Light

Light works differently in Noih than it does in our world.

For one, it can be collected with specialised equipment and compressed into a liquid (Bykaas has one such machine). Artificial sources of light in are connected to a reservoir of liquid light through pipes.

The light is also a source of heat. It warms up the land and, when in its liquid state, quickly evaporates if not contained. Even contained light slowly evaporates while heating the vessel it's in. The rate of this depends on the material's ability to insulate. Plants need light to grow, but this mechanism apparently isn't photosynthesis.

There are theoretical unpleasant uses of liquid light. It can be injected, but the result would be the same as with hot water. Light torture is also a thing, during which the victim is sprayed with searing hot liquid light, but since the same can be done more cheaply with water, it's not common.