If this device can produce energy cheaper than some other methods; then it will carve out a niche in the market.
If massive government subsidies are required — then that too is all you need to know about the economic viability of the technology.
BTW, storage would not have to be a big problem. First off, you would only need to store a couple of days worth of hydrogen. That's a lot easier to manage than storing fuel for a month or more (as in the propane tanks). Also, hydrogen storage isn't limited to pressure tanks. There are a great many alternatives, including metal hyrdides.
Actually, there is an engineer in (I think it was) New Jersey who built his own home "hydrogen energy system". For storage, he used old propane tanks. He just used bigger tanks and stored under lower pressure. His "one off" system was quite expensive, but most of that was "in the engineering". He was developing a business to sell such systems to "rich guys who own islands" and who wanted all the amenities of civilization, but cheaper than boating in diesel. His estimated cost per system wasn't all "that" unreasonable for "boonies" operations. I'll see if I can find that article again....it's been a few years since I read it.