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Flexible BIPV (Building Integrated Photovoltaic) – Solar Energy

Some California homebuilders are already in the business of generating solar power, and for those who haven’t yet considered building solar homes, it could be only a matter of time. That is, if consumer preferences and governmental requirements have anything to say about it.

Many homebuyers want solar power. Since California’s 2001 energy crisis, many existing homeowners and new-home buyers have been looking for ways to contribute to the power solution and have more control over their energy costs. In fact, a 2004 survey of likely voters in California found that 68 percent of those polled would be more interested in buying a home if it included solar energy, and 63 percent would be willing to pay more to buy a solar home. (The Public Attitudes and Support for Solar Power survey was conducted for the Environment California Research & Policy Center.)

And interest was high even before the energy crisis struck. In 1996, a Sacramento Municipal Utility District customer survey indicated that, if given the choice of a generation resource, solar-energy generation was at the top of the list.

But while some homebuyers might want solar homes, government could soon be requiring their construction.

In the past two years, there have been no less than four separate legislative efforts to require California homebuilders to install photovoltaic systems on new homes. In August 2004, Governor Arnold Schwarzenegger challenged the building industry to install photovoltaic systems on 1 million new and existing homes over the next 13 years. Proposed legislation to support the Governor’s plan — in the form of Senate Bill 199, by Senator Kevin Murray, D-Los Angeles — was killed before reaching the Governor’s desk last year over a union-supported prevailing wage issue, but the Administration plans to pursue solar legislation again this year.

Knowing the inevitability and significance of this topic for its members, CBIA is working with the Administration, photovoltaic system manufacturers, and the environmental community to develop solar legislation that provides a smooth transition for the homebuilding industry.

In the meantime, what should you do to respond to the growing interest in solar power? Educate yourself about the topic. Here is what you need to get started.

PHOTOVOLTAICS 101

The primary purpose of a photovoltaic system — which converts light into electricity — is to produce a home’s on-site electricity, thereby lowering the amount of energy purchased from the local utility company.

To maximize the benefits of a photovoltaic system, you must first reduce overall energy usage in a home. Installing energy-efficient appliances, insulating and sealing the home properly, and ensuring the HVAC system is properly installed are all important first steps when considering photovoltaic systems as a home feature. If these measures are applied in the initial building process, a photovoltaic system can effectively lower the electricity usage of a home by half or more, providing substantial monthly savings and protecting the homeowner from future electricity rate hikes.

Photovoltaic cells are the primary units of power generation for solar collectors. The cells are made from silicon semi-conducting material that usually is treated with various additives to enhance electricity production. There are three cell types: crystalline, polycrystalline, or thin-film.

Photovoltaic cells are fixed together in panels or manufactured in sheets of thin film. The cells are organized in individual modules, grouped panels, and larger arrays to form the system that transforms light from the sun into electricity as direct current (DC). The power can be used as direct current but is more commonly transformed into alternating current (AC), which is provided to the home’s electrical system or sent to the utility electrical grid.

The key piece of equipment used to transform DC power to AC power is an inverter. The inverter is a complicated electronic device that includes an anti-idling breaker, which shuts down current flow to the grid in the event of a power failure. This mechanism isolates the home’s system and keeps utility line crews safe from potential photovoltaic system power shocks.

Inverters operate at about 90 percent to 95 percent efficiency and usually come with a performance-monitoring device and a five-year warranty. The panels themselves generally carry a 20-year-plus warranty. Roofers usually install the roof collection system, while electricians install the inverter and connect the system to the utility grid.

Grid-connected systems require some form of “net metering” offered by the local utility. Net metering allows the home’s electric meter to spin backward and credits the owner’s utility account at retail prices up to the total annual use of electricity. If the photovoltaic system provides more electricity than it uses, the surplus typically goes to the utility — free of charge.

Photovoltaic systems are either attached to the home’s surface or integrated into the home design, termed building-integrated photovoltaics. California builders continue to use both types, but the trend is moving toward building-integrated systems. For integrated roof systems, the cost of the photovoltaic system is included in the cost of the roofing.

The photovoltaic panels are rated by their capacity to provide DC power in kilowatts and will generate a flow of electrons in the form of kilowatts per hour. The more sunshine, the more power generated. Power is generated from sunlight, not heat. Heat actually increases the resistance to the flow of electricity, which suggests that the ideal climate is one with a lot of sunshine and low temperatures. Thus systems typically generate more electricity in the cooler morning hours than in the afternoon, when temperatures are at their highest.

CONSIDER THIS

Homebuilders interested in offering photovoltaic systems have a lot to consider. The following considerations — plus more detailed information on photovoltaic system design and installation procedures, protocols, and checklists — are available at the Building Industry Institute Web site, http://www.TheBII.org. See the section titled “Reports, Protocols, and Scopes of Work.”

o Properly size and orient the photovoltaic system to provide the expected power and energy output.

o Use sunlight- and weather-resistant materials for all outdoor equipment.

o Properly seal any roof penetrations with roofing industry-approved methods.

o Minimize any shading from objects, such as foliage, vent pipes, or adjacent structures.

o Comply with all applicable building and electrical codes.

o Minimize electrical losses from wiring, over-current protection, switches, and inverters.

o Properly ground system components to reduce the possibility of shock hazards and induced power surges.

o Properly house and manage any battery backup systems.

o Follow applicable utility interconnect requirements and procedures.

o Be aware of applicable State and local planning and building code requirement (e.g. solar access).






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