Our client’s objective was to add a grid tie system with as much Solar PV to his home as possible with the available roof space at the rear of the house. In addition the client wanted a battery backup system that would automatically supply a priority electrical panel with critical circuits whenever the grid (Utility) power was lost.
Two solar arrays were installed. The first array, consisting of 8 KYOCERA 315W (KD315GX-LFB) solar panels (2.5kW) powered a grid tie SMA Sunny Boy 3000W inverter (SB3000-US) which connects directly into the existing main house electric panel functioning as a typical grid tie Solar PV system.
The second solar array consisted of 30 KYOCERA 245W (KD245GX-LFBS)solar panels (7.3 kW) which powers a SMA Sunny Boy 7000w grid tie inverter (SB7000-US). This inverter connects into the SMA Smartformer, a device that converts single phase 120 VAC into split phase 240 VAC and also acts as an automatic transfer switch.
During normal operation the 7.3 kW solar PV array operates as a normal grid tie solar PV system. When grid power is lost, the Smartformer in conjunction with the SMA Sunny Island ( inverter/charger) automatically disconnects the grid feed from the main Electrical panel while maintaining AC power to the newly installed priority circuits electrical subpanel (refrigeration, alarm, basic lighting, etc.).
The SMA Sunny Island is powered from the battery bank. The battery bank consists of 8 Concord Sun Xtender PVX-2580L AGM maintenance free batteries which provides power (Approx 500A-Hr@48V) when no sun energy is available. While in the off grid mode when sun is available, the 7.3 kW solar array through the SB7000 powers the priority electrical panel while Sunny Island recharges the batteries so there will be plenty of energy available during the evening (non-sun) hours.
The entire system operates independent of users interface automatically changing between backup power and grid power as needed. The system is maintenance free. The battery bank is protected from overcharging or over discharging providing maximum battery life.