Yes, REDUNDANCY is a Scrabble word!

Letter values in Scrabble US: R 1, E 1, D 2, U 1, N 1, D 2, A 1, N 1, C 3, Y 4.

Is it a valid word?

REDUNDANCY is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

repetition of messages to reduce the probability of errors in transmission
the attribute of being superfluous and unneeded
(electronics) a system design that duplicates components to provide alternatives in case one component fails
repetition of an act needlessly

Not playable in Scrabble US: REDUNDANCE.