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Latest green advance: zero energy buildings
May 24, 2013, Friday
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A new kind of innovation has given birth to an exciting approach to green building
The net-zero energy building, or NZEB, focuses less on the means and more on the end result, which is a building that generates as much energy as they use.
A building's energy production may be more than it needs at certain periods in time, explains David Riley, professor of architectural engineering at Pennsylvania State University and executive director of the university's Center for Sustainability. But it qualifies as net-zero only if "the meter has not moved by the end of the year."
The NZEB approach has been gaining momentum for some time, but in the past few years virtually all the major players - government agencies, academia, the military, not-for-profits and increasingly the business community - have become actively engaged in demonstrating the near-term potential of NZEB at residential, community and commercial scales.
High cost
The challenge at the residential level isn't technical; it's financial.
While it is possible to build a net-zero house for less, it usually means a much smaller building with fewer amenities.
In an effort to bring NZEB within reach of the average homeowner, the GridSTAR Center, a smart-grid education and research institute at Penn State, is focusing much of its work on the development of an affordable net-zero demonstration house.
The goal, says Riley, who is also the principal investigator for the GridSTAR Center, is to create a home that generates all of the energy necessary "to meet the needs of the house and is a wise investment for the homeowner."
And the first step toward achieving that aim is to make the 2,400 square-foot demonstration house, located at the Philadelphia Navy Yard, as energy efficient as possible.
That way, Riley explains, "It won't need a whole lot energy generation to serve its needs."
The amount of energy that the house generates and consumes at any one time depends on a number of constantly shifting variables - time of year, time of day, weather conditions and the owner's behavior, to name just a few.
Run the meter backwards
On a sunny summer day, when the family is out of the house, the photovoltaic roof shingles and the solar thermal collector, which helps provide both hot water and space heat, are likely to generate more energy than the house uses, in effect running the meter backwards.
But on a cold winter night, when family members are home cooking and using everything from computers to televisions, the meter is likely to be running in the other direction.
The net-zero goal is achieved if at the end of a year, the meter is in the same place that it was at the beginning.
The next net-zero frontier is at the community level: "At the level of a single home, it's generally not a good investment to have a house that produces a lot more energy than you need," Riley states.
While utilities may allow a homeowner to run his or her meter backwards at times, very few will pay for excess power beyond what the house uses in the course of a year.
But things change when a whole community of houses, or a neighborhood of mixed residential and commercial buildings, aims for net-zero.
SAP's pioneering work
The American headquarters of German software giant SAP points the way toward net-zero commercial buildings.
Of the 21 commercial building identified as net zero by the New Buildings Institute (15 measured as net zero, plus six "credibly modeled"), 15 are less than 10,000 square feet and only one is at the same scale as the SAP facility in Newtown Square, Pennsylvania.
Thanks to the pioneering work of SAP and others - including the National Renewable Energy Lab (NREL) in Golden, Colorado, which built the one net-zero building of comparable scale, the US$64 million, 220,000 square-foot Research Support Facility (RSF) - a few strategies have been identified that will support the design and construction of large-scale commercial net-zero buildings.
Respond to the outside
Until recently, most large commercial structures have been sealed off from the natural world. But future energy-efficient buildings will undoubtedly take the opposite approach, responding continually to what is happening outside. The SAP facility, for example, has a lighting system that "harvests daylight" by using sensors to dim the lighting levels and raise or lower window shades based on the level of sunlight coming through the triple-glazed glass exterior wall.
The NREL facility combines a similar window-shading technology with light-bending window louvers that cast rays up into the interior office spaces.
Occupants are central to the success of net-zero buildings.
People use less energy, for instance, when they are made aware of how much they are using and how they can cut back. At the RSF, an icon pops up on occupants' computer screens whenever it makes sense for them to open a nearby window (windows that are out of reach are operated automatically).
