Solar panels work best when the entire panel receives direct sunlight. When choosing where to install the panels, avoiding shade is one of the most important considerations.
Avoid shading
A shadow on even a small part of a solar panel can reduce its power much more than you might expect.
A solar panel contains many solar cells that work together. If some of these cells are shaded, they can limit the electrical output of the panel. This means that 10% shade does not necessarily mean only 10% less power. Depending on where the shadow falls, the loss can be much greater.
For a solar water pumping system, reduced solar power may cause the pump to:
- Start later in the morning
- Run at a lower speed
- Stop earlier in the afternoon
- Pump less water during the day
For this reason, choose a location where the whole surface of every solar panel receives direct sunlight for as much of the day as possible.
Look for anything that can cast a shadow
Before installing the panels, check the surrounding area carefully. Common sources of shade include:
- Trees and branches
- Buildings, walls, fences, and poles
- Chimneys, vents, antennas, and roof railings
- Grass and other vegetation around ground-mounted panels
Pay attention even to small or narrow shadows. For example, grass growing across the bottom edge of a panel can reduce its output much more than the small, shaded area might suggest.
One shaded panel can affect other panels
Solar panels are often electrically connected together in a group called a string.
When panels are connected in a string, a shaded panel can also limit the power produced by the other panels in that string. Therefore, it is important that all panels, not just most of them, are installed in a location with clear access to sunlight.
Check for shade at different times and seasons
A location that is sunny now may not always remain free from shade.
The sun moves across the sky during the day, so a shadow that does not reach the panels in the morning may cover them later in the afternoon.
The position of the sun also changes with the seasons. When the sun is lower in the sky, shadows become longer. A location that receives full sunlight in summer may therefore be shaded in winter.
When choosing the installation location, consider:
- Shadows at different times of the day
- Longer shadows during different seasons
- Trees and bushes that may grow
- New buildings, fences, or other structures that could create shade in the future
Face the panels toward the sun
After choosing a location that is free from shade, orient the panels so that they receive as much sunlight as possible during the day.
As a general rule:
- In the Northern Hemisphere, panels should face south.
- In the Southern Hemisphere, panels should face north.
Correct orientation helps the solar pump start earlier, operate for longer, and pump more water during the day.
Keep the panels clear and clean
Anything that blocks sunlight from reaching the solar cells can reduce the power available to the pump.
Dust, dirt, leaves, pollen, and bird droppings can have a similar effect to shade. Grass and other vegetation can also grow in front of ground-mounted panels.
Inspect the panels regularly and:
- Remove leaves and other objects covering the panels.
- Keep surrounding vegetation trimmed.
- Clean the panels when necessary.
Follow the panel manufacturer's cleaning instructions. Do not use materials that could scratch or damage the panel surface.
Key points
For the best possible pump performance:
- Avoid shade on any part of the solar panels.
- Check for shadows at different times of day and during different seasons.
- Remember that one shaded panel can affect other panels connected to it.
- Face the panels toward the direction that receives the most sunlight.
- Keep the panels clean and vegetation under control.
A small shadow can have a large effect. Careful positioning of the solar panels helps ensure that the pump receives the power it needs and delivers as much water as possible.
