Doodads and Whatchamacallits.
Hi Tom,
Well without revealing the exact process, there is a "whazzit" metallic polymer layer sandwiched between another polycarbonate layer and kevlar armor, that absorbs body heat and a "doodad" thingy that carries a charge through this layer and turns the heat into electricity where it is stored like a heat sink into shielded "whatchamacallit."
Thats about as much as I know or can reveal ;-) To be found in military surplus stores sometime around 2025.
Best wishes,
SDAI-Tech1