Design of a new three-degree of freedom spherical motor for photovoltaic-tracking systems

Photovoltaic (PV) panels directly convert the solar energy to electrical energy. The amount of electrical energy converted by PV panels mainly depends on incident solar radiation. Sun tracking systems can be used to maximize energy production since they ensure keeping the photovoltaic panels perpendicular to the incoming solar radiation. Spherical motors, which have the linear and circular movement ability in three independent dimensions, can be used for precisely tracking the sun as a solution. In this study, a spherical motor controlled by a micro-controller is designed for a PV-tracking system with the ability to move on two axes. Performance of PV-tracking system over a fixed tilted one is evaluated for the climate condition of Denizli, Turkey. The designed sun tracking system is observed to be improving this performance apparently using the output voltages obtained for one day.     

Performance of off-grid residential solar photovoltaic power systems using five solar tracking modes in Kunming,China

This paper compares the performance of a 2.02 kW_p off-grid residential solar photovoltaic (PV) power system using PVSYST simulation software for a household in Kunming, Yunnan province, China. The monthly available solar energy; missing energy; array, final, and reference yields, performance ratio; and array capture and system losses were analyzed for five solar tracking modes: fixed tilted plane, seasonal tilt adjustment, horizontal axis tracking, vertical axis tracking, and dual axis tracking. Although there were some similar aspects across the five systems, minimum available solar energy (2461 kWh/y) and maximum missing energy (134.68 kWh/y) were obtained using the fixed tilted plane system (tilt angle = 25°, azimuth angle = 0°), whereas maximum available solar energy (3081 kWh/y) and minimum missing energy (48.53 kWh/y) in October were obtained using the dual axis tracking system. Average monthly performance ratio was maximal for the fixed tilted plane system (0.689), and minimal for the dual axis tracking system (0.596).     

Efficiency enhancement of stationary solar energy based power conversion systems in Canada

This paper presents the optimum energy conversion conditions of stationary photovoltaic panels used for electrical power generation. The results are arrived at after performing calculations for 180 days in a given year at the latitude of St. John’s, Newfoundland. The latitude of this city is close to other Canadian major population centers. Various angular orientations of sun’s rays on the earth are considered. On a given day, the incident energy flux of sun is resolved into three components, and the conversion efficiency is based on the flux normal to the panels. The efficiency of conversion of the incident energy is measured with respect to a solar tracking process. The numbers of days in a given year are divided into two groups – one between the winter solstice and the spring equinox, and another between the spring equinox and the summer solstice.     

The effect of using sun tracking systems on the voltage–current characteristics and power generation of flat plate photovoltaics

An experimental study was performed to investigate the effect of using different types of sun tracking systems on the voltage–current characteristics and electrical power generation at the output of flat plate photovoltaics (FPPV). Four electromechanical sun tracking systems, two axes, one axis vertical, one axis east–west and one axis north–south, were designed and constructed for the purpose of investigating the effect of tracking on the electrical values, current, voltage and power, according to the different loads (variable resistance). The above mentioned variables were measured at the output of the FPPV and compared with those on a fixed surface. The results indicated that the volt–ampere characteristics on the tracking surfaces were significantly greater than that on a fixed surface. There were increases of electrical power gain up to 43.87%, 37.53%, 34.43% and 15.69% for the two axes, east–west, vertical and north–south tracking, respectively, as compared with the fixed surface inclined 32° to the south in Amman, Jordan.     

A review of principle and sun-tracking methods for maximizing solar systems output

Finding energy sources to satisfy the world's growing demand is one of society's foremost challenges for the next half-century. The challenge in converting sunlight to electricity via photovoltaic solar cells is dramatically reducing $/watt of delivered solar electricity. In this context the sun trackers are such devices for efficiency improvement.The diurnal and seasonal movement of earth affects the radiation intensity on the solar systems. Sun-trackers move the solar systems to compensate for these motions, keeping the best orientation relative to the sun. Although using sun-tracker is not essential, its use can boost the collected energy 10–100% in different periods of time and geographical conditions. However, it is not recommended to use tracking system for small solar panels because of high energy losses in the driving systems. It is found that the power consumption by tracking device is 2–3% of the increased energy.In this paper different types of sun-tracking systems are reviewed and their cons and pros are discussed. The most efficient and popular sun-tracking device was found to be in the form of polar-axis and azimuth/elevation types.     

