February 2008 Newsletter

by Gordy Slack

Per Peterson’s designs would take the excess heat produced by reactors and put it to use converting nearby domestic raw materials like tar sands into liquid fuel.

The popularity of nuclear power took a nosedive in the US two decades ago with accidents at Three Mile Island and Chernobyl plants. But several things have changed since then, causing even many environmentalists to embrace nuclear power, notes Peterson. One huge difference is the rise of human-caused climate change as perhaps the world’s most pressing environmental problem. Nuclear power is one of the most promising technologies on the horizon that could replace the carbon-intensive energy sources now fueling that crisis.

Per Petersen, UC Berkeley Professor of Nuclear Engineering.

“Using nuclear process heat and hydrogen, we can convert tar sand, coal, and even bio-mass into transportation fuels with negligible emission of carbon,” he says. “All the carbon in these resources ends up in the fuel that goes into the vehicles.”

The process heat from AHTRs would also make the conversion of tar sand into liquid fuel both economical and relatively clean. Opening up North America’s vast tar sand fields (Canada’s fields “dwarf the oil fields of Saudi Arabia,” says Peterson) could loosen America’s dependency on foreign oil.

The small-footprint AHTRs would be cooled with liquid fluoride salts, which have outstanding heat transport properties, says Peterson. The new cooling method would allow the plants to run at much higher temperatures than today’s plants, which are generally cooled with water. In addition, because they are much smaller than traditional plants, AHTRs can be located adjacent to chemical facilities and to sources of natural materials that could be converted into liquid fuels. The valuable steam heat generated by the nuclear reactors is hard to transport long distances, as are the heavy raw materials. But unlike today’s huge reactors, the new plants themselves are small and versatile enough to be built near the material sites.

“There is much less to attack and less that can go wrong with these systems,” says Peterson. “You do not need a large security force to protect them.”

The new generation of reactors would be cooled with liquid fluoride salts, which have outstanding heat transport properties and would allow for much simpler, safer, and more efficient cooling systems than today’s nuclear plants.

Peterson believes the new designs could be commercially available in 12 to 20 years. He suspects that as the country takes to heart its need for new clean, safe sources of power and fuel, it will grow eager to embrace new technologies like the AHTR. He imagines a day when zero-emission electric cars will run off of carbon-free nuclear generated power, and airplanes will burn liquid fuel made from tar sands, coal, and bio mass that are created using excess heat from the same nuclear power plants that energize America’s cities and towns.

by Gordy Slack

Nineteenth century naturalist and writer John Muir called the Sierra Nevada Mountains the ‘Range of Light’ because of the stunning luminosity of its peaks viewed from California’s Great Central Valley. Today, Muir would be heartbroken to see his favorite mountains obscured by the thick soup of pollution that so often fills the valley these days.

The particulate constituents of that smog, which blows east from the Pacific coast’s urban areas, are generated by highway traffic and agricultural activity in the valley itself, and come increasingly from other valley-based industries as the region’s economy grows. Air pollution is effectively trapped in the valley, which is capped by an inversion above and by mountain ranges that define its north, south, and eastern edges. In winter, the inversion layer drops and concentrates the trapped and dirty air, leading to health crises for asthmatics and others with allergies and lung conditions. And it is just plain unhealthy for everyone else. According to the US EPA, five of America’s ten most air-polluted cities are in California’s Central Valley.

Later this year, Shawn Newsam will begin pointing cameras at the horizon to gather data he hopes will provide easy to access, constantly updated information about air quality throughout California’s Central Valley.

It is not a very scientific approach to measuring particulates in the air, acknowledges Newsam, but right now, there is really no better working alternative. With only a handful of point measurements of particulate matter for the entire Central Valley, air quality warnings just are not local enough to be of much use. “Air quality in the valley is a quickly changeable and highly localized affair,” Newsam says. A reading from Fresno, say, may not reflect the air conditions in nearby Modesto or Clovis.

Supported partly with a grant from CITRIS, Newsam is developing a network of several dozen cameras that can collect data and possibly analyze air particulates around the Central Valley. The project could provide a quick, easily accessible way to evaluate local air quality in real time.

This spring, Newsam will aim digital cameras at the horizon and analyze the resulting atmospheric images in hope of finding meaningful associations between them and the particulates in the air they depict. Broadly speaking, he will be taking two approaches, one from above the data, the other from beneath.

First, from above, he will develop models of the different light dispersal effects of different size particles. “We may then be able to automate the application of such analyses to the images for lots of real time data about both the concentration of particulates in the air and the size of the particles themselves,” he says.

The size of airborne particles matters as much as their composition, says Anthony Wexler, UC Davis Professor of Mechanical and Aeronautical Engineering and a specialist on air pollution. “Larger particles affect the health of the lung, whereas smaller ones can penetrate into the bloodstream, circulate, and affect other organs,” says Wexler, who is consulting with Newsam on the project.

But there may be a simpler way to establish the correlation between what Newsam’s camera’s record and the air particles' size and concentration. Simple data mining, Newsam says, may be a shortcut to just as potent a result. By capturing and analyzing numerous images and then comparing them to direct particulate measurements (which are much more expensive) simultaneously taken and analyzed by the San Joaquin Valley Air Pollution Control District (Valley Air District), Newsam may be able to find correlations between the two.

To accomplish this, Newsam will apply different data mining techniques, including Bayesian classifiers, decision tree classifiers, neural network classifiers, and support vector machines.

The health effects of particulates are determined by both the concentration of the particles in the air and by their size. Newsam’s project could allow easy and instant evaluation of both.

One way or the other, Newsam expects his research to bear fruit. As his research is, as he calls it “investigatory, very experimental,” he does acknowledge the possibility that neither the modeling nor the data mining will result in reliable ways to draw useful particulate information from his photographs.

“The Holy Grail would be finding a quick way to draw conclusions about particulates from images,” Newsam says. “But even if I do not get that, we will still have a far more complete track record of whether visibility is getting worse or better and by how much.”

Such a record will become more valuable as the human population in the valley grows and, in all likelihood, as air quality worsens, Newsam says. And with the aid of projective computer technologies, graphic what-if scenarios could be accurately illustrated. “If a politician or bureaucrat wanted to know what the Sierra Nevada viewed from the Merced Campus would look like ten years from now given different economic and emission scenarios, we could show them,” Newsam says.

The data collected by his widely distributed cameras may serve another purpose as well. As photons become an increasingly important source of energy in the valley, the need to make accurate, short-term predictions about how much energy the sun will contribute to the grid at any given time becomes increasingly important. Newsam’s images could provide up-to-the minute projections of solar irradiance over large geographic areas and thus make inexpensive forecasts of the potential output of photovoltaic systems in the area. Newsam has approached PG&E with his research plan, and the energy company has shown interest in developing a real-time map of solar irradiance. In this way, by aiding solar energy’s reliability, reading air pollution could have the side effect of reducing it. That would please John Muir as well as Newsam’s kids, who just want to play outside.