Historically, the vast majority of the world’s power has been consumed as quickly as it is made, or it's wasted. But climate change has made governments interested in renewable energy, and renewable energy is variable—it can't be dispatched on demand. Or can it? As research into utility-sized batteries receives more attention, the economics of adding storage to a grid or wind farm are starting to make more sense.
But grid-tied energy storage is not new; it has just always been limited to whatever resources a local power producer had at the time. Much like electricity production itself, storage schemes differ regionally. Power companies will invest in batteries that make sense on a local level, whether it is pumped storage, compressed air, or lithium-ion cells.
Looking at the kinds of storage that already exist is instructive in helping us see where storage is going to go, too. Lots of the latest battery projects merely build on engineering that has been in service for decades.
arstechnica.com has compiled a list of these projects here.