Thursday, December 21, 2006
Will 2006 be even higher?
In 2005, carbon emissions from the burning of fossil fuels climbed to a record high of 7.9 billion tons, an increase of some 3% from the previous year. Annual global emissions have been increasing since the beginning of the Industrial Revolution in the late eighteenth century, when humans first began burning fossil fuels on a large scale to produce energy. Since the early 1900s, emissions have been rising at an increasingly rapid pace. Annual emissions have grown by a factor of fifteen since 1900, advancing nearly 3% a year over that time. Half of all energy-related carbon emissions come from only four countries. The United States, with less than 5% of the world?s population, accounts for 21% of carbon emissions. It is followed by China, which emits 18%. Both countries are heavy users of coal, the most carbon-intensive fossil fuel. Russia accounts for 6% of carbon emissions, just ahead of Japan, which produces 5% of the global total. Other major contributors to global carbon emissions are India, Germany, Canada, the United Kingdom, South Korea, and Italy. The United States, Australia, and Canada each emit roughly 5 tons of carbon per person each year. This is five times the figure in China and 17 times that in India. Some 40% of energy-related emissions come from the burning of fossil fuels, such as oil, coal, and natural gas, to generate electrical power. The transportation sector is the second-largest source worldwide, responsible for 20% of all carbon emitted. Residential and commercial buildings account for roughly 15% of the total, and the industrial sector, another 15%. The remaining 10% of energy-related emissions come from a variety of minor uses, including fuels burned by sea-going ships. As global emissions of carbon increase, they raise the levels of carbon dioxide (CO2) in the atmosphere. The average atmospheric concentration of CO2 reached 380 parts per million by volume in 2005, up 2.2 parts per million from 2004 levels and up 103 parts per million from pre-industrial times. The Intergovernmental Panel on Climate Change (IPCC), a global body of some 2,000 scientists, estimates that the current atmospheric CO2 concentration has not been exceeded over the last 420,000 years and probably not during the past 20 million years. Experts predict that the effects of global warming will be far more dramatic if carbon emissions force atmospheric CO2 levels above 550 parts per million. Beyond this threshold, widespread flooding, droughts, and storms will be more severe. If carbon emissions continue to increase as projected, this level is likely to be reached in the second half of this century. To prevent this from happening, scientists estimate that carbon emissions must be cut by some 70%.
Why do we hear so little about the permafrost meltdown
Siberia's permafrost is melting: Arctic permafrost in Siberia covers endless miles, contains massive amounts of methane. The melting soil releases the methane into the air, where it is now expected to massively and irrevocably accelerate global warming. It's a process that has already begun, but just. This massive climate bomb literally has the potential to end civilization. Its discovery should have not only been the year's top story, but an impetus for all humanity to unite in a common struggle for survival. Maybe in 2007. Or 2009, when someone who believes in science occupies the White House.
Monday, December 18, 2006
A new way to create hydrogen using solar power
Researchers in Switzerland have demonstrated more-efficient water-splitting solar cells based on a cheap, abundant, and long-lasting material: rust. The advance could lead to a cheap and energy-efficient way to generate hydrogen for fuel-cell vehicles using solar energy.
Water-splitting solar panels would have important advantages over existing technologies in terms of hydrogen production. Right now, the primary way to make hydrogen is to separate it from natural gas, a process that generates carbon dioxide and undercuts the main motivation for moving to hydrogen fuel-cell vehicles: ending dependence on fossil fuels. The current alternative is electrolysis, which uses electricity to break water into hydrogen and oxygen, with the two gases forming at opposite electrodes. Although electrolysis is costly, it can be cleaner if the source of the electricity is wind, sun, or some other carbon-free source.
But if the source of the electricity is the sun, it would be much more efficient to use solar energy to produce hydrogen by a photochemical process inside the cell itself. By improving the efficiency of such solar panels, Michael Grätzel, chemistry professor at the Ecole Polytechnique Fédérale de Lausanne, in Switzerland, and his colleagues have taken an important step toward this goal.
The researchers have shown that by including small amounts of silicon and cobalt, they can grow nanostructured thin films of iron oxide that convert sunlight into the electrons needed to form hydrogen from water. And the iron oxide films do this more efficiently than ever before with this material.
Iron oxide has long been an appealing material for such solar panels, in part because it holds up well in contact with water. But although it can absorb sunlight, the resulting charge carriers could not easily escape the material, so they recombined, canceling each other out before they could split any water. By doping the rust with silicon, the researchers coaxed the material to form cauliflower-like structures with extremely high surface area, ensuring that a large part of the atoms in the material were in contact with the water, or very close to it. That way, holes could easily escape into the water, where they prompt the generation of oxygen gas. The silicon also improves electron conductivity in the material, which is important for generating hydrogen gas at an opposite electrode. The researchers further improved the process by adding cobalt, which acts as a catalyst for the reactions.
Grätzel's new iron-oxide films can convert an impressive and, according to the researchers, "unprecedented" 42 percent of ultraviolet photons in sunlight into electrons and holes. But the system's overall efficiency is only about 4 percent, in part because iron oxide doesn't absorb all the parts of the solar spectrum.
