Geothermal Energy Tapping the Earth's Heat

Geothermal energy has been used for thousands of years in some countries for cooking and heating. It is simply power derived from the Earth's internal heat.This thermal energy is contained in the rock and fluids beneath Earth's crust. It can be found from shallow ground to several miles below the surface, and even farther down to the extremely hot molten rock called magma.

 

 

 

These underground reservoirs of steam and hot water can be tapped to generate electricity or to heat and cool buildings directly.

 

 

 

A geothermal heat pump system can take advantage of the constant temperature of the upper ten feet (three meters) of the Earth's surface to heat a home in the winter, while extracting heat from the building and transferring it back to the relatively cooler ground in the summer.

This Ggeothermal power plant in Reykjavik, Iceland, is using their underground reservoirs of steam and hot water to generate electricity and to heat and cool buildings directly.

Geothermal water from deeper in the Earth can be used directly for heating homes and offices, or for growing plants in greenhouses. Some U.S. cities pipe geothermal hot water under roads and sidewalks to melt snow.

 

 

 

To produce geothermal-generated electricity, wells, sometimes a mile (1.6 kilometers) deep or more, are drilled into underground reservoirs to tap steam and very hot water that drive turbines linked to electricity generators. The first geothermally generated electricity was produced in Larderello, Italy, in 1904.

 

 

 

There are three types of geothermal power plants:

• dry steam,
• flash, and
•  binary.

1. Dry steam, the oldest geothermal technology, takes steam out of fractures in the ground and uses it to directly drive a turbine.
2.  Flash plants pull deep, high-pressure hot water into cooler, low-pressure water. The steam that results from this process is used to drive the turbine.
3. In binary plants, the hot water is passed by a secondary fluid with a much lower boiling point than water. This causes the secondary fluid to turn to vapor, which then drives a turbine. Most geothermal power plants in the future will be binary plants.

 

 

 

Geothermal energy is generated in over 20 countries. The United States is the world's largest producer, and the largest geothermal development in the world is The Geysers north of San Francisco in California. In Iceland, many of the buildings and even swimming pools are heated with geothermal hot water. Iceland has at least 25 active volcanoes and many hot springs and geysers.

 

 

 

There are many advantages of geothermal energy. It can be extracted without burning a fossil fuel such as coal, gas, or oil. Geothermal fields produce only about one-sixth of the carbon dioxide that a relatively clean natural-gas-fueled power plant produces. Binary plants release essentially no emissions. Unlike solar and wind energy, geothermal energy is always available, 365 days a year. It's also relatively inexpensive; savings from direct use can be as much as 80 percent over fossil fuels.

 Environmental Problems

 

 

But it has some environmental problems. The main concern is the release of hydrogen sulfide, a gas that smells like rotten egg at low concentrations. Another concern is the disposal of some geothermal fluids, which may contain low levels of toxic materials. Although geothermal sites are capable of providing heat for many decades, eventually specific locations may cool down.

 

Biofuels The Original Car Fuel

Biofuels have been around as long as cars have. At the start of the 20th century, Henry Ford planned to fuel his Model Ts with ethanol, and early diesel engines were shown to run on peanut oil.




But discoveries of huge petroleum deposits kept gasoline and diesel cheap for decades, and biofuels were largely forgotten. However, with the recent rise in oil prices, along with growing concern about global warming caused by carbon dioxide emissions, biofuels have been regaining popularity.

Gasoline and diesel are actually ancient biofuels. But they are known as fossil fuels because they are made from decomposed plants and animals that have been buried in the ground for millions of years. Biofuels are similar, except that they're made from plants grown today.



Much of the gasoline in the United States is blended with a biofuel—ethanol. This is the same stuff as in alcoholic drinks, except that it's made from corn that has been heavily processed. There are various ways of making biofuels, but they generally use chemical reactions, fermentation, and heat to break down the starches, sugars, and other molecules in plants. The leftover products are then refined to produce a fuel that cars can use.



Countries around the world are using various kinds of biofuels. For decades, Brazil has turned sugarcane into ethanol, and some cars there can run on pure ethanol rather than as additive to fossil fuels. And biodiesel—a diesel-like fuel commonly made from palm oil—is generally available in Europe.



On the face of it, biofuels look like a great solution. Cars are a major source of atmospheric carbon dioxide, the main greenhouse gas that causes global warming. But since plants absorb carbon dioxide as they grow, crops grown for biofuels should suck up about as much carbon dioxide as comes out of the tailpipes of cars that burn these fuels. And unlike underground oil reserves, biofuels are a renewable resource since we can always grow more crops to turn into fuel.



