Quantity of sunlight on solar panel and its capacity depends on its angle to Earth’s surface.
In fact the Earth is sphere-shaped and it moves round the Sun making a complete circle in one year. Therefore the Sun angle depends on latitude and season. Below we will study other factors that impact the capacity of a solar panel and the best way of installing it to maximize power generation.
The sunlight, we are used to, can be split into two types: direct and diffused.
Direct sunlight is the light that reaches Earth’s surface directly from the Sun. This light carries a massive amount of energy as our Sun in one second produces more energy than mankind has consumed throughout its history. The density of solar power reaching the Earth is around 1.4 kW/m2. Unfortunately, around 30% of this energy is reflected back into space and only 1 kW/m2 arrives to our planet’s surface. However final sunlight power will depend on solar elevation angle, i.e. geographic latitude, season, time, atmosphere clarity and module incline.
Diffused sunlight is the light reflected from the earth surface and diffused by the upper atmosphere. After numerous reflections from the earth, clouds, snow and other surfaces this light can also give significant power even in gloomy weather. By the way, this is why in winter on frosty days with clear sky, when the white snow is blinding you, total electricity generation can be higher than in summer.
Thus for maximum capacity solar panels should be positioned at a specific angle to the earth’s surface – perpendicularly to sunlight, if possible. Unfortunately, in most cases solar panels are mounted firmly on a house roof or on the ground while sun angle is changing constantly throughout the day and year because our Earth’s movement round the Sun, which results in seasonal changes in sun angle.
In winter the light falls on the surface at significantly lower angle than in summer. In order to ensure efficient power generation panels should be positioned at a high angle to the ground. Additionally this allows solar cells to absorb the light reflected from the snow and solves the problem of snow accumulation on the panels in northern countries. And in summer, on the contrary, panel angle should be lower.
It would be perfect to mount solar panels on a structure with adjustable tilt (so that to change panel angle in winter and summer) or on a tracker that follows the sun throughout the day. If you do not have an opportunity to change your panel position twice a year you should mount modules at the angle equal to latitude of your location.
The optimum tilt for adjustable structures is defined based on the following formula:
- For winter – latitude plus 10-15 degrees;
- For summer – latitude minus 10-15 degrees;
Any minor deviations from these values will not have serious effect on panel efficiency.
The most efficient method is to use a tracker. Using light sensors such trackers can follow the sun in one or two axes and provide up to 50% of additional power through a year. This is comparable to 50% increase in number of solar panels.