PV rising

• Photo courtesy of SunPower, San Jose, Calif.

The numbers are staggering. According to the International Energy Agency, worldwide energy consumption is expected to increase nearly 25 quadrillion British thermal units by 2030. This carries an estimated price tag of $10 trillion for electricity generation, transmission and distribution assets alone.

And consider these facts from the 2007 Buildings Energy Data Book concerning U.S. residential and commercial buildings:

• Internal gains, or energy loads, account for as much as 27 percent of a home's cooling load.
• The average new single-family home has increased in size by about 700 square feet since 1980.
• In 2006, 50 percent of all new homes were built in the South, meaning the amount of energy used for cooling is increasing.
• U.S. buildings' carbon dioxide emissions (630 million metric tons of carbon) approximately equal the combined emissions of France, Japan and the United Kingdom.
• Lighting uses more energy than cooling in the residential sector. This emphasizes the importance of breakthrough lighting technologies.

This data underscore the fact that many buildings currently in use are extremely energy-inefficient.

According to the white paper, "A Primer on Energy Efficiency: Conservation Gets a New Name" by San Francisco-based Thomas Weisel Partners LLC, buildings nationwide account for 40 percent of all energy used, 38 percent of all carbon dioxide emissions, 36 percent of all greenhouse gases and 72 percent of all electricity consumed—accounting for 80 percent, or $238 billion, of total electricity expenditure in the U.S.

A 5 percent increase in building efficiency with renewable energy would translate to roughly $45 billion in savings at a national rate of 6 to 7 cents per kilowatt, according to Thomas Weisel Partners.

As energy costs continue to escalate, many roofing contractors and building owners are beginning to turn to photovoltaic (PV) roofing options to save energy and money. Although only a small percentage of PV systems currently are in use, they offer great potential to remedy increasing building energy costs. As the popularity and economic viability of PV systems increase, it will be important for you to be well-versed and knowledgeable about their background, benefits and installation details.

About PV

PV cells are small semiconductor devices that are either round or square, typically made of silicon and about 10 by 10 centimeters in size. A single PV cell generates a minimal amount of electricity, so cells are combined into panels, typically made of 36 cells, to generate usable amounts of electricity for homes and businesses.

As sunlight shines on a PV panel, a semiconductor device (composed of n- and p-types), absorbs the light and converts it to energy. The n-type silicon has excess electrons, and the p-type silicon has excess holes. Sandwiching these together creates a p/n junction at their interface, thereby creating an electrical field. The electrons begin to loosen and move freely within the panel, forming an energy current when paired with the cells' voltage.

Although a newer fixture in the roofing market within the past 10 years, PV cells were introduced during the 1950s with initial support from the federal government to power the Vanguard satellite, the oldest artificial satellite still in space.

PV technology gained momentum in the building industry during the past three decades with technological advances and growing government support through tax credits and initiatives such as the Renewable Energy and Energy Efficiency Technology Competitiveness Act and PV for Utility Scale Applications (PVUSA), developed in the 1980s.

The Renewable Energy and Energy Efficiency Technology Competitiveness Act was developed to improve the operational reliability of PV modules, increase efficiency, decrease manufacturing expenses and improve electric power production costs.

PVUSA was created to analyze and market the viability of utility-scale PV electricity-generating systems and provide a unique hands-on experience to assess PV technology, provide product testing for manufacturers, and create a line of communication between the PV industry and utilities.

System types

There are two PV offerings available for roof system applications—amorphous and crystalline silicon systems.

PV cells in amorphous systems can be used with glass, membrane and roof-mounted tile products to provide direct current (DC) electricity. There also are flexible thin-film generations available, which allow a PV system to be installed directly over a roof membrane. These PV systems provide an efficiency rate of only 9 percent and typically need more surface area to generate the same amount of energy provided by crystalline systems.

Crystalline systems can be installed directly over a rooftop or by penetrating a roof substrate. With a 34 percent efficiency rate, these PV systems are durable and lightweight, making them easy to install on any low-slope roof system. Crystalline systems that require rooftop penetration also require extra waterproofing.

Inverters are the most important part of PV systems. An inverter converts DC electricity to an alternating current that is commonly used in residential and commercial buildings. Also, inverters keep complete records of the time, day and how much energy is produced. These records are necessary because most rebates depend on the energy produced versus the total energy systems installed.

Electricity output depends on an inverter's efficiency. The more efficient the inverter, the more energy it can produce.

Positioning PV panels also is important to ensure a PV system receives maximum sunlight. Currently, PV systems only collect one color and/or wavelength of rays from the spectrum of the sun's rays that reach Earth. (Next-generation PV panels are being developed for the Mars Rover, which will create energy from many different wavelengths and be more efficient.)

Although a sunny day provides maximum efficiency for a PV system, some electricity can be generated on cloudy days, as well. Shadows of surrounding equipment can harm PV systems' energy production; therefore, shadowing a panel should be avoided.

Why PV?

According to the Earth Policy Institute, PV system production in 2007 increased to 3,800 megawatts, which is up an estimated 50 percent from 2006. PV system use has been growing by an average of nearly 50 percent each year since 2002 and production has doubled every two years, making PV energy the world's fastest-growing energy source. The top four countries producing PV systems are Germany, Japan, the U.S. and China.