Unfortunately, it's not so simple. The process of growing the crops, making fertilizers and pesticides, and processing the plants into fuel consumes a lot of energy. It's so much energy that there is debate about whether ethanol from corn actually provides more energy than is required to grow and process it. Also, because much of the energy used in production comes from coal and natural gas, biofuels don't replace as much oil as they use.



For the future, many think a better way of making biofuels will be from grasses and saplings, which contain more cellulose. Cellulose is the tough material that makes up plants' cell walls, and most of the weight of a plant is cellulose. If cellulose can be turned into biofuel, it could be more efficient than current biofuels, and emit less carbon dioxide.

Hydropower Going With the Flow

Hydropower is electricity generated using the energy of moving water. Rain or melted snow, usually originating in hills and mountains, create streams and rivers that eventually run to the ocean. The energy of that moving water can be substantial, as anyone who has been whitewater rafting knows.




This energy has been exploited for centuries. Farmers since the ancient Greeks have used water wheels to grind wheat into flour. Placed in a river, a water wheel picks up flowing water in buckets located around the wheel. The kinetic energy of the flowing river turns the wheel and is converted into mechanical energy that runs the mill.



In the late 19th century, hydropower became a source for generating electricity. The first hydroelectric power plant was built at Niagara Falls in 1879. In 1881, street lamps in the city of Niagara Falls were powered by hydropower. In 1882 the world’s first hydroelectric power plant began operating in the United States in Appleton, Wisconsin.



A typical hydro plant is a system with three parts: an electric plant where the electricity is produced; a dam that can be opened or closed to control water flow; and a reservoir where water can be stored. The water behind the dam flows through an intake and pushes against blades in a turbine, causing them to turn. The turbine spins a generator to produce electricity. The amount of electricity that can be generated depends on how far the water drops and how much water moves through the system. The electricity can be transported over long-distance electric lines to homes, factories, and businesses.



Hydroelectric power provides almost one-fifth of the world's electricity. China, Canada, Brazil, the United States, and Russia were the five largest producers of hydropower in 2004. One of the world's largest hydro plants is at Three Gorges on China's Yangtze River. The reservoir for this facility started filling in 2003, but the plant is not expected to be fully operational until 2009. The dam is 1.4 miles (2.3 kilometers) wide and 607 feet (185 meters) high.



The biggest hydro plant in the United States is located at the Grand Coulee Dam on the Columbia River in northern Washington. More than 70 percent of the electricity made in Washington State is produced by hydroelectric facilities.



Hydropower is the cheapest way to generate electricity today. That's because once a dam has been built and the equipment installed, the energy source—flowing water—is free. It's a clean fuel source that is renewable yearly by snow and rainfall.



Hydropower is also readily available; engineers can control the flow of water through the turbines to produce electricity on demand. In addition, reservoirs may offer recreational opportunities, such as swimming and boating.



But damming rivers may destroy or disrupt wildlife and other natural resources. Some fish, like salmon, may be prevented from swimming upstream to spawn. Technologies like fish ladders help salmon go up over dams and enter upstream spawning areas, but the presence of hydroelectric dams changes their migration patterns and hurts fish populations. Hydropower plants can also cause low dissolved oxygen levels in the water, which is harmful to river habitats.

Fuel Cells Energy Source of the Future

According to many experts, we may soon find ourselves using fuel cells to generate electrical power for all sorts of devices we use every day. A fuel cell is a device that uses a source of fuel, such as hydrogen, and an oxidant to create electricity from an electrochemical process.

 

 

 

Much like the batteries that are found under the hoods of automobiles or in flashlights, a fuel cell converts chemical energy to electrical energy.

 

 

All fuel cells have the same basic configuration; an electrolyte and two electrodes. But there are different types of fuel cells, based mainly on what kind of electrolyte they use.

 

 

 

Many combinations of fuel and oxidant are also possible. The fuel could be diesel or methanol, while air, chlorine, or chlorine dioxide may serve as oxidants. Most fuel cells in use today, however, use hydrogen and oxygen as the chemicals.

 

 

 

Fuel cells have three main applications: transportation, portable uses, and stationary installations.

