Then there is pumped storage, an old technology that in Europe and China already has made a comeback with a new generation of plants.
In the United States, some pumped-storage projects were built decades ago, often in conjunction with nuclear and coal-fired power plants that might crank out more power than needed.
Today, the big dollars required for construction are a formidable obstacle, and power markets have not fully valued the storage they provide. But there is fresh interest in the West, where the rugged terrain makes for good sites, and surging power production from California solar farms and regional wind projects offer opportunities.
London-based National Grid hopes to develop two pumped-storage sites -- one in southern Oregon and another near Goldendale in southern Washington. Those projects collectively could yield enough power to provide electricity to more than 1 million homes.
A prime place for wind
Gordon Butte, in central Montana, would be smaller. But it is further along. Last year, it cleared a significant hurdle and obtained a license from the Federal Energy Regulatory Commission. Yet so far, no utility or major power user has committed to the project.
The project would be built near Martinsdale, an aging ranch community with fewer than 60 people that still has a bar but years ago lost its grocery store, bank and last gas station.
Borgquist was drawn here by an ample source of water, which is now used to irrigate an alfalfa field and could be diverted to fill the 60-acre bottom reservoir and 80-acre top reservoir more than 1,000 feet above. The site -- most important -- is less than 6 miles from the Colstrip transmission lines that now carry coal power west, but could one day send Gordon Butte hydropower.
"I knew the property, and I said, oh my God -- this is my site, right here," said Borgquist, an attorney-turned-renewable-energy-developer.
The butte also is a prime place for wind. Six turbines have operated atop the plateau since 2012, and have turned in a strong performance that ranks among the best in the nation.