storing luggage in Dublin

There is bag storage at the airport but I'm not optimistic about your options in the city center (not at the train and bus stations). You might ask the apartment owner if there's an option near them.

We are in the same bind but our hotel said we can store our bags until we can check in. So you might check your accomadations.
Good luck

I saw a post a few months ago that mentioned baggage storage at the main bus station in central Dublin. A couple of other options were discussed, including the airport, but the bus station had a good price and a couple of choices for size of locker and duration of storage. I have not used this I just recall seeing a post. The central station is just north of the river and a few blocks north of the Customs House. You might give the bus station web site a look if your apartment is near there.