 

 

 

In the future, fuel cells could power our cars, with hydrogen replacing the petroleum fuel that is used in most vehicles today. Many vehicle manufacturers are actively researching and developing transportation fuel cell technologies.

 

 

 

Stationary fuel cells are the largest, most powerful fuel cells. They are designed to provide a clean, reliable source of on-site power to hospitals, banks, airports, military bases, schools, and homes.

 

 

 

Fuel cells can power almost any portable device or machine that uses batteries. Unlike a typical battery, which eventually goes dead, a fuel cell continues to produce energy as long as fuel and oxidant are supplied. Laptop computers, cellular phones, video recorders, and hearing aids could be powered by portable fuel cells.

 

 

 

Fuel cells have strong benefits over conventional combustion-based technologies currently used in many power plants and cars. They produce much smaller quantities of greenhouse gases and none of the air pollutants that create smog and cause health problems. If pure hydrogen is used as a fuel, fuel cells emit only heat and water as a byproduct. Hydrogen-powered fuel cells are also far more energy efficient than traditional combustion technologies.

 

 

 

The biggest hurdle for fuel cells today is cost. Fuel cells cannot yet compete economically with more traditional energy technologies, though rapid technical advances are being made. Although hydrogen is the most abundant element in the universe, it is difficult to store and distribute. Canisters of pure hydrogen are readily available from hydrogen producers, but as of now, you can't just fill up with hydrogen at a local gas station.

 

 

 

Many people do have access to natural gas or propane tanks at their houses, however, so it is likely that these fuels will be used to power future home fuel cells. Methanol, a liquid fuel, is easily transportable, like gasoline, and could be used in automobile fuel cells. However, also like gasoline, methanol produces polluting carbon dioxide.

 

Words better suited to a high school chemistry class than a high-level policy debate—terms such as praseodymium and dysprosium—have raised alarms around the world about the future of the alternative energy economy.

Seventeen metals on the periodic table of elements have caused the commotion from Tokyo to Washington, D.C. They are known as rare-earth metals, important ingredients in making the motors and batteries of hybrid and electric cars, high-efficiency LED lights, solar panels and wind turbines. The vast majority of the world’s supply of these metals comes from one source—China—raising the issue of whether foreign dependence will bedevil the new energy economy just as it has been a standing feature of the economy powered by fossil fuel.

‘A One-Nation OPEC’

Rare-earth metals, also called rare-earth minerals, include element number 21, scandium; number 39, yttrium; and the 15 lanthanides, numbers 57-71, on the periodic table. However, the name is a misnomer. Rare-earth metals are often found in a cluster, but are not actually rare. Rather, they are valuable because it is difficult to find the minerals concentrated in great enough amounts so that mining the deposit makes economic sense.

The United States, second only to China in energy consumption, is not devoid of rare-earth metals. But the only U.S. mine, near the Mojave National Preserve in Mountain Pass, California (map), became inactive in 2002 after 50 years of production, largely because of economic and environmental issues. The mine, for a time owned by Chevron, was taken over in 2008 by Molycorp Minerals LLC, which has spent more than $400,000 since that time lobbying Congress on rare-earth minerals, according to its Senate disclosure records. On its website, Molycorp says it has plans to modernize and expand the mine and bring it back into full production “with appropriate federal assistance for research, development and capital costs.”

Legislation already has been proposed in the U.S. Congress to extend subsidies and funding to reopen domestic mines, and the focus on the issue intensified after a dispute erupted between Japan and China over rare-earth minerals last week. Japanese industry sources accused China of withholding crucial supplies, an accusation that Beijing denied, but the Japanese government vowed to take action. Foreign Minister Seiji Maehara of Japan said Friday that Tokyo aims to secure more mining development rights overseas to diversify its sources of rare-earth minerals. “Relying on one country is not good,” Maehara said at a news conference.

The discussion this week was much the same in Washington, D.C. Last year, 90 percent of the U.S. imports for rare-earth metals were from China, according to data from the U.S. Geological Survey. But this year, according to USGS, the figure is 97 percent.

“Just as we’ve seen with our reliance on foreign oil, the United States’ total reliance on foreign sources of rare earths puts us in a perilous situation,” said Republican Senator Lisa Murkowski of Alaska, in a prepared statement accompanying legislation she introduced to create a U.S. strategic stockpile of rare-earth minerals and to provide federal loan guarantees to assist the domestic mining industry. “Some have compared China to a one-nation OPEC for rare earths— and China’s recent actions signal that they are well aware of their immense power over the supply of this sought-after commodity.”

