All Environmental Engineering

Inventions whose working principle is the protection of water, air and land and the use of natural energy flows in the built environment: devices that clean or desalinate water and equipment that gathers heat from the sun for ordinary use. Belongs here: desalination plants, water purification systems and solar water heaters. Does not belong here: dams, canals and water supply works, which sit with civil engineering, ships' ballast and propulsion systems, which sit with marine engineering, and photovoltaic cells, which sit with electrical engineering.