The main achievement of Grätzel's new research, which appears in the current issue of the Journal of the American Chemical Society, is that it examines the interactions at work in the system in great detail, says Brian Holcroft, CEO of Hydrogen Solar, a company based in Guildford, UK, that is developing ways to mass-produce panels inspired by Grätzel's materials. The findings suggest several strategies that could help the iron-oxide-based panel reach the 10 percent efficiency level that would make the technology competitive with current ways of creating hydrogen, Holcroft says. (Iron oxide could theoretically be as much as 20 percent efficient.) These include adjusting the amount and arrangement of silicon and cobalt, and improving the structure of the films.
If this level of efficiency can be met, hydrogen-generating solar energy could mitigate some of the challenges that threaten to make hydrogen fuel-cell vehicles impractical, says George Sverdrup, hydrogen technology manager at the National Renewable Energy Laboratory (NREL), in Golden, CO. For example, if consumers and businesses used these panels to make hydrogen, rather than getting hydrogen from a large facility, it would cut out the cost of shipping hydrogen, making hydrogen more affordable. Solar-to-hydrogen panels would be more efficient than small electrolysis machines, and they would ensure that the hydrogen comes from a renewable source.
But challenges remain. Researchers at Hydrogen Solar, for example, are looking for a replacement for the expensive platinum now used in one of the cell's electrodes, which will be important for keeping down costs, especially as demand increases for platinum in this and other applications, such as fuel cells. Meanwhile, Sverdrup says other researchers, including those at NREL, are working with materials that are much more efficient than iron oxide but so far have lasted only hours. If researchers can make them last longer, the materials could challenge iron oxide.
Water-splitting solar panels would have important advantages over existing technologies in terms of hydrogen production. Right now, the primary way to make hydrogen is to separate it from natural gas, a process that generates carbon dioxide and undercuts the main motivation for moving to hydrogen fuel-cell vehicles: ending dependence on fossil fuels. The current alternative is electrolysis, which uses electricity to break water into hydrogen and oxygen, with the two gases forming at opposite electrodes. Although electrolysis is costly, it can be cleaner if the source of the electricity is wind, sun, or some other carbon-free source.
But if the source of the electricity is the sun, it would be much more efficient to use solar energy to produce hydrogen by a photochemical process inside the cell itself. By improving the efficiency of such solar panels, Michael Grätzel, chemistry professor at the Ecole Polytechnique Fédérale de Lausanne, in Switzerland, and his colleagues have taken an important step toward this goal.
The researchers have shown that by including small amounts of silicon and cobalt, they can grow nanostructured thin films of iron oxide that convert sunlight into the electrons needed to form hydrogen from water. And the iron oxide films do this more efficiently than ever before with this material.
Iron oxide has long been an appealing material for such solar panels, in part because it holds up well in contact with water. But although it can absorb sunlight, the resulting charge carriers could not easily escape the material, so they recombined, canceling each other out before they could split any water. By doping the rust with silicon, the researchers coaxed the material to form cauliflower-like structures with extremely high surface area, ensuring that a large part of the atoms in the material were in contact with the water, or very close to it. That way, holes could easily escape into the water, where they prompt the generation of oxygen gas. The silicon also improves electron conductivity in the material, which is important for generating hydrogen gas at an opposite electrode. The researchers further improved the process by adding cobalt, which acts as a catalyst for the reactions.
Grätzel's new iron-oxide films can convert an impressive and, according to the researchers, "unprecedented" 42 percent of ultraviolet photons in sunlight into electrons and holes. But the system's overall efficiency is only about 4 percent, in part because iron oxide doesn't absorb all the parts of the solar spectrum.
The main achievement of Grätzel's new research, which appears in the current issue of the Journal of the American Chemical Society, is that it examines the interactions at work in the system in great detail, says Brian Holcroft, CEO of Hydrogen Solar, a company based in Guildford, UK, that is developing ways to mass-produce panels inspired by Grätzel's materials. The findings suggest several strategies that could help the iron-oxide-based panel reach the 10 percent efficiency level that would make the technology competitive with current ways of creating hydrogen, Holcroft says. (Iron oxide could theoretically be as much as 20 percent efficient.) These include adjusting the amount and arrangement of silicon and cobalt, and improving the structure of the films.
If this level of efficiency can be met, hydrogen-generating solar energy could mitigate some of the challenges that threaten to make hydrogen fuel-cell vehicles impractical, says George Sverdrup, hydrogen technology manager at the National Renewable Energy Laboratory (NREL), in Golden, CO. For example, if consumers and businesses used these panels to make hydrogen, rather than getting hydrogen from a large facility, it would cut out the cost of shipping hydrogen, making hydrogen more affordable. Solar-to-hydrogen panels would be more efficient than small electrolysis machines, and they would ensure that the hydrogen comes from a renewable source.
But challenges remain. Researchers at Hydrogen Solar, for example, are looking for a replacement for the expensive platinum now used in one of the cell's electrodes, which will be important for keeping down costs, especially as demand increases for platinum in this and other applications, such as fuel cells. Meanwhile, Sverdrup says other researchers, including those at NREL, are working with materials that are much more efficient than iron oxide but so far have lasted only hours. If researchers can make them last longer, the materials could challenge iron oxide.
