Solar stills are devices that use solar thermal energy to:

Concept

A solar still is a passive thermal-separation device.

Solar energy heats impure or saline water so that water evaporates; the vapour then condenses on a cooler surface, separating it from many non-volatile impurities.

Application

In this device, the collected product is condensed water. The heat drives evaporation, and the cover guides the condensate into a collection channel.

Contrast

• Drying grain transfers heat to moist kernels and removes their moisture with air; the grain itself remains the product.

• Generating electricity requires photovoltaic conversion or a heat-engine cycle whose product is electrical power.

• Pumping water uses mechanical work to create flow or pressure and move liquid from one level or place to another.

Cross-check

The evaporation-condensation cycle is the defining distillation cycle, and the collected condensate is purified water rather than grain, electrical power, or pumped flow.

Therefore, solar stills use solar thermal energy to distil water.