Optimum tilt angle and orientation for solar collector in Brunei Darussalam

One of the important parameters that affects the performance of a solar collector is its tilt angle with the horizontal. This is due to the fact that the variation of tilt angle changes the amount of solar radiation reaching the collector surface. A mathematical model was used for estimating the total (global) solar radiation on a tilted surface, and to determine the optimum tilt angle and orientation (surface azimuth angle) for the solar collector in Brunei Darussalam on a daily basis, as well as for a specific period. The optimum angle was computed by searching for the values for which the total radiation on the collector surface is a maximum for a particular day or a specific period. The results reveal that changing the tilt angle 12 times in a year (i.e. using the monthly-averaged optimum tilt angle) maintains approximately the total amount of solar radiation near the maximum value that is found by changing the tilt angle daily to its optimum value. This achieves a yearly gain in solar radiation of 5% more than the case of a solar collector fixed on a horizontal surface.     

OPTIMUM TILT ANGLE FOR SOLAR COLLECTION SYSTEMS

For non-tracking solar collection systems, the tilt angle has a predominant effect on the quantity of energy that the system can intercept. In the present work, a computational algorithm is developed for the calculation of the optimum tilt angle that would orient a non-tracking solar collection system (concentrating or non-concentrating) in its best position for the maximum average daily, monthly seasonal or yearly intercepted radiation. The optimum tilt angles were obtained for latitudes ranging from l0–50oN on monthly, seasonal and yearly bases. A case study is applied on Riyadh City (latitude 24.9°N) to investigate the sensitivity of intercepted radiation when the tilt angle varies from that of the optimum value. The results show that, on a monthly basis when the collector is mounted at the yearly optimum tilt angle, the loss of radiation intercepted is less than 10% as compared to the monthly optimum tilt angle. The optimum seasonal tilt angle reduces the incident radiation by less than 2% from that of the monthly optimum tilt angle.     

A numerical comparison among different water-based hybrid nanofluids on their influences on natural convection heat transfer in a triangular solar collector for different tilt angles

Natural convection inside a triangular solar collector is investigated numerically for different nanofluids and hybrid nanofluids in this study. The individual effects of Al₂O₃–water, carbon nanotubes (CNT)–water, and Cu–water nanofluids are observed for different solid volume fractions of nanoparticles (0%–10%). Three types of hybrid nanofluids are prepared using different ratios of Al₂O₃, CNT, and Cu nanoparticles in water. A comparison is made varying the Rayleigh numbers within laminar range (10³–10⁶) for different tilt angles (0°, 30°, 60°, and 90°) of the solar collector. The inclined surface of the triangular solar collector is isothermally cold and the bottom wall (absorber plate) is isothermally hot, whereas the vertical wall with respect to the absorber plate is considered adiabatic. Average Nusselt numbers along the hot wall for different parameters are observed. Streamlines and isotherm contours are also plotted for different cases. Dimensionless governing Navier–Stokes and thermal energy conservation equations are solved by Galerkin weighted residual finite element method. Better convective heat transfer is found for higher Rayleigh number, solid volume fraction, and tilt angle. In the case of hybrid nanofluid, increasing the percentage of the nanoparticle that gives better heat transfer performance individually results in enhancing natural convection heat transfer inside the enclosure.     

General models for optimum tilt angles of solar panels: Turkey case study

This paper deals with finding the optimum tilt angle of solar panels for solar energy applications. The optimization of tilt angles was performed using solar radiation data measured for eight big provinces in Turkey. The optimum angle for tilted surfaces varying from 0° to 90° in steps of 1° was calculated by searching for the values of which the daily total solar radiation was at a maximum for a specific period. It was found that the optimum tilt angle changed between 0° and 65° throughout the year in Turkey. It was seen that the optimum tilt angle reached a minimum of 0° in June and July and, the monthly average daily total radiation at this angle was generally at a maximum. In addition, the optimum tilt angle increased during the winter months and reached a maximum in December in all provinces. Likewise, general correlations were developed to estimate the optimum tilt angle of solar collectors used in Turkey and their accuracies were compared on the basis of statistical error tests of Mean Bias Error (MBE), Root Mean Square Error (RMSE), t-statistic (t-stat) and correlation coefficient (r).     

