Walk into a big home improvement store in Alabama,
Alaska or Arizona and pick up some indoor–outdoor carpeting and vinyl siding
for your house. You, the store and the manufacturers all expect them to last
years in the sun, but how can such polymer materials be tested in a accurate,
reproducible way — so that both will survive in hot and wet, cold and wet,
and hot and dry climates, each exposed to a slightly different UV spectrum?
For the last twenty years, the National Institute of Standards and Technology (NIST) has been working with industry and academics to come up with a better way of simulating weathering — and has found it in the shape of an 'integrating sphere'.
An integrating sphere
|“UV testing chambers have come a long way since 1920.”|
The sphere, an aluminum ball 2 meters in diameter, can reproduce almost any climate/radiation regime found in nature, and each of its 32 ports — where the samples are placed for testing — can be individually tailored, so the siding can be put in Alabama, Alaska and Arizona simultaneously.
Jonathan W. Martin, the group leader for the sphere at the NIST Building & Fire Research Lab in Maryland, says that UV testing chambers have come a long way since 1920. "Early chambers used lamps that heated specimens as hot as 60 °C, which is near the upper limit of exposure temperatures found in the natural environment: the surfaces of samples were not irradiated uniformly; and conditions varied over time during testing," he says. "In addition, most specimens were exposed to lots of radiation below 290 nm — a part of the spectrum that is filtered out by the atmosphere."
Simulating the right environment
|“The temperature and relative humidity within an exposure chamber can be precisely set to the desired parameters.”|
The integrating sphere is designed to avoid these problems. Six microwave-powered lamps are arranged around a port at the top of the sphere, but they do not directly illuminate the specimens. Dichroic mirrors reflect the light, subtracting much of the infrared and visible spectrum, and thus insuring that the base temperature does not rise above 30 °C — unless the manufacturer needs to test a material at higher or lower temperatures. In these cases, the temperature and relative humidity within an exposure chamber can be precisely set to the desired parameters.
|“Acid rain and freeze-thaw environments can also be simulated.”|
The interior of the sphere is lined with polytetrafluoroethylene (PTFE), a powder which reflects uniformly in every direction, so that each of the 32 sample chambers is bathed in uniform light. The high-intensity lamps are filtered to remove almost all of the radiation below 290 nm. In addition, because construction materials are often subject to mechanical loads in service, "we added that capability to each chamber," Martin says. Acid rain and freeze-thaw environments can also be simulated in the sphere.
Origins of the sphere
Where did the sphere come from? "In the late 1980s," Martin says, "we began developing a new methodology for testing polymeric materials used in construction and the automotive field. Similar techniques were already in use in the electronics, medical and nuclear industries, but they were new for construction materials. In 1994, two major coatings companies came to NIST and asked us to help create an industry–government–academic consortium to speed up the introduction of these methods for construction. We are now in our third 3-year phase of research, and the results have been so successful that we created a similar consortium with the sealants industry in 2001."
Corporations involved in the consortium have provided both financing and their own expertise, with additional input from universities and other government sources. "The Smithsonian Environmental Research Center, the Air Force, the Federal Highway Administration and other agencies have all collaborated with us," he says. Industry was interested in better testing methods, he adds, both to produce longer-lasting products and to reduce their liability when poorly performing products were sold. In addition, having the NIST test products with the sphere saves industry a lot of money. "Both suppliers and customers were often testing the same product, using different methods. Now both rely on the precision and lack of variability in our testing program."
