Which device powers the 28-volt electrical system in the aircraft?

The device that powers the 28-volt electrical system in most aircraft is typically an alternator. Alternators are designed to convert mechanical energy into electrical energy and maintain the electrical system's voltage while supplying power to the aircraft's electrical loads during flight. They are efficient, providing a consistent voltage output and being capable of producing more power at higher engine speeds compared to batteries or generators.

In many aircraft designs, especially those with more advanced electrical systems, the alternator is the primary source of electrical power once the engine is running. It recharges the aircraft's battery and ensures that the electrical system operates reliably. The battery serves as a backup and is primarily used for starting the engine and providing power when the engine is not running.

Generators, while they can also power electrical systems, are less common in modern aircraft due to their limitations compared to alternators in terms of efficiency and power output at various engine speeds. Solar panels, although they can contribute to powering systems, are generally not a primary source for an aircraft's electrical needs in the traditional sense.