Heat Transfer Analysis of Solar Air Heating System for Different Tilt Angles

Solar Air Heater is a simple, cheap and most widely used for various applications such as textile industries, agricultural, desalination and space heating. Generally collectors are tilted so as to absorb maximum radiation, so it is necessary to calculate the optimum tilt angle to maximize the solar radiation falling on the collector area to gain maximum useful energy. The maximum solar radiation can be collected by using a tracking mechanism. Tracking systems are expensive and complicated in construction. The working operation of solar integrated tracking system is difficult. This paper presents the mechanism of evaluating the overall heat transfer coefficient of the solar air-heater at variable intensities and inlet velocities. The experimental setup is integrated with blower at inlet to the solar air heater in order to pump air at different velocities. The work focus on comparative study of solar air heating system for different tilt angles ranging from 250 to 600 and determines the overall heat transfer coefficient so as to find the optimum tilt angle of a solar flat plate collector.     

Performance optimization of evacuated tube collector for solar cooling of a house in hot climate

Evacuating the space connecting cover and absorber significantly improves evacuated tube collector (ETC) performance. So, ETCs are progressively utilised all over the world. The main goal of current study is to explore ETC thermal efficiency in hot and severe climate like Kuwait weather conditions. A collector test facility was installed to record ETC thermal performance for one-year period. An extensively developed model for ETCs is presented, employing complete optical and thermal assessment. This study analyses separately optics and heat transfer in the evacuated tubes, allowing the analysis to be extended to different configurations. The predictions obtained are in agreement with experimental. The optimum collector parameters (collector tube length and diameter, mass flow rate and collector tilt angle) are determined. The present results indicate that the optimum tube length is 1.5 m, as at this length a significant improvement is achieved in efficiency for different tube diameters studied. Finally, the heat generated from ETCs is used for solar cooling of a house. Results of the simulation of cooling system indicate that an ETC of area 54 m², tilt angle of 25° and storage tank volume of 2.1 m³ provides 80% of air-conditioning demand in a house located in Kuwait.     

Performance of flat plate solar collectors in off-south orientation in India

This paper presents the effect of off-south orientation on the performance of flat plate solar collectors. This study is done, taking into consideration the building's off-south orientation. The present work investigates collector performance and optimum tilt as functions of the off-south angle, collection temperature, latitude and wind velocity. The three latitudes considered are of New Delhi(L = 28.38°N), Bangalore (L = 12.97°N) and Madras (13.0°N). It has been found that, for the best average winter performance, the tilt is latitude angle +15°, whereas, for the best average summer performance, it is latitude angle ?15°. It has also been confirmed that, for year round operation, the maximum solar energy is collected when the tilt is 0.9 times the latitude angle. Further, it has been noticed that there is an optimum value of collector tilt for a given azimuthal angle at which yearly effectiveness is a maximum. The effect of increase in off-south angle is to decrease the yearly effectiveness.     

Experimental study of a refrigerant charged solar collector

The performance of a heat-pipe solar collector was investigated experimentally using refrigerants R11 as the working fluid. The unit is fabricated locally and its performance is evaluated under Beirut Solar conditions. The heat transfer from the heat pipes to the hot-water storage tank took place through a circular end condenser section of the heat-pipe integrated within the collector frame. Tests of single heat pipes showed that the thermal performance of the heat pipe were dependent on its tilt angle, condenser section length and configuration, and type of internal wick used. A circular condenser end of the heat-pipe performed better than a straight condenser due to increased surface area for heat transfer. The R11-charged solar collector with integrated condenser for secondary cooling of water had an efficiency in early operation hours that reached values higher than 60% for the forced circulation mode. The instantaneous system efficiencies varied from 60 to 20%, which are in the range of conventional water solar collectors. System response was fast and sensitive to the incident solar radiation. The thermosyphonic mode of the system operation generated build up of stored energy in the condenser, resulting in oscillating-type flow thus reducing system efficiency below values obtained with forced circulation. © 1998 John Wiley & Sons, Ltd.     

Investigating different diffuse solar radiation models to analyse solar radiation on inclined surfaces in Oman

In this paper, a detailed analysis of the solar radiation on horizontal and tilted surfaces for six locations in Oman is presented. The locations are (from North to South): Majis/Sohar, Sur, Fahud, Masira, Marmul, and Salalah. These locations spread over Oman and cover different types of landscape. The method is validated through the use of measured data. The effect of tilt angle and orientation on the incident solar radiation is presented along with optimum surface tilt angles and directions for maximum solar radiation collection in these six locations. The solar radiation models used in this paper show good agreement with measured data. The results presented in this paper are extremely useful for quick estimation of solar radiation for calculations of buildings’ cooling load and solar collector system performance. This can be easily extended for other locations with similar landscapes and geographical conditions.     

