Glumac's Sacramento Office Photovoltaic System

by Ryan Cartwright, Sacramento Senior Electrical Designer, and Todd Ferris, Sacramento Energy Analyst

Glumac's Sacramento office incorporated a solar photovoltaic (PV) system to reduce the carbon footprint of the office.  The system also achieved several credits for the design phase submittal of the United States Green Building Council's Leadership in Energy and Environmental Design (LEED) rating system.  The project also followed the new State Fire Marshal installation guidelines for PV systems.     

The installed PV system is a 7.7 kW single array comprised of 54 Suntech 170W modules.  The system will generate an estimate of 14,276 kWh per year.  The actual energy produced is tracked by the local electric utility, and by a monitoring system that tracks the hourly energy production.  During January of this year, the system produced one fifth of their total electricity usage for the month.  

This reduction in electric energy use also helps lower Glumac's carbon footprint.  The amount of energy a building uses can be converted to an estimated amount of carbon dioxide(CO₂)  that is released into the atmosphere.  Utilities provide an emission factor which is used to estimate the amount of CO₂ released per kWh of electricity, and is derived from the ratio of the pollution created versus the amount of electricity produced.  Using this calculation, each saved kWh can be related to the quantity of CO₂ that would have been released during its production.  Using the national average emission factor of 1.37 lbs CO₂/kWh from the United States Environmental Protection Agency (USEPA) the system deferred 1,568 pounds of CO₂ last month, and could save 21,699 pounds or 10.8 tons by the end of the year. 

The installation of a renewable energy source such as a PV system is beneficial to a building that is pursuing LEED certification. The installed PV system helped achieve LEED credits for the Energy and Atmosphere (EA) section by increasing the buildings Optimized Energy Performance (EAc1) percentage from 39% to 49%.  This increase in performance provided one additional credit, and the project was able to achieve the maximum available credits for this category.   For the 7% savings over the maximum credit threshold of 42%, the project achieved an additional exemplary performance ID credit.  For the On-site Renewable Energy section (EAc2) the PV system provided 14.2% of the buildings energy supply, achieving three additional credits.  The total LEED credits earned for the PV system is five, which is enough to raise the potential certification level for the project from gold to platinum.

Another notable feature of the building is the amount of daylighting provided by the Sun Optics skylights that contribute a substantial energy savings by allowing the interior lighting to be turned off when sufficient natural light is available.  The installation of the PV system and the skylights required coordination to comply with new guidelines developed by California Department of Forestry and Fire Protection Office of the State Fire Marshal.  The new guidelines that local enforcing agencies are adopting significantly reduce the amount of available roof space to mount PV systems for both commercial and residential installations. The guidelines address roof access, pathways, smoke ventilation, and other installation recommendations to assist the installation industry and the fire protection community.  The access recommendations include providing a six foot perimeter around the edge of the roof.  The access area can be reduced to four feet if the length of the building is less than 250 feet.  The recommendations require that pathways should be over structural members, with four feet of clearance around skylights, ventilation hatches, and standpipes.  Smoke ventilation recommendations include that PV arrays should be no more than 150 feet long.  Ventilation opening pathways between array sections shall be a minimum of 8 feet or 4 feet when bordering skylights or roof hatches.  If a 4 foot by 8 foot "venting cutout" is provided every 20 feet on alternating sides of the pathway, a 4 foot pathway is allowed.