Silicon Planar In the silicon planar configuration, non-concentrated sunlight falls onto a planar array of silicon cells. Cells are passively cooled by radiating from their own surfaces. They are partly protected from harmful radiation by thick silica glass windows and substrate. Cells are periodically annealed to repair damage from energetic particles. A modular box-frame structure maintains the shape of the solar array. Because the silicon planar concept does not concentrate sunlight, it has an advantage over other power conversion systems in that the SPS does not have to precisely face the sun. The SPS can be oriented perpendicular to the plane of its orbit. This reduces stiffness and control requirements, so the structure and attitude control systems can be less massive. However, it introduces inefficiency near solstices when sunlight does not strike the cells perpendicularly. The useful lifetime of silicon cells in the geostationary orbit (GEO) environment is questionable because multiple annealing of silicon cells has not been demonstrated. High-temperature silicon cells being developed now may solve this problem [3], If repeated annealing cannot be effective, some redesign of the silicon SPS will be needed. Two possible changes are to use thicker cover glass and substrates, or to use a larger array area. Using a larger array is preferred, since doubling array size gives the same end-of-life (EOL) performance as a tenfold increase in cover glass thickness [4], Silicon Planar Design Description The solar cells and panels are similar to those of the Earth baseline design. It was assumed that the silver grid fingers of the original design could be replaced with lunar aluminium. In earlier studies, solar cell panels were connected and supported by plastic adhesive tape. This incurred a large non-lunar mass. SRA chose a grid of aluminium wires to support the panels. At edges of the grid the support wires are connected to catenary cables which attach to the primary bay structure. Rods connect the panels to the support grid. The panels are canted at 12 degrees to the SPS's longitudinal axis (Fig. 2). The SPS is rotated 180 degrees at each equinox so that the panels never face more than 12 degrees away from the sun. This reduces solstice losses from 8.29% to 2.19%.
RkJQdWJsaXNoZXIy MTU5NjU0Mg==