At the new Larkspur Library, 40kW of solar and a 60kWh battery — and a debate over when to spend it
Public Works Director Julian Skinner walked the Climate Action Forum through the guts of the new Larkspur Library's power system Wednesday: a 40kW rooftop solar array paired with a 60kWh battery storage system that can be scaled up with two additional 60kWh units. The battery charges off either the sun or the grid, trims the building's draw during peak demand hours, and during an outage can keep lights, outlets, and IT and security systems running. What it cannot run is the HVAC — Skinner explained that the motors' startup loads are too high, so an outage could mean clerestory windows and fans instead of heating or air conditioning.
The building itself was structurally upgraded to seismic level 4, meaning it is designed to remain occupied after an earthquake — the backbone of its intended role as a community resiliency hub. How the battery gets used day to day is still an open question. One member urged programming the batteries to discharge during peak utility rate hours on ordinary days to save money, then overriding that setting to hold a full charge ahead of announced PSPS shutoffs, noting the practice also frees grid capacity for the surrounding neighborhood. Staff's plan is more cautious: monitor a full year of actual building energy use before locking in charge-and-discharge protocols.
Forum member JJ Andre raised a different worry — whether residents would even know to head to the library during an outage, and whether advertising the library as backup power might discourage households from investing in their own solar and storage.
The harder money question followed. The forum discussed whether the city should stop renting a diesel backup generator and buy one, at a cost of roughly $200,000, possibly cost-shared or arranged as mutual aid with neighbors like Corte Madera. Skinner said he is personally open to buying, and pointed out that the most critical load isn't the library at all — it's the pump stations that keep roughly 200 homes from flooding. One member suggested tallying what the city has already spent on rentals, plus the "cost of headaches" of scrambling for equipment mid-emergency. Asked about cleaner options, including grants and Bloom Energy fuel cells, Skinner said diesel remains the only practical choice for pump-station-sized loads today, but staff will keep checking emerging alternatives — hydrogen, mobile solar-battery units — before committing.