Abstract: A solar electric conversion unit and system includes substantially increased efficiency with reduced losses and increased acceptance angles. The system employs a short focal length fresnel lens extruded to further include depending side walls. The free edges of the sides carry a heat sink supporting a photovoltaic cell. The extruded side walls function as light pipes for carrying light directly to the photovoltaic cell. The walls are reflective inwardly of the unit to further avoid loss of stray light.

Abstract: In general, a block and retaining wall formed by a number of such blocks are interconnected between courses by a plurality of Z-shaped anchor elements having an upper and lower body part of substantially rectangular cross-section as viewed in plan. The upper body part is offset from the lower body part. The offset of one course of blocks relative to the course beneath will be a predetermined fixed amount determined by the offset of the body parts of the interlocking Z-shaped anchor elements. A tie-back arrangement includes means for attaching a sheet of geosynthetic material to the embedded end of a block so as to leave the open cells within and those formed between the blocks unobstructed from above and available for filling with pea gravel or other drainage fill material.