Solar panels work most efficiently when they are directed towards the sun and their surface is perpendicular to the sun’s rays. How to determine such a position of solar panels in which they will generate the maximum amount of energy per day? What is the best orientation for solar panels? The sun moves across the sky from east to west. The position of the Sun in the sky is determined by 2 coordinates – declination and azimuth. Declination is the angle between the line connecting the observer and the Sun and the horizontal surface. Azimuth is the angle between the direction to the Sun and the direction to the south (see the figure to the right).
Declination and azimuth. Solar panel orientation
It should also be borne in mind that the direction to the magnetic south (i.e. by the compass) does not always coincide with the direction to the true south. There are true and magnetic poles that do not coincide. Accordingly, there are true and magnetic meridians. And from both, you can count the direction to the desired object. In one case, we will deal with the true azimuth, in the other – with the magnetic one. True azimuth is the angle between the true (geographic) meridian and the direction to a given item. Magnetic azimuth — the angle between the magnetic meridian and the direction to a given object. It is clear that the true and magnetic azimuths differ by the same amount by which the magnetic meridian differs from the true one. This value is called magnetic declination. If the compass needle deviates from the true meridian to the east, the magnetic declination is called east, if the needle deviates to the west, the declination is called west. The eastern declination is often denoted by the “+” (plus) sign, the western – by the “-” (minus) sign. The magnitude of the magnetic declination is not the same in different areas. So, for the Moscow region, the declination is +7, + 8 °, but in general, on the territory of Russia, it changes in more significant limits. See also “How to Calculate True Bearing from Declination and Magnetic Bearing”.
Generally speaking, there are only three options to increase the exposure of the solar panel to direct sunlight:
- Installation of solar panels on a fixed structure at an optimal angle
- Installation on a two-axis tracker (a turntable that can rotate behind the sun in two planes)
- Installation on a single-axis tracker (the platform can only change one axis, most often the one that is responsible for the tilt)
Options No. 2 and No. 3 have their advantages (a significant increase in the operating time of the solar battery and some increase in energy production), but there are also disadvantages: a higher price, a decrease in the reliability of the system due to the introduction of moving elements, the need for additional maintenance, etc. .NS.). We will consider the feasibility of using trackers in a separate article, but for now, we will only talk about option # 1 – a fixed structure, or a fixed structure with a variable angle of inclination.
Solar panels are usually located on a roof or supporting structure in a fixed position and cannot track the position of the sun during the day. Therefore, usually, solar panels are not at the optimal angle (90 degrees to the sun’s rays) all day long. The angle between the horizontal plane and the solar panel is commonly referred to as the tilt angle.
Sun angle 1 1 orientation of solar panels, tilt angle
Due to the movement of the Earth around the Sun, there are also seasonal variations. In winter, the sun does not reach the same angle as in summer. Ideally, solar panels should be positioned more horizontally in summer than in winter. Therefore, the angle of inclination for work in summer is chosen less than for work in winter. If it is not possible to change the angle of inclination twice a year, then the panels should be located at the optimal angle, the value of which lies somewhere in the middle between the optimal angles for summer and winter. Each latitude has its own optimal angle of inclination of the panels. Only for areas near the equator, the solar panels should be located almost horizontally (but even there they are installed at a slight angle to allow rain to wash away dirt from the solar panel).
- Optimal tilt angles of solar panels for different latitudes
- Optimal tilt angles of solar panels for different latitudes
Usually, for spring and autumn, the optimal angle of inclination is taken equal to the value of the latitude of the area. For winter, 10-15 degrees are added to this value, and in summer 10-15 degrees are subtracted from this value. Therefore, it is usually recommended to change the slope angle from “summer” to “winter” twice a year. If this is not possible, then the angle of inclination is chosen approximately equal to the latitude of the terrain. Moreover, the angle of inclination also depends on the latitude of the terrain. See the table to the right.
The share of energy production from a photovoltaic system at an inclination of 45 degrees, for an area latitude of 52 degrees north latitude.
West southwest south southeast east
78% 94% 97% 94% 78%
Yield is at its maximum (100%) when the panels are angled 36 degrees and oriented south. As you can see from the table, the difference between the directions to the south, southeast and southwest are negligible.
For example, in summer, the optimum angle of inclination is 30-40 degrees, and in winter – more than 70, depending on the latitude of the area. In spring and autumn, the angle of inclination has an average value between the value of the angle for summer and winter.
For autonomous systems, the optimal tilt angle depends on the monthly load schedule, that is, if more energy is consumed in a given month, then the tilt angle must be chosen optimally for this particular month.
The optimum tilt angle for latitude 52 degrees (North) for grid-connected systems is 36 degrees.
Small deviations up to 5 degrees from this optimum have little effect on module performance. The difference in weather conditions has a greater impact on the generation of electricity. For autonomous systems, the optimum tilt angle depends on the monthly load schedule, i.e. if more energy is consumed in a given month, then the angle of inclination should be chosen optimally for this particular month. Also, you need to consider what kind of shading there is during the day. For example, if you have a tree on the east side, and everything is clear on the west side, then, most likely, it makes sense to shift the orientation from the exact south to the southwest.
Dependence of the production of solar cells on the direction to the Sun
The width of the sunbeam depending on the location of the Sun.
The calculation of the amount of solar energy received by solar panels when the sun’s rays fall at an angle other than 90 °, consider the following example:
Example: solar panels are oriented south, no longitudinal tilt. The sun shines from the southeast. The line drawn perpendicularly between the solar panels and the direction to the Sun has an angle equal to 360/8 = 45 degrees. The width of one beam of incident solar radiation will be tan (| 90-45 |) / sin (| 90-45 |) = 1.41, and the amount of solar energy received by the solar panels will be equal to 1 / 1.41 = 71% of the power that was would be obtained if the Sun shone exactly from the south.
A good article describing experimental tests of the production of solar panels installed at different angles – Full-scale tests of the optimal installation angle of the SB, the effect of cleaning solar panels installed at different angles from snow is also considered there.
If you are faced with difficulties while choosing solar panels, grid inverters for your solar power plant, or you need help with installation – please contact us, our engineers will be able to offer the best option. We have been working in the solar panels market for over 18 years, during this time we have accumulated good experience, and we will be happy to help you.