Technology Research

NREL's building researchers are developing and testing a variety of building technologies to improve energy efficiency in buildings. Technologies within our R&D capabilities include the following:

Building-Integrated Photovoltaics (PV)

BIPV systems are solar electric systems that are integrated into the building so they serve dual functions: they produce electricity and also act as a building material. A few examples are solar electric roof shingles and solar panels that act as window awnings or porch covers. BIPV systems can be integrated into almost any type of building to supplement grid-supplied power, reduce energy costs, and provide emergency back-up power during utility power outages. For more information, visit NREL's PV for Buildings.

Daylighting

Research has shown that electrical lighting makes up a significant portion of energy use in buildings, especially commercial buildings. Re-designing new buildings to optimize the use of natural light or "daylighting" to replace electrical lighting in areas such as atriums, hallways, cafeterias, and playrooms can have a significant impact on energy reduction. NREL has provided design and technical assistance for daylighting for many commercial and residential buildings that are considered some of the most energy-efficient buildings in the country today. For more information, visit our residential or commercial buildings projects pages.

Electrochromic Windows

Researchers evaluate and test electrochromic or "smart" windows that save energy by controlling the amount of solar heat that passes through the window glass. For example, in winter, they lighten and allow lots of heat to pass through the glass but not back out, reducing the amount of energy needed for home heating. In summer, they darken without blocking visible light to reduce the amount of heat coming into the home and decrease cooling costs. Electrochromic windows darken or lighten by a chemical reaction that is set off by a small voltage (you can run an entire house on the voltage required to run one light bulb).

Although they can technically be classified as electrochromic materials, the new reflective hydrides that are being developed behave in a noticeably different way. Instead of absorbing light, they reflect it. Thin-film solar cell material made of nickel-magnesium alloy is able to switch back and forth from a transparent to a reflective state. The switch can be powered by electrochromic or hydrogen and oxygen gases (gas-chromic technology). Furthermore, this material has the potential to be even more energy efficient than other electrochromic materials. Several of NREL's research partners are now producing electrochromic window prototypes, including Schott Donnelly, SAGE Electrochromics, Eclipse Energy Systems and Gentex Corporation. SAGE has developed a product that has passed DOE standards for testing and is partnering with Honeywell to provide switching capability. Eclipse Energy Systems is working on flexible plastic electrochromic. Gentex manufactures electrochromic automobile mirrors and is working with PPG Industries to make electrochromic window systems for airplanes.

Research challenges are achieving low costs, high durability, thermal stability, switching reliability, and practical sizes. We conduct durability testing on electrochromic windows to understand their performance and degradation, as wells as developing the durability standards for the windows. For more information, see Windows.

Heating, Ventilation, and Air-Conditioning Systems

Researchers work with the building industry and academia to develop advanced and environmentally sound technologies that use waste heat from onsite electricity production in buildings to power heating, ventilation, and cooling (HVAC) systems.

Our award-winning work in computational fluid dynamics includes experimental and numerical analysis of the fluid flow and heat transfer performance of transpired solar air heaters for buildings, geothermal binary cycle power plants, enhanced heat transfer surfaces, polymer heat exchangers, natural convection cooling towers, solar domestic water systems, and the development of corrosion barrier polymer coatings. For more information, visit Distributed Thermal Energy Technologies.

Passive Solar

Researchers are developing high-performance, whole-building design methods that integrate passive solar, energy efficiency and renewable technologies that can be used by the building industry to reduce building energy consumption. Many of these buildings use passive solar to offset significant electrical loads, such as replacing electrical lighting with natural light or "daylighting" and reducing heating and cooling loads by storing heat and cool air in building materials such as brick and Trombe walls. For more information, see passive solar homes. For passive solar commercial building project information, see case studies.

Solar Water Heating

Low-cost solar hot water systems can significantly contribute to reaching the goal of cost-effective energy savings greater than 50% in most climates. However, the current cost of solar water heating discourages some homebuilders. We analyze, test, and evaluate low-cost solar hot water systems in research homes that can lead to 40%-60% energy savings levels at a radically reduced first cost. The field evaluation of these low-cost solar hot water systems will include an analysis of cost/performance/reliability trade-offs between these solar systems, conventional solar systems, and other emerging water heating technologies.

NREL also provides guidance and design review to the Building America teams when they are considering the use of solar water heating systems in BA research homes. In FY05, NREL developed a solar domestic hot water (SDHW) sizing tool to help support successful integration of solar hot water systems in Building America research projects. The user-friendly tool, built on the TRNSYS energy simulation program, provides performance evaluations based on climate, system type, building hot water loads, and use of Solar Rating and Certification Corporation (SRCC) packaged solar hot water systems. The simple tool assists users with solar collector and storage tank sizing, selection of system type, and integration with back-up systems.

NREL is also researching a new solar hot water/HVAC combination system will allow people to heat water while heating and cooling their space in one system. Many research challenges still lie ahead for this new technology and it could be another 10 to 20 years before this technology reaches the marketplace.