A new subdivision 50 miles east of Los Angeles includes 20 net-zero-energy homes that will help California builders and electric utilities get ready for new residential efficiency requirements that take effect in 2020.
The Electric Power Research Institute (EPRI), which is leading the effort, says the Sierra Crest development in Fontana, Calif., is the first net-zero-energy community in the state. The 20 net-zero houses are part of a much larger subdivision being built by Arizona-based Meritage Homes. The houses will help the California Public Utilities Commission and others evaluate how clusters of net-zero buildings equipped with photovoltaic (PV) systems can be integrated onto the grid most effectively.
In 2020, all new houses in California will be required to produce as much energy as they use on an annual basis. Sierra Crest is designed in part to proving the concept is workable, says Clay C. Perry, a EPRI spokesman.
“Over the next several years, the project team will study how these houses and their advanced technologies can be effectively integrated into the utility’s electric grid,” EPRI said. “Simultaneously, researchers will investigate avenues that improve the scalability and economic feasibility of these communities across the state.”
Other project participants include BIRAenergy, Itron, and Southern California Edison.
Houses are ready for sale
CR Herro, vice president for environmental affairs at Meritage, says there are 187 lots at Sierra Crest, divided into three communities. The net-zero houses are split into two groups, one in the “Grand Canyon” neighborhood and another 11 clustered in the “Yosemite” neighborhood.
Meritage, Herro said, is the eighth largest homebuilder in the U.S. and constructs some 8000 homes per year, principally in warm-weather parts of the country (Fontana, for example, is in Climate Zone 3). The company has focused on energy-efficient construction over the last six years and now makes solar and net-zero performance available on every home it builds, anywhere in the country, he added.
“What we hope to do is demonstrate that what most customers think is a future potential is available right now,” he said in a telephone interview. “You don’t have to wait. It’s something that consumers should learn to demand from their new homes.”
Some of the features in houses at Sierra Crest include:
- Advanced framing techniques with 2×4 walls that are insulated with a continuous layer of R-5 polystyrene on the outside of the walls, and stud cavities insulated with open-cell polyurethane foam for a total R-value of roughly 19.
- Conditioned attics insulated with 6 in. of open-cell foam. (The roughly R-24 of the insulation falls below the level required by the International Energy Conservation Code, but Herro says Meritage follows a performance path allowed under California’s Title 24.)
- Heat pump hot water heaters.
- Variable speed air-source heat pumps for heating and cooling.
- LED lighting.
- Air tightness of between 1 and 1.2 air changes per hour at a pressure difference of 50 pascals.
- Uninsulated, post-tensioned concrete slabs.
- Low-e, double-glazed windows with a solar heat-gain coefficient of 0.22 and a whole-window U-value of 0.34.
- Grid-tied PV with an average capacity of 4kw.
The net-zero energy houses range in size from about 1900 sq. ft. to 2900 sq. ft., with costs from about $379,000 to $432,000. HERS scores on the houses average -3.
Developers will study PV impact
Both of the clusters of net-zero energy houses will be connected to batteries, but in different ways. In the smaller of the two groups, each house will have its own 3kwh lithium-ion battery provided by Sun Power; in the Yosemite neighborhood, net-zero houses will be connected to a single, larger battery.
In each case, batteries are designed to even out the load on the grid over the course of the day, not provide long-term backup power.
What worries utilities serving solar customers is something called the duck curve, which represents production and demand for electricity in houses with grid-tied PV systems and their impact on the grid as a whole. During the day, there’s typically an over production of electricity, but when the sun fades in late afternoon and PV production falls off there’s a spike in demand as those houses begin drawing on utility power. In chart form, the demand curve looks a lot like a duck.
Dividing the houses into two groups–one with residential-size batteries and another with a communal battery–will help utility researchers understand PV grid integration a little better. But the idea is the same: the excess power produced during the middle of the day can be applied to the grid when PV production declines in the evening.
“The Holy Grail now is how do you make this a win-win,” as Herro puts it. “And the big win is we need to make flat load shapes.”
“It’s not a case of whether renewable energy is good or bad, it’s how to you integrate it,” he continued. “We shouldn’t be optimizing for southern exposure, we should be optimizing for western exposure. We should think about smart ventilation practices and smart HVAC design and controls and thermal mass should come back in. Nobody’s talked about thermal mass for 20 years but thermal mass is the best opportunity to start leveling these really energy-efficient homes out.”
Net-zero energy still not in high demand
California’s upcoming requirement for net-zero performance represents a big shift in residential building, but at the moment even consumers who are given the chance to buy a net-zero house often don’t.
Meritage can offer a net-zero option to any homebuyer in the country for a relatively modest increase in cost, Herro said, but only about 1% of buyers take advantage of it.
“I don’t think it’s whether they want to or not,” he said, “it’s whether they’re even aware they can have it … If you’re a new homebuyer, you’re kind of overwhelmed by location, design and price and you’re not yet challenging the homes you’re looking at for these advanced features. You should, but I think it’s really a matter of of homebuyer sophistication and the quicker buyers start expecting more from the homes the faster the market will change.”
“They don’t even know they can have what they can have, so they’re settling for conventional,” he added.
A 2800-sq. ft. home built by Meritage would typically need about $12,000 in solar panels in order to hit the net-zero mark. When that’s rolled into a mortgage, Herro said, the incremental increase in payments is more than offset by lower energy bills.
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A test community in California will give utilities, builders and state regulators a chance to see how net-zero-energy houses equipped with photovoltaic arrays and batteries for storage can be integrated onto the grid. California is heading for a 2020 adoption of the net-zero standard for new residential construction.
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It is really amazing to know how advanced we are with the aide of high-tech technology and its endless devices. Energy storage technology has been around for quite some time now but to add on to that feature by implementing PV arrays and its likes, is just astounding. We have already reaped and are continuing to reap benefits technology has got to offer, but to make it even more fruitful is definitely a bonus.