Serving as an obstacle, powerless doors have lost their connection to whatever power source allows them to operate, and can only open if their power is restored. This can be done by scanning a nearby Interface Module, using the Thermal Visor and Wave Beam to energize Power Conduits, draining or giving energy to a terminal with the Grapple Voltage, inserting an Energy Cell into a station or eliminating an obstruction restricting power flow.
Metroid Prime scan
"This door has no power. A nearby Power Conduit must be energized for it to open. A blast of electrical energy will energize the conduit. The conduit radiates some heat that is invisible in the normal spectrum."