What do you do when your project has close to 40,000 square foot of roof space in one city block, good sun exposure, and no shading impediments? Go solar, of course, and generate your own electricity with a renewable energy source.
Mosaica, one of the largest green, mixed-use projects located in San Francisco, California, boasts a 130 kW solar photovoltaic (PV) system which is the largest residential system in San Francisco. The system’s estimated annual production of 189,000 kWh of clean energy is expected to offset at least 75% of the 470 kva common area electrical load.
The five story multi-building complex includes 228,000 square foot of circulation and common area spaces that are supported by 3 elevators, 4 boilers, heat pumps, fan coil units, booster pumps, fire alarm system, ventilation system, laundry washing machines, telephone entry systems, light fixtures, and other energy consuming equipment.
Mosaica’s solar PV system is the fourth system built by its developer, Citizens Housing Corporation (CHC), a San Francisco based non-profit affordable housing developer that is leading the way in developing responsible, green, and sustainable communities. When asked about why CHC incorporated a solar PV system into the project, CHC Project Manager Desiree Espinoza stated that:
“Even before we entered this economic downturn, CHC has always been proactive in developing projects that help reduce the operational costs of managing affordable housing properties. Given the size of Mosaica’s development and what that meant both in dollars and our environmental footprint, it made clear sense to add a PV system to this site to help reduce energy bills. Now that we are in a time where it is getting increasingly difficult to develop affordable housing due to city, state and federal budget cuts, we feel confident that this was a smart decision and we’ll see a return on the investment sooner rather than later. We hope others can learn from what we have done here.”
CHC selected Borrego Solar to design and install its 130 kW solar photovoltaic system consisting of Sharp PV modules and a Satcon 135 kW inverter. Borrego Solar handled not only the tedious permitting process, but also diligently worked with the general contractor, James E. Roberts-Obayashi Corporation to coordinate the PV system’s multiple interfacing with roof framing, roofing, mechanical, plumbing, and electrical work.
Most impressively, with the help of a crane, Borrego Solar loaded 748 PV modules onto the roof in one day. This was achievable because Borrego Solar pioneered the “component pre-fabrication process” in which they pre-wired and pre-racked the PV modules on to 1 x 4’s in a warehouse. This process enabled them to control the quality of the product and save production time. In the field, pre-fabrication allowed them to quickly drop and bolt the module racks on to the mounting frames in a systematic and efficient manner.
Borrego Solar’s Senior Energy Consultant David Potovsky believes that we as a community need to go solar because:
“Going solar is not only about being a good corporate citizen, but it is also about saving money. And while it is important for everyone to save money, it is even more valuable to affordable housing developers who can apply the cost savings from utility bills to other expenditures that allow them to improve the quality of life for their tenants.”
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