Braving a harsh winter with snow-covered solar panels, the Net-Zero Energy Residential Test Facility (NZERTF) in Washington DC has come up trumps in a year-long study of its energy harvesting capabilities. Located on campus at the National Institute of Standards and Technology (NIST), researchers used computer simulation to replicate the energy consumption of a family of four. At the end of its first 12 months, there was a large enough surplus to power an electric car for 1,440 miles (2,317 km).
The 2,700 ft sq (252 sq m) two-story construction was developed to look like a regular home, but function as a laboratory for clean energy research. Much like the Honda Smart Home, NIST's effort combines stable ground temperatures with geothermal systems to minimize heating and cooling loads throughout the building. Another factor in overall energy efficiency is a doubling of insulation levels, sealed by special sheeting that reportedly heals itself when pierced.
"The most important difference between this home and a Maryland code-compliant home is the improvement in the thermal envelope – the insulation and air barrier," says NIST mechanical engineer Mark Davis.
On July 1 2013, the research team began the experiment by moving a virtual family into the home. A computer simulator syndicated the energy consumption with that of a typical American family of four, the inhabitants going about everyday activities such as taking showers, watching TV and charging laptops. There was more at play than a life-sized game of The Sims, however, with the researchers able to gain realistic insights into the energy efficiency and how viable planting such a home into a real-life American neighborhood could be.
The energy surplus and the home's claim to net-zero living was compounded by a stretch of severe weather. For 38 days through winter, the 32 photovoltaic panels were largely covered in snow and ice, hampering their ability to harvest energy from the sun. But over the 12 month period, the home generated 13,577 kWh of energy. This surpassed the virtual family's energy usage by 491 kWh, an excess that could in theory be directed toward an electric vehicle or back into the grid.
"We made it, and by a convincing margin," said Hunter Fanney, the mechanical engineer who leads NZERTF-based research. "From here on in, our job will be to develop tests and measurements that will help to improve the energy efficiency of the nation's housing stock and support the development and adoption of cost-effective, net-zero energy designs and technologies, construction methods and building codes."
Despite boasting the aesthetics of a typical suburban house, adoption of the technologies used will largely come down to cost. NIST estimates that fitting out a similar-sized house with all the bells and whistles of its test home would cost around US$162,700. On the upside, it puts savings in electricity costs at $4,373 for the year.
Further research will center on how the measurements of the home can improve its energy efficiency and addressing the difference in up-front costs and long term savings. NIST is hopeful its findings will lead to improved energy efficiency standards as a resource for builders, regulators and home buyers.
The video below gives an overview of the project.