Adapted from Knowledge@Wharton, http://knowledge.wharton.upenn.edu. To read the original, please visit: http://knowledge.wharton.upenn.edu/article.cfm?articleid=3247
The net-zero energy building, or NZEB, focuses less on the means and more on the end result, which is a building that generates as much energy as they use.
A building's energy production may be more than it needs at certain periods in time, explains David Riley, professor of architectural engineering at Pennsylvania State University and executive director of the university's Center for Sustainability. But it qualifies as net-zero only if "the meter has not moved by the end of the year."
The NZEB approach has been gaining momentum for some time, but in the past few years virtually all the major players - government agencies, academia, the military, not-for-profits and increasingly the business community - have become actively engaged in demonstrating the near-term potential of NZEB at residential, community and commercial scales.
High cost
The challenge at the residential level isn't technical; it's financial.
While it is possible to build a net-zero house for less, it usually means a much smaller building with fewer amenities.
In an effort to bring NZEB within reach of the average homeowner, the GridSTAR Center, a smart-grid education and research institute at Penn State, is focusing much of its work on the development of an affordable net-zero demonstration house.
The goal, says Riley, who is also the principal investigator for the GridSTAR Center, is to create a home that generates all of the energy necessary "to meet the needs of the house and is a wise investment for the homeowner."
And the first step toward achieving that aim is to make the 2,400 square-foot demonstration house, located at the Philadelphia Navy Yard, as energy efficient as possible.
That way, Riley explains, "It won't need a whole lot energy generation to serve its needs."
The amount of energy that the house generates and consumes at any one time depends on a number of constantly shifting variables - time of year, time of day, weather conditions and the owner's behavior, to name just a few.
Run the meter backwards
On a sunny summer day, when the family is out of the house, the photovoltaic roof shingles and the solar thermal collector, which helps provide both hot water and space heat, are likely to generate more energy than the house uses, in effect running the meter backwards.
But on a cold winter night, when family members are home cooking and using everything from computers to televisions, the meter is likely to be running in the other direction.
The net-zero goal is achieved if at the end of a year, the meter is in the same place that it was at the beginning.
The next net-zero frontier is at the community level: "At the level of a single home, it's generally not a good investment to have a house that produces a lot more energy than you need," Riley states.
While utilities may allow a homeowner to run his or her meter backwards at times, very few will pay for excess power beyond what the house uses in the course of a year.
But things change when a whole community of houses, or a neighborhood of mixed residential and commercial buildings, aims for net-zero.
SAP's pioneering work
The American headquarters of German software giant SAP points the way toward net-zero commercial buildings.
Of the 21 commercial building identified as net zero by the New Buildings Institute (15 measured as net zero, plus six "credibly modeled"), 15 are less than 10,000 square feet and only one is at the same scale as the SAP facility in Newtown Square, Pennsylvania.
Thanks to the pioneering work of SAP and others - including the National Renewable Energy Lab (NREL) in Golden, Colorado, which built the one net-zero building of comparable scale, the US$64 million, 220,000 square-foot Research Support Facility (RSF) - a few strategies have been identified that will support the design and construction of large-scale commercial net-zero buildings.
Respond to the outside
Until recently, most large commercial structures have been sealed off from the natural world. But future energy-efficient buildings will undoubtedly take the opposite approach, responding continually to what is happening outside. The SAP facility, for example, has a lighting system that "harvests daylight" by using sensors to dim the lighting levels and raise or lower window shades based on the level of sunlight coming through the triple-glazed glass exterior wall.
The NREL facility combines a similar window-shading technology with light-bending window louvers that cast rays up into the interior office spaces.
Occupants are central to the success of net-zero buildings.
People use less energy, for instance, when they are made aware of how much they are using and how they can cut back. At the RSF, an icon pops up on occupants' computer screens whenever it makes sense for them to open a nearby window (windows that are out of reach are operated automatically).
Adapted from Knowledge@Wharton, http://knowledge.wharton.upenn.edu. To read the original, please visit: http://knowledge.wharton.upenn.edu/article.cfm?articleid=3247
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