E

ven though demand for rare-earth minerals presumably would rise as electric cars and more alternative energy and efficiency applications came to market, consumption of those products has actually decreased dramatically during the economic downtur

n, according to a USGS report. In 2009, the estimated value of these products imported by the United States was $84 million, a 55 percent decrease from $186 million imported in 2008.

Some academics aren’t too concerned that the United States would be held hostage by China over rare-earth minerals.

“The fact is that the more the Chinese and American economics are interrelated, the less likely conflict might be,” said Jerry Taylor, senior fellow at the Cato Institute, a libertarian public policy think tank in Washington, who has written extensively on energy issues. “What would it [China] gain at the end of the day? They would risk a trade war with a country where a huge volume of its liquid capital assets are invested.”

At the hearing Thursday, one of the witnesses, Roderick Eggert, a professor and director of the division of economics and business at the Colorado School of Mines, confirmed that mineral resources were still abundant, and that China’s supply and low prices are currently sufficient to meet the world’s needs.

“Markets provide incentives for investments that reinvigorate supply and reduce supply risk, Eggert said. “The Chinese mineral deposits are quite large and rich . . . and will satisfy [world demand] and have been meeting demand in the last few years.”

Critical to National Defense?

But there’s an important backstory: national defense.

Besides green energy, rare-earth minerals are essential in creating weapons. “Smart bombs” that use neodymium-iron-boron magnets to control the direction when dropped from an aircraft, lasers that employ neodymium, yttrium-aluminum-garnet used to determine the range of enemy targets at distances over 22 miles, and neodymium-iron-boron permanent magnets used for sound system components used in psychological warfare are among the many, according to a 2004 USGS paper.

The U.S. Department of Defense is currently in the early stages of evaluating its dependency on these minerals, as well as the potential national security risks, according to a study by the U.S. Government Accountability Office.

The jury is still out on alternative energy. With the advancement of new technology, certain products, such as high-efficiency solar cells, do not even need rare-earth metals. Other renewable energy products, such as wind turbines, can be created without rare-earth minerals, but their use is highly advantageous and makes for a much more efficient process.

“Are they critical to the [alternative energy] sector? It’s hard to say that they have the choke hold on the industry,” said Mark Brownstein, deputy director of the energy program at the Environmental Defense Fund. “These are valuable materials in that they have facilitated a tremendous innovation in some of the basic building blocks of renewable energy and energy efficiency technologies. The continued access isn’t only important to existing renewable energy, but also for future advances.”

Expect More Floods as Global Water Cycle Speeds Up

There is nearly 20 percent more freshwater flowing into the world's oceans than there was 10 years ago--a sign of climate change and a harbinger of more flooding.
A new indicator has joined the century-long rise in temperature to signal that the planet's climate is changing: the global water cycle is speeding up. Using satellite observations, NASA and university researchers have found that rivers and melting ice sheets delivered 18 percent more water to the oceans in 2006 than in 1994.
The findings, which appear in this week's Proceedings of the National Academy of Sciences, suggest that the volume of water running off the land toward the sea is expanding by the equivalent of roughly one Mississippi River each year.
On the face of it that might sound like a good thing--more water in rivers means more water to tap for agriculture, industry, and growing cities. But most of the increase is occurring in places where extra water isn't needed, like the wet tropics or the remote Arctic, or is being delivered through torrential storms that overwhelm human infrastructure and coping capacities. Though no single weather episode can be pinned to climate change, the massive rains that recently flooded a fifth of Pakistan is the kind of event scientists expect to see more of--and that nations should prepare for.
Why is the water cycle speeding up?
As the atmosphere warms from the addition of carbon dioxide and other greenhouse gases, it can hold more moisture. As a result, more water evaporates from the oceans, leading to thicker clouds that then dump more rainfall over the land. That heavier-than-normal rain can then produce massive flooding as it runs back toward the sea, where the cycle begins all over again.
Scientists have expected global warming to speed up the water cycle in this way, but the use of satellite data allowed the trend to be observed and measured for the first time. The research team, led by Jay Famiglietti of the University of California at Irvine, used satellite records of sea level rise, precipitation, and evaporation to compile a unique 13-year record, the first of its kind.
As the scientific evidence mounts that more severe floods and droughts are on the horizon, getting on with ways of adapting to climatic change becomes just as urgent as slowing the pace of that change.