Energy production of photovoltaic systems: Fixed, tracking, and concentrating

This work compares the energy production (EP) of four photovoltaic system configurations: fixed, 1-axis and 2-axis tracking flat plate, and concentrating photovoltaics (CPV). The EP comparison is based on real performance data from systems installed in Spain in 2009. These systems are located close to each other but house different configurations. Many of the systems analyzed are new installations in 2008, including two of the largest CPV systems in the world that together have 9.3 MW and represent more than 50% of the world's total CPV. The EP analysis shows: (1) compared with the fixed flat plate systems, 1-axis and 2-axis tracking flat plate systems have 22.3% and 25.2% gain in the annual EP, respectively. These real EP gains are less than 32.1% for 1-axis and 38.7% for 2-axis tracking, which are the predicted gains when only considering the difference of captured illumination by these configurations (based on the data from Photovoltaic Geographical Information System (PVGIS)). (2) The EP from CPV systems is quite close to that from fixed flat plate systems. This differs from the predicted 16.1% gain from CPV when only considering the illumination difference. Besides comparing the energy production, the performance ratio (PR) is also estimated and analyzed for the different configurations, based on the best available irradiation data. PR measures the agreement between the operation of a real system and of an ideal system that only considers the nominal module efficiency loss. The analysis shows the PR decreases in the order: fixed, 1-axis, 2-axis tracking flat plate, CPV.     

Determining optimum tilt angles and orientations of photovoltaic panels in Sanliurfa, Turkey

The performance of a photovoltaic (PV) panel is affected by its orientation and its tilt angle with the horizontal plane. This is because both of these parameters change the amount of solar energy received by the surface of the PV panel. A mathematical model was used to estimate the total solar radiation on the tilted PV surface, and to determine optimum tilt angles for a PV panel installed in Sanliurfa, Turkey. The optimum tilt angles were determined by searching for the values of angles for which the total radiation on the PV surface was maximum for the period studied. The study also investigated the effect of two-axis solar tracking on energy gain compared to a fixed PV panel. This study determined that the monthly optimum tilt angle for a PV panel changes throughout the year with its minimum value as 13° in June and maximum value as 61° in December. The results showed that the gains in the amount of solar radiation throughout the year received by the PV panel mounted at monthly optimum tilt angles with respect to seasonal optimum angles and tilt angel equal to latitude were 1.1% and 3.9%, respectively. Furthermore, daily average of 29.3% gain in total solar radiation results in an daily average of 34.6% gain in generated power with two-axis solar tracking compared to a south facing PV panel fixed at 14° tilt angle on a particular day in July in Sanliurfa, Turkey.     

Performance comparison of a double-axis sun tracking versus fixed PV system

In the present study, performance results of two double axis sun tracking photovoltaic (PV) systems are analyzed after one year of operation. Two identical 7.9 kWp PV systems with the same modules and inverters were installed at Mugla University campus in October 2009. Measured data of the PV systems are compared with the simulated data. The performance measurements of the PV systems were carried out first when the PV systems were in a fixed position and then the PV systems were controlled while tracking the sun in two axis (on azimuth and solar altitude angles) and the necessary measurements were performed. Annual PV electricity yield is calculated as 11.53 MW h with 1459 kW h/kWp energy rating for 28 fixed tilt angle for each system. It is calculated that 30.79% more PV electricity is obtained in the double axis sun-tracking system when compared to the latitude tilt fixed system. The annual PV electricity fed to grid is 15.07 MW h with 1908 kW h/kWp for the double axis sun-tracking PV system between April-2010 and March-2011. The difference between the simulated and measured energy values are less than 5%. The results also allow the comparison of different solutions and the calculation of the electricity output.     

