...their best test shows 152 Watts in and 221 Watts out
Interest from a well-known defence contractor is disclosed for the first time.
A COP of 221/152 is pretty low and won't be sufficient to obtain commercial interest.
Looks like their current harvesting technology is not the best solution.
I would tend to think they need a different technology with higher yield.
Interest from defence is a different issue. It's probably the fundamental cause of energy gain that will interest defence rather than their current product solution. They have more resources to further improve the energy harvesting.