St. Croix Cinema 400kWh Battery Storage Project

Greentech Renewables supported the installer in designing an installation in St. Croix that would prove competitive with the $0.45/kWh utility electric rate and be able to generate the cinema's own power when the grid was disrupted. Diesel offered a viable option at $.30/kWh, but diesel is not a clean power source, is noisy, and is subject to pricing and availability fluctuations. Mitigating the cons of diesel while remaining focused on the property owner's goals, the final solution was a solar-diesel hybrid system with GS Battery storage.

The property owner wanted Greentech Renewables and Electricity Wise Strategies (EWS) to integrate PV with the gensets to minimize fuel use, drive down the cost, and allow for scheduled use and refueling periods for the diesel gensets. The system could operate independently for self-electricity generation and maintain adequate storage in preparation for natural disasters, achieving resiliency while adhering to a fixed budget. 

Greentech Renewables analyzed the anticipated energy usage at the site and proposed integrating 200 kilowatts (kW) of PV with an additional 400 kilowatt-hours (kWh) of energy storage capacity to run most hours without diesel.

In order to meet the strict budget target, Greentech Renewables needed to find an ultra-high-efficiency lead acid battery and develop custom energy management software (EMS) to transition from the PV system to the batteries or to diesel without any fluctuations to the power supply, which would allow sensitive streaming and protect the equipment.

• Batteries
  • 336VDC GS Battery - 5000 Cycles at 70% DOD
  • REAP BMS - Custom BMS, monitoring every cell of the battery bank
• Energy Management System (EMS)
  • Custom (EMS) built by diesel-solar specialists and based on a local Dell industrial PC
  • Sequence of Operations (SEO) - Run on solar as much as possible, with diesel as the backup in case of load spikes or low PV production weather events
• Inverter Description
  • 6 x EPC Stability 30
• Generator Description
  • 3 x Caterpillar 135kW
• Sequence of Operations Description
  • Quiet Time - Battery only during the nighttime
  • Fuel Save - Always run on PV when available
• Results
  • Operating savings can reach $140,000 per year, resulting in an extremely short payback period for this system.
  • UPDATE: Hurricane Maria damaged a number of roofs on the cinema; nevertheless, the system continued to save the building owner money by running on the hybrid diesel/energy storage mode. The system is actively being repaired and transitioned back to a full solar + storage + diesel genset hybrid operation.