Niels-Arne Baden has a problem: The factory he’s building for Green Hydrogen Systems is too small.

Plans for the Denmark site to be one of the largest for assembling the machines that make hydrogen from electricity were finalized about a year ago. But demand for those electrolyzers is growing so fast that Baden’s now planning to double its size.

"When I joined this company in 2014, there was no market,” Baden said. "Then last year, it was ‘Kaboom!’ — and we were up to our ears in opportunities.”