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Technologies
Part of the high-performance building process involves combining good design with energy efficiency and solar technologies to reduce energy consumption. Solar technologies tap directly into the infinite power of the sun and use that energy to heat, light, and power buildings. Solar technology combines building design and materials that reduce electrical demand with solar thermal panels for heating water and solar electric panels for powering items such as appliances, lights, and computers.
Energy Efficiency Energy EfficiencyEnergy efficiency means using your building's individual components to do the same job as less efficient components for less money over the long-term. Energy-efficient building components applies to everything from the building envelope, which includes energy efficient windows, lighting, insulation, foundation, and the roof, to office equipment that doesn't waste energy sitting idle and equipment with built-in power management features. It also applies to space heating and cooling, which are aided through the use of automated controls, ventilation, improved duct systems, and other advanced technologies. Energy efficiency can also apply to water heating when combined with water-efficient appliances and fixtures that will save water, energy, and money.Passive SolarPassive solar design is the technology of heating, cooling, and lighting a building naturally with sunlight rather than with mechanical systems because the building itself is the system. Basic design principles are large south-facing windows with proper overhangs, as well as tile, brick, or other thermal mass material used in flooring or walls to store the sun's heat during the day and release it back into the building at night or when the temperature drops. Passive solar also takes advantage of energy efficient materials, improved insulation, airtight construction, natural landscaping, and proper building orientation to take advantage of the sun, shade, and wind. Passive solar designs can also include natural ventilation for cooling. Incorporating passive solar designs can reduce heating bills as much as 50%.Solar Water HeatingSolar water-heating systems use collectors, generally mounted on a south-facing roof, to heat either water or a nontoxic antifreeze that is circulated from the collector to the water storage tanks. The heated water is then stored in a water tank similar to one used in a conventional gas or electric water-heating system.Collectors heat water either "passively" or "actively." Passive solar water-heating systems use natural convection or water pressure to circulate water through a solar collector to a storage tank. They have no electric components that could break, a feature that generally makes them more reliable, easier to maintain, and possibly longer lasting than active systems. An active system uses an electric pump to circulate water or a nontoxic antifreeze through the system. Active systems are usually more expensive than passive systems, but they are also more efficient. Active systems are easier to retrofit than passive systems because their storage tanks do not need to be installed above or close to the collectors. Also, the moving water in the system will not freeze in cold climates. But because these systems use electricity, they will not function in a power outage. That's why many active systems are now combined with a small solar-electric panel to power the pump. The amount of hot water a solar water heater produces depends on the type and size of the system, the amount of sun available at the site, proper installation, and the tilt angle and orientation of the collectors. Solar ElectricitySolar electricity or photovoltaic technology converts sunlight directly into electricity. The space program and agricultural industry have used solar electricity for decades. Advances in solar technology and changes in global electric utility restructuring have expanded the market for solar electricity to urban buildings.Solar electric systems all consist of basically three main items: modules that convert sunlight into electricity; inverters that convert that electricity into alternating current so it can be used by most appliances and computers; and sometimes batteries that store excess electricity produced by the system for emergency backup power or for nighttime power. The remainder of the system comprises equipment such as wiring, circuit breakers, and support structures. Grid connected systems do not require batteries, however, some grid-connected systems use them for emergency backup power. In remote areas, solar electricity is often an economic alternative to expensive distribution line extensions incurred by a customer first connecting to the utility grid. Electricity produced by solar electric systems in remote locations is stored in batteries. Today's modules can be built into glass skylights and walls. Some resemble traditional roof shingles. In over thirty states, any electricity not being used by a building's solar electric system can be fed back to the electric grid for credit from the utility through an agreement called "net metering." What type of system to purchase will depend on the energy-efficiency of the building, its location, and project funding. Before purchasing a system, energy consumption should be reduced through energy-efficient measures. Purchasing energy-saving appliances and lights, for example, will reduce your electrical demand and allow you to purchase a smaller solar-electric system to meet your energy needs or get more value from a larger system. For more information, visit Photovoltaics for Buildings. |
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U.S. Department of Energy
Last updated: 10 December 2007