. The effects of reflection and transmission losses and of polarization of the incident light were included. Correction was also made for the finite size of the reflector. It was found that the optimum orientation has the collector plane almost perpendicular to the plane of the reflector. This optimum orientation is approximately independent of the sun's azimuthal dependence. The optimum reflector angle is found to be between 0° and 10° above the horizon for winter solar conditions. For typical winter operating conditions the enhancement in light gathering power for direct solar radiation is about a factor of 1·4–1·7. This results in an effective increase of 100% in the useful winter heat output from a practical reflector-collector combination with a reflector angle of 0°, over the useful heat output obtained with an optimally oriented simple flat-plate collector. An approximate calculation was also made of the overall enhancement in useful heat output for diffuse solar radiation; an increase by a factor of about 1·5 is predicted. Comparison with the preliminary analysis of the performance of the Coos Bay, Oregon solar house shows substantial agreement with the predictions of the present analysis.

• calculations for various angles, latitudes and sun angles.
• collector orientation perpendicular to reflector plane is optimum. Independent of time of day.

Collector performance enhancement with flat reflectors - 1975^[2][edit | edit source]

Abstract - The use of diffuse and specular flat reflectors to enhance the performance of flat-plate solar collectors has been explored by means of Fortran routines which optimize the size, shape, and placement of reflector and collector. Configuration factors for systems with a diffuse reflector and a collector whose absorptance varies with incidence angle are presented. Specular reflectors are more effective than diffuse reflectors, and, if south-facing, should be used with collectors which are elongated in the east-west direction. Design curves for the specific system of horizontal collector and south-facing reflector are presented. In this system, a moderately sized reflector can increase the midwinter yield per unit collector area by several times.

• model for horizontal collector with top-reflector(south facing)
• diffuse and specular reflectors
• specular more effective

The use of planar reflectors for increasing the energy yield of flat-plate collectors - 1977^[3][edit | edit source]

Abstract- A mathematical model to simulate the performance of flat-plate collector-reflector systems is presented. First the collector energy balance is modified to account for the reflected energy. Then the exchange area for a diffuse reflector is obtained by integrating over both reflector and collector surfaces. For the specular reflector, the collector area exposed to reflected radiation is calculated from geometrical relations. Shading effects are also found from the system geometry. Fair agreement is obtained between the model and some experiments on a water heating collector in Brisbane, Australia. Finally, the model is used to predict the annual performance of a water heating system with several values of the reflector angle.

• flat plate collectors tested (solar thermal collection)
• diffuse reflectors found to have insignificant effect
• mathematical calculation approach

Augmented solar energy collection using different types of planar reflective surfaces; theoretical calculations and experimental results - 1978^[4][edit | edit source]

Abstract - The use of planar reflective surfaces can substantially improve the performance of both active and passive solar collectors. In this paper the results of theoretical calculations and experimental tests are presented on the use of different types of flat reflective surfaces to increase the collection of solar energy by flat collectors. Specular, diffuse, and combination specular/diffuse reflective surfaces are discussed. This present work differs from that of other investigators principally in that an attempt has been made to describe the reflective properties of surfaces in more generalized terms than simple specular or simple diffuse. Most real surfaces possess a combination of specular- and diffuse-like reflectivities. The reflectivity properties of a given surface can be measured in the laboratory as a function of incident and reflected angles, and these measured reflective properties can be used in the computer model to predict the increase in collector performance with such a reflector. Thus outdoor tests of a given reflector can be avoided if desired, and yet it is possible to make an estimate of the reflector's contribution to the collector's overall performance. Theoretical calculations of collector energy inputs were done for several distinct types of reflecting surfaces. These calculations based on indoor laboratory measurements of the reflective properties of the surfaces, were compared with experimental results obtained from an outdoor simulation apparatus. Predictions of system performance were made for various collector/reflector configurations, and compared with the performance of an optimally oriented collector without a reflector.

