Take a heavily insulated box with a window on one side and put a parabolic reflector in it. Point the reflector at the clear night sky, and you can create ice at the focus.
All objects are in a balance between incoming and outgoing heat, so when all the heat going out it sent into a sink - such as the clear night sky - the object will drop in temperature.
The effect isn't huge, but it's real. The system described in the submitted article here has nothing like the energy generating potential required to become a sensible source of renewable energy, but it's a nice effect, and a nice system.
Take a heavily insulated box with a window on one side and put a parabolic reflector in it. Point the reflector at the clear night sky, and you can create ice at the focus.
All objects are in a balance between incoming and outgoing heat, so when all the heat going out it sent into a sink - such as the clear night sky - the object will drop in temperature.
The effect isn't huge, but it's real. The system described in the submitted article here has nothing like the energy generating potential required to become a sensible source of renewable energy, but it's a nice effect, and a nice system.