Wouldn’t it be great if your house produced more energy than it consumed? Does that mean negative utility bills? Indeed it does, because solar panels
can return power to the grid and make your meter spin backwards.
Japanese companies are fascinated with net-zero energy buildings, usually incorporating transportation as part of the mix. Panasonic’s Eco Ideas House
, with solar, a fuel cell, battery back-up and a plug-in Toyota Prius, has long stood next to a company headquarters in Tokyo, and the company is also developing a green-themed housing development. In Japan, Toyota is also heavily invested in green communities.
The house design is pleasant enough, but you won’t see its green features just by looking at it. Innovations include:
A 9.5-kilowatt solar array, backed up by a 10-kilowatt-hour lithium battery and a 10-kilowatt DC car charger. The solar will generate more than enough energy to heat the house, supply the appliances, and power a Honda Fit electric car. With direct DC fast charging, the Fit can be back on the road in two hours. Michael Koenig, Honda’s Smart Home project leader, said that converting DC to AC wastes energy, so this is a DC-based project.
The Home Energy Management System (HEMS) optimizes the house’s microgrid, so that the Fit can charge during the low-demand nighttime, and run on stored solar power. A geothermal system with eight, 20-foot deep boreholes uses a heat pump to heat and cool the home’s floors and ceiling all year.
LED lighting, with five times the efficiency of conventional illumination, is used throughout. UC Davis’ lighting center worked with Honda on a system that mimics the natural circadian rhythms of day and night. For instance, amber hallway lights are bright enough for occupants to navigate the corridor, but not disruptive of the human eye’s production of rhodopsin (which helps us see in darkness, and return to sleep quickly after a bathroom break). Blue light during the day helps maintain alertness.
The home also features a passive design that maximizes heating and cooling (the south-facing windows) and natural light and ventilation (the north-facing windows). The property is also five times more water-efficient than the normal house, with low-flow fixtures and short-run hot-water pipes. Graywater was used for irrigation, natural ash replaced half the foundation’s cement (production of which produces five percent of global CO2 emissions), and certified lumber was used throughout.
Over a year, the house is expected to generate a 2.6-megawatt-hour surplus (compared to the average home’s consumption of 13.3 megawatts). California’s official plan calls for all new homes to be net zero by 2020, so Honda’s house is tomorrow’s dwelling today.
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