The SPV Power Packs for mini loads are primarily intended for operating small or medium domestic and office loads. Typically loads such as fluorescent lamps, tubes, audio video equipment, personnel computers, printers, fans etc. can be hooked on to these systems. The systems for mini loads are available in various configurations i.e. 500 VA, 850 VA and 1400VA. Systems for higher end loads are also available in configurations of 2.5 KVA, 5 KVA, 7.5 KVA and 10 KVA. The Power Pack basically consists of the following major items also shown in the typical schematic block diagram.
BHEL make type L24250 PV module having output of 250 15 WP at STC of 100mW/cm2, AM 1.5 at 25C. The maximum power point voltage is 35volts. The module consists of 72 nos. solar cells electrically connected in series and laminated in between two layers of EVA sheets with high transmission, toughened glass on the top & polyester -TEDLAR- polyester at the back.
Sealed maintenance free lead acid battery (also called VRLA – valve regulated lead acid battery) having efficiency of 90% minimum are used in the systems. The battery bank voltage generally would be of 24 V or 48 V for mini loads and around 96 V and above for higher loads. Alternatively, LMLA battery can also be supplied if specifically need. The battery along with the Power Conditioning Unit is to be located inside the building/utility area, but adjacent to the SPV array.
Galvanized MS sections are used for module support structures.
The Power Conditioning Unit comprises of a charge controller, mains charger and inverter.
In the Charge controller, precision comparators are employed to monitor battery voltage & there by control the state of charge of the battery. Battery is thus protected from deep discharge & overcharge. Battery low, battery over charge indications are provided through LEDs. Battery on charge indication is also provided through LED. A blocking diode is provided in the PV array - battery path to eliminate discharge of battery through “PV” during nighttime. The system is protected against battery reverse connection.
The inverter is of either MOSFET or IGBT based push pull type. No load current is less than 5 mA & efficiency is greater than 90%.
PVC insulated 2 runs of single core cable with sheathing will be provided for interconnecting the PV modules, Battery and system electronics.
As mentioned before, only general domestic and office loads like lights, fans, Personnel Computers, printers, fax machines etc. only should be connected to the Solar mini power packs. Collectively the connected loads should not exceed 80% of the VA rating of the SPV system chosen.
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