Buildings that consume no outside energy are being developed today using existing technology. Innovation is critical to the success of these green building, and according to Harvey Bernstein, vice president of Industry Insights and Alliances at McGraw-Hill Construction, “The acceleration of the green building marketplace around the world is creating markets for green building products and technologies, which in turn will lead to faster growth of green building.”
Even smaller innovative companies are getting into the game, thanks to Hartford, Conn.-based United Technologies Corporation (UTC). According to Jacqueline Jenkins, program executive for the Wharton Small Business Development Center’s Energy Efficient Buildings project, UTC is subcontracting with smaller companies, “providing revenue for the companies, as well as a track record, which is key.” And, she notes, the relationship with UTC allows innovations that might not otherwise get into the market to be tested there.
But while considerable attention is being focused on innovative products and technologies — the means of achieving green building — another kind of innovation has given birth to an exciting new approach.
The net-zero energy building, or NZEB, focuses less on the means and more on the end result, which is a building or group of structures that generate as much energy as they use. A building’s energy production may be more than it needs at certain periods in time, explains David Riley, professor of architectural engineering at Pennsylvania State University and executive director of the university’s Center for Sustainability. But it qualifies as net-zero only if “the meter has not moved by the end of the year.”
The NZEB approach has been gaining momentum for some time, but in the past few years virtually all the major players — government agencies, academia, the military, not-for-profits and increasingly the business community — have become actively engaged in demonstrating the near-term potential of NZEB at residential, community and commercial scales.
The residential challenge is affordability: As part of a research project, The National Institute of Standards and Technology (NIST) recently built a net-zero test home in the Washington, D.C. area. “This home has all the features and aesthetics you would find in an upscale Washington, D.C. metro home,” Hunter Fanney, chief of NIST’s energy and environment division, told U.S. News and World Report. “There’s really nothing exotic about it and nothing that can’t be readily done with conventional construction.”
But the challenge at the residential level isn’t technical; it’s financial. Betsy Pettit, president of Building Science Corporation, told Reuters that a house similar to the NIST house, built in Concord, Mass., cost about $600,000 — and that didn’t include the cost of the land. While it is possible to build a net-zero house for less, it usually means a much smaller building with fewer amenities. According to Pettit, a house that approached net-zero energy use was built for Habitat for Humanity for just $150,000, but it measured only 1,200 square feet, less than half the size of an average single-family house in the U.S. in 2011.
In an effort to bring NZEB within reach of the average homeowner, the GridSTAR Center, a smart-grid education and research institute at Penn State, is focusing much of its work on the development of an affordable net-zero demonstration house. The goal, says Riley, who is also the principle investigator for the GridSTAR Center, is to create a home that generates all of the energy necessary “to meet the needs of the house and is a wise investment for the homeowner.” And the first step toward achieving that aim is to make the 2,400 square-foot demonstration house, located at the Philadelphia Navy Yard, as energy efficient as possible. That way, Riley explains, “It won’t need a whole lot energy generation to serve its needs.”
None of the energy-saving features in the modular home is exotic and many are installed in the controlled environment of the factory that is making the building components. In addition, since the emphasis is on reducing both construction and operating costs, load-managing appliances are being installed. Homeowners can run these appliances whenever they want, but the appliances advise the owners when electricity is least expensive in the region, and can be programmed by the homeowner to run when the rates are lowest.
The amount of energy that the house generates and consumes at any one time depends on a number of constantly shifting variables — time of year, time of day, weather conditions and the owner’s behavior, to name just a few. On a sunny summer day, when the family is out of the house, the photovoltaic roof shingles (installed at the factory) and the solar thermal collector, which helps provide both hot water and space heat, are likely to generate more energy than the house uses, in effect running the meter backwards. But on a cold winter night, when family members are home cooking and using everything from computers to televisions, the meter is likely to be running in the other direction. The net-zero goal is achieved if at the end of a year, the meter is in the same place that it was at the beginning — in other words, the net energy use for the year is zero.
One element that is critical to achieving this goal is the 10-kilowatt battery that sits inside the house. It serves two essential purposes. One is as a backup in case the grid ever goes down (according to Bloomberg Business Week, 18% of American households have either permanent or portable backup generators, a number that continues to climb as mega-storms like Sandy continue to knock out the grid).
The battery’s other use is to “level the load,” says Riley. “That battery can charge up at night when the electricity is cheap and deploy during peak times to discharge into the grid. So instead of just sitting there waiting for the grid to go down, this battery can actually generate revenue every day.” And the battery may turn out to be less expensive than it might otherwise have been. GridSTAR is evaluating the practicality of re-using the 16.5 kilowatt-hour lithium-ion battery pack from a Chevy Volt plug-in hybrid after its useful life in the car is over. (GridSTAR is the first test site for the reuse of a Volt battery in a residential storage application.)