Sensor-controlled heliostat with an equatorial mount

A heliostat having a photo-sensor sun-tracking system was developed and evaluated. The sensor was composed of a set of two photo-cells placed side by side on the bottom of the small box. Sun-tracking can be achieved by rotating the heliostat equipped with the sensor, while maintaining the two photo-cells under illumination by the sun through a slit in the box. A preliminary tracking evaluation of the sensor was carried out with the aid of a mirror-telescope system, and the tracking error was estimated to be less than 0.6 mrad in clear weather. The developed heliostat employed an equatorial mount system that permits the rotating speed of the right-ascension axis to be nearly constant for the diurnal motion of the sun. The use of two additional sensors, a cloud sensor and a primary sensor, permitted stable tracking with high accuracy even in a cloudy sky. Field tests of the heliostat revealed that an angular error within 2 mrad was achieved in fine weather. In cloudy weather, the heliostat operated stably with the cloud sensor within an error of 10 mrad.     

Optimisation and techno-economic analysis of autonomous photovoltaic–wind hybrid energy systems in comparison to single photovoltaic and wind systems

A techno-economic analysis for autonomous small scale photovoltaic–wind hybrid energy systems is undertaken for optimisation purposes in the present paper. The answer to the question whether a hybrid photovoltaic–wind or a single photovoltaic or wind system is techno-economically better is also sought. Monthly analysis of 8 year long measured hourly weather data shows that solar and wind resources vary greatly from one month to the next. The monthly combinations of these resources lead to basically three types of months: solar-biased month, wind-biased month and even month. This, in turn, leads to energy systems in which the energy contributions from photovoltaic and wind generators vary greatly. The monthly and yearly system performances simulations for different types of months show that the system performances vary greatly for varying battery storage capacities and different fractions of photovoltaic and wind energy. As well as the system performance, the optimisation process of such hybrid systems should further consist of the system cost. Therefore, the system performance results are combined with system cost data. The total system cost and the unit cost of the produced electricity (for a 20 year system lifetime) are analysed with strict reference to the yearly system performance. It is shown that an optimum combination of the hybrid photovoltaic–wind energy system provides higher system performance than either of the single systems for the same system cost for every battery storage capacity analysed in the present study. It is also shown that the magnitude of the battery storage capacity has important bearings on the system performance of single photovoltaic and wind systems. The single photovoltaic system performs better than a single wind system for 2 day storage capacity, while the single wind system performs better for 1.25 day storage capacity for the same system cost.     

不停电独立光伏系统的优化设计

为零缺电率负载供电的独立光伏系统是对设计要求最高的光伏系统,必须慎重地进行优化设计。研究表明,如果采用一般的独立光伏系统优化设计程序来进行设计,只要用蓄电池维持天数等于零代入,即可确定太阳电池方阵的容量,同时可以用当地辐照量最低的月份得到最大辐照量所对应的倾角作为方阵的最佳倾角。确定蓄电池容量时应以当地最长连阴雨天数作为蓄电池维持天数的依据。通过实例分析,取得了良好的效果。     

A novel prediction algorithm for solar angles using solar radiation and Differential Evolution for dual-axis sun tracking purposes

This paper deals with a dual-axis sun tracking system for a photovoltaic system. Its trajectories are determined by an optimization procedure. The optimization goal is the maximization of the electrical energy production within a photovoltaic system, by considering the tracking system consumption. The procedure used for determining the tilt angle and azimuth angle trajectories is described as a nonlinear and bounded optimization problem. Since an explicit form of the objective function is unavailable, a stochastic search algorithm called Differential Evolution is applied as the optimization tool. In order to evaluate the objective function, models for calculating the available solar radiation and tracking system consumption are applied together with the efficiencies of solar cells, a DC/DC converter and inverter. A new algorithm is introduced for the time dependent prediction of available solar radiation. It is based on the length of a sunbeam’s path through the atmosphere and the statistical data of a pyranometer measured total and diffuse solar radiation at a given location on the Earth. The optimization bounds are given in the form of angular speed, lower and upper bounds for both angles and angle quantization. The results presented in this paper show, that the optimal trajectories can help to increase the electrical energy production within photovoltaic systems by sun tracking.     

Simple tracking strategies for solar concentrations

Consideration is given to the validity of single axis tracking systems for solar concentrators of low to medium concentration ratios having moderate acceptance angles. If the misalignment between the sun and reflector normals is within the acceptance angle perfect tracking can be assumed. Rotation about a fixed polar axis gives a constant misalignment equal ot the sun's declination angle on that day. Rotation about a declination axis gives perfect alignment at noon, but increasing misalignment towards each end of the day varying with the time from the equinoxes. Data is also given for monthly adjustment of the declination axis. All the results are independant of latitude.     

