Autovent

An autovent is a device for maintaining a greenhouse or conservatory within a range of temperatures. The basic principle is that as greenhouse heats above ambient the air inside becomes lighter, the vent opens when a certain temperature is reached and lets the hot air out - drawing cooler air in from outside.

Mechanism

The force to open the vent is provided a number of ways, the most common being through thermal expansion and by electric motors. Thermal expansion based actuators use either the differential expansion rate of different materials (bimetallic strips) or special fluids with large coefficient of thermal expansion in pistons. This approach is cheap, reliable and passive (requires no external energy).

Electric motors (usually servo motors) are usually controlled by an electronic sensor, and can be more accurately programmed. The vents can form part of a more complex climate control system for controlling humidity, fresh air rate and temperature. The most sophisticated systems use a dedicated computer to control watering, cooling (usually evaporative cooling), heating, lighting, CO2 injection fertilization and air flow.

gollark: And after just 20ish months and hundreds of millions of doses administered!
gollark: It seems like it's already quite bad, and this would presumably be good for the booster shots some places are talking about.
gollark: With the mRNA/viral vector vaccines, it would be pretty easy to swap out the spike protein for delta-variant ones and probably get better immunity to it, right? Is anyone doing this? It seems like a very obvious idea.
gollark: This "gematria" thing reminds me of that excellent excessively pun-heavy bible fanfiction I read but not funny.
gollark: Like the xkcd about playing conspiracy theories off against each other?
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