Solar heat collectors

Collectors that turn sunlight into useful heat for water, buildings, drying, cooking and industry.

Capture · Solar · No. 23

• Capture
• Output: Heat

A simple glazed rooftop collector captures about two-thirds of the sunlight striking it as hot water.

Chart: Illustration: Solar heat collectors

Where it comes from

Chart: Map of where it comes from

A coated absorber under glass soaks up sunlight and hands the heat to water or antifreeze, which carries it to a storage tank.

Three things to know

1. Solar district heating serves 346 towns and cities; Bracht in Germany gets 75-80% of its heat from the Sun.
2. Only about 1,315 industrial solar heat systems existed in 2024, though half of factory heat is needed below 400 C.
3. Evacuated tubes made up about 69% of world collector capacity in 2021.

The journey

1. 1 SunlightFalls on a roof or collector field
2. 2 AbsorberCoated metal under glass or vacuum
3. 3 FluidWater or antifreeze carries the heat
4. 4 Storage tankFrom household tanks to giant pits
5. 5 UsesHot water, heating, drying and factory steam

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