Solar energy availability at Tehran: Performance of different types of solar collectors

In this report, the optimum tilt of the solar collectors in Tehran is computed through a computer program. The annual optimum tilt of the collector is found to be 30°. The summer and winter optimum tilts are found to be 0° and 50°, respectively. Based on these optimum tilts, the annual performance of different types of solar collectors which have experimental efficiency curves is predicted. The variation of the performance of the collectors with the optimum tilts is found to be small. The difference between the outlet temperatures of these collectors is also found to be small. The effect of changing the incident angle from zero degrees is found to increase the efficiency of the flat-plate collectors and to reduce the efficiency of the evacuated collectors.In the coldest month of the year, the flat-plate collector can collect heat up to 70°C, while the tubular one can collect heat with temperature more than 90°C. In the other months, all the collectors collect heat with temperatures more than 90°C. The performance of a well-mixed storage tank used with one of the flat-plate collectors is annually predicted. For the initial storage tank temperature assumed at 20°C, the minimum and maximum temperatures are found approximately to equal 42°C and 93°C, respectively. The results show the high potential of the solar collectors in Tehran.     

Determining seasonal optimum tilt angles,solar radiations on variously oriented,single and double axis tracking surfaces at Dhaka

The performance of a solar radiation conversion system is affected by its orientation and tilt angle with the horizontal plane. This is because both of these parameters change the amount of solar energy received by the surface of solar system. Three mathematical models- the Isotropic, the Klucher and the Perez model for the point source with parameters optimized for a variety of climatic conditions have been employed to determine hourly and seasonal optimum tilt angles. Theoretical optimum tilt angles (10° for Mar–Sep and 40° for Oct–Feb) were compared with measured data for Nov 2007 to Oct 2008 at Dhaka. The anisotropic Perez model showed least rmse of 0.09 for monthly tilt factor estimation. This model was also used for theoretical study of solar radiation on variously oriented, single axis and double axis tracking surfaces.     

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.     

Optimization of tilt angle for solar panel: Case study for Madinah,Saudi Arabia

This article analyzes the optimal choice of the tilt angle for the solar panel in order to collect the maximum solar irradiation. In this paper, the collector surface is assumed to be facing toward equator. The study is based upon the measured values of daily global and diffuse solar radiation on a horizontal surface. It is shown that the optimal angle of tilt (β_opt) for each month, allows us to collected the maximum solar energy for Madinah site. Annual optimum tilt angle is found to be approximately equal to latitude of the location. It is found that the loss in the amount of collected energy when using the yearly average fixed angle is around 8% compared with the monthly optimum tilt β_opt.     

Optimum tilt angle for a flat plate solar collector

One of the important parameters that affects the performance of a flat plate solar collector is its angle of tilt with the horizontal. This is due to the fact that the variation of tilt angle changes the top loss coefficient and the amount of solar radiation reaching the absorber plate. A mathematical model has been developed for calculating the useful energy gained by a flat plate collector under various operating conditions. The model is then used to determine the optimum tilt angles for a typical collector in Basrah on a daily basis, as well as on the basis of a specified period. The optimum tilt angle is found by searching its value for which the useful energy gained by the collector is a maximum for a particular day or a specified period.From the results, it is observed that changing the tilt angle eight times in a year determines the useful energy in Basrah near its value which is found by changing the tilt angle daily to its optimum value. Furthermore, the influence of various operating parameters is studied on the daily optimum tilt angle.     

A new methodology to optimise solar energy extraction under cloudy conditions

The orientation and tilt position of the solar panel affect the amount of solar radiation that falls on the panel surface over the course of the day and indeed the year. The choice of tilt angle for a solar panel is fundamental to its efficient operation because incorrectly positioning the solar panel leads to an unnecessary loss in potential power. In the past, much work has been done by authors to determine the optimum tilt angle by applying existing models to their locations. This approach has been successful in climates with the most favourable solar potential, where greater than 90 percent of the solar radiation arrives as direct beam radiation. The accuracy of these models in these locations has been attributed to the low presence of cloud cover and the consequential dominance of the beam radiation portion of the global radiation. Countries located above 45°N however, (Northern Europe), require a different approach to optimising the tilt angle as they receive the least amount of direct radiation with approximately half arriving as diffuse radiation, due to frequent, heavy cloud cover. This paper reviews existing methods and describes a means of predicting the solar radiation in a frequently overcast climate and proposes a method for choosing the optimum tilt angle in such a climate. The effect of different load profiles on the optimum tilt angle is also investigated. The solar radiation model is then used to predict the solar radiation for Cairo, Egypt to show that the model has a global application and is not limited to frequently overcast climates.     

