The move brings the 65,000-tonne future flagship of the Royal Navy closer to becoming an operational warship.
The first of the ship's four generators was officially started by defence procurement minister Philip Dunne.
The warship is due to be handed over to the Ministry of Defence in 2016 ahead of being put into service in 2020.
Work is already under way on a second aircraft carrier, HMS Prince Of Wales.
HMS Queen Elizabeth's diesel generator sets will provide sufficient electrical power to drive the ship at cruise speeds. However, when higher speed is required, two gas turbine alternators will also be used.
Together they will produce 109MW of power - enough to power a medium-sized town.
HMS Queen Elizabeth is the lead ship of the Queen Elizabeth-class of aircraft carrier, the largest warship ever built for the Royal Navy and capable of carrying up to forty aircraft. She was named by Queen Elizabeth II on 4 July 2014, and is scheduled to commission in 2016.
Fitting out will take until the end of 2015 and the crew will move aboard in May 2016 ahead of sea trials beginning in August 2016 and delivery in May 2017. Flight trials with helicopters will begin in 2017 and F-35B flight trials towards the end of 2018. An "operational military capability" will be declared in 2020
The two members of the Queen Elizabeth class (her sister ship being HMS Prince of Wales) are each expected to be capable of carrying forty aircraft, a maximum of thirty-six F-35s and four helicopters. The 2010 SDSR anticipated the routine deployment of twelve F-35Bs, but a typical warload will be 24 F-35Bs and some helicopters. These could be a Maritime Force Protection package of nine anti-submarine Merlin HM2 and five Merlin Crowsnest for airborne early warning; alternatively a Littoral Manoeuvre package could include a mix of RAF Chinooks, Army Apaches, Merlin HC4 and Wildcat HM2. As of September 2013 six landing spots are planned, but the deck could be marked out for the operation of ten medium helicopters at once, allowing the lift of a company of 250 troops. The hangars are designed for CH-47 Chinook operations without blade folding and the V-22 Osprey tiltrotor, whilst the aircraft lifts can accommodate two Chinooks with unfolded blades.
Defensive weapons include the Phalanx Close-In Weapons System for anti-aircraft and anti-missile defence; also 30mm Automated Small Calibre Guns and Miniguns for use against fast attack craft.
Highly Mechanised Weapon Handling System (HMWHS)
Incorporated into the first two blocks is a sophisticated handling and deployment system for air weapons, with the aim of achieving a sortie generation rate which is about six times faster than any previous Royal Navy aircraft carrier. The system requires only 50 people and could be operated with as few as 12 in an emergency; it is estimated that 160 would be needed to produce the same efficiency with conventional equipment. The system moves munitions on pallets by means of remotely controlled electric vehicles and lifts
SOURCES - BBC News, Wikipedia