In the real world, a Dallas homeowner goes to a hardware store and asks: "If I paint my deck with this, how many years will it last?" NIST intends to deliver numbers. This research, Martin says, "will eventually result in quantitative estimates of the service life of polymeric materials in a given service environment. Such estimates are possible because each of the exposure variables is precisely controlled and the photodegradation response of an exposed material is quantitatively measured." In addition, his lab is trying "to identify the chemical and physical precursors of changes in the appearance of a product used by consumers in judging whether a product has failed."
|“In practice, the SPHERE provides an embarrassment of quantitative riches.”|
Smithsonian Environmental research center
The Air force
The federal highways Administration
andd loop to the
Exxon Mobil gives $100m to Stanford-led Energy Project
21 November 2002
|First published: 20-Nov-02
By Richard Knee, CNI
SAN FRANCISCO (CNI)--ExxonMobil will contribute nearly half the funding for a ten-year, $225m (€225m) research project to develop affordable energy sources that do not add carbon dioxide (CO2) to the atmosphere, the company said Wednesday.
ExxonMobil hopes the Stanford University-led effort, called the Global Climate and Energy Project (G-CEP) will produce ways "to very substantially reduce greenhouse gases" while providing economic growth and improving individuals lifestyles, especially in developing countries, said Frank Sprow, the company's vice president for safety, health and the environment.
Sprow's comments followed a public announcement of the project's launch at the university's campus in nearby Palo Alto, California.
Major investments, according to Stanford, will include $100m from ExxonMobil, $50m from General Electric (GE) and $25m from Schlumberger.
In addition, E.ON, Europe's largest privately owned energy service provider, has said it plans to contribute $50m and join G-CEP along with other academic and corporate sponsors from Europe, Stanford said.
The university said the total matches that for all corporate-sponsored research at Stanford during the past decade.
Lynn Orr, a professor of petroleum engineering, is stepping down as dean of Stanford's school of earth sciences to direct the project.
G-CEP's approach is to combine the faculty and student depth of Stanford and other universities with the research and commercial capabilities of the corporate sector to bring "new processes and products that will benefit our customers and society as a whole," Sprow said.
Stanford is especially strong in the biological- and computer-technology fields and the results of the research will be available to everyone, he said.
The project drew criticism from environmental and consumer groups concerned about the corporate-funding aspect.
Shannon Wright, coordinator of the Clean Energy Now campaign at Greenpeace, told CNI that ExxonMobil's involvement is a way of buying public relations while actually delaying progress toward an international agreement on greenhouse-gas reduction.
Sprow responded by noting that Stanford is heading G-CEP.
He emphasised the view that new energy sources and systems must prove not only effective but also affordable, particularly for developing countries.
Sprow said: "I don't recall any instance where governments or environmental groups have brought new products to the marketplace."
Putting the Sun
into Syngas 15 November 2002
|Australia, blessed with vast
amounts of sunlight and adequate reserves of natural gas, has found a
way to combine the two, creating a transportable fuel and reducing
greenhouse gas emissions.
CSIRO, the government's research agency, working with Solar Systems Pty Ltd has built a reactor that sits on the solar collector and uses steam reforming of methane to produce syngas which can be further processed to produce hydrogen and carbon dioxide.
The reactor sits at the centre of a tracking paraboloidal concentrating dish that collects the sun's energy to drive the reforming reactions. This reaction converts methane and water into carbon monoxide and hydrogen, adding 250 kJ of solar energy in the process.
"This syngas can be used as fuel or a chemical feed stock for producing methanol," Duffy says.
But a second stage makes it possible for carbon dioxide — a greenhouse gas — to be sequestered and removed. "You can further convert the carbon monoxide via a water gas shift reaction to carbon dioxide and more hydrogen. You then end up with a gas at pressure containing around 20% carbon dioxide and 80% hydrogen," Duffy says.
"The fact that the gas is at pressure facilitates the removal of the CO2."
Compared to burning methane itself — a common fuel for gas turbine power plants — the syngas releases about 20% less greenhouse gas per unit of energy, he adds, even without a way to bury or utilize the CO2, which would further increase the scheme's environmental attractiveness.The dish now in operation uses 44 kW thermal of natural gas, but a full scale concentrator dish would handle 120 kW. Single dishes might be attractive for coal mines or waste dumps which generate small amounts of methane that is often wasted now. A big power plant would use multiple dishes or other types of solar collectors, Duffy says.
Industry — News in Brief 29 November 2002