• Type I Specular Alcoa Alzak aluminum sheet
• Plywood sheet painted with good quality exterior white latex paint
• Plywood sheet painted with inexpensive Paint Pot Chrome Aluminum 30 spray paint
• A 1/4" plate-glass PPG back-surface silvered mirror

Effect of off-south orientation on optimum conditions for maximum solar energy absorbed by flat plate collector augmented by plane reflector - 1980^[5][edit | edit source]

Abstract - A complete analysis of the off-south oriented, simple flat plate collector, augmented by flat sheet specular reflector, is developed. The enhancement of heat flux absorbed by solar collector due to the use of reflector is calculated as a function of solar altitude and azimuth angles, off-south orientation angle of collector and relative sizes and tilt angles of both collector. The shading effect due to the presence of the reflector is considered in the analysis. The collector and reflector variables are optimized for maximum solar energy flux absorbed by the collector during a pre-specified period of time. The Hooke and Jeeves optimization technique has been used in the analysis.

• Investigation for off-south collector orientation. Analysis for 21.5°(Jedah)
• Divide collector plane in different areas - optimized individually to get max energy yield sum.
• Improvement in System performance if reflector-collector tilt angle changed once a year(min).
• Divides year into two - Oct-Mar(winter) and rest(summer)

Planar concentrators for flat-plate solar collectors - 1981^[6][edit | edit source]

Abstract- A systematic study has been made of the effectiveness of planar specular reflectors for solar energy collectors. Two daily averaged indices of performance were used. One, the area ratio, indicates the amount by which the reflector extends the effective receiver area. The other is the enhancement factor, which is used to compare the energy received by an augmented collector with that by a reference collector at optimum tilt.

A reflector can be mounted either above or below a flat-plate collector. Both combinations are evaluated fully, by varying separately the angular position and dimensions of the reflector and of the collector. The principal parameters are identified and the main characteristics summarised as a series of performance curves. These curves provide an easy method for determining optimum reflector geometries.

Use of the performance curves may be extended to obtain the configuration of the two reflectors in a trough concentrator. This also allows the single-reflector system to be compared directly with the trough concentrator. Evidence is presented which shows the advantages of an asymmetrical trough configuration over a symmetrical concentrator.

• performance influenced primarily by the reflector/cover width ratio
• reflector angular position and collector tilt also important
• optimum angle of reflector varies a lot with seasonal movement of sun

Stationary reflector-augmented flat-plate collectors - 1981^[7][edit | edit source]

Abstract-A general procedure for determining the optimum geometry of a reflector-augmented solar collector which produces a desired pattern of flux-augmentation is described. The example used for illustration is a stationary collector whose winter performance is to be improved. Consideration of both a flat-plate collector with a bottom reflector and one with a top reflector led to distinct differences in their optimum configuration and performance being identified. Since either systems can be used to augment winter flux, a criterion for selecting the appropriate system is given. This criterion is based on the displacement in collector tilt from latitude inclination.

• performance factors - reflector width ratio, reflector angle, panel tilt angle from latitude
• performance curves to decide b/w top- and bottom-reflectors.
• unity reflector width ration suggested.

Effect of concentration on the performance of flat plate photovoltaic modules - 1984^[8][edit | edit source]

Abstract - The effect of low concentration ratios on the performance of passively cooled conventional photovoltaic modules has been investigated. Peak power outputs of up to 140 W per square metre of module area have been obtained with single crystal modules of high cell packing factor using a 2.2X plane mirror concentrator. Both cell temperature and series resistance losses are found to be important in limiting module efficiency. Performance simulations indicate that the use of a 4X concentrator with polar axis tracking will increase annual peak output by a factor of 3.2 over that of a fLxed fiat plate module

• Reflectors of geometric width: 2.2, 1.6 and 1 x
• Max Effective Concentration of 1.85
• Temperature increase of cell: 1x - 28-32°C, 1.6x - 40-45°C, 2.2x - 50-55°C
• Effect of concentration ratio and cell temperature on fill factor
• Polar axis tracking with concentration modelled (Perth, Western Australia)
• Max output at 4x concentration
• 3.2 times greater than fixed 1x panel

Collector, collector-reflector systems—an an analytical and practical study, Energy Conversion and Management - 1986^[9][edit | edit source]

This paper investigates the use of planar reflectors which substantially improve the performance of flat-plate solar collectors. The experimental setup includes a collector panel and collector-reflector system with maximum useful heat gain. A computer simulation of the analytical and experimental recordings was made to study the comparative features of the systems. The performance study is illustrated as a function of solar altitude, azimuth angles, hour angle and the relative sizes and tilt angles of both the collector and reflector. The use of a booster mirror produces an increase of 10–15°C in water temperature. The shading effect due to the presence of the reflector has also been considered in the present analysis.

