Green power: Sustainable building techniques and technologies
Green power: Sustainable building techniques and technologies
(Continued from p. 70 of the July 2008 issue of BD+C)
GEOTHERMAL HEAT PUMP SYSTEMS
As an established and proven source of renewable energy, geothermal building technologies, in particular heat-pump systems, are promoted by green building advocates the world over. The U.S. Environmental Protection
Federal tax incentives passed into law in 2005 under EPAct 2005, plus the newly legislated Renewable Portfolio Standards in a number of western states, are driving growth of geothermal development. According to the U.S. Geothermal Energy Association, 61 large new geothermal projects were under way as of 2006.
Not surprisingly, many say there is considerably more untapped potential for geothermal. According to a recent Massachusetts Institute of Technology study, current system types could yield millions of gigawatts of geothermal energy, providing 10% of U.S. energy needs by 2050, if sufficient resources were invested in development.
“In spite of its enormous potential, the geothermal option for the United States has been largely ignored. In the short term, R&D funding levels and government policies and incentives have not favored growth of the U.S. geothermal capacity,” states the DOE-sponsored MIT report, “The Future of Geothermal Energy,” http://www1.eere.energy.gov/geothermal/future_geothermal.html.
Although it has a long way to go before being signed into law, the National Geothermal Initiative Act of 2007, now in Senate committee, could potentially ease things in the right direction. The bill seeks to invest $75 million in
Beware of short looping Matt Ebejer, PE, vice president and healthcare market focus leader for Syska Hennessy Group, Los Angeles, cautions against short looping, which can jeopardize the efficiency of a geothermal project. “Short looping is not installing enough geothermal fields, so that the geothermal heat pump units operate at peak capacity all the time,” he explains. “The system heats and cools the building, but the equipment that was designed to operate at 0.70 kilowatts per ton operates at 0.9 kilowatts per ton because the loop field temperature is 90 F instead of the designed 70 F.” To guard against such an eventuality, Ebejer advises that “the construction documents must tell the contractor exactly what the engineer wants, from bore size, depth of bore, spread spacing, type of grout, etc. The engineer cannot leave these items up to the contractor.” |
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geothermal technology development this year, and $110 million per year, from 2009 to 2013. The bill also aims to expand geothermal energy production from a handful of western states to at least 25 states nationwide.
Obstacles and Opportunities
Besides a need for additional funding and development, life cycle benefits often need to be prioritized over first costs for geothermal projects to be viable.
“We see the geothermal systems being more applicable in institutional-type facilities, 40- to 50-year buildings, where the owner is savvy about long-term life cycle costs,” says Penn, whose firm Image Engineering Group has designed more than 150 geothermal systems for K-12 school districts in Texas. Facilities designed for “the developer market where the buildings are for an investment to turn over in a few years, where first cost prevails, typically are not good candidates,” he adds.
Also built into that first cost are such expenses as permitting and inspection fees, and the hard-to-predict value of drilling, especially in cases where a few drilling firms have a monopoly on a particular local market. At the same time, Carson points out, “The number of specialty well-drilling contractors has grown in the past five years, and this has brought down the cost of drilling new well fields.”
Building designers and contractors also complain that even without discussing first cost, they experience resistance from owners, developers, and even local officials simply because these parties lack understanding about the benefits of geothermal technology and how it works. Some see this stumbling block even when working with some MEP engineers and financial institutions.
One other challenge comes from environmentalists: Though interested in the energy profile of the systems, they are concerned about the invasiveness of geothermal installations and operations. Do underground wells pose a significant threat to soils and the ecosystem generally? Ebejer notes that closed-loop systems have been shown not to affect the groundwater, and the EPA considers geothermal systems to be environmentally safe.
“After the borehole is drilled and the loops placed in the hole, the borehole is grouted to provide sanitary protection for a water supply by preventing leakage downward along the borehole,” adds the Oregon Institute of Technology’s Boyd. “Also, the grouting protects water-bearing formations by preventing the migration of water between aquifers, and will preserve the hydraulic characteristics of artesian formations and prevent leakage upward along the borehole.”
Carson does acknowledge that geothermal technology isn’t environmentally perfect, mainly because a small percentage of food-grade propylene glycol circulates through the pipes to prevent freezing. Yet the cradle-to-cradle analysis—overall reduced carbon footprint, no added emissions, reduced energy use—makes a strong environmental case for geothermal.
In addition to the environmental and energy-saving advantages, geothermal development also helps stimulate local economic activity, as opposed to purchasing energy from outside utilities or overseas suppliers. Although increased financial incentives and R&D will be necessary to more fully realize geothermal’s potential, many are optimistic. “I foresee geothermal use greatly increasing in the next few years,” predicts Ebejer. “As the cost of fossil fuels increases, an inexpensive source will be required, and geothermal offers that.”
WIND POWER FOR BUILDINGS
Wind is another environmentally friendly and cost-effective way to generate power. Wind energy is plentiful, renewable, and clean, and it can reduce greenhouse gas emissions by replacing conventional electricity. By the
end of last year, wind-powered generators had a worldwide capacity of about 94 gigawatts—a mere 1% of the world’s electricity. But the supply of wind power has grown fivefold since the year 2000.
Since the 1980s, the modern wind turbine has been used for electricity generation of small facilities in conjunction with battery storage in remote areas. Grid-connected turbines in the 1-10 kW range can power entire light commercial structures and use grid energy storage to save power for peak use. Users of small-scale turbines who are off the grid must adapt to intermittent power or opt to use batteries, diesel, or photovoltaic diesel systems to supplement their turbines.
A consistent 10-12 mile per hour wind is ideal for using wind turbines. In urban, industrial, and commercial locations, where it is difficult to sustain a consistent amount of wind energy, smaller systems may still be used to run low-power equipment, such as parking meters or wireless Internet routers.
There are surprisingly few limitations on wind power in zoning codes and local laws on the use of wind power in urban areas, other than those related to height. One common obstacle, however, is local opposition to erecting wind turbines, says Preston Koerner, a lawyer, environmentalist, and creator of the online journal Jetson Green (www.jetsongreen.com). Residents are often concerned about cost, noise, or installation disturbances of wind turbines, which tend to be minimal as compared to other project types. Koerner remains optimistic, however: “It’s an innovation space,” he says. “A lot of money is going into clean technology right now, and we need it.”
Koerner and other experts point to a number of successful large-scale applications of commercial wind power outside the U.S., most notably the World Trade Center tower in Bahrain. New, state-of-the-art buildings in planning or under construction that will use wind power include the Pearl River tower in China, Core Tower in Florida, and the Clean Technology Tower in Chicago. Houston’s Discovery Tower will feature its own rooftop wind farm. With these developments, industry experts believe, the United States alone is poised to provide 20% of the world’s electrical grid by wind alone.
About the authors
C.C. Sullivan is a communications consultant and author specializing in architecture and construction. Barbara Horwitz-Bennett is a writer and contributor to construction industry publications.
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