Karo Mumkin » Paper Recycling

Karo Mumkin » Paper Recycling

Russia Fires, Pakistan Floods Linked? Extreme weather driven partly by global warming, experts say.

A family leaves flooded Baseera, Pakistan, this week.
They're raging a continent apart, but two deadly natural disasters—the Russian wildfires and the Pakistan floods—may be connected by the Asian monsoon, one of the most powerful atmospheric forces on the planet, scientists say.
That's because the monsoon—a seasonal wind system that brings rain and floods to Pakistan and much of the rest of Asia in summer—also drives the circulation of air as far away as Europe, said Kevin Trenberth, a senior scientist at the Boulder, Colorado-based National Center for Atmospheric Research.
Air pumped into the upper atmosphere by monsoon winds has to come down somewhere. And with the monsoon's giant reach, much of that air seems to be settling over Russia, where it's creating high-pressure conditions, which favor heat waves, Trenberth said. Near high-pressure systems, air tends to sink, which discourages clouds from forming.
Such circulation patterns are normal, but they're also being enhanced by rising sea temperatures due in part to global warming, he added.
For instance, the northern Indian Ocean has warmed 2 degrees Fahrenheit (1.1 degrees Celsius) since the 1970s. Warmer water releases more moisture into the air, which can supercharge monsoon rains.
"The key message is that it's not just natural variability and not just global warming" but a combination of both, Trenberth said. For instance, the last months of a recent El Niño—a cyclical warming of tropical waters in the central and eastern Pacific Ocean—likely contributed to the high sea temperatures in the Indian Ocean.
He also cautioned that the monsoon link between the Russia fires and Pakistan floods is difficult to prove, since it's based on observations and interpretations of past research.
Fires, Floods, Heat: Record-Breaking Extremes in 2010
This year's fierce monsoon rains have spawned Pakistan's worst flooding in 80 years, affecting nearly 14 million people, according to the New York Times.
And in Russia, widespread fires are stoked by the worst heat wave in Russian memory. Around Moscow, choked with fire-related smog, temperatures have hovered around 100 degrees Fahrenheit (38 degrees Celsius) for weeks and show no sign of letting up soon, according to the Bloomberg news agency.
Trapping the smoke are anticyclones, atmospheric high-pressure centers that occur when monsoon winds form a stable layer of air a few thousand feet above Earth's surface.
Both Russia and Pakistan are also experiencing "remarkable" temperatures in 2010, which is shaping up to be one of the hottest years since record-keeping began in the late 1880s, Jeff Masters, director of meteorology for the Weather Underground website, told National Geographic News in July.
Nine countries have shattered heat records, including Pakistan, which on May 26 logged a mercury reading of 128.3 degrees Fahrenheit (53.5 degrees Celsius)—the highest ever seen in Asia, Masters said.
Extreme events such as heat waves, drought, and monsoon floods are believed by some scientists to be increasing with global warming, and the disasters in Russia and Pakistan may be indications of this, Rosanne D'Arrigo, a research professor at Columbia University's Lamont-Doherty Earth Observatory, said in an email. (See a world map of potential global warming impacts.)
However, D'Arrigo said, it's not possible to ascribe any one event to global warming.
Atmospheric "Logjam" Prolonging Russia Fires, Pakistan Floods
D'Arrigo added that there's a "possible relationship" between the monsoon and the fires—for instance, the Asian monsoon has been linked before in various ways to higher-latitude conditions, such as in the North Atlantic, she said.

Deke Arndt, head of the Climate Monitoring Branch of the U.S. National Oceanic and Atmospheric Administration's National Climatic Data Center, agreed it's likely that the fires can be traced back to the monsoon.
He noted that the events may also be prolonged by an atmospheric "logjam" that's common in the summer but which has been unusually "stubborn and long-lasting" this year.
The blockage occurs when atmospheric winds lock climate phenomena—such as large storms or heat waves—into place for a long period of time. In the United States in the summer, for example, storms will "squat on a place and sit and spin for a week," Arndt said.
"These features, while they're strong, are also really persistent," he said. They "show up [as] day after day of rainfall in India and Pakistan ... and day after day of oppressive conditions in western Russia."
Overall, scientists often struggle to quantify how the climate fits in with such natural occurrences, Arndt said.
But the likely link between the Russian fires and the Pakistan floods "is a great example that things that happen in the atmosphere don't occur in isolation."

