The owners say that power is not expected to be back on before 5 pm.
Odyssey Trust spokesman Adrian Doyle said the power cut out at 2.30 am this morning.
A team of specialist contractors have been drafted in to fix the problem.
“We would ask any groups who are booked to attend W5 this morning not to travel as the building will not be able to open,” said Mr Doyle.
“The car park will operate manually today.”