Solar
View slide show on solar power.
The Naval Air Station North Island has an unusual parking garage—a structure covered with approximately 81,470 square feet of PV panels, which provides more than 1 million kWh of energy each year.
Resource and Technologies
Solar energy—energy from the sun—can be used directly for heating or for generating electricity. Technologies used in the federal sector include the following:
- Electricity generation—Photovoltaics, or solar cells, made of semiconducting materials that directly convert sunlight into electricity. The simplest cells power watches and calculators, while more complex systems provide power to on- or off-grid applications. The size of systems used in the federal sector range from several watts to 1.1 megawatts (MW). A typical photovoltaic cell converts approximately 10 percent of the energy striking its surface into usable electricity. As an alternative to photovoltaics, mirrors can also be used to concentrate the sun's energy for use in thermal electricity generation.
- Solar water heating—Solar thermal collectors are used directly or indirectly, using a heat transfer fluid to heat water. A typical system will reduce the need for conventional water heating by about two-thirds. High-temperature solar water heaters can provide energy-efficient hot water and hot-water heat for large commercial and industrial facilities.
- Preheating of ventilation air—A solar ventilation system can be used in cold climates to preheat air as it enters a building. This technology is used primarily in buildings with large requirements for ventilation air, such as airplane hangars, warehouses, factories, and chemical storage buildings.
- Passive solar heating, cooling, and daylighting in buildings—Buildings with passive solar features and daylighting often incorporate large south-facing windows and building materials that absorb and slowly release the sun's heat. No mechanical systems are needed in passive solar heating. Incorporating passive solar design features can reduce heating bills as much as 50 percent. Passive solar designs can also include natural ventilation for cooling.
Applications at Federal Facilities
Approximately 31.2 gigawatt-hours (GWH) are being generated in the federal sector by solar technologies annually (July 2003). Here are some examples of solar water heating and photovoltaic projects that contribute to the total.
The U.S. Coast Guard (USCG) installed 62 solar water heaters at its Kia'i Kai Hale housing project in Honolulu, Hawaii, in 1998. The average cost of each system was $4,000. The local utility, the Hawaiian Electric Company, provided an $800 rebate to the USCG for each system. FEMP's technical assistance program monitored these systems in 2002 and 2003. Performance monitoring confirmed that each system was saving 3139 kilowatt-hours (kWh) each year. The simple payback of these systems is calculated to be 8.4 years.
The National Weather Service (NWS) in the U.S. Department of Commerce, National Oceanic and Atmospheric Administration, installed a 10-kW photovoltaic array to power a radar system in Miramar, California. The PV system is grid-tied and supplies approximately 9 percent of the facility's annual needs. The system shaves peak demand at the site and directly offsets the utility's "on peak" charges for electricity. The State of California provided a 50 percent rebate for the cost of this system.
The NWS also received cost sharing and design assistance from the FEMP program. The simple payback after California's rebate was 12.6 years. The simple payback for the costs to NWS, subtracting both the state rebate and the contribution from the FEMP program, was 6.5 years. NWS operates more than 150 nearly identical radar sites throughout the country, and they could potentially replicate the design of this project.
Other benefits of both these projects include protecting the environment and reducing our dependence on (and vulnerability to) foreign petroleum products.
Additional Resources
EERE Solar Web site
For more general information on solar, visit the Office of Energy Efficiency and Renewable Energy solar Web site.
Resource Maps
FEMP provides resource maps showing the federal market potential for solar technologies. FEMP and Resource Assessment staff at the National Renewable Energy Laboratory used energy resource and economic assessments to map potential federal markets for solar water heating, photovoltaic (PV) systems, and solar ventilation-air preheating (e.g., "solar walls").