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 on the list, then unfortunately you will have to look on Google for the latitude of the place you have chosen for the installation of the solar panel, which is usually your hometown. Choose from the list of locations or cities in the drop-down menus. If your city is not on the list, then 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. Lean it on the slope of the roof and place the second ruler or spirit level vertically, and then read the result. There are several types of protractors—some you can buy and some you can make yourself. If we use a protractor as in the picture, it is necessary to lean the long side on the roof and place the ruler vertically. The value is read 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. If a part of the roof faces north, north-northwest, or north-northeast, its exploitation in terms of mounting solar panels will not be taken into consideration. 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. It is enough to enter the dimensions of the roof’s length and width (take care to enter the dimensions as shown in the picture). As a result, you will get, calculated according to Liu Jordan’s approximation, the surface utilization rate of the roof and the annual theoretical profit of electrical energy. Another option is the selection of the solar panel grid (again, follow the principles as shown in the picture), the number of rows, and the number of columns. It is assumed that the panels are connected regularly. In that case, apart from the expected electrical energy, we will also get output power, according to which we can further dimension the inverter.
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 mouse on house and read latitude. Let’s examine the location on the Google map. In our case, it is 44.117 degrees north. We will see the orientation of the house is south east – north west. Of course, we will use the roof that faces south-east.
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. If a part of the roof faces north, north-northwest, or north-northeast, its exploitation in terms of mounting solar panels will not be taken into consideration. We can easily determine if at least one part of the roof faces south with the help of a compass.
As we can see from the pictures, the useful part of the roof is oriented in the south-southeast direction 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. For this purpose, we will use the force of gravity. A protractor is a board on which a divided circle of +-90 degrees (semicircle) is glued. A hole was drilled at the coordinate beginning, and a pointer with a small weight was inserted there.
The roof slope is 44 degrees. Now we already have all three data points for the calculation. Based on them, we can calculate the radiation during the months and get approximate data on the expected profit from the installation of solar panels. 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.
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
And now we can analyze the data. I personally use Libre office. There are three rows in the table. Received solar radiation, energy per square meter if we assume a panel utilization rate of 0.2 and the energy we get from the same panel measuring 1.65 m x 1 m (65 inch x 79 inch)
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 good usability during the winter months in early spring and late autumn. But then the days are short. During the summer, the situation is unfavorable because of this slope. I also have a relatively unfavorable orientation of the house, even at 46 degrees from the south, which further complicates the situation. All in all, I had a slight increase from January to April, a drop in the summer months, and a stabilization during the fall. The average is 260 W from the panel, which is not bad, but it can always be better.
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