Odd for a kickstarter
This is of interest to me as we are off grid. However, given the choice of a passive chemical battery with no moving parts and something that has to run in a vacuum to close tolerances etc.,, I know which option I'll take. Now if they want to work on getting the nickel-iron battery into shape, that seems interesting. But as there is little patent potential (haha!) in it, as it was invented yonks ago, it's unlikely to be developed through the standard western greed model. See http://opensourceecology.org/wiki/Nickel-Iron_Battery
My requirements as one off grid are not necessarily the ability to store power for very long periods of time, just enough time when power from my few solar panels and my small turbine wane. Five days is acceptable. Given what I have learnt about the joys of running the mechanical wind turbine over the different joys of managing the passive lead acid battery, I know I would not choose a dynamic option such as a flywheel. By the way, my battery bank is a smidge over 15kwHrs.
I would much rather have a NiFe battery that can take un-ideal charge states when power comes in, and most of all, I would rather the battery bank did not deteriorate the way lead acid ones do, leading to replacement after 5-7 years even with careful management. I always laugh like a drain when battery how-to's talk about charging a battery using so-many amps at so-many volts when in the real off-grid world you're simply grateful for ANY amps at ANY voltage that flow in.