Best Angle for Solar Panels
Welcome to this informative article.
Do you want to build a really efficient solar power system but you don't know how to evaluate the correct orientation of the solar panels and how to calculate the perfect angle of inclination?
No problem, on this page you will find all the information and advice that will allow you to know step by step the correct orientation (azimuth angle) and the best inclination of your panels (tilt angle) according to the seasonal period in which you have higher electricity demand and to the geographical location where you want to install the solar power system.
In fact, thanks to a mathematical formula and our map of United States latitude, you will learn to calculate the optimal inclination for your city both in the summer and in the winter, without wasting time and for free.
In which direction should the panels be oriented?
When designing a solar power system it is essential to choose the roof side on which to mount the panels. We must therefore know on which side there is higher solar radiation for the whole day in order to have the maximum possible power production. Since solar panels are more productive when the sun's rays are perpendicular to their surfaces, the certainly best orientation is the one directly true SOUTH (azimuth angle = 180 °). On the contrary, in the countries of the southern hemisphere (such as South Africa and Australia), the best orientation is true NORTH.
In the event that installation in the South direction is not possible or we have shading problems (such as a very tall tree), it is possible to slightly change the orientation of the panels.
It is in fact useful to know that, if solar panels face outside true south, up to a maximum of 45° (south-east and south-west), the annual production undergoes a rather limited reduction (1-3%). The solar radiation that the panels receive is almost the same. However, if the panels are turned at an angle greater than 45 ° compared to true south, production begins to decrease significantly.
At 90° from true south (therefore east and west), production can drop to 30%. This decline is due to the fact that solar panels, during most of the day, are exposed to weak and not perpendicular sunlight. These panels will certainly produce solar energy but to a lesser extent than panels facing directly south.
What is the optimal tilt angle for solar panels?
Well, now that we know that the optimal direction is south, we need to find the optimal tilt angle.
First of all, in the choice of the tilt angle for solar panels on a house roof we are bound to satisfy two basic needs: the need for energy production and the need for an aesthetically pleasing and long-lasting final result. The roof of a house already has its own inclination and slope, so a compromise must be sought between these two needs. Knowing the optimal angle for production purposes will allow us to choose the best compromise for our installation.
If, on the other hand, you wish to build the structure for a sunshade canopy with solar panels or the structure for a ground-mounted solar system or for an innovative parking space covered by multiple panels wired in series or wired in parallel, this guide will be very useful in the design phase of the structure as it will provide you with the optimal inclination angle of the structure relative to the horizontal plane.
The optimal tilt angle that our solar panels will have is essentially influenced by two factors:
• the latitude of the geographical place where we want to mount them
• the time of year when we need more energy
How does latitude affect angle of inclination?
As I said earlier, the more a solar panel is perpendicular to the sun's rays, the more it produces electricity. The maximum energy production is achieved at midday, when the sun reaches its maximum altitude on the horizon. We therefore need to know, during the year, the maximum and minimum altitude of the sun at midday in order to discover how many degrees our panels have to be tilted. For this purpose, two special days of the year come to our aid.
As many of you already know, there is a day of the year in which we have less hours of light and a day of the year in which we have more hours of light. These days are called ...
• winter solstice
• summer solstice
The summer solstice, in which we have more hours of light, is 20 or 21 June and the sun at midday is at its highest annual altitude (see figure); while the winter solstice, in which we have less hours of light, is December 21 or 22 and the midday sun is at its lowest annual altitude (see figure).
Based on the latitude in which we live, the maximum and minimum annual altitude of the sun at midday also changes. As can be seen from the figure below (map credit: Mapsofworld.com), the latitude of Continental United States is between about 49° North (Alaska excluded), up to just over 26° South (Texas). To know the altitude of the Sun during the summer and winter solstice, we just have to identify the degrees of latitude in which we want to install our solar power system. Let's look at the figure below. For example, if we are in Chicago, the latitude will be around 42°.
Latitude of Continental United States
Calculating maximum Sun height at noon
Once the latitude has been identified, we must subtract 23° (current approximate angle of the Earth's tilt). The last mathematical operation is: 90 - (result obtained). In the case of Chicago we will have the culmination point of the Sun at 71°, obtained from the calculation 90 - (42-23). To get the maximum energy efficiency during the summer solstice, the solar panels in Chicago must face SOUTH and be tilted 19° (90-71). In this way, at noon the panels will be perfectly perpendicular to the sun's rays.
Calculating minimum Sun height at noon
To calculate the sun height at midday during the winter solstice, instead of subtracting, we must add 23°. The subsequent mathematical operation remains unchanged. The result for Chicago is 90 - (42 + 23) = 25°. To get maximum energy efficiency during the winter solstice, the solar panels in Chicago must face SOUTH and be tilted 65° (90-25). In this way, at noon the panels will be perfectly perpendicular to the sun's rays.
From the calculations it is immediately evident that a high tilt angle of the panels will favor a greater energy production during the winter season, while a low tilt angle of the panels will favor a greater energy production during the summer season.
Which tilt angle to choose for our system? Simple, the one that meets our energy needs.
If we are in Chicago and we need energy only in the winter season it is good to choose a tilt angle between 53° and 65° (example 59°), while if we need only in the summer it is good to choose a tilt angle between 19° and 30° (example 24.5°). On the other hand, if we have a greater need during the summer season it is good to have a tilt angle between 19° and 42° (for example 30°). If instead, we have a greater need during the winter season it is good to have a tilt angle between 42° and 65° (for example 53°).
If our energy needs in Chicago are constant all year round then we can opt for a middle ground, such as 42°, always with orientation towards the SOUTH direction.
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