Engineers Tap Algae Cell for Electricity

With the help of photosynthesis plants convert light energy to chemical energy. This chemical energy is stored in the bonds of sugars they use for food. Photosynthesis happens inside a chloroplast. Chloroplasts are considered as the cellular powerhouses that make sugars and impart leaves and algae a green hue. During photosynthesis water is split into oxygen, protons and electrons. When sunrays fall on the leaves and reach the chloroplast, electrons get excited and attain higher energy level. These excited electrons are caught by proteins. The electrons are passed through a series of proteins. These proteins utilize more of the electrons’ energy to synthesize sugars until the entire electron’s energy is exhausted.

Now researchers at Stanford are inspired by a new idea. They intercepted the electrons just after they had been excited by light and were at their highest energy levels. They put the gold electrodes inside the chloroplasts of algae cells, and tapped the electrons to create a tiny electrical current. It may be the beginning of the production of “high efficiency” bioelectricity. This will be a clean and green source of energy but minus carbon dioxide.

Stanford University researchers got their work published in the journal Nano Letters (March, 2010). WonHyoung Ryu is the main author of this work. He says, “We believe we are the first to extract electrons out of living plant cells.” The Stanford research team created an exclusive, ultra-sharp gold nanoelectrode for this project.

They inserted the electrodes inside the algal cell membranes. The cell remains alive throughout the whole process. When cells start the photosynthesis, the electrodes attract electrons and produce tiny electric current. Ryu tells us, “We’re still in the scientific stages of the research. We were dealing with single cells to prove we can harvest the electrons.” The byproducts of such electricity production are protons and oxygen. Ryu says, “This is potentially one of the cleanest energy sources for energy generation. But the question is, is it economically feasible?”

Ryu himself provides the answer. He explained that they were able to extract just one picoampere from each cell. This quantity is so little that they would require a trillion cells photosynthesizing for one hour just to get the same amount of energy in a AA battery.

Another drawback of such an experiment is that the cells die after an hour. It might be the small trickles in the membrane around the electrode could be killing the cells. Or cells may be dying because they’re not storing the energy for their own vital functions necessary to sustain life. To attain commercial viability researchers have to overcome these hurdles.

They should go for a plant with larger chloroplasts for a larger collecting area. For such experiment they will also need a bigger electrode that could tap more electrons. With a longer-surviving plant and superior collecting ability, they could harness more electricity in terms of power.

Carbon-based Solar Cells

Solar panels need silicon for absorption of light. Silicon doesn’t come cheap.This cost-factor is preventing people from using solar energy on a large scale. Scientists utilize another substance i.e. ruthenium for solar cells. Rutheniumcan is cheaper than silicon but ruthenium is a rare metal on Earth. It is as rare as platinum. Naturally it can’t be available for mass production. Compared to silicon, carbon is cheap and abundant. The graphene, another form of carbon, is capable of absorbing a wide range of light frequencies.

Graphene is a single sheet of carbon, one atom thick. Graphene has potential to be utilized as an effective, less toxic and cheaper than other alternatives for solar cells. Chemists at Indiana University Bloomington are trying to come up with a better alternative than silicon. If successful, this can be a path breaking discovery.

Other people too took this initiative of using carbon sheets for solar power. But they encountered some hurdles. They used the graphene form of carbon for solar cells. Grephene is akin to graphite used in pencil lead. Graphene absorbs a wide range of light frequencies. Scientists have found large sheets of graphene to be too unmanageable to work with. Large sheets are sticky and get attached with other sheets. Now Indiana University Bloomington researchers are trying to deal with this problem. They are trying to develop non-sticky graphene sheets that are stable. They are putting their efforts on “attaching a semi-rigid, semi-flexible, three-dimensional sidegroup to the sides of the graphene.” They know how to derive energy from carbon. Now chemists from Indiana University Bloomington are graduating to the next logical step i.e. conversion of that energy into electricity. If everything will turn out alright then carbon can be an alternative to expensive silicon and ruthenium, which is as rare as platinum.

Chemists and engineers kept on trying to work out a solution for the stickiness of graphene. They devised many methods for keeping single graphene sheets separate. Till now the most effective solution prior to the Indiana University Bloomington scientists’ experiment has been breaking up graphite (top-down) into sheets and wrap polymers around them. But this method has its own disadvantage. Those graphene sheets are too large for light absorption for solar cells. Indiana University chemists devised a completely new method for carbon sheets. They utilized a 3-D bramble patch between the carbon sheets. This method helped the scientists to dissolve sheets containing as many as 168 carbon atoms. They are successful in making the graphene sheets from smaller molecules (bottom-up) so that they are uniform in size. Till now, it is the biggest stable graphene sheet ever made with the bottom-up approach.

