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 afterwards transfer the heat directly to the pool. The heat of the sun is a continuous source of energy, and is transferred directly from the sun to your pool. Because  the inferior part of the slat is black, it will keep the sunlight from entering water in your pool and, as a result, limit the proliferation of algae in the pool.

Thanks to the water circulation, the heat will be equally transferreded from the surface to the rest of the water in your pool, while the cover is closed.