According to research conducted by the Silicon Valley Leadership Group, San Jose, Calif., solar roofing currently accounts for only 2 percent of the commercial roofing market in the U.S. But with rising utility costs around the world estimated at $1 trillion and increasing interest in "green" building efforts, PV systems offer huge potential savings for your customers.

According to the Earth Policy Institute, Washington, D.C., photovoltaic production in 2007 increased to 3,800 megawatts, an estimated 50 percent increase from 2006.

Not only will a PV roof system save energy costs, but the federal government and some states, such as California, Connecticut, Hawaii and New Jersey, offer rebates and tax credits to companies that invest in solar energy.

For example, a $6.54 million 1-megawatt system installed in California will cost only $820,000 after rebates and depreciation. PV systems also will lower a building's utility bills and operating costs.

Currently, the cost of installing a rooftop PV system remains high in the U.S. compared with the total cost of the system itself; however, other countries provide better standardization of the products and application methods.

For example, the installation cost of a PV system on a roof in Germany or Japan is 50 percent lower than in the U.S. This is one of the areas in which U.S. companies can improve and, if focused properly, they can become competitive not only in the U.S. but in the global PV market.

Leadership in Energy and Environmental Design™ (LEED) points also can be earned from using PV systems. To earn LEED points, a building must follow strict guidelines in the following categories: sustainable sites, water efficiency, energy and atmosphere, materials and resources, indoor environmental quality, and innovation in design and process.

PV systems can fall into three of LEED's categories—energy and atmosphere, materials and resources, and innovation in design and process—leading to a possible higher LEED rating for a building and translating into significant cost savings.

Organizations such as the Million Solar Roof Initiative run by the U.S. Department of Energy have been working for the past 20 years to encourage private industry to use PV systems on rooftops and reduce greenhouse gas production. The California Public Utilities Commission also recently started a Million Solar Roofs Initiative in 2006 to reduce dependence on fossil fuels and nuclear power through the use of PV systems as a renewable energy source.

The U.S. government recently updated energy-efficiency requirements for federal/municipal, residential, commercial, industrial and school buildings in the 2007 Energy Bill. For new commercial buildings, the bill sets a national goal to reduce commercial building energy use and achieve zero net energy by 2030. All existing buildings are expected to meet this goal by 2050.

What PV means to you

Although PV systems can be more expensive than traditional roof membrane systems, according to the World Business Council for Sustainable Development's 2007 Building Efficiency report, perceptions for the costs of adding green enhancements to a building are significantly higher than the actual costs.

I recommend you work with your customers to develop customized financing programs. These programs, along with state and federal rebate programs, tax credits and possible LEED points, will help customers see the benefits of going solar. You also can line item your customer's total cost after rebates and credits and highlight their average monthly savings.

When considering installing a PV system, it is important to evaluate how it will work with a roof system. Because of heavy foot traffic on rooftops, PV systems are ideal for use with fully adhered commercial roof membranes with protective walkway mats. Other roof system types, such as those that are mechanically attached, can cause wind flutter on a roof membrane and affect a PV system's performance. It also is key to note that dissimilar materials expand and contract at different rates, so be aware of differential movement between a PV system and roofing materials.

Although minimal maintenance is required for PV systems, it is important you work with your customers to set up maintenance programs to manage their roof assets. The most important step to protect a roof is to conduct biannual spring and fall inspections. Also, many roofing manufacturers require that roof systems be maintained to uphold warranty agreements. With proper ongoing maintenance, some manufacturers will allow your customers to extend their warranty coverage.

In some cases, it is recommended PV systems be installed in conjunction with a new roof system. It also is recommended that PV systems be used with fully adhered roof systems backed by dependable 20- to 25-year warranties. This ensures a roof membrane lasts as long as a PV system.

If a roof system is less than seven years old, maintenance can ensure the system works properly for several years to come. Keep in mind the cost of a new roof system compared with a PV system is minimal; therefore, greater judgment should be used when deciding not to reroof.

Presently, few commercial roofing contractors are trained to install PV systems. However, some roofing materials manufacturers work directly with solar panel manufacturers to train roofing contractors to install PV systems.

Also, it is important for you to have substantial financial backing when working with PV systems. Unfortunately, it only makes sense to install PV systems in key states with rebates to be profitable. Once the prices of solar cells decrease and standardized installation systems enter the roofing market, most roofing contractors will be able to install these systems.

Although roofing contractors have all the necessary equipment to install PV systems, they still have to hire electricians to install wiring and make a connection to junction boxes and the inverter. When working with a PV system and electricity, you should know how to get a building permit for a PV system; be well-versed in electric generation, installation and efficiency of the system; and, most important, be aware of safety issues.

Reaping the benefits

As energy costs escalate, you need to be knowledgeable of new energy-efficient roofing options for your customers. As more states pass legislation for rebates and incentives for solar power, PV systems are slated to have enormous growth within the next few years. Installing PV systems can offer your customers an eco-friendly and aesthetically pleasing roofing option with a 25- to 40-year life expectancy while providing you with a lucrative business.

Riaz Hasan is accessories product manager for Firestone Building Products Co. LLC, Indianapolis.