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Old August 6th, 2008, 05:23 AM   #1
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GRAND BUILD @ Technology

In Canada, a rammed-earth wall for the ages

The relationship between architecture and nature rarely gets more explicit than with rammed-earth construction. The 18-foot-high western exterior wall of the Nk’Mip Desert Cultural Center in Osoyoos, British Columbia, stretches for 260 feet, making it the longest rammed-earth wall in North America, according to Vancouver-based Hotson Bakker Boniface Haden Architects (HBBH). But the size is downplayed by the ruddy material, much of which was excavated on-site to capture the desert colors of the South Okanagan Valley.

Bruce Haden, a principal at HBBH, says he tried to resist the traditional choice of ersatz regional architecture, like that found in Santa Fe’s fake adobe buildings. “We wanted a building that was simultaneously modern and spoke to the landscape and the contemporary traditions of the Osoyoos Indian Band,” he says. Although the 12,000-square-foot center—used as an exhibition and meeting space by the Osoyoos—disappears behind the earthen wall and under a vegetated roof, these two highly visible sustainable design elements support a comprehensive energy-efficient project that also relies on radiant heating and cooling.

The west-facing, 24-inch-wide rammed-earth wall, bolstered with an internal layer of Styrofoam insulation, performed well enough to resist summertime temperatures that can reach 100 degrees F. The wall consists of local dirt, with organic matter filtered out, combined in a mix of 10 percent concrete and color additives (to get that clean, layered look). Contractors from British Columbia’s Terra Firma Rammed Earth Builders laid down each strip and then mechanically tamped it down to 50 percent of its original height. Haden says it was more labor intensive and expensive than concrete, but his hope is to encourage more rammed-earth architecture in the region by training locals in the construction methods. “If this could become a more generic material, it could foster a modern and regional aesthetic,” Haden says.

By Russell Fortmeyer (Architectural Record)
Photo courtesy Brady Dunlop/HBBH
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Old August 7th, 2008, 07:36 AM   #2
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Learning to Live on Alternative Energy

Three landmark projects show us how to integrate renewable-energy strategies into architecture, without compromising design.

An alternative can only exist when we have a choice. Architects have that choice now when it comes to energy. We can incorporate alternative energy sources, even electricity generation, into our projects, or we can just hook them up to the grid and let someone else worry about it. There are advantages and disadvantages to both, of course, but soon we may reach the point where we have no choice, and then we will need to find ways to successfully integrate alternative energy strategies into our projects. The three case studies that follow—in Chicago, Washington, D.C., and New York—provide some answers.

Near North Apartments, Chicago, 2007

Near North Apartments, a year-old, 96-unit, single-room occupancy in Chicago, was designed by Murphy/Jahn and developed by the nonprofit organization Mercy Housing Lakefront as a model of sustainability. While most of the building’s green technologies, such as a graywater recycling system that flushes toilets and a rainwater cistern for landscape irrigation, are hidden behind the scenes, its most visible ecofriendly feature is also its most experimental: A horizontal-axis wind-turbine system created by Chicagoan Bil Becker forms a lacy crown atop architect Helmut Jahn’s streamlined design.

Becker is a professor of industrial design at the University of Illinois and the founder of Aerotecture. Although he first applied for a patent for the Near North installation’s technology in 2000, his research dates to the 1970s. Becker, an acolyte of Buckminster Fuller, won in 1979 one of the Carter administration’s last research grants devoted to alternative energy.

“Windmills only work out on the farm,” Becker says of his first foray into an urban turbine almost three decades ago. But although capturing urban wind offers the opportunity of producing clean energy within cities, the location of the turbines also entails special limitations. Specifically, if a turbine were to display “runaway” behavior, throw ice, or transfer high vibration or sound loads to interior occupants, its chances of gaining a building permit would be slim.

Four years into his research, Becker realized that traditional propellers were not commensurate with urban needs, and in the following three years, he experimented with helical blades: In wind-tunnel environments, cardboard models of this Savonius rotor did not require much wind speed to start turning. Moreover, “They wouldn’t overspin. They would get in their own way rather than fly faster and faster, because it has a limited amount of lift—about 10 percent lift to 90 percent drag, he says.”

Becker proceeded to combine the Savonius rotor with a Darrieus rotor, which looks like an oversize whisk and “can bring you to a high rate of speed and power.” Thanks to their differing starting torques and speeds, the hybrid rotor can generate power in a variety of wind environments. In fact, the Savonius and Darrieus rotors play off one another’s strengths. Comparing the Darrieus to “second gear,” Becker explains, “If I didn’t have the Savonius blades, the Darrieus might not start. It’s like the starter motor in your car. We wouldn’t be driving internal combustion engines if we didn’t have an electric ignition.”

