THE HALF RULE IS IN EFFECT:

Battery developer Eos Energy Storage claims to have solved key problems holding back a battery technology that could revolutionize grid energy storage. If the company is right, its zinc-air batteries will be able to store energy for half the cost of additional generation from natural gas--the method currently used to meet peak power demands.

Company officials say that current prototypes demonstrate twice the energy density of lithium-ion batteries. They claim their final product will last for 30 years in grid-scale applications with a cycle life that is orders of magnitude greater than that of lead-acid batteries, making it one of the longest-lasting battery types around.

Follow @brothersjudd