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This PV system will consist of a 2.5 kW PV array, a 2.5 kW sinewave inverter delivering 230 volts at 50 Hz to an all-ac load with a battery bank for storing the energy. Circuit breaker combining boxes will be mounted near the PV modules. A dc power center will contain the necessary disconnects, overcurrent protection, charge control, and system monitoring device.
The design and components will meet minimum USA safety standards and be specified for durable operation by untrained persons.
The dc system will operate at a nominal 24 volts. Forty-eight Siemens M55 modules with a nominal voltage of 12-volts will be connected in series sets of two to meet the 24-volt nominal system voltage requirement. Twelve of the sets of modules will be connected to a dc combining box that will contain circuit breakers for overcurrent protection of the modules and the module interconnections. The remaining twelve sets of PV modules will be connected to a second dc combining box. Exposed, weather-resistant cable will be used for the module connections.
The output of the two combining boxes will be transferred to the dc power center through heavy cables directly buried in the ground at least 24 inches deep. The dc power center will include disconnects, overcurrent protection, and charge control functions for the system. Conduit will be routed from, the dc power center to both the inverter and the battery bank. Heavy conductors will carry currents between the power center, the inverter and the batteries.
The battery bank will consist of 16 flooded lead-acid batteries installed in heavy plastic boxes. The will require periodic maintenance which will consist mainly of adding distilled water.
The inverter will deliver 230V 50Hz power to an ac load center that will have three circuits for the loads in the building.
Electrical loads planned for the school include three computers with Internet access via a satellite communications system, fluorescent lamps, and a television and VCR.
