The house of tomorrow is now 90 percent here, according to Michael Koenig. He leads a project that has added the remaining 10 percent of needed innovation to construct a prototype home that is actually net-positive in its energy use—i.e., it is anticipated to produce more energy than its own operations consume on an annual basis. With a connected battery-storage system and a battery-electric vehicle (BEV) in the garage, it’s also capable of responding to utility calls for power and entirely operating independently from the connected grid.
“It’s the house of the near-future,” Koenig said at the March 25 unveiling of the house on the University of California, Davis (UCD) campus, emphasizing the speed with which the home’s related technologies are developing. The house is the brainchild of energy specialists at Honda; the structure’s official name is the Honda Smart Home. It’s intended as both proof-of-concept and a real-world testing ground for a range of smart-grid capabilities, including residential-based ancillary grid services, vehicle-to-grid communications and controls, and advanced power management. And it isn’t just a laboratory. A member of the UC Davis community will live in the house and drive the companion Honda Fit BEV to help evaluate how the systems perform for an actual homeowner.
The house’s brain—the home energy management system (HEMS)—is the biggest piece of the near-future technology, and it’s far smarter than anything now on the market. It ties together the 9.5-kilowatt (kW) rooftop solar photovoltaic (PV) installation with the BEV’s charger and separate energy-storage batteries, along with in-house energy-monitoring intelligence and external, grid-supplied data. Honda’s team worked with local utility Pacific Gas and Electric (PG&E) on this aspect of the design, which adds significantly more interactivity and on-site usage to standard PV-system installations.
The HEMS pulls together all of the ideas that everyone has been talking about, according to Ryan Harty, American Honda’s manager for environmental business development.
“These are things that nobody has done in a coordinated way together,” he said.
A primary advantage of the HEMS is its ability to manage electricity created by the rooftop PV panels. In typical installations, these panels feed the local utility grid. The direct current (DC) power the panels generate is inverted to alternating current (AC) for utility-system use, bypassing the home entirely. Instead, in the Honda Smart Home, the panels are connected to the HEMS, where their DC power can be redirected to charge the BEV directly. This is thanks to the vehicle’s fast-charge “CHAdeMO” connector, a type commonly found in Japan, as opposed to the Society of Automotive Engineers designs, which predominate on all BEVs in the United States except Nissan’s Leaf.
If the vehicle isn’t connected, PV power will flow, instead, to the home’s lithium-ion batteries. The batteries were selected to test how well products initially designed for automobiles could serve other energy-storage purposes.
The HEMS, located in the home’s garage, also serves as a go-between with the home’s meter and the grid. Its internal inverter can turn the PV-supplied DC power into grid-friendly AC once the batteries are charged. In addition, it constantly monitors PV production and draws on the batteries as needed to ensure the combined system’s output remains constant, even if passing clouds slow PV production. The HEMS even monitors the utility’s generation supply, so it draws on grid-supplied power only when sources with the lowest carbon footprint are online.
Finally, the HEMS also incorporates an automatic transfer switch—not standard in grid-connected residential PV systems—which enables the home to separate itself from the grid. The feature allows it to respond to utility demand-response signals and to continue powering the home in the case of an outage without endangering repair personnel who might be working on the utility’s lines or other equipment.
This isn’t Honda’s first foray into residential solar. In February, the company announced a partnership with PV installer SolarCity to establish a $65 million fund as a financing vehicle for Honda and Acura automobile owners interested in rooftop panels.
With the Honda Smart Home’s construction complete, the research of how these systems actually work in tandem will soon begin. Honda, UCD and PG&E are planning at least three years of study. The home’s PV system is larger than such an efficient residence would need, so unforeseen opportunities can be researched. The company said it has no current plans to commercialize the HEMS; it will be making much of the data available to other researchers, which could help other product developers in their efforts to bring today’s house of the future to the rest of us—perhaps tomorrow or just the day after.