![]() |
Best Practice Guide |
|
Commercial Office Buildings |
||
![]() |
Distributed GenerationSolar EnergyAccording to data from the Energy Information Administration, net generation in the US came to over 3.9 billion megawatt hours (MWh) in 2005 while retail power sales during that year were about 3.6 billion MWh. Transmission & Distribution losses amounted to 239 million MWh, or 6.1% of net generation. Source: http://www.renewableenergyaccess.com/rea/news/story?id=49238 Solar energy and other renewables produced on-site help to address the inefficiency of power transmission over long distances. Since 1983, solar electricity in California has grown by an astonishing 37,950 percent, with photovoltaic (PV) installations generating as much as 759 million kWh per year - enough to power more than 125,000 California households. The total capacity of the 14,000 grid-connected PV installations in California is about 100 megawatts, not including the many more PV systems that serve as stand-alone energy sources. The rise in grid-connected PV installations since 2000 has been truly tremendous, and includes installations at residential, commercial, industrial, and institutional sites. Solar energy can be employed both actively and passively. Active uses collect solar radiation through mechanical devices that convert it into either heat (thermal collectors) or electricity (PV panels). Passive uses of solar energy, on the other hand, require no devices other than normal building components, like windows and walls that are designed and positioned to provide heating, cooling, or daylighting. While only PV systems are considered as distributed generation, all forms of solar energy can be cost-effectively implemented in a building or facility.
PV systems transform sunlight into usable, clean and renewable electricity. While humankind has always benefited from the indirect use of solar energy, such as calories derived from food crops, it is only in our relatively recent history that advances in technology and engineering have allowed us to tap the sun as a direct source of electricity. Photovoltaics were first invented in the early 1950s, with the initial focus of research on space satellite applications. Terrestrial applications were not widely explored until the 1970s after the nation suffered its first oil shock. It took another 20 years before the first grid-supported system was installed by PG&E in Kerman, California, near Fresno, in 1993. PV systems consist of cells made of silicon semiconductors in which the movement of electrons when struck by sunlight creates electricity. Today's commercially sold PV cells have an efficiency of about 15 percent, meaning that they capture and transform about one-sixth of the sunlight hitting their surface; in the laboratory, it is possible to achieve efficiencies as high as 30 percent. Standard PV cells measure about five inches squared. These cells are grouped together as modules, with each module holding about 40 cells. Modules then are assembled as pre-wired, ready-to-install panels. Panels are installed as arrays, with about ten modules in each array - it takes roughly 10 to 20 arrays to power a single household, but hundreds can function together as a single PV system. The cost of PV panels has dropped by 90 percent since the 1970s when they were first commercially available. These lower installation costs, coupled with rising energy costs from conventional utility generation, make PV systems a viable DG option. Incentives, like buy-down rebates and tax breaks, have reduced costs even further and are widely available across the state - these incentives will not last as the market for solar electricity expands. With rebates, PV systems cost about $4-5 per kWh; the cost per kilowatt-hour generally decreases as the size of the installation increases. For a complete list of current financial incentives as well as applicable rules, regulations, policies, and programs, search the Database of State Incentives for Renewable Energy. Given that PV panels last 20 to 30 years, these systems make a sound long-term investment.
PV systems provide several benefits to building owners and managers. First, photovoltaics reduce a facility's total energy consumption from central power generators. Because PVs are basically cost free to operate once installed, the total cost of energy is reduced. Second, the maximum electrical output of PV panels perfectly coincides with peak energy demand, usually between noon and 7 p.m. during the summer months. Peak hours are the most expensive time to purchase energy, so any reduction in demand for utility power can have a major impact on overall costs. For ratepayers under time-of-use or real time pricing schedules, this is particularly important. Besides reducing the cost of electricity, PV systems afford many additional benefits. A PV system can serve as backup power, helping to improve energy reliability at a facility. Power generated from PV panels is quiet, clean and sustainable, and can be easily integrated into building rooftops, facades, canopies, and windows. With no moving parts, PV systems are relatively easy and cheap to operate and maintain. Finally, public relations are improved; businesses that install PV systems typically receive positive media attention and are noted for their actions as good corporate neighbors to the local and state communities. A recent report quantified public benefits stemming from PV systems as between $0.22 - 0.36 per kilowatt-hour of installed capacity. More than half of these savings stem from reduced consumption of natural gas. Even though California's energy portfolio consists of a variety of energy sources - hydroelectric, wind, coal, nuclear, and geothermal, to name a few - natural gas is the most common and the predominant source of peak power. Reducing the need for peak power means that less natural gas is consumed, which in turn helps stabilize gas prices and lower air emissions associated with the burning of fossil fuels. Solar electricity helps defer or avoid the costs of developing new generation and capacity to the grid system. Million Solar Roofs Bills
Business ExamplesCypress Semiconductor worked with PowerLight Corporation to install a 325 kW photovoltaic system on two of the rooftops at its corporate campus in San Jose. This generates enough energy to power more than 330 homes and helps Cypress reduce energy use during peak hours. Besides providing cost-effective energy, the PV system reflects solar radiation and protects the roof membrane from degradation. Cypress' experience was so positive it is investigating more solar projects for its San Jose campus. The Natural Resources Defense Council's Santa Monica offices use 44 percent less energy than comparable Title-24 compliant buildings. A 7.5 kW photovoltaic system is installed on the rooftop, providing about 20 percent of the total electricity demand. The rest of their energy load is met through purchases of renewable energy credits for wind generation. As such, the office is run on 100 percent renewable energy. Resources Database of State Incentives for Renewable Energy. California Energy Commission, Consumer Energy Center, Solar Cells or Photovoltaics (PV). National Renewable Energy Laboratory, webpage About Solar Energy. Smeloff, E., Quantifying the Benefits of Solar Power for California. White paper for the Vote Solar Initiative. Sandia National Laboratory, Photovoltaic Systems Program. Solar Electric Power Association, webpage What Are Photovoltaics? |