The Stand-Alone Laboratory is a station part which has everything necessary to serve as a one piece functional space station.
It comes equipped with built-in Solar Panels to re-charge its on board batteries (stored as cargo), a rocket engine with internal fuel tanks (which can be re-filled). It also comes equipped with eight cargo slots pre-loaded with 2 Batteries, 2 Oxygen Tanks, 2 Carbon Dioxide Scrubbers, and 2 Water Tanks. Its solar panels generate 100 electricity (without the batteries on-board), of which it consumes 6. It is essentially NASA's space station Skylab, made out of a Saturn V third stage.