On the optimum exposure of flat-plate fixed solar collectors

With the increasing range and scale of applications of solar energy conversion systems a detailed knowledge of the available solar fluxes on surfaces of various tilt and slope aspect is required. The widely used engineering routines for siting and exposing of solar collector arrays may not always be consistent with the maximum available solar energy income. In the present study a computational algorithm is proposed suitable for the calculation of optimum tilt angles of a solar collector, receiving the maximum insolation for given values of direct beam, global and diffuse radiation, and given surface reflectivity. Formulas are derived also for the calculation of optimum tilt angles yielding maximum daily insolation for each month of the year. The dependence of the optimum tilt angle on the diffuse-to-global radiation ratio, as well as on the surface reflectivity is evaluated.     

A tubular solar still integrated with a heat pipe

The aim of this work is to explore the thermal performance of a tracked tubular solar still (TSS) with a parabolic trough concentrator in Baghdad (33.27° N, 44.37° E) in September 2022. The present tubular still is distinguished by its hexagonal glass cover. The effect of integrating the TSS with a heat pipe, the still tilt angle (10°, 15°), and the depth of saline water inside the still partitions on the productivity of freshwater are investigated. The results showed that using heat pipe enhances the freshwater productivity by 25%–40% and the efficiency by 25%. For the still integrated with heat pipe, as the water depth is increased from 5.5 to 6.5 cm the productivity of freshwater is increased by 16% and 20% for tilt angles 10° and 15°, respectively.     

太阳能集热系统过热影响因素分析

通过分析太阳能供热系统集热、蓄热和用热各个子系统的动态热量热平衡关系,建立太阳能集热系统热量传递数学模型,并结合集热系统内部流体过热汽化原理,提出集热系统过热度评价指标,并对集热系统在不同流量、水箱容积以及不同连接方式等条件下的过热程度进行分析计算。结果表明,集热系统过热度随热媒流量、集热器倾角和水箱容积取值的增大而减小,并通过对上述3种因素进行敏感性分析得到集热器倾角对系统过热度的影响最大。     

Model evaluation and optimum collector slope for a tropical country

Various models proposed in the literature, viz. the Beam method, proposed by Morse & Czarnecki; two methods proposed by Liu & Jordan, using hourly values and average daily values of solar radiation: and Klucher's method are compared in this paper using measured hourly values of global and diffuse radiation on a horizontal surface and the total radiation on a tilted surface. It was observed that the model proposed by Klucher estimates the radiation more consistently with the experimental observations for clear as well as cloudy sky conditions.

This method was used for predicting the year round radiation availability on (i) a fixed collector inclined at an optimum tilt, (ii) a partially tracking collector in which the slope is fixed but following the sun's azimuth angle, and (iii) a fully tracking collector. In this analysis, measured values of hourly global and diffuse solar radiation on a horizontal plane for four widely separated Indian stations, viz. Delhi (28°38′N), Poona (18°29′N), Calcutta (22°36′N), and Madras (13°8′N) as per India Meteorological Department classification for climatic analysis, have been used.

With the model proposed, the radiation availability on different slopes for all the twelve months of the year for a fixed and partially tracking collector have been evaluated and optimum tilts for various seasons of a year for different solar energy applications for all the four Indian stations have been determined. For a typical winter month at New Delhi in the semi-arid zone of India, a fixed collector, a partially tracking collector and a fully tracking collector receive 60, 80 and 95% more radiation compared to that received on a horizontal plane respectively. Another observation is that the variation of the insolation received on inclined surfaces is not at all sensitive to the angle of tilt in the neighbourhood of the optimum angle of operation.     

Performance analysis of Azimuth Tracking Fixed Mirror Solar Concentrator

The fixed mirror solar collector (FMSC) fixes reflector and mobiles receiver to collect solar energy. However, this type of concentrator has a low efficiency and short operating duration in practical applications. In this paper, we propose to install the FMSC on an azimuth tracking device (ATFMSC) and the reflectors are arranged by intermission to avoid the shading of neighbor reflector for incidence angle of less than 10° to improve its optical performance. Through the integration of the reflected solar radiation distribution function over any reflection point, and then the whole collector aperture, we develop the analytical expressions of various system efficiencies to numerically simulate the performance of ATFMSC with evacuated tube receiver in different design parameters. It is validated by the ray tracing results. The result shows that the mean annual net heat efficiency of the whole system would be up to 61% with the operating temperature of 400 °C, which is higher than parabolic trough collector and traditional FMSC. This is because the longitudinal incidence angle of ATFMSC always remains zero by tracking the sun azimuth, so the end loss of the concentrator can be avoided and enables it to operate with high efficiency continually.