Larkspurdetails solar-plus-battery library system, weighs generator and mutual-aid options
Loading...
Summary
City staff said the new Larkspur library will have about 40 kW of solar and a 60 kWh battery bank (30 kW inverter) that can keep critical systems running for short outages; officials debated programming the battery for cost savings versus emergency reserve and whether to secure a diesel generator or mutual-aid leasing for longer outages and pump-station needs.
Public Works Director Julian Skinner provided a technical and operational briefing on the new library's solar and battery system at the Feb. 11 forum.
Skinner said designers installed roughly 40 kilowatts of rooftop solar and a battery array initially sized at about 60 kilowatt-hours, with physical space to add two more 60 kWh units if needed. The battery system uses a 30 kW inverter. "If your batteries were fully charged... you'd have about two hours worth of use" at full load, he said, noting that typical PG&E interruptions are usually measured in minutes rather than hours.
Staff emphasized the system's multiple functions: daily peak shaving (reduce grid bills by discharging during high-rate periods), storing excess solar production, and providing limited backup for critical systems such as lights, receptacles, servers and security cameras. Skinner cautioned the battery cannot reliably start large HVAC motors; consequently, the battery bank alone cannot sustain full building environmental systems during prolonged outages.
That limitation led to a broader discussion about backup power strategy. Skinner said the original project included a provision for a drive-up connector so the city can connect a generator if prolonged power loss requires it. He described the practical options: short-duration outages handled by the batteries; multi-day events would likely require a generator. "It's the most efficient way to get backup power now," he said.
Participants debated environmental trade-offs and procurement models: buy a diesel generator and maintain it (more customizable), lease or rent one when needed (cheaper short-term but availability risk), or pursue mutual-aid county pooling to reduce duplication. Several speakers recommended examining subscription rental models that guarantee delivery within a specified time window and checking recent heavy-duty EV listings at procurement fairs.
Attendees also discussed using the library as a resiliency hub. Skinner said the building was upgraded to the highest occupancy/resilience structural standard so it could remain habitable after a major earthquake, but stressed planning is needed to set battery charge-management protocols, public messaging, and mutual-aid arrangements for pump stations that, if kept powered, can prevent neighborhood flooding.
Next steps: staff will run usage scenarios across a year to fine-tune battery operating parameters, seek applicable grants and rebates for batteries and chargers, and continue conversations about whether to lease, subscribe to, or buy a backup generator and how to structure mutual-aid agreements for pump-station support.