The Near North installation looks remarkably unchanged from Becker’s cardboard models. Becker mounted eight 520H turbines—each one featuring Savonius and Darrieus rotors welded onto a central shaft—on the roof in a horizontal axis. A vertical installation could produce 30 percent more energy, but it would have surpassed local height restrictions.

The turbines produce three-phase AC power from ARE 2,500-watt alternators mounted on each module. Each turbine also includes an Aurora 7200 Wind Interface Unit and an Aurora 3,600-watt inverter, manufactured by Magnetek. The interface converts the AC to variable DC and protects downstream inverters from high voltage surges via a diversion load. The inverter then converts that DC power into building-compatible 208-watt, 60-hertz variable amperage power. The project forgoes batteries, Becker explains, in order to minimize on-site toxicity and maintenance, and to assuage fire fears.

In Near North Apartments’ first months, the Aerotecture installation was producing a paltry 100 kilowatt-hours per module per month, but Becker has slowly improved average production to 300 kilowatt-hours per module per month. Currently, the 520Hs yield approximately 60 percent energy conversion, producing about 10 percent of the building’s power. Becker says his electronics could be optimized even further, although the alternator is proving an obstacle to achieving 80 percent efficiency: Just as the wind interface units were not designed for Savonius rotors, so most alternators are suited for the high rpm of internal combustion engines. Making another comparison to automobiles, Becker describes the disjunction between his rotors and his alternator as “having a car that’s too heavy for its engine. It runs, but it’s going to be sluggish on the hills.” To perfect his invention, Becker continues his search for an alternator suited for lower rpm, or may prototype one himself. David Sokol

Solar Decathlon House, Washington, D.C., 2007

“What we teach here is not just about generating energy in a building, but conserving energy within a building,” says Barbara Gehrung, an assistant professor in the department of architecture at the Technical University in Darmstadt, Germany. Gehrung was one of the faculty advisers on Darmstadt’s winning entry in the third annual Solar Decathlon sponsored by the U.S. Department of Energy in October 2007. The Decathlon program requires university teams to design 800-square-foot prototype houses that rely entirely on solar photovoltaics (PVs) for electricity during the 10-day competition on the National Mall in Washington, D.C.

Darmstadt’s wood post-and-beam house incorporates photovoltaics in three ways: on the roof, on skylights, and on louvered doors. The team used Integrated Simulation Environment Language (INSEL) software, developed in Germany, to analyze the potential energy gains from the sun, as well as to lay out the best orientation for the house’s active photovoltaic systems on the roof. Since the team wanted a flat roof, they realized they were at a disadvantage when compared to other houses with sloped roofs. This led them to incorporate the louvers on the east, west, and south facades.

The roof consists of a 7.8-kilowatt array of 40 photovoltaic modules provided by Sunpower, as well as exterior canopies consisting of 2 kilowatts worth of translucent thin-film photovoltaics provided by Sunways and sandwiched between plates of glass. The canopies cover porches that counted toward the house’s square-footage allotment, but also provided a buffer for ventilation. Schott amorphous silicon photovoltaic cells, generating 2 kilowatts at peak load, clad the louvers, which were designed with automatically actuated controls that would track the sun to increase output throughout the day. Gehrung says these actuators were so difficult to design and install that she doubts the team would use them again.

The PV system feeds four separate electrical bus systems for lighting, mechanical systems, entertainment, and controls. The team could document energy production and consumption, as well as indoor air temperature, humidity, and carbon dioxide values through the controls. They used more software programs, such as the Transient Systems Simulation Program (TRNSYS), for analyzing the reversible heat-pump system and the rooftop solar water heaters that helped the project meet its energy goals.

Although each Decathlon project relies on solar photovoltaics for electricity, Gehrung emphasizes her team’s energy-efficiency strategies as the primary motivation for design. Germany’s “Passivhaus” program, which is similar to the U.S. Environmental Protection Agency’s Energy Star rating program, inspired the team to design for local conditions, which in Washington meant a hot and humid subtropical climate. The 19 Darmstadt team members originally wanted to design an all-glass house. Site analysis (the longer sides of the house would face north and south once installed on the mall) indicated the need for less exposure, in order to minimize heat gain without restricting daylighting opportunities. The east and west facades are solid panels finished on the interior with gypboard embedded with phase-change materials (PCMs) that increase the insulation values while providing thermal mass. In this case, the PCMs are paraffin microcapsules called Micronal, manufactured by BASF. Once the temperature of the house reaches around 74 degrees F, the capsules melt and absorb the energy, helping to cool the non-air-conditioned house. In the evenings, the capsules harden to release stored heat. “Sometimes this worked too well,” says Gehrung. “We had so many visitors and we let them stay in the house too long, so we never had enough time to cool the building the way we wanted.”

