The Covrex® Solar heats your pool by absorption of the solar heat.
Sunlight will heat the black inferior part of the Covrex® Solar and increase the temperature in the hollow chambers, which will after transfer this heat directly to the pool. The heat of the sun is a continuous source of energy, and is transferred directly from the sun, to the pool. the fact that the inferior part of the slat black is, will avoid sunlight to enter the pool water, and hence limit the proliferation of algae in the pool.
With a water circulation on while the cover is closed will transfer the heat equally from the surface to the rest of the pool water.