Buildings that consume no outside energy are being developed today using existing technology. This is the first of a two part series.
Innovation is critical to the success of green buildings, and according to Harvey Bernstein, vice president of Industry Insights and Alliances at McGraw-Hill Construction: "The acceleration of the green building marketplace around the world is creating markets for green building products and technologies, which in turn will lead to faster growth of green building."
Even smaller innovative companies are getting into the game, thanks to Hartford, Connecticut-based United Technologies Corporation (UTC). According to Jacqueline Jenkins, program executive for the Wharton Small Business Development Center's Energy Efficient Buildings project, UTC is subcontracting with smaller companies, "providing revenue for the companies, as well as a track record, which is key." And, she notes, the relationship with UTC allows innovations that might not otherwise get into the market to be tested there.
But while considerable attention is being focused on innovative products and technologies — the means of achieving green building — another kind of innovation has given birth to an exciting new approach.
The net-zero energy building, or NZEB, focuses less on the means and more on the end result, which is a building or group of structures that generate 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.
The residential challenge is affordability: As part of a research project, the National Institute of Standards and Technology (NIST) recently built a net-zero test home in the Washington, DC area. "This home has all the features and aesthetics you would find in an upscale Washington DC metro home," Hunter Fanney, chief of NIST's energy and environment division, told US News and World Report. "There's really nothing exotic about it and nothing that can't be readily done with conventional construction."
But the challenge at the residential level isn't technical; it's financial. Betsy Pettit, president of Building Science Corporation, told Reuters that a house similar to the NIST house, built in Concord, Massachusetts, cost about $600,000 — and that didn't include the cost of the land. While it is possible to build a net-zero house for less, it usually means a much smaller building with fewer amenities. According to Pettit, a house that approached net-zero energy use was built for Habitat for Humanity for just $150,000, but it measured only 1,200 square feet, less than half the size of an average single-family house in the US in 2011.
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 principle 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."
None of the energy-saving features in the modular home is exotic and many are installed in the controlled environment of the factory that is making the building components. In addition, since the emphasis is on reducing both construction and operating costs, load-managing appliances are being installed. Homeowners can run these appliances whenever they want, but the appliances advise the owners when electricity is least expensive in the region, and can be programmed by the homeowner to run when the rates are lowest.
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. On a sunny summer day, when the family is out of the house, the photovoltaic roof shingles (installed at the factory) 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 — in other words, the net energy use for the year is zero.
One element that is critical to achieving this goal is the 10-kilowatt battery that sits inside the house. It serves two essential purposes. One is as a backup in case the grid ever goes down (according to Bloomberg Business Week, 18% of American households have either permanent or portable backup generators, a number that continues to climb as mega-storms like Sandy continue to knock out the grid).
The battery's other use is to "level the load," says Riley. "That battery can charge up at night when the electricity is cheap and deploy during peak times to discharge into the grid. So instead of just sitting there waiting for the grid to go down, this battery can actually generate revenue every day." And the battery may turn out to be less expensive than it might otherwise have been. GridSTAR is evaluating the practicality of re-using the 16.5 kilowatt-hour lithium-ion battery pack from a Chevy Volt plug-in hybrid after its useful life in the car is over. (GridSTAR is the first test site for the reuse of a Volt battery in a residential storage application.)
"General Motors engineered the battery to outlast the car," explains Riley. "The company doesn't want someone to buy a Volt and have to face an expensive battery replacement over the life of the car. But that battery is still going to have some use and discharges left, and it actually has the perfect capabilities to become a community-storage or a residential-scale battery."
The recycling of used hybrid car battery packs for stationary use is also being explored at the University of California, San Diego.
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 actually 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. Katrina Managan, of Johnson Control's Institute for Building Efficiency, notes in a recent white paper ("Net Zero Communities: One Building at a Time") that such communities offer two key advantages: economies of scale in energy generation and a mix of buildings with varying occupancy patterns and energy use that can balance the energy load across an entire neighborhood. Communities also have the potential to generate enough excess energy to interest local utilities in negotiating revenue-generating agreements.
Such communities are just starting to appear. Motivated by the need to achieve energy security and independence, the US Army is piloting a net-zero installation at Fort Bliss, located outside of El Paso, Texas. Occupying more than 1 million acres of land in Texas and New Mexico, and with a total population in excess of 90,000, Fort Bliss is aiming to transform the base into a net-zero energy community by 2015. Balancing budgetary and security concerns, Fort Bliss is modeling various possibilities, ranging from a waste-to-energy system, using the waste from the city of El Paso, to a geothermal plant, to be used in conjunction with energy-efficiency projects and load-balancing solutions, such as solar photovoltaics.
Outside of the military, the largest net-zero energy community in the US is already nearing its goal of generating on site all of the energy used in its residential, community and commercial spaces. When completed, the West Village at the University of California, Davis, will include a village square and a network of open spaces, parks, gardens, pathways and courtyards; housing for 3,000 students, faculty and staff (in 662 apartments and 343 single-family homes); 42,500 square feet of commercial space; a recreation center; and eventually, a preschool/day care center.
As with the Grid STAR demonstration house, the first concern at West Village was energy efficiency. The roof uses solar-reflective material and radiant barrier sheathing, and thick 2" x 6" exterior walls add an extra level of insulation. Other architectural features, such as roof overhangs and window sunshades, combine with high-efficiency lighting, air conditioning units and appliances to reduce energy consumption to 50% below what would normally be expected if the buildings were simply built to code.
A four-megawatt photovoltaic system, including rooftop solar installations and solar canopies over parking areas, is designed to meet the needs of the first 1,980 apartment residents and commercial spaces. After that, the plan calls for a biogas generator, based on technology developed at UC Davis, which will convert dormitory table scraps, animal waste from the campus dairy and plant waste from agricultural research fields into electricity.
The views expressed in this article are the author's own and do not necessarily reflect Fair Observer’s editorial policy.
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