Abstract: A hardened solar thermal energy collector (STEC) system that is adapted to withstand a nuclear detonation or other powerful explosion in the vicinity. The STEC system comprises a plurality of collector tubes arranged side by side in an array that carry and circulate a working fluid, each of the plurality of collecting tubes having an upper radiation collection surface having a diffractive optical structure and a bottom surface, a supporting tray upon which each of the collector tubes is securely mounted, an insulated housing set beneath a ground surface level enclosing the plurality of collector rubes and supporting trays, and a secured underground geothermal storage unit fluidly coupled to the array of collector tubes. The housing, the plurality of collector tubes, and the tray are positioned such that topmost portions thereof are at the ground surface level or below.