Performance comparison of wedge-shaped and planar luminescent solar concentrators

A wedge-shaped luminescent solar concentrator (LSC) with the capability of high collection efficiency and flux gains is described. Monte Carlo simulations of direct insolation conditions for a mid-latitude location are used to form a comparison of a realistically sized wedge LSC and conventional LSC with the same area footprint. The results show that when the sun is high in the sky, such as during early summer, the planar LSC outperforms the wedge LSC in terms of efficiently concentrating light. Under these conditions, the average wedge LSC concentrator efficiency is 3.5%, while the planar LSC achieves an efficiency of 6.3%. However, when the sun stays low in the sky, such as during early winter, the wedge LSC concentrates light with a maximum efficiency of 32.8%; more than four times greater than that of the planar LSC at 7.6%. Moreover, on a seasonal basis, the wedge LSC is estimated to produce more electrical energy per square meter of PV cells than a planar LSC or conventional solar panel placed parallel to the horizon.     

Novel high efficient offline sensorless dual-axis solar tracker for using in photovoltaic systems and solar concentrators

In this study, a novel high accurate offline sensorless dual-axis solar tracker is proposed that can be widely used in photovoltaic systems and solar concentrators. The offline estimated data extracted from solar map equations are used by the tracker to find the sun direction where the maximum value of solar energy is captured. The solar tracker has been built, and it is experimentally verified that 19.1%–30.2% more solar energy can be captured depending on the seasons by utilizing the tracker. The contribution of this work is that the proposed offline sensorless dual-axis solar tracker not only has a very simple structure with a fabrication cost much less than sensor based solar trackers but also high accurately tracks the sun direction with a very small tracking error of only 0.43° which is less than the other sensorless and sensor based dual-axis solar trackers reported in the literature excluding the sensor based dual-axis solar trackers equipped with expensive sensors mounted on high accurate mechanical carriers. Furthermore, unlike all sensor based solar trackers, since the technique is offline, the proposed tracker does not use any feedback signal, and thus, its operation is independent from external disturbances and weather conditions such as cloudy sky.     

A simple and efficient sun tracking mechanism using programmable logic controller

To increase the unit area illumination of solar ray on PV panel, it is required to track the sun throughout the day. So to reach the goal various type of sun tracking mechanism is already developed but in this paper we designed two different types of sun tracking mechanism: single axis and dual axis tracking using programmable logic controller (PLC) as it has numbers of unique advantages like??it is faster, reliable, requires less maintenance and reprogrammable. A comparative study between those two systems is also presented in this paper. The whole system has been designed and tested using GE, FANUC PLC.     

Mapping of solar energy potential and solar system capacity in Iran

Studies of the DLR Mediterranean – Concentrated Solar Project indicate Iran can be a part of the Mediterranean renewable power generation chain in 2050 to provide the electrical power demand of Europe. However, Iran as a developing country and due to its large area has some limitations on the number of synoptic stations. Hence, the aim of this study is to determine the theoretical solar irradiation potential in Iran by using an Niroo Research Institute irradiation model based on the geographical and meteorological data. Monthly, seasonal, and annual values of irradiation on the ground surface, and extracted solar energy from different tracking systems, are estimated across the country. A typical photovoltaic system, parabolic trough, and dish concentrator are considered and extracted solar energy of them is illustrated on the map. Results of this study make clear that the presented solar atlas can provide appropriate tools for primary study of solar energy potential and extracted energy in Iran.     

