IDeAs - Building-integrated photovoltaics

Daylighting	Natural ventilation/radiant heat	Ground Source Heat	Integrated design
Advanced Glazing & Insulation	Energy-saving office equipment	Renovation Not Green-field
Energy-efficient lighting	Energy Control & Monitoring	Building-integrated photovoltaics

A roof-integrated, grid-tied, net metering photovoltaic system powers this all-electric building. It is sized to deliver 30kW AC for an estimated 56,000 kilowatt-hours per year. If load estimates are correct, this should amount to net 100% of the building’s energy requirements.

If the building had been designed as a traditional, rather than high-energy performance building, a roof approximately twice this size would have been necessary. To apply a transportation-industry analogy, you can run a car off a hydrogen fuel-cell battery today – but not a fully loaded SUV.

Rooftop Photovoltaic Panels

Building-integrated photovoltaics (BIPV) are employed due to their compactness and efficiency. The design team estimates that a traditional photovoltaic system of equal size would require approximately 200 roof penetrations for structural supports. With this system a support structure is unnecessary and each panel serves as both a photovoltaic power source and a roof membrane. The Solarsave^TM Roofing Membrane (SolarSave SP-450), a unique roof membrane integrated photovoltaic system manufactured by Open Energy Corporation, combines a single ply PVC, fire rated, white, waterproof roofing membrane with high efficiency SunPower A300 monocrystaline solar cells. The A300 solar cells have the highest efficiency (20 to 21.5%) of any commercially produced PV cell. The product is lightweight, 2.5 lbs per sf and does not require ballast, special support structure, or structural penetrations, further reducing cost.

Southwall Sunshade

A second BIPV system using SolarsaveTM Architectural PV Glass (SolarSave SP-225), a laminated integrated photovoltaic system manufactured by Open Energy Corporation will be installed as a sunshade over the main entrance at the south side of the building. The modules are manufactured to allow filtered light to pass through the module and to allow occupants to view the photovoltaic cells in the modules from below when entering or leaving the building.

Renewable Energy Incentives

A key impediment to reaching a 100% net energy generation goal is the high cost of photovoltaic systems. The costs for the system were mitigated in three ways: The first is state energy rebates. Our current estimate for the size of the system is 30kW AC, the California Public Utilities Commission (CPUC) offers rebate currently set at a $2.50 per watt (9/1/06) for systems 30kW and above (CPUC 2006) and the California Energy Commission (CEC) offers a rebate currently set at $2.60 per watt (9/1/06) for systems less than 30kW (CEC 2006). Since our system will be very close to 30 kW our current strategy is to apply under the CEC rebate.

Roughly the same value as the state rebates, the new federal tax credit available for photovoltaic systems purchased in 2006 and 2007, allows commercial building owners to reduce their federal income taxes by 30% of the cost of the PV system and state income taxes by 30% of the cost of the PV system less any financial incentives.

Finally, an accelerated 5-year depreciation is available for photovoltaic systems. These state and federal incentive programs together will assist in reducing the cost of the photovoltaic systems by over 85%.