Solar panels need silicon for absorption of light. Silicon doesn’t come cheap.This cost-factor is preventing people from using solar energy on a large scale. Scientists utilize another substance i.e. ruthenium for solar cells. Rutheniumcan is cheaper than silicon but ruthenium is a rare metal on Earth. It is as rare as platinum. Naturally it can’t be available for mass production. Compared to silicon, carbon is cheap and abundant. The graphene, another form of carbon, is capable of absorbing a wide range of light frequencies.

Graphene is a single sheet of carbon, one atom thick. Graphene has potential to be utilized as an effective, less toxic and cheaper than other alternatives for solar cells. Chemists at Indiana University Bloomington are trying to come up with a better alternative than silicon. If successful, this can be a path breaking discovery.

Other people too took this initiative of using carbon sheets for solar power. But they encountered some hurdles. They used the graphene form of carbon for solar cells. Grephene is akin to graphite used in pencil lead. Graphene absorbs a wide range of light frequencies. Scientists have found large sheets of graphene to be too unmanageable to work with. Large sheets are sticky and get attached with other sheets. Now Indiana University Bloomington researchers are trying to deal with this problem. They are trying to develop non-sticky graphene sheets that are stable. They are putting their efforts on “attaching a semi-rigid, semi-flexible, three-dimensional sidegroup to the sides of the graphene.” They know how to derive energy from carbon. Now chemists from Indiana University Bloomington are graduating to the next logical step i.e. conversion of that energy into electricity. If everything will turn out alright then carbon can be an alternative to expensive silicon and ruthenium, which is as rare as platinum.

Chemists and engineers kept on trying to work out a solution for the stickiness of graphene. They devised many methods for keeping single graphene sheets separate. Till now the most effective solution prior to the Indiana University Bloomington scientists’ experiment has been breaking up graphite (top-down) into sheets and wrap polymers around them. But this method has its own disadvantage. Those graphene sheets are too large for light absorption for solar cells. Indiana University chemists devised a completely new method for carbon sheets. They utilized a 3-D bramble patch between the carbon sheets. This method helped the scientists to dissolve sheets containing as many as 168 carbon atoms. They are successful in making the graphene sheets from smaller molecules (bottom-up) so that they are uniform in size. Till now, it is the biggest stable graphene sheet ever made with the bottom-up approach.

What are biofuels? Are all forms of biofuels good?

Biofuels, a form of bioenergy used as transport fuel, can be made from a wide range of plant materials (biomass) such as sugar, wheat, vegetable oils, wood and straws. Those biofuels currently on the market are often made from conventional agricultural crops. They are sometimes referred to as ‘agrofuels’ due to their production from agricultural products.

Biofuels are only one form of energy made from biomass. Other forms of bioenergy, for example biogas, heat and electricity produced from biomass, generally have a higher efficiency with less associated environmental concerns compared with biofuels. If managed sustainably, bioenergy from renewable sources has its merits and is key to tackle global climate change.

Andy Hay (rspb-images.com) Rapeseed is a major feedstock to make biodiesel in Europe Zoom In | Hi-Res

First-generation biofuels

Current biofuels are often called ‘first generation biofuels’ because they are made with relatively simple technologies. Bioethanol can be produced from any feedstocks that contain a high starch or sugar content such as corn (maize), wheat, sugarcane, and sugar beet. After fermentation and distillation, this bioethanol can be mixed with petrol/gasoline in various proportions for car use. Biodiesel, on the other hand, is made through transesterification of vegetable oil such as palm oil, rapeseed oil, soya bean oil and even used-cooking oil.

