Researchers at the National Institute of Standards and Technology recently announced results from the first six months of a virtual family of four living in an energy efficient home and how the house has performed. During the first six months, a prototypical family of four earned about $40 by exporting 328 kilowatt hours of electricity into the local grid, while meeting all of their varied energy needs. The goal of this experiment is to demonstrate that a net-zero energy house—one that produces as much energy as it consumes over the course of a year—can fit into any neighborhood. Following the year-long experiment, the facility will be used to test existing and new energy efficient technologies and develop methods of test that better reflect how those technologies will perform in a real home, rather than a laboratory.
To date, these virtual residents of the Net-Zero Energy Residential Test Facility (NZERTF) located on the campus of the National Institute of Standards and Technology (NIST), about 20 miles north of Washington, D.C., didn't have to skimp even a bit on any of the creature comforts of 21st century living. Their amenities ranged from indoor temperatures maintained between 21.1 and 23.8 degrees Celsius (70 to 75 degrees Fahrenheit) to a complete array of modern-day kitchen and laundry appliances, and from personal computers, a video gaming system, and two TVs to a pair of stereos, a hairdryer, and curling and clothes irons.
Both a laboratory and a home, the 2,700-square-foot (252-square-meter) NZERTF is a two-story, four-bedroom, three-bath house that incorporates energy-efficient construction and appliances, as well as energy-generating technologies such as solar water heating and solar photovoltaic systems. There, NIST scientists and engineers and their collaborators will develop and validate measurement and test methods for evaluating energy-efficient designs, materials and technologies.
Over the course of a year, the facility is designed to produce at least as much energy as it consumes. On July 1, 2013, a research team led by NIST engineer Hunter Fanney launched a year-long trial to determine whether NZERTF, as originally designed and built, meets these net-zero-energy expectations, despite the vagaries of local weather.
Though daily routines and energy-consuming habits are scripted and imitated by computer, this virtual clan behaves like the average family, based on standard occupant profiles developed by the Department of Energy. The virtual family bathe, shower, cook, turn on lights when they enter rooms, do the laundry, and relax by watching TV, listening to music, posting on Facebook, or playing video games. Computers even control devices that mimic the heat and moisture of the virtual family's breathing and perspiring.
The house has more than 500 sensors to track the energy consumption of every single device. NIST has gathered a lot of valuable information to develop improved test methods and performance metrics for high-efficiency and alternative-energy devices and systems.
As of December 31, 2013—the halfway point in the initial trial run—the NZERTF generated an energy surplus of 328 kilowatt hours, roughly the amount of energy that a dishwasher uses over one year. From July through October, the facility registered monthly surpluses. In November and December, when space-heating demands increased and the declining angle of the sun reduced the energy output of photovoltaic system, NZERTF ran monthly deficits.
To learn more about NZERTF and to follow its energy performance, go to: www.nist.gov/el/nzertf/ .