Bloom Energy and Deeya Energy are two hot storage companies. Bloom hasn't even released its product yet, a 25-kilowatt device, and Deeya just started shipping its first units.

And both companies already have splinter companies.

EnerVault has been formed by former Bloom execs. Not sure what they do and the website is equally vague.

Primus Power, meanwhile, is a spin off of Deeya. They are raising money and are not related to the camp stove.

Bloom makes a solid oxide fuel cell, which is a tub of chemicals that generates electricity, while Deeya has a flow battery. Deeya's redox flow batteries are aimed at providing a low-cost alternative to lithium-ion and other advanced batteries – about 10 to 20 times less expensive, the company says. Redox flow batteries work by moving an electrolyte through a reactor that converts their chemical energy to electricity. Spent electrolyte is recovered for recharge while newly energized electrolyte is pumped back in.

Deeya's units can hold about 2 kilowatts of energy. It is selling them first to cellular companies to provide power to cell towers. Its first market is India.

Another company in flow batteries to watch: Enstorage.