Abstract: Low-cost off-peak electric energy or electric energy from natural energy sources is used for heating of cooling of system air, which is moved in a closed circuit to heat or cool the energy storage medium of permeable concrete and sized gravel in the exterior walls of the structures. The heated or cooled system air is pressurized by a blower, and is moved horizontally outward through the energy storage medium, to store energy therein, as heat or cold. When stored heat or cold is required inside the structure, system air is moved horizontally, inward, through the energy storage medium, and is heated or cooled thereby, thus moving heat or cold to the material forming the interior surfaces of the exterior walls. Those surfaces then provide radiant heat transfer and convection heat transfer, with materials of the interiors of the structure, and with contents and occupants thereof. The energy storage walls are constructed of large energy storage blocks, lapped for added strength.