Comparison of the performance of PV water pumping systems driven by fixed, tracking and V-trough generators

Photovoltaic pumping systems with solar tracking, coupled to low concentration cavities, have been proposed as a viable alternative to reduce the final cost of the pumped water volume. V-trough concentrators are particularly appropriate for photovoltaic applications since, for certain combinations of the concentration ratio (C) and vertex angle (Ψ), they provide uniform illumination on the region where the modules are located. Water pumping systems are only operational when the irradiance is larger than a minimum irradiance level (I_C). Solar tracking increases the average collected irradiance and, for a system operating with a given critical irradiance level (I_C), it is verified that the smaller the relationship , the larger the useful energy. Thus, the gain, in terms of pumped water volume, provided by solar tracking systems, can be larger than the gain in collected solar radiation. The combination of both devices, tracking and concentration provides an additional increase of the benefits resulting from the use of solar trackers. By means of the “Utilizability Method”, we estimate the long-term gains of pumped water volume, for tracking systems, with and without concentration, against fixed systems. The long-term water volume has been calculated using the characteristic curve of a tested PVP system with a tracking V-trough concentrator. Results show that, for the climate of the city of Recife (PE-Brazil), the annual pumped water volume of the tracking system is 1.41 times the value obtained with the fixed system. In that case, the gains observed for the collected solar energy were around 1.23. For the PVP system with tracking V-trough concentrator the annual benefits for pumped water volume are around 2.49, while for collected solar radiation we found 1.74. The annualized cost of the cubic meter of pumped water has been estimated for the three configurations. Results show a cost reduction of the order of 19% for the tracking system and of 48% for the concentrating system, when compared to the fixed configuration.     

Correlation analysis and MLP/CMLP for optimum variables to predict orientation and tilt angles in intelligent solar tracking systems

Different solar tracking variables have been employed to build intelligent solar tracking systems without considering the dominant and optimum ones. Thus, several low performance intelligent solar tracking systems have been designed and implemented due to the inappropriate combination of solar tracking variables and intelligent predictors to drive the solar trackers. This research aims to investigate and evaluate the most effective and dominant variables on dual‐ and single‐axis solar trackers and to find the appropriate combination of solar variables and intelligent predictors. The optimum variables will be found by using correlation results between different variables and both orientation and tilt angles. Then, to use the selected variables to develop different intelligent solar trackers. The results revealed that month, day, and time are the most effective variables for horizontal single‐axis and dual‐axis solar tracking systems. Using these variables in cascade multilayer perceptron (CMLP) and multilayer perceptron (MLP) produced high performance. These predictors could predict both orientation and tilt angles efficiently. It is found that day variable is very effective to increase the performance of solar trackers although day variable is neither correlated nor significant with both orientation and tilt angles. Linear regression predicted less than 70% of the given data in most cases, whereas nonlinear models could predict the optimum orientation and tilt angles. In single‐axis tracker, month, day, and time variables achieved prediction rates of 96.85% and 96.83% for three hidden layers of MLP and CMLP, respectively, whereas the MSE are 0.0025 and 0.0008, respectively. In dual‐axis solar tracker, MLP and CMLP predicted 96.68% and 97.98 % respectively, with MSE of 0.0007 for both.     

Performance modeling and investigation of fixed, single and dual-axis tracking photovoltaic panel in Monastir city, Tunisia

Presented in this paper was an overview on research works on solar radiation basics and photovoltaic generation. Also, a complete PV modeling and investigation on the effect of using multi-axes sun-tracking systems on the electrical generation was carried out to evaluate its performance using the case study of the Monastir city, Tunisia. The effects of azimuth and tilt angles on the output power of a photovoltaic module were investigated. The instantaneous increments of the output power generated by a photovoltaic module mounted on a single and dual-axis tracking system relative to a traditional fixed panel were estimated. The results show that the yearly optimal tilt angle of a fixed panel faced due to the south is close to 0.9 times Monastir latitude. The gain made by the module mounted on a single-axis tracking panel relative to a traditional fixed panel was analyzed. The monthly increments of the gain are more noticeable for two critical periods which correspond to those surrounding the summer and the winter solstice dates. It reaches the value of 10.34% and 15% in the summer and winter solstice periods, respectively. However, the yearly gain relative to a fixed panel installed with the yearly optimal tilt angle is 5.76%. In some applications, covering loads at early morning or late afternoon hours and in order to more optimize the solar systems exploitation suggest the adjustment of the PV panel orientation to azimuth angles different from the south direction by using a dual-axis tracking installation. The gain made by this recommendation relative to a traditional fixed panel is evaluated. This gain reaches 30% and 44% respectively in the winter and summer solstice days.