Mostrando entradas con la etiqueta hydrogen. Mostrar todas las entradas
Mostrando entradas con la etiqueta hydrogen. Mostrar todas las entradas

viernes, noviembre 16, 2007

TECHNOLOGY: New technique creates cheap, abundant hydrogen


US researchers have developed a method of producing hydrogen gas from biodegradable organic material, potentially providing an abundant source of this clean-burning fuel, according to a study released Monday.

The technology offers a way to cheaply and efficiently generate hydrogen gas from readily available and renewable biomass such as cellulose or glucose, and could be used for powering vehicles, making fertilizer and treating drinking water.

Numerous public transportation systems are moving toward hydrogen-powered engines as an alternative to gasoline, but most hydrogen today is generated from nonrenewable fossil fuels such as natural gas.

The method used by engineers at Pennsylvania State University however combines electron-generating bacteria and a small electrical charge in a microbial fuel cell to produce hydrogen gas.

Microbial fuel cells work through the action of bacteria which can pass electrons to an anode. The electrons flow from the anode through a wire to the cathode producing an electric current. In the process, the bacteria consume organic matter in the biomass material.

An external jolt of electricity helps generate hydrogen gas at the cathode.

In the past, the process, which is known as electrohydrogenesis, has had poor efficiency rates and low hydrogen yields.

But the researchers at Pennsylvania State University were able to get around these problems by chemically modifying elements of the reactor.

In laboratory experiments, their reactor generated hydrogen gas at nearly 99 percent of the theoretical maximum yield using aetic acid, a common dead-end product of glucose fermentation.

"
This process produces 288 percent more energy in hydrogen than the electrical energy that is added in the process," said Bruce Logan, a professor of environmental engineering at Penn State.

The technology is economically viable now, which gives hydrogen an edge over another alternative biofuel which is grabbing more headlines, Logan said.

"
The energy focus is currently on ethanol as a fuel, but economical ethanol from cellulose is 10 years down the road," said Logan.

"First you need to break cellulose down to sugars and then bacteria can convert them to ethanol."

One of the immediate applications for this technology is to supply the hydrogen that is used in fuel cell cars to generate the electricity that drives the motor, but it could also can be used to convert wood chips into hydrogen to be used as fertilizer.

The study appears in the Proceedings of the National Academy of Sciences.



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lunes, abril 09, 2007

RENEWABLES: Searching for alternative sources of energy

by Yury Zaitsev*
The development of unconventional and renewable energy sources is a major challenge facing humankind in the twenty-first century. Technologies such as nuclear fusion and biofuels will prove vital if humankind is to find an alternative to hydrocarbons.

Under a bill that was recently signed by U.S. President George W. Bush, so-called "corn fuel" will account for 7.5 billion gallons of total national fuel consumption by 2015. President Bush probably decided to follow the Brazilian example because that country has been obtaining ethanol from sugar cane and using it as a motor fuel for a long time.

The European Union, which initially planned to increase the share of alternative power-generation sources in its energy mix to 10% by 2012, will probably achieve this goal by as soon as 2010. French nuclear power plants now generate 80% of all domestic power.

Russian scientists are also working hard to develop unconventional and renewable energy sources, which may soon be included in the national power-generation network. For example, small gas-turbine thermal power plants burning wood splinters and coal have an impressive potential and are expected to generate 5% of all electricity nationwide by 2020. They will mostly be used in Arctic regions, which now utilize small diesel generators and low-capacity furnaces burning huge amounts of expensive hydrocarbons. It costs, for example, $1,000 to deliver one metric ton of diesel fuel and $150 for one ton of heating oil to the Russian Arctic.

Environmentally friendly alternative sources of energy are an attractive power-generation option. "Dirty" organic fuels, such as coal, heating oil and firewood, now account for 70% of the energy balance in northern Russia.

Russia can also harness solar and wind energy from along its 12,000 km Arctic coast. Windmills are considered cost-effective when average annual wind speeds exceed 4-5 meters per second. Arctic winds blowing at over 5-7 meters per second can generate 45 billion kWh.

Likewise, solar panels can be located in the south of the Sakha (Yakutia) Republic, in north-east Russia. The weekly amount of solar energy falling on the Earth exceeds the total energy potential of global oil, coal and gas deposits. Alexander Asseyev, director of the Semiconductor Physics Institute at the Siberian department of the Russian Academy of Sciences, estimated the country's total solar-energy potential as equivalent to over two trillion tons of fuel. By placing solar batteries with an average efficiency of 12% over 4,000 square kilometers, it would be possible to completely meet the national electric power demand.

The Earth's crust contains tremendous amounts of silica, exceeding deposits of uranium ore 100,000 times over. Obtaining this highly expensive element cost-effectively is the key to mass-producing solar batteries. Moreover, Russian scientists have mastered the production of multi-crystalline silicon for solar power engineering. Work is also proceeding apace to produce highly efficient gallium arsenide solar cells.

The first Russian tidal power plant, which was built on the Kola Peninsula, made it possible to design similar power plants capable of generating tens of millions of kilowatt-hours (kWh) of electricity.

In the mid-20th century, Russian scientists suggested using hot volcanic vapors to generate cheap geothermal electric power. In 1966, the 11,000 kWh Pauzhetskaya geothermal power plant was built on the Kamchatka Peninsula. The recently commissioned Verkhne-Mutnovskaya geothermal power plant generates 25% of all electricity in the Kamchatka Region. There are plans to expand its capacity by 20 kWh by installing additional power units running on recycled hot thermal water. Though geothermal plants are quite expensive, future operating costs are reduced because they harness "free" natural energy.

Russian coal deposits contain an estimated 260 trillion cubic meters of methane, which can be used as a separate fuel. Gennady Gritsko, director of the Coal and Coal Chemistry Institute at the Siberian department of the Russian Academy of Sciences, said methane can be extracted from small deposits, domes and traps. This cost-effective method does not require any expensive mining operations. Gritsko said ventilation flows contain an unlimited amount of methane and can trap more gas than coal mines.

Coal can also be used to obtain synthetic gasolene and hydrogen for fuel. Hydrogen, the ideal environmentally friendly fuel of the future, produces nothing but water when it is burned. The hydrogen power industry would therefore help reduce toxic emissions and solve the global warming problem.

Another promising technology is thermonuclear reactors. Unlike conventional nuclear power plants that use heavy-element fission, they fuse the nuclei of two light atoms into heavy elements. Scientists set the task to simulate the fusion that takes place in the Sun in laboratory conditions and to harness it for commercial power-generation purposes. Deuterium and tritium isotopes, which fuse together inside the Sun, create chemically inert helium and emit tremendous amounts of energy, hundreds of times more than is emitted during uranium fission at conventional NPPs.

Research by Soviet and Russian scientists made it possible to solve the problem of thermonuclear fusion. Russia is now a full participant in the International Thermonuclear Experimental Reactor (ITER) project. Vladimir Fortov, member of the Russian Academy of Sciences, said thermonuclear power plants may start generating household electricity by 2040. However, Nobel Prize winner Zhores Alfyorov, also a member of the Russian Academy of Sciences, said this would take much longer to happen.

*Yury Zaitsev is an academic adviser at the Russian Academy of Engineering Sciences.

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