Solar rooftop projects are built with a ploy of maximizing energy density in the available roof area. Solar rooftop panels are mostly tilted based on their geographical location to achieve their most efficient performance. These tilted panels, in turn, cast shadows to the successive panels behind them, necessitating a defined gap between them to reduce the losses that may incur due to shadow. Therefore, an optimum spacing between the panel rows needs to be decided. Let us see in detail about the row spacing and automating the row spacing for rooftop projects in this article.
To have a clear overview about row-spacing among rooftop panels let us consider the image below,
In this picture, one could clearly visualize the effect of one panel on another with regards to the shadow imposed. You can also see the panels are placed with a defined spacing along the rows to eliminate the effect of shadows.
To conceptualize the row spacing let us consider the below illustration.
It is clear from the above illustration that row spacing plays a significant role in the performance of the rooftop panels by adding or preventing shades. To find the desired row-spacing for any rooftop it is obvious that there are certain panel characteristics, location and available area. Optimizing of use of available roof being the ultimate goal for any consumer could be achieved by effective row spacing.
The effective row spacing between the panels are decided by,
- Panel Tilt (β)
- Panel width (w)
- Height difference (H)
- Shadow angle and Azimuth angle(α)
The Tilt angle of a panel varies with the location of the roof and is the most significant factor deciding the row spacing. It is the angle between the solar panel and the roof base. The shadow pattern is derived from the tilt as well as the height of the panel. The shadow angle is calculated mostly on the winter solstice when one can experience more shadows for any objects owing to the Sun’s position.
The azimuth angle is the angle through which the sun rays penetrate the panels. The tilt angle is decided in such a way that panel is almost perpendicular to the direction of the solar radiation. This ensures the panel to have an optimal generation from solar radiation.
Steps involved to find the optimum row spacing are,
Step 1: Height difference
Using the table width and tilt angle, we can find the height difference of a panel.
Height difference (H) = Panel width × Tilt (sin of tilted degrees)
Step 2: Module row spacing
With height difference and solar angle, we can find the module row spacing using,
Module row spacing = Height difference / Tan (Solar elevation angle)
Step 3: Minimum module row spacing
This is the minimum distance required to be decided between the modules to effective performance of solar panels.
Minimum module row spacing = Module Row Spacing x Cos (Azimuth Correction Angle)
One should get their sun elevation angle and azimuth correction details from this article Sun chart program. You will get access to the pattern of solar elevation angle and associated shadow and azimuth from this resource. One must consider their desired time for calculation of shading effects on any roof in a given region.
The solar elevation article is found for a particular time say 9 am to 4 pm, that is, draw a line horizontal from 9 – 4-time slot to find the respective solar elevation angle. 27 degrees in this case. Similarly, draw a line from the same point between 9-4 to find the azimuth correction angle. 51 degrees from the x-axis in this case.
We could use the basic trigonometry functions to find the distance between the 2 rows.
If we have panel width as 1m and tilt 20 degrees, we get the height difference as
- Height difference (H) = 1 * sin 20 = 0.342m
- Module row spacing = 0.342/tan (27) = 0.675 m
We have seen the calculation part for the module row spacing but, in case of roof, we have rows as well columns. One more parameter needs to be considered for evaluation which is the row width. The distance between one row ends to the successive row tail or end. We use the minimum row spacing between the modules to find the row width as,
- Minimum row spacing = Module Row Spacing x cos (Azimuth Correction Angle)
= 0.675 * Cos 52 = 0.415 m
- Row width(W)= Minimum Module Row Spacing + cos (Tilt Angle) x Module Width
= 0.415 + (0.939) = 1.354 m
By these steps one can fairly estimate the required row spacing data for rooftop projects.
Auto row-spacing in The Solar labs.
By following the above methods, we could able to find the row spacing for any south-facing roof projects. In The Solar Labs, we can find the auto row-spacing values for any rooftop projects. On entering the desired panel make, mount height and tilt, the design studio automatically estimates the required row-spacing.
Further, there are also various solar roof spacing calculators available in the website for references.
Row-spacing in solar rooftop projects is the most integral part of designing. Manually estimating these values consumes our valuable time. Therefore, one could design their rooftop solar projects efficiently and accurately using automated software like the Solar Labs for auto-row spacing and other salient design features. Careful consideration should be given for the below-listed factors for efficient row spacing,
- Tilt angle and location of the mounted panel
- Mount height and width of the solar panel
- Azimuth angle and direction of panel.
- Sun Chart Program http://solardat.uoregon.edu/SunChartProgram.php