Parameters for solar angle calculation

user interface

SPAC user interface in brief

The web application SPAC calculates theoretical quantities (angles and radiation) as well as practical quantities (annual electricity and profit gain). The application window consists of 3 sections.

The main section on top with required 3 most important data enter fields

1. Location section (Latitude)

2. The Roof Angle of house or Tilt Angle or Slope

3. The roof orientation to the south

first parameter

Latitude

Latitude of your place …

If we have found a side that is completely or partially facing south, we can continue with further calculations. Another parameter that you need to know and that the solar calculator requires is your latitude. But don’t worry; you don’t have to look for it on maps or Google. Simply choose from the list of locations or cities in the drop-down menus. If your city is not included in the list, you will need to search Google for the latitude of the location you have selected for the solar panel installation, which is typically your hometown. Choose from the list of locations or cities in the drop-down menus. If your city is not included in the list, select the nearest city.

That would be the basis. And now the most interesting thing: how much electricity we can get from our roof or solar power plant.

SECOND parameter

Tilt angle - slope

The second parameter that the solar calculator requires is the tilt angle, or roof pitch, of your roof. You will have to measure that. An ordinary protractor is sufficient for this purpose. Place it on the roof’s slope, align the second ruler or spirit level vertically, and then read the result. Some protractors are homemade, while others are sold. If we use a protractor as shown in the picture, we must lean the long side against the roof and place the ruler vertically. Read the value on the left side of the protractor.

third parameter

Roof orientation

The first and main parameter is the orientation of the roof. At least one side of the roof must be completely or partially facing south. This means that the roof does not have to be strictly facing south, but south-southwest or south-southeast is acceptable. We will not consider the exploitation of a part of the roof facing north, north-northwest, or north-northeast for solar panel mounting purposes. We can easily determine if at least one part of the roof faces south with the help of a compass.

roof dimensions

Solar panel section

First, select the desired solar panel from the database. The list box contains the basic data on the dimensions and power panels. Then choose one of the two options. The first is the installation of the panels on the roof. Simply input the length and width of the roof, making sure to enter the dimensions exactly as they appear in the picture. Consequently, Liu Jordan’s approximation will yield the surface utilization rate of the roof and the annual theoretical profit of electrical energy. Another option is to select the solar panel grid, again adhering to the principles depicted in the picture, and specifying the number of rows and columns. We assume a regular connection between the panels. In that scenario, in addition to the anticipated electrical energy, we will also receive output power, allowing us to further optimize the design of the inverter.

Alert The following example was created for the previous version of the program, which only calculated the theoretical values of angles and radiation. It serves to display the measurement of basic parameters.

example

Let's take a look on example

Latitude and orientation

For our example, we will take a house in the countryside. We can use Google Maps to determine the latitude. All right, just point your mouse at the house and read the latitude. Let’s examine the location on the Google map. In our case, the coordinates are 44.117 degrees north. We will observe that the house is oriented towards the southeast and northwest. Of course, we will use the roof that faces south-east.

The pictures show that the useful part of the roof faces south-southeast at an angle of 46 degrees when viewed from the south.

Roof slope

We still have to measure the slope of the roof. We will do that with a primitive do-it-yourself protractor. We will utilize gravity for this purpose. A protractor is a board that has a divided circle of +-90 degrees (semicircle) adhered to it. We drilled a hole at the beginning of the coordinate and inserted a pointer with a small weight there.

The roof slope is 44 degrees. We now possess all three data points necessary for the calculation. They allow us to calculate monthly radiation and estimate solar panel installation profits. So let’s do it.

Choose any option because we’ll enter the data manually anyway. Next, enter data for latitude, orientation, and roof slope.

Please note Due to the custom latitude selection and the fact that I do not know "monthly sunshine days for location", all calculations are based on latitude.

Press “Calculation” button

The picture above shows the ideal angles of the panels for each months. However, our roof ( and panel) are at a fixed angle, we proceed to the next step

We can now analyze the data. I personally use LibreOffice. There are three rows in the table. The table displays the received solar radiation, energy per square meter, assuming a panel utilization rate of 0.2, and the energy obtained from a panel measuring 1.65 m x 1 m (65 inches x 79 inches).

Table – data analys and chart

What can we conclude?

We have a fairly winterized roof with a high angle value of 44 degrees, which guarantees excellent usability during the winter months in early spring and late autumn. But then the days are short. The slope creates an unfavorable situation during the summer season. The house’s relatively unfavorable orientation, even at 46 degrees from the south, adds to the complexity of the situation. All in all, I had a slight increase from January to April, a drop in the summer months, and a stabilizer during the fall. The average output from the panel is 260 W, which is not bad, but it can always be improved.

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Parameters for solar angle calculation – 3 essential