The Innovation Center’s 83 kW rooftop PV system – powered by SunPower X21-335 high-efficiency modules – produces enough power for the entire building plus six electric vehicle charging stations. The PV system powers a battery storage solution consisting of a refrigerator-size LG Chem 30 kW / 45 kWh lithium-ion battery and an Ideal Power inverter, both controlled by a Geli Energy Operating System. With low electricity rates currently available through its local electric coop, RMI opted to remain connected to the grid. In the future, the Innovation Center’s power system will enable microgrid islanding, through which the building could supply its own power totally disconnected from grid.

The “brains” of the solar-plus-storage system, the Geli EOS, determines when to charge the battery (from the PV system or the grid) and when to discharge the battery to power the building. For example, if the Innovation Center draws an average of 50 kW or more from the grid in any 15-minute period during a month, the building is pushed into a rate tariff that imposes demand charges. The Geli EOS is programmed to automatically switch the system to battery power before hitting the 50 kW threshold.

Lithium-ion Battery