Net Zero Homes: The Solar Wave of the Future?

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More smart homes appear around the county, many using solar power to contribute to a home that not only saves energy but also produces energy to share.  

What if your home could not only provide enough energy to power itself, but also power your EV and still have some to spare? This is exactly what the Honda Smart Home at UC Davis is promising to do. Now, what if your home could not only survive the next polar vortex but even thrive in it? This is what the Enertia home promises to do. 

Following a growing trend, builders all over the country are using solar power, along with wind, geothermal, and other energy alternatives, to create buildings that are energy independent. We’ve written about some larger-scale projects, such as the Walgreens in Illinois, the Skaneateles Village Hall muncipal building in New York State, and the David and Lucile Packard Foundation headquarters in Los Altos, CA.

Honda Smart Home US

Yesterday, UC Davis and Honda opened Honda Smart Home US on Davis’ West Village Campus. This house is capable of producing more energy on-site from solar than it consumes annually, including enough energy to power a Honda Fit EV for daily commuting. A 9.5kW solar PV system mounted on the roof will generate more energy than the home and Fit EV consume on an annual basis, due in large part to the efficient design of the home. All of the energy for space heating, space cooling, ventilation, lighting, hot water, appliances, and consumer loads, in addition to the transportation energy for the Honda Fit EV, is supplied by the solar panels on the home. 

Honda Smart Home is expected to generate a surplus of 2.6 megawatt-hours of electricity over the course of a year, while a comparable home will consume approximately 13.3 megawatt-hours. This results in a net offset of nearly 13,100 pounds of CO2 per year.

A Honda-developed home energy management system and an energy-efficient design will allow the home’s occupant to use less than half of the energy of a similarly sized new home in the Davis area for heating, cooling and lighting. The home is also three times more water-efficient than a typical U.S. home. This fits in well at UC Davis’ West Village, which is the largest planned zero net energy housing development in the U.S. Opened in 2011, West Village is home to the university’s research centers focused on energy efficiency, sustainability, and transportation.

The sustainability efforts at UC Davis go far beyond solar. Aggressive recycling, composting, and reuse efforts prevent more than 63% of campus waste from entering landfills annually. Through its Climate Action Plan, the campus has reduced greenhouse gas emissions below year 2000 levels and expects to reach year 1990 levels by 2020. 

One lucky UC Davis member will be selected to live in the house and drive the car. This person wil be a part of the living laboratory of the house, where Honda, along with researchers from UC Davis and Pacific Gas and Electric (PG&E), will evaluate new technologies and business opportunities at the intersection of housing, transportation, energy, and the environment.

The environmental efforts at HSH address two of the primary sources of CO2 emissions: cars and homes. Together, energy used to power homes and light-duty vehicles contributes to approximately 44% of U.S. greenhouse gas emissions in the United States. So, finding technology that enables distributed renewable energy generation to supply power to homes and cars seamlessly could be a potential pathway to addressing climate change.

The house includes these features:

