This 40 kW building-integrated PV system was installed at Western’s Elverta Maintenance Facility. Sacramento Municipal Utility District (SMUD) funded the PowerLight Corp. PowerGuard system and Western contributed funds equivalent to the cost of replacing the facility roof. Co-funding also was provided by the Utility Photovoltaic Group (UPVG) through TEAM-UP, with support from the U.S. Department of Energy. The PowerGuard PV tiles, which were first demonstrated at Western’s Folsom, CA, facility in 1994, were used to reroof the building, saving conventional roofing material and the cost of tearing off the old roof.

The 420 PV tiles incorporate high-efficiency polycrystalline silicon cells from Solarex. The system features horizontal tiles and tile with an 8-degree southerly tilt for increased annual energy production. In addition to generating clean, renewable energy, the lightweight system provides R10 roof insulation for improved building comfort and mem-brane protection for extended roof life.

Facility Information

• System Owner: SMUD
• Building Owner: Western Area Power
• Site Location: Elverta, CA

Contractor

• Prime/System Integrator: Powerlight

Electrical Design

• AC Output: 120 V single phase
• PV Configuration (per string): 7 series; 8 parallel
• Number of Strings: 7.5
• DC Current and Voltage (per string): 24.8 A @ 218 Vmp

PV Roof Tiles

• PV Cell Material: Solarex polycrystalline silicon
• No. PV Roof Tiles: 420
• Tile Size: 40″ × 46″
• Insulation Value: R10

Performance Parameters

• Power Capacity: 40 kW peak DC; 36 kW AC
• Annual Energy (est.): 70,000 kWh/year
• Lifetime CO₂ Savings: 2400 tons
• NOX: 9 tons
• SOX: 17 tons
• Life Expectancy: 20 years

Schedule

• Installation Completed: May 1996
• Contract to Construction: 4 months
• Construction Duration: 7 days