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Building Integrated Solar Technologies

In his 2006 State of the Union address, President Bush announced the Advanced Energy Initiative. Included in this initiative are plans to accelerate the research and development of solar electric and solar thermal technologies that can be directly incorporated into a building. NREL researchers are investigating and developing ways of using building integrated solar technologies to optimize whole-building energy performance, including lighting and space heating.

Building Integrated Photovoltaics

NREL develops and evaluates photovoltaic (solar electric) construction products that can be integrated into a building directly (i.e., solar electric roof shingles and slates) so a builder can produce a traditional looking home while getting dual use out of a building material to reduce construction costs and generate electricity at the same time. Researchers look at how solar electricity works with buildings both as a source of on-site power and as a building material (i.e., solar powered roof shingle). In addition, NREL is developing new building integrated solar systems that will combine solar electricity and solar heating in one system and plans to introduce them in the future through the Building America Program. For more information, visit NREL's PV for Buildings page.

Daylighting

New residential and commercial buildings can be designed to use natural light to offset a significant portion of electrical lighting loads. Lighting is the largest single end use in commercial buildings, at 30% of the total energy used. From a national perspective, the potential for daylighting savings is significant. NREL has extensive knowledge of the application side of lighting systems and making daylighting work in the built environment (see case studies).

To maximize the use of natural light in a building, daylighting design involves care in the specification of building orientation, window area, the performance of windows and overhangs, interior design, and the control of electric lighting systems. A barrier to daylighting is its inherent complexity-a number of elements must be carefully integrated to ensure energy savings. NREL is using a whole-building integrated design approach to carefully integrate all of these factors to optimize whole-building energy performance.

Heating and Cooling Buildings with Solar Energy

NREL works in conjunction with building engineers, architects, and other building professionals to reduce electrical consumption in homes and businesses by developing new building design packages and processes that harness the sun's energy to heat and cool buildings. Some of these new design packages and processes have reduced energy consumption in new commercial buildings by as much as 70% or more. Among the most well-known are the Zion Visitor Center in Zion National Park, Utah and the Big Horn Home Improvement Center in Silverthorne, Colorado. The Big Horn project uses a transpired solar collector, for which NREL won an R&D 100 award in 1994. This simple but sophisticated technology uses strategically placed holes to capture solar energy that is used to heat and ventilate buildings. With an efficiency of 70%, this technology also won a "Best of What's New" award from Popular Science magazine. NREL also studies the use of passive solar technology to reduce energy consumption in homes. For more information, see passive solar homes.

Solar air conditioning is a promising new area of research. NREL is working to significantly reduce the life-cycle energy cost of solar absorption cooling technology; improve the technical feasibility of advanced-cycle solar absorption cooling; and bring the technology closer to commercialization. For more information, see Thermally Driven Air Conditioning.

NREL also works with industry and academia to develop advanced and environmentally sound technologies that use waste heat from on-site electricity production to power heating, ventilation, and cooling (HVAC) systems for buildings. For more information, visit the Distributed Thermal Energy Technologies Project.

Solar Water Heating

Today there are basically three types of solar collectors for heating water: flat-plate, which are commonly used for homes; evacuated-tube, which are commonly used in commercial buildings; and concentrating collectors, which are used in large-scale applications. Concentrating collector systems are quite large and achieve much higher temperatures than the first two, making them more suitable for industrial applications. For the last decade, NREL's solar water heating research has focused on the investigation of new materials, especially low-cost polymers or plastics to reduce system cost because cost is still a major barrier to widespread market acceptance of the technology.

A new research approach to heating water may solve the cost and efficiency problem. NREL is researching a hybrid solar water/HVAC system that will allow people to heat water, and heat and cool their space in one system. NREL is just beginning this work now and there are still many research hurdles to overcome, which means we might see this on the market in 10 to 20 years. For more information, see: Solar Heating.