A Solar Power System for a Microwave Terminal Site

The Lorain Products Corporation, Division of Reliance Electric, has designed, built and installed a photovoltaic energy conversion system as the prime source of power for a microwave terminal site in Appleton City, Missouri, U.S.A. The basic components of the system are the solar array, the power board, and the battery plant. The raw DC voltage and current generated by the solar array is conditioned by high-efficiency, high-frequency voltage regulators and stored in the battery plant. During periods of darkness or low insolation the battery plant provides power for the microwave equipment load. Peculiar to this solar power system is a special battery charging scheme which very efficiently transfers solar energy to the battery plant and the load, while preventing overcharging and excessive gassing of the batteries. During the charging cycle, digital control circuitry monitors battery response to system charging techniques and adjusts charge voltage and current according to battery requirements and available solar energy. The three controlled voltage regulators, one per sub-array, are capable of applying either an equalize or float voltage to the batteries, and capable of restricting battery charging current, in response to commands from the digital control circuitry. System metering includes an instantaneous indication of battery state-of-charge and provides for the automatic activation of commercially powered standby rectifiers in the event that battery state-of-charge decreases to a predetermined low level. Extended alarms and status indicators are provided for remote monitoring of system operation.