Solar Systems x .5
Technologies collectively known as concentrating photovoltaics are starting to enjoy their day in the sun, thanks to advances in solar cells, which absorb light and convert it into electricity, and the mirror- or lens-based concentrator systems that focus light on them. The technology could soon make solar power as cheap as electricity from the grid.
The idea of concentrating sunlight to reduce the size of solar cells--and therefore to cut costs--has been around for decades. But interest in the technology has picked up in the past year. Last month, Japanese electronics giant Sharp Corporation showed off its new system for focusing sunlight with a fresnel lens (like the one used in lighthouses) onto superefficient solar cells, which are about twice as efficient as conventional silicon cells. Other companies, such as SolFocus, based in Palo Alto, CA, and Energy Innovations, based in Pasadena, CA, are rolling out new concentrators. And the company that supplied the long-lived photovoltaic cells for the Mars rovers, Boeing subsidiary Spectrolab, based in Sylmar, CA, is supplying more than a million cells for concentrator projects, including one in Australia that will generate enough power for 3,500 homes.
The thinking behind concentrated solar power is simple. Because energy from the sun, although abundant, is diffuse, generating one gigawatt of power (the size of a typical utility-scale plant) using traditional photovoltaics requires a four-square-mile area of silicon, says Jerry Olson, a research scientist at the National Renewable Energy Laboratory, in Golden, CO. A concentrator system, he says, would replace most of the silicon with plastic or glass lenses or metal reflectors, requiring only as much semiconductor material as it would take to cover an area the size of a typical backyard. And because decreasing the amount of semiconductor needed makes it affordable to use much more efficient types of solar cells, the total footprint of the plant, including the reflectors or lenses, would be only two to two-and-a-half square miles. (This approach is distinct from concentrated thermal solar power, which concentrates the heat from the sun to power turbines or sterling engines.)
"I'd much rather make a few square miles of plastic lenses--it would cost me less--than a few square miles of silicon solar cells," Olson says. Today solar power is still more expensive than electricity from the grid, but concentrator technology has the potential to change this. Indeed, if manufacturers can meet the challenges of ramping up production and selling, distributing, and installing the systems, their prices could easily meet prices for electricity from the grid, says solar-industry analyst Michael Rogol, managing director of Photon Consulting, in Aachen, Germany.
But the approach has been difficult to implement. "It has not delivered on the promise, mostly because of the complexity of the systems," Rogol says. The goal is to engineer a concentrating system that focuses sunlight, that tracks the movement of the sun to keep the light on the small solar cell, and that can accommodate the high heat caused by concentrating the sun's power by 500 to700 times--and to make such a system easy to manufacture.
The idea of concentrating sunlight to reduce the size of solar cells--and therefore to cut costs--has been around for decades. But interest in the technology has picked up in the past year. Last month, Japanese electronics giant Sharp Corporation showed off its new system for focusing sunlight with a fresnel lens (like the one used in lighthouses) onto superefficient solar cells, which are about twice as efficient as conventional silicon cells. Other companies, such as SolFocus, based in Palo Alto, CA, and Energy Innovations, based in Pasadena, CA, are rolling out new concentrators. And the company that supplied the long-lived photovoltaic cells for the Mars rovers, Boeing subsidiary Spectrolab, based in Sylmar, CA, is supplying more than a million cells for concentrator projects, including one in Australia that will generate enough power for 3,500 homes.
The thinking behind concentrated solar power is simple. Because energy from the sun, although abundant, is diffuse, generating one gigawatt of power (the size of a typical utility-scale plant) using traditional photovoltaics requires a four-square-mile area of silicon, says Jerry Olson, a research scientist at the National Renewable Energy Laboratory, in Golden, CO. A concentrator system, he says, would replace most of the silicon with plastic or glass lenses or metal reflectors, requiring only as much semiconductor material as it would take to cover an area the size of a typical backyard. And because decreasing the amount of semiconductor needed makes it affordable to use much more efficient types of solar cells, the total footprint of the plant, including the reflectors or lenses, would be only two to two-and-a-half square miles. (This approach is distinct from concentrated thermal solar power, which concentrates the heat from the sun to power turbines or sterling engines.)
"I'd much rather make a few square miles of plastic lenses--it would cost me less--than a few square miles of silicon solar cells," Olson says. Today solar power is still more expensive than electricity from the grid, but concentrator technology has the potential to change this. Indeed, if manufacturers can meet the challenges of ramping up production and selling, distributing, and installing the systems, their prices could easily meet prices for electricity from the grid, says solar-industry analyst Michael Rogol, managing director of Photon Consulting, in Aachen, Germany.
But the approach has been difficult to implement. "It has not delivered on the promise, mostly because of the complexity of the systems," Rogol says. The goal is to engineer a concentrating system that focuses sunlight, that tracks the movement of the sun to keep the light on the small solar cell, and that can accommodate the high heat caused by concentrating the sun's power by 500 to700 times--and to make such a system easy to manufacture.
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