  • Honda Home Energy Management System. Honda Smart Home US implements Honda’s home energy management system (HEMS), a proprietary hardware and software system that monitors, controls, and optimizes electrical generation and consumption throughout the home’s microgrid. A 10kWh battery energy storage system in the garage, using the same lithium-ion cells that are used in the Honda Fit EV, allows stored solar energy to be used at night, when household demand typically peaks and electric vehicles are usually charged. Honda’s HEMS leverages the battery to balance, shift, and buffer loads to minimize the home’s impact to the electric grid. The system will also enable Honda to evaluate the second life, or re-use, of EV batteries in grid applications, home-to-grid (H2G) connectivity, and other concepts. Honda’s HEMS is also capable of improving grid reliability by automatically responding to demand response signals and providing other grid services. If the electricity grid is overloaded, for example, Honda Smart Home is capable of shedding its load and even supplying power back to the grid. This type of smart grid connectivity will enable the mass deployment of electric vehicles and renewable energy without sacrificing grid reliability.
  • DC-to-DC electric vehicle charging. The Honda Fit EV included with the home has been modified to accept DC power directly from the home’s solar panels or stationary battery, eliminating up to half of the energy that is typically lost to heat during DC-to-AC and AC-to-DC power conversion. When the solar panels are generating electricity at full capacity, the vehicle can fully recharge in approximately two hours directly from sunlight.
  • Geothermal radiant heating  and cooling. In homes and cars, heating and air conditioning systems consume significant amounts of energy. In the ground beneath the backyard of the house, eight 20-foot deep boreholes allow a geothermal heat pump to harness the ground’s relatively stable thermal sink to heat and cool the home’s floors and ceiling throughout the year. Researchers from UC Davis will evaluate the performance of the system to determine its adaptability to mainstream use.
  • Pozzolan infused and post-tensioned concrete. Concrete accounts for approximately 5% of global, man-made CO2 emissions. This large CO2 footprint is a result of producing cement — the concrete’s “glue” — by heating limestone to more than 100 degrees Celsius. This heating requires the burning of fossil fuels, while the chemical reaction itself also releases CO2. A naturally- occurring substance called pozzolan was infused into the Honda Smart Home’s concrete to replace half of the cement typically needed. A technique called post-tensioning, which uses steel cables to compress the concrete slab, was also used to reduce the amount of concrete and steel needed. 
  • Advanced lighting. The LED lighting used throughout the home is not only five times more energy-efficient than conventional lighting; it is also designed to support the health and wellness of the home’s occupants. Honda worked with researchers from the California Lighting Technology Center at UC Davis to explore new circadian color control logic. Mimicking the natural shifts in daylight that occur from morning to night, the circadian-friendly lighting design allows occupants to select lighting that complement occupants’ circadian rhythms and support nighttime vision. The amber hallway night lights, for example, provide enough light to navigate through the home in darkness without depleting a photopigment in the human eye called rhodopsin that helps humans see in low-light conditions. This allows occupants to move about safely and return to sleep quickly and easily. Exposure to bright, blue-rich light during the day helps put body and mind in an alert and energetic state, but at night, blue light can disrupt circadian sleep cycles. Therefore Honda Smart Home minimizes the use of blue light at night.
  • Passive design. Honda Smart Home is designed to be extremely energy efficient by taking into account local weather conditions, sun direction, and the home’s outer shell. Known as “passive design,” these techniques reduce the energy needed for heating and cooling while maintaining comfortable living conditions. The Honda Smart Home’s south-facing windows are optimized for heating and cooling, while the north-facing windows are positioned to maximize natural light and ventilation. This will keep the home naturally cool in the summer and warm in the winter. Double stud walls, cool roofing material, and a fully insulated concrete slab all contribute to the home’s energy efficiency.
  • Sustainable materials and waste management. Sustainable materials were used throughout the construction process. Rather than cover the concrete foundation with wood, diamond pads were used to create a smooth, polished finish. For the roof, metal was selected, which is more recyclable than asphalt. All lumber used in the construction process was sustainably harvested from forests certified by the Forest Stewardship Council (FSC), while advanced framing techniques were used to reduce the amount of material needed. Additionally, 96% of the construction waste associated with the project, including drywall, brick, plastics, and lumber, was recycled.
  • Surpassing California’s 2020 zero net energy goal. The Honda Smart Home US was designed to address specific challenges associated with the transportation and energy sectors in the United States. California’s Energy Efficiency Strategic Plan, for example, sets a goal for all new homes to be zero net energy beginning in 2020. Through a combination of advanced technology integration, energy efficiency measures, and sustainable design techniques, Honda Smart Home surpasses that goal by producing enough energy to power the home and an electric vehicle on a daily basis.

Enertia Extreme EX homes

Tackling the challenges of solar homes from another angle, Enertia, which has been manufacturing the Green Kit Home for the last 25 years, has just released three new kits designed to thrive in the kinds of extreme weather conditions the U.S. has been experiencing in the last few years. Enertia homes generate their electricity through PV panels and metal seamed roofs. Energy efficiency is built into the homes, from an interaction of solar and geothermal power through passive house type construction concepts.  

For the vicious Polar Vortex conditions, EX models implement a full house-within-a-house strategy, by doubling the east and west wall, as well as the north wall. The new versions of Arcadia, Equinox, and Southern Pines carry Enertia’s house-within-a-house concept to the extreme while sticking to an economical easy-to-build kit form. Extra wind, earthquake, and tornado resistance are a side benefit to the doubled-wall technique.  

More information

These projects demonstrate the growing demand for energy indepencence in our homes and the importance of solar in achieving this goal.

More information on the Honda Smart Home can be found at www.hondasmarthome.com. More information on Enertia Green Solar Homes can be found at http://www.enertia.com