hydroelectric power potential of the Caroni River, Guayana, Venezuela represents more than half of Venezuela's installed electric capacity, and is part of the world's second largest hydroelectric complex (10 GW) completed in 1986. With further additions about 17 GW capacity, will be completed by 2000 providing abundant electrical energy at a very competitive price. The existence of a transmission system provides several options for the location of a microwave beam transmitting antenna. Specific locations considered are in areas where the terrain is flat, rainfall is moderate, so as not to reduce beam transmission efficiency, environmental effects of construction are minimized and societal cooperation is likely. In 1989, Brazil had a total capacity of 54 GW with 96% supplied by hydroelectric power. Brazil's capacity expansion efforts have centered around large hydroelectric projects, such as the 12 GW Itaipu Binacional station located at the Paraguyan border. Other large projects include the 7.3 GW Tucurui station in the Amazon Basin. The upper Amazon has the potential for the development of very large hydroelectric capacity in the future. The Power Relay Satellite Concept The configuration of a PRS is shown in Figure 1. In this system, electricity is fed to microwave generators operating at a frequency of 2.45 GHz or 5.8 GHz. The microwave generators are incorporated in a phased-array antenna for transmitting the microwave energy in a controlled beam that is focused onto the microwave reflector in the PRS. The reflector redirects the beam to a receiving antenna on Earth in the desired location, where the microwave beam is directly converted safely and efficiently into electricity. The de output of the receiving antenna is fed to the power grid. The receiving antenna can be located at a preferred location. The functional systems requirements as they relate to the implementation of a PRS are indicative of the appropriate combination of technologies as shown in Table 1. The majority of technology developed for WPT systems has been at microwave frequencies, e.g., 2.45 GHz and at 5.8 GHz. Both frequencies are located in the Industrial - Scientific - Medical (ISM) band, thus permission to transmit at these frequencies is not needed as long as interference with other systems outside this band is avoided. Atmospheric attenuation is nominal up to 3 GHz. The 5.8 GHz frequency has a slightly higher loss caused by atmospheric attenuation. Transmission windows also exist in the atmosphere at 35 GHz and 94 GHz. Systems developed to operate at these frequencies enjoy the advantages of smaller antenna apertures. However, additional power margin must be factored into the system design to compensate for increased atmospheric attenuation, making these frequencies unattractive for a PRS. Microwave PRS System Description The PRS comprises three, stand-alone subsystems: • Transmitting antenna (transmitter) • Receiving antenna (rectenna) • Relay satellite reflector
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