• specular reflectivity 0.8
• reflector-on-collector shading effect neglected but not vice-versa
• 9.07% incr. in solar irradiation - one adjustment a year

Enhancement of solar energy on flat-plate collector by plane booster mirrors - 1988^[10][edit | edit source]

Abstract - A comprehensive analysis of a system consisting of a flat-plate collector augmented with two reflectors is presented. The model facilitates the prediction of the total energy absorbed by the collector at any hour of the day for any latitude for random tilt angles and azimuth angles of the collector and reflectors. The effect of overlapping of the shadows of the two reflectors has been taken care of. The model was numerically simulated for conditions prevailing in three different Indian stations. For each station, the variation of the total input energy, with tilt angles of the reflectors was studied for three different months for the case of collector tilt angle (1) equal to zero and (2) equal to latitude

• Enhancement of solar energy on flat-plate collector by plane booster mirrors
• system simulation for three different locations in india
• Reflector - 30°-110°(for top) 0°-90°(for bottom)
• Max enhancement in dec - more with incr. in latitude

Modeling daylight availability and irradiance components from direct and global irradiance - 1990^[11][edit | edit source]

Abstract - This paper presents the latest versions of several models developed by the authors to predict short time-step solar energy and daylight availability quantities needed by energy system modelers or building designers. The modeled quantities are global, direct and diffuse daylight illuminance, diffuse irradiance and illuminance impinging on tilted surfaces of arbitrary orientation, sky zenith luminance and sky luminance angular distribution. All models are original except for the last one which is extrapolated from current standards. All models share a common operating structure and a common set of input data: Hourly (or higher frequency) direct (or diffuse) and global irradiance plus surface dew point temperature. Key experimental observations leading to model development are briefly reviewed. Comprehensive validation results are presented. Model accuracy, assessed in terms of root-mean-square and mean bias errors, is analyzed both as a function of insolation conditions and site climatic environment.

• Models for predicting relevant quantities like solar energy in short intervals and availability of light - can be used for specific user needs.
• First model relates irradiance value to the light from sun/sky as comprehended by the human eye.
• Second approximates illuminance and irradiance for horizontally surface tilted.
• Third - angular distribution of light instead of the diffuse values.

A Comprehensive Physical Model for Light Reflection - 1991^[12][edit | edit source]

Abstract - A new general reflectance model for computer graphics is presented. The model is based on physical optics and describes specular, directional diffuse, and uniform diffuse reflection by a surface. The reflected light pattern depends on wavelength, incidence angle, two surface roughness parameters, and surface refractive index. The formulation is self consistent in terms of polarization, surface roughness, masking/shadowing, and energy. The model applies to a wide range of materials and surface finishes and provides a smooth transition from diffuse-like to specular reflection as the wavelength and incidence angle are increased or the surface roughness is decreased. The model is analytic and suitable for Computer Graphics applications. Predicted reflectance distributions compare favorably with experiment. The model is applied to metallic, nonmetallic, and plastic materials, with smooth and rough surfaces.

• Light reflection explained
• Components of light reflection

Energy contribution by booster mirrors^[13][edit | edit source]

Abstract - The standard textbooks and research publications hint at possible methods for computing the energy contribution by plane booster mirrors but do not elaborate the specific stages of a computational procedure. We hope the algorithm presented in this paper fills this gap. An algorithm to assess the contribution of solar energy on a horizontal receiver by plane booster mirrors is discussed in this paper. The choice of horizontal receiver reduces the number of variables and, therefore, simplifies the analysis and enhances understanding of the phenomenon of energy contribution by booster mirrors. The original impetus for this work was to study the input variables in a solar cooker, widely distributed in India. In these cookers, the aperture is invariably horizontal and a single plane booster mirror is the standard complement

• theoretical model created for using (top, bottom, or wing mirrors)
• 3d model determines area illuminated and shadowed by reflector
• computer code used beam radiation values calculated by Hottel's (model of clear sky atmospheric transmittance)
• algorithms can be applied to 3d model for PV reflector