What is the impact of shading on photovoltaic panels?

A photovoltaic panel produces electricity by reacting to sunlight. The more a panel is irradiated, the more electricity it produces. Any shade should therefore be avoided.

The photovoltaic effect is a physical phenomenon specific to semiconductor materials that generate electricity when exposed to light. Crystalline silicon is one of these semiconductor materials, which is now widely used in photovoltaic panels.

Light is composed of photons, which generate the flow of electrons in the silicon cells by the photovoltaic effect. A direct electric current is created. 

These electrons then flow from cell to cell through metal connections. 

The continuous electricity is finally collected at the junction box of the photovoltaic panel.

A shadow means that a mask prevents the arrival of photons on the photovoltaic cells. If a cell is in the shade, its current production is degraded. The photovoltaic cells of a solar panel are connected in series. The cell that produces the least current imposes its current on all the cells of the panel.

This is why by-pass diodes are fitted to photovoltaic panels to minimize the production degradation of one or more neighboring cells.

A shadow is as impactful on clear weather as on very cloudy days. 

A cloud filters the light and deflects the sun's rays in a multitude of directions, we speak of diffuse radiation. Direct rays are much less powerful.

A nearby mask such as a chimney, a tree, a neighboring building, ... blocks the photons of the direct rays.

How Solar Panels work [Guide]