“General Motors engineered the battery to outlast the car,” explains Riley. “The company doesn’t want someone to buy a Volt and have to face an expensive battery replacement over the life of the car. But that battery is still going to have some use and discharges left, and it actually has the perfect capabilities to become a community-storage or a residential-scale battery.”
The recycling of used hybrid car battery packs for stationary use is also being explored at the University of California, San Diego.
The next net-zero frontier is at the community level: “At the level of a single home, it’s generally not a good investment to have a house that produces a lot more energy than you need,” Riley states. While utilities may allow a homeowner to run his or her meter backwards at times, very few will actually pay for excess power beyond what the house uses in the course of a year.
But things change when a whole community of houses, or a neighborhood of mixed residential and commercial buildings, aims for net-zero. Katrina Managan, of Johnson Control’s Institute for Building Efficiency, notes in a recent white paper (“Net Zero Communities: One Building at a Time”) that such communities offer two key advantages: economies of scale in energy generation and a mix of buildings with varying occupancy patterns and energy use that can balance the energy load across an entire neighborhood. Communities also have the potential to generate enough excess energy to interest local utilities in negotiating revenue-generating agreements.
Such communities are just starting to appear. Motivated by the need to achieve energy security and independence, the U.S. Army is piloting a net-zero installation at Fort Bliss, located outside of El Paso, Texas. Occupying more than one million acres of land in Texas and New Mexico, and with a total population in excess of 90,000, Fort Bliss is aiming to transform the base into a net-zero energy community by 2015. Balancing budgetary and security concerns, Fort Bliss is modeling various possibilities, ranging from a waste-to-energy system, using the waste from the city of El Paso, to a geothermal plant, to be used in conjunction with energy-efficiency projects and load-balancing solutions, such as solar photovoltaics.
Outside of the military, the largest net-zero energy community in the U.S. is already nearing its goal of generating on site all of the energy used in its residential, community and commercial spaces. When completed, the West Village at the University of California, Davis, will include a village square and a network of open spaces, parks, gardens, pathways and courtyards; housing for 3,000 students, faculty and staff (in 662 apartments and 343 single-family homes); 42,500 square feet of commercial space; a recreation center; and eventually, a preschool/day care center.
As with the Grid STAR demonstration house, the first concern at West Village was energy efficiency. The roof uses solar-reflective material and radiant barrier sheathing, and thick 2″ x 6″ exterior walls add an extra level of insulation. Other architectural features, such as roof overhangs and window sunshades, combine with high-efficiency lighting, air conditioning units and appliances to reduce energy consumption to 50% below what would normally be expected if the buildings were simply built to code.
A four-megawatt photovoltaic system, including rooftop solar installations and solar canopies over parking areas, is designed to meet the needs of the first 1,980 apartment residents and commercial spaces. After that, the plan calls for a biogas generator, based on technology developed at UC Davis, which will convert dormitory table scraps, animal waste from the campus dairy and plant waste from agricultural research fields into electricity.
Residents also play a key role, and are being given access to a web-based tool that enables energy use monitoring by unit. And a smartphone app lets residents turn off lamps and plugged-in electronics remotely.
A little more than a year into the project and about halfway toward its target population of 3,000, West Village appears to be on track to achieve zero net energy use in 2013. The preliminary data is promising but not definitive, according to developer Carmel Partners of San Francisco. The solar panels are performing as expected and residents are using the anticipated amount of electricity. Efforts are underway to educate those residents whose energy use is higher than average on ways to reduce consumption.
All of this comes at a cost, however. In addition to $300 million invested by West Village Community Partnership, a joint venture of Carmel Partners of San Francisco and Urban Villages of Denver, the project received nearly $7.5 million in federal and state energy research grants. And apartment rents are said to be at the high end of the Davis market.
But then, West Village is a demonstration project intended to test and refine ideas that can be replicated elsewhere at market rates. Other projects around the country are also developing concepts and tools that can help make net-zero communities a reality, including the following:
- One challenge to planning such communities, especially in existing neighborhoods and cities, is figuring out which retrofits make the most sense and where. Simulation models exist for single buildings, but using these to try to make sense of large groups of buildings is nearly impossible, says Ali Malkawi, a Penn architecture professor and the director of the T.C. Chan Center for Building Simulation and Energy Studies. As part of his work at the U.S. Department of Energy’s Energy Efficient Buildings Hub (EEB Hub) at the Philadelphia Navy Yard, Malkawi’s team has come up with “computational tools that enable us to simulate a large number of buildings of varying types and to test interventions in neighborhoods and cities.” This allows architects and engineers to test ideas at scale before making decisions, and it allows developers and investors to evaluate, ahead of time, which interventions will be most cost-effective.
