Concentrated solar still

While a simple solar still is a way of distilling water by using the heat of the sun to drive evaporation from a water source and ambient air to cool a condenser film, a concentrated solar still uses a concentrated solar thermal collector to concentrate solar heat and deliver it to a multi-effect evaporation process for distillation, thus increasing the natural rate of evaporation.

[citation needed] A typically 25% efficiency standard solar still (not allowing for any recovery of rejected latent heat), as the latent heat of vaporization of water is 2.26 MJ per kilogram,[3] should evaporate 2.4 kg (or liters) of water per m2 per day in a region with an average daily solar irradiation of 21.6 MJ/m2 (250 watts/m2), or 873 liters per year (like a precipitation height of 873 mm, 2.86 ft).

A twenty times more productive still would have a daily output of 48 mm (1.9 in) or 17.5 m (57 ft) yearly.

[4] The final evaporation stage produces distillate vapor that is considered to be at very poor state conditions.

In the latter case, the heat pump effectively "upgrades" the state conditions of the latent heat to more usable conditions (higher temperature and pressure) by performing work (e.g., compression).