Energy-producing Honda Smart Home gives more than it takes
By Nick Lavars
April 1, 2014
With homes and light-vehicles accounting for roughly 44 percent of total greenhouse gases emitted in the US, neutralizing these emissions would certainly go a long way towards a clean energy future. What if these sources of pollution could not only be nullified, but play an active role in reducing our environmental footprint? Such is the thinking behind the Honda Smart Home US unveiled last week, which generates enough solar energy to power both car and home, with a little left over to feed back into the grid.
Constructed on campus at the University of California (UC), Davis, the Honda Smart Home US follows in the footsteps of the Honda Smart Home System, which the company demonstrated in Japan in 2012. But in addition to outlining an off-grid living solution, its latest effort hones in on the potential of smart connectivity between the home and main grid to impact overall energy reliability.
The Honda Smart Home US is driven by the company's home energy management system (HEMS). This proprietary system, the brains of the operation, is housed in the garage to monitor and optimize electrical consumption across the home's micro-grid.
Sitting alongside the HEMS is a 10 kWh battery that uses the same lithium-ion cells you'll find in Honda's Fit EV. This battery stores the energy collected by the 9.5 kW solar photovoltaic system mounted on the roof for night time usage (when demand peaks and vehicles are likely in need of recharging).
Laying a foundation
A typical concrete slab for a house requires a large amount of cement to hold it together. Producing this cement, which involves heating it to more than 1,000° C (1,832°F), requires significant amounts of energy, while the chemical reaction itself produces carbon dioxide.
The team replaced around half of the cement with pozzolan, a substance that occurs naturally in the earth as a result of volcanic ash deposits. As pozzolan doesn't need to be heated to the same high temperatures as cement, integrating it into the concrete mix meant Honda was able to reduce the carbon emissions typically associated with the construction of a home.
Heating and cooling
A geothermal heat pump provides the house with heating, cooling and hot water all from the one machine. Water is heated in a tank and delivered to the shower. As the shower drains, the grey water is used to help preheat the cold city water, helping to reduce the energy required to provide hot water to the home.
Once it has fulfilled its hot water duties, the shower drainage is pumped into four thermal tanks underneath the backyard. Here, heat from the earth warms the liquid further, turning it into what the team calls Ground Source Fluid. This fluid is then returned to the house and driven through pipes located in the floor, roof and ceiling to provide heating. Alternatively, cold water can be pumped through the system to cool the house in the summer months.
In designing the home, the team took into account local weather conditions with north-facing windows positioned to maximize natural light and ventilation, while south-facing windows are designed to optimize heating and cooling. Double-stud walls, a cool metal roofing material and an insulated concrete base are other elements that Honda says contribute to the overall energy efficiency of the dwelling.
For coming and going
The home is equipped with a Honda Fit EV, the solar panels providing enough juice for a typical daily commute. Honda modified the electric vehicle to accept DC power directly from the home's solar panels or its battery bank, which it says prevents a loss of energy that occurs during a DC to AC conversion. Honda claims the vehicle can be recharged in around two hours when the solar panels are working at full capacity.
Shedding some light (and energy)
LED lighting is used throughout the home to reduce energy consumption and also as a means of contributing to the well-being of the residents. Honda worked in collaboration with the California Lighting Technology Center at UC Davis to explore a new form of circadian color control lighting.
Its lighting solution mimics shifts in natural lighting throughout the day and night. Using bright blue-rich light in the daytime, the lights are designed to optimize alertness and energy, while using an amber tone creates a more relaxed atmosphere after the sun goes down.
All of these factors result in a home that Honda says is three times more water-efficient and uses half the energy of similar-sized homes in the Davis area. It estimates that, while a comparable home in the area consumes 13.3 MWh of electricity per year, the smart home will generate a surplus of 2.6 MWh. Honda says this equates to an offset in carbon emissions of nearly 13,100 lb (5,942 kg) per year. If you factor in the energy typically involved in powering a vehicle in addition to the home, this figure is around 23,500 lb (10,659 kg).
So when can I move in?
Honda and researchers from UC Davis and Pacific Gas and Electric are currently using the home as a laboratory to carry out ongoing evaluations of new technologies and real-world applications in the housing, transportation and energy sectors.
This will allow Honda to assess how viable the use of EV batteries could be in home-to-grid connectivity and other applications. It says the smart HEMS model, which feeds power back to the main grid when the home's micro-grid is overloaded, has the potential to enable large-scale implementation of electric vehicles and renewable energy systems through improving overall grid reliability.
You can hear from some of the people behind the design and construction of the Honda Smart Home US in the video below.