For a German team designing an American house, some things got lost in translation. For example, the team scored low on the hot-water challenge, since the German showerhead limited the temperature to below the American requirement of 104 degrees F. “In the end, our energy-efficiency strategies helped us win,” says Gehrung, who won’t be involved in Darmstadt’s 2009 entry. “And it was a lot of fun.” Russell Fortmeyer

One Bryant Park, New York City, 2008

Though already common in industrial applications, combined heat and power [CHP] technology is rarely used in buildings in the U.S., even though it can provide a more efficient and lower greenhouse-gas-emitting alternative to traditional grid-supplied power. But one project that is a CHP pioneer is under construction in Midtown Manhattan and is headed for completion later this year.

Designed by Cook+Fox Architects, and jointly owned by the its primary tenant, the Bank of America, and the developer, the Durst Organization, the 55-story One Bryant Park will have a 4.6-megawatt CHP system. The designers and owners say that the building will be the first high-rise commercial office tower in the country to use this technology at such a scale. The CHP plant will satisfy about one third of One Bryant Park’s peak power demands and will provide for almost 70 percent of its energy needs on an annual basis.

Also known as cogeneration, CHP involves simultaneous production of electricity and useful thermal energy (typically steam) from a single fuel source (often natural gas). At One Bryant Park, the heat produced by its natural-gas-fired turbines will be used to make steam, which in turn will be used to heat the building and the domestic water supply, and to operate an absorption chiller for cooling.

Relying on CHP for much of its energy needs should significantly reduce the carbon emissions of the tower compared to a conventional office building dependent solely on the grid. Part of these savings are due to its distributed energy strategy. The term “distributed energy” refers to a generation source that is an alternative or enhancement of traditional grid-supplied power, located in close proximity to the building it supplies. Such systems can be more efficient than centralized generation since electricity carried over the grid loses 7 to 8 percent of its power in transmission, according to some estimates. However, retaining this electricity is a relatively minor contributor to the efficiency of CHP, since a much larger portion (about two thirds) of the energy generated at traditional power plants escapes through smokestacks. “By preventing transmission loss, CHP does save something on an overall Btu basis,” says Don Winston, Durst director of technical services. “But it is the heat recovery that really makes the system work,” he says.

About 86 gigawatts of CHP capacity are currently operating in the U.S.; however, the vast majority of these facilities are located at industrial sites rather than in individual buildings, according to Richard Sweetser, president of Exergy Partners, a consulting firm based in Herndon, Virginia. Sources say a number of factors make cogeneration a good choice for industrial applications, including a relatively flat demand for energy over the course of the day and through the various seasons. But in buildings, this demand is generally more variable, creating challenges for making the most of a cogeneration system’s thermal output. “If you are sending steam to the roof, CHP doesn’t make [economic] sense,” says Vinnie Galatro, director of technical services for the Fulcrum Group, commissioning agent for the One Bryant Park project.

The heat produced as a by-product of electrical generation will be used to make steam for heating
the building and the domestic water supply, and to operate an absorption chiller for cooling (above).
A thermal energy storage system (below) will help reduce demand during peak hours.
Diagrams courtesy: Fulcrum Group (top); Doyle Partners for Cook+Fox (bottom).

In order to avoid wasting valuable thermal energy, One Bryant Park includes a thermal storage system that will produce ice at night from excess steam. Then, during peak daytime hours, the ice will be used for cooling, resulting in “a nice and even load profile 24 hours a day,” says Galatro. Other challenges with which the One Bryant Park team had to contend included routing natural gas lines through a densely occupied structure, and the isolation of the CHP equipment for noise and vibration. There were also permitting and regulatory hurdles, though New York City officials are working to reduce such barriers to achieve a goal of 800 megawatts of installed clean distributed energy by 2030.

But impediments aside, CHP proponents say that the technology is an economically and environmentally viable alternative to the construction of additional conventional centralized generation capacity. According to Scott Frank, partner at Jaros Baum & Bolles, the project’s mechanical engineer, “generating electricity on-site and using the waste heat just makes sense.” Joann Gonchar, AIA

By David Sokol, Russell Fortmeyer & Joann Gonchar, AIA
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