Batteries or Hydrogen or Both for Grid Electricity Storage Upon Full Electrification of 145 Countries with Wind-Water-Solar?

Grids require electricity storage. Two emerging storage technologies are battery storage (BS) and green hydrogen storage (GHS) (hydrogen produced and compressed with clean-renewable electricity, stored, then returned to electricity with a fuel cell). An important question is whether GHS alone decreases system cost versus BS alone or BS+GHS. Here, energy costs are modeled in 145 countries grouped into 24 regions. Existing conventional hydropower (CH) storage is used along with new BS and/or GHS. A method is developed to treat CH for both baseload and peaking power. In four regions, only CH is needed. In five, CH+BS is lowest cost. Otherwise, CH+BS+GHS is lowest cost. CH+GHS is never lowest cost. A metric helps estimate whether combining GHS with BS reduces cost. In most regions, merging (versus separating) grid and non-grid hydrogen infrastructure reduces cost. In sum, worldwide grid stability may be possible with CH+BS or CH+BS+GHS. Results are subject to uncertainties.