Cassidy Turley, a leading commercial real estate services provider, takes a different approach. The company was recently recognized by the EPA as a 2013 Energy Star Partner of the Year for its centralization of more than 350 buildings into one Energy Star Portfolio Manager account — creating a virtual community of sorts. This aggregation of buildings, notes CEO Joseph Stettinius, allows the firm to set benchmarks, and quickly identify and deal with anomalies that pop up any of the buildings. As a result, says Stettinius, “We can more effectively manage where we want to focus our remediation efforts.” The portfolio approach also allows the company to replicate what they learn in one building throughout the portfolio.
- The National Renewable Energy Laboratory (NREL) estimates that 62% of commercial buildings could reach net zero by 2025, but “it is rarely cost-effective to upgrade all buildings and equipment at once to get to net zero energy,” notes Managan. She recommends developing an optimal sequencing of steps — delaying upgrades to HVAC systems, for instance, until load-reducing steps have been taken, or taking advantage of “compelling events,” such as tenant vacancies or the end-of-life replacement of building systems to make needed upgrades.
- Energy storage is even more important at the community level than it is in single-family homes, both for backup in the event of disruptions to the grid and for load balancing. Riley notes a promising pilot program involving several hundred homes and a nearby wind farm. Wind power is notoriously variable: Sometimes the wind farm generates not only more energy than the community can use, but even more than the grid can safely absorb. At such times, the water heaters in all the homes are turned on, acting essentially as batteries by storing the energy for use later on.
The American headquarters of German software giant SAP points the way toward net-zero commercial buildings: Of the 21 commercial building identified as net zero by the New Buildings Institute (15 measured as net zero, plus six “credibly modeled”), 15 are less than 10,000 square feet and only one is at the same scale as the SAP facility in Newtown Square, Pa., near Philadelphia. (The building is also built to a high standard, and is certified LEED Platinum. The airy structure features a green roof, rainwater collection and geothermal energy.)
The relatively small scale of these buildings points to the difficulty of creating a large net zero energy building. As Malkawi notes, “As you get into larger and more complex structures, it is very difficult to figure out how the building is going to perform,” which is why the T.C. Chan Center and other research institutions are working to develop sophisticated simulation models for larger buildings.
But thanks to the pioneering work of SAP and others — including the National Renewable Energy Lab (NREL) in Golden, Colo., which built the one net-zero building of comparable scale, the $64 million, 220,000 square-foot Research Support Facility (RSF) — a few strategies have been identified that will support the design and construction of large-scale commercial net-zero buildings.
Hermetically sealed high-rises won’t get you to zero: Until recently, most large commercial structures have been sealed off from the natural world. But future energy-efficient buildings will undoubtedly take the opposite approach, responding continually to what is happening outside. The SAP facility, for example, has a lighting system that “harvests daylight” by using sensors to dim the lighting levels and raise or lower window shades based on the level of sunlight coming through the triple-glazed glass exterior wall. The NREL facility combines a similar window-shading technology with light-bending window louvers that cast rays up into the interior office spaces. And lower-than-average cubicle partitions allow the daylight to penetrate deep into the building.
The same openness to nature characterizes both buildings’ approach to heating and cooling. The SAP building uses geothermal wells to both heat and cool areas of the building whenever the temperature inside rises above or falls below the constant temperature of the earth tapped by the wells. The NREL building uses both a massive concrete heat sink in the sub-basement to store radiant heat and windows that open automatically or manually to use outside air whenever it’s efficient to do so.
Design and construction are a team sport: In order to ensure that all the various systems and features of a building work well together, everyone involved in the design, construction and maintenance of the building also needs to work together from the very beginning. At a recent conference in San Francisco, speakers from NREL made this point, discussing how the architects, engineers, contractors and operations/maintenance company involved in the RSF communicated with each other to ensure that their individual efforts would support the goal of net-zero energy. The result of this kind of teamwork is a building that functions as the SAP facility does. Brian Barrett, SAP’s manager of capital projects, who coordinated construction of the Newtown Square building, notes how systems throughout the facility “are interconnected and are part of a holistic system.”
Occupants are central to the success of net-zero buildings: “There has been a lot of work done related to human behavior in relation to energy reduction,” says Malkawi. “It is very well understood from a psychology perspective.” (He points out, however, that developing computational models that can incorporate this information is a work in progress.)
People use less energy, for instance, when they are made aware of how much they are using and how they can cut back. At the RSF, an icon pops up on occupants’ computer screens whenever it makes sense for them open a nearby window (windows that are out of reach are operated automatically).
At SAP, says Barrett, “Education was provided to each employee who was moved into the building so they would understand key features. Informing the people who will actually use the building is important. There were notes on the waterless urinals and explanation of the light sensors at the desk outlets and the lights above, which turn off after a selected period of time. A great deal of time was spent with literature and tours at the onset of the move-in process for the employees.”
The result of all these efforts is that the SAP facility is performing even better than expected, consuming 49% to 51% less energy than a conventionally built and managed building. And both SAP and NREL are continuing to make improvements and help nudge the commercial building sector toward net zero.