Significant obstacles to acceptance of SPS have been the large unpopulated land area (about 40 kmA2) needed for a receiving antenna (rectenna) and the large quantities of power provided by each rectenna (usually 5 GW). Locations suitable for selling 5 GW of power typically have high land prices. Remote locations with inexpensive land are far from population centers and require construction of power transmission lines. This dilemma could be resolved if smaller rectennae providing less power were available. (Smaller rectennae providing the same power would exceed the peak intensity limit of 300 W/m*2.) For fixed wavelength and transmission distance, reduction of the rectenna diameter requires increasing the effective diameter of the transmitting antenna by the same factor. Increasing actual antenna size would be costly and would increase resistance losses in conductors, with an effective limit of about 2 GW of power at the ground. The effective antenna size might be increased at lower cost by placing a large lens in front of the antenna. An appropriate lens design is discussed in section 5.4. This concept is promising and deserves further study.
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