Even though such biofuels are made from plant material and hence are a renewable source, they are not as ‘green’ as they seem. To produce biofuels, large amount of land is need to cultivate the crop, together with irrigation, use of fertilizers, transportation, conversion and refinery processes, all these require energy input and emit carbon dioxide. There are a large and growing number of studies that suggest that the use of current biofuels would save very little greenhouse gas, destroy wildlife habitats, as well as affect indigenous and rural poor communities around the world. (more on their Impacts)

Second-generation bio fuels

Due to the generally lower carbon emission and the greater possibility to use waste material, there are high hopes for so-called ‘second generation bio fuels’, which are mainly made from non-edible feed stocks as lignocellulosic materials like wood and straw. However, the cost of converting such biomass into bio ethanol or bio diesel or other types of transport fuels is still very high, and the technology still remains in the demonstration phase. Technological breakthroughs will be needed to bring the cost down, and depending on the technology it is estimated that second generation bio fuels will not become fully commercial for several years to come and will need of significant government support (IEA 2008). There are also uncertainties about their potential to provide transport fuel in a large scale due to the logistical challenge of transporting biomass material to large production facilities (OECD, 2007). Moreover, they have their share of environmental concerns as their production can also involve the requirement of land which can lead to direct and indirect land use change.

It is important to indicate that the terminology of these fuel sources might be misleading, as it suggests that first-generation bio fuels are a necessary first step to second generation or that the first are older than the second. On the contrary second generation bio fuels were firstly developed in 1930 in Germany converting biomass to liquids and for the production of each of these an entire different infrastructure is needed.

Is Global Warming Real?

Snow-mantled crags frame the severe beauty of Queen Maud Land in central Antarctica.

In recent years, global warming has been the subject of a great deal of political controversy. As scientific knowledge has grown, this debate is moving away from whether humans are causing warming and toward questions of how best to respond.

Signs that the Earth is warming are recorded all over the globe. The easiest way to see increasing temperatures is through the thermometer records kept over the past century and a half. Around the world, the Earth's average temperature has risen more than 1 degree Fahrenheit (0.8 degrees Celsius) over the last century, and about twice that in parts of the Arctic.

This doesn’t mean that temperatures haven't fluctuated among regions of the globe or between seasons and times of day. But if you average out the temperature all over the world over the course of a year, you see that temperatures have been creeping upward.

Although we can't look at thermometers going back thousands of years, we do have some records that help us figure out what temperatures and concentrations were like in the distant past. For example, trees store information about the climate in the place where they live. Each year, trees grow thicker and form new rings. In warmer and wetter years, the rings are thicker. Old trees and wood can tell us about conditions hundreds or even several thousands of years ago.

Keys to the past are also buried under lakes and oceans. Pollen, creatures, and particles fall to the bottom of oceans and lakes each year, forming sediments. Sediments preserve all these bits and pieces, which contain a wealth of information about what was in the air and water when they fell. Scientists reveal this record by inserting hollow tubes into the mud to collect sediment layers going back millions of years.

For a direct look at the atmosphere of the past, scientists drill cores through the Earth's polar ice sheets. Tiny bubbles trapped in the gas are actually pieces of the Earth's past atmosphere, frozen in time. That's how we know that the concentrations of greenhouse gases since the industrial revolution are higher than they've been for hundreds of thousands of years.

Computer models help scientists to understand the Earth's climate, or long-term weather patterns. Models also allow scientists to make predictions about the future climate. Basically, models simulate how the atmosphere and oceans absorb energy from the sun and transport it around the globe. Factors that affect the amount of the sun's energy reaching Earth's surface are what drive the climate in these models, as in real life. These include things like greenhouse gases, particles in the atmosphere (such as from volcanoes), and changes in energy coming from the sun itself.

Global Warming Solutions What Can We Do?

The evidence that humans are causing global warming is strong, but the question of what to do about it remains controversial. Economics, sociology, and politics are all important factors in planning for the future.

Even if we stopped emitting greenhouse gases (GHGs) today, the Earth would still warm by another degree Fahrenheit or so. But what we do from today forward makes a big difference. Depending on our choices, scientists predict that the Earth could eventually warm by as little as 2.5 degrees or as much as 10 degrees Fahrenheit.

A commonly cited goal is to stabilize GHG concentrations around 450-550 parts per million (ppm), or about twice pre-industrial levels. This is the point at which many believe the most damaging impacts of climate change can be avoided. Current concentrations are about 380 ppm, which means there isn't much time to lose. According to the IPCC, we'd have to reduce GHG emissions by 50% to 80% of what they're on track to be in the next century to reach this level.

Is this possible?

Many people and governments are already working hard to cut greenhouse gases, and everyone can help.

Researchers Stephen Pacala and Robert Socolow at Princeton University have suggested one approach that they call "stabilization wedges." This means reducing GHG emissions from a variety of sources with technologies available in the next few decades, rather than relying on an enormous change in a single area. They suggest 7 wedges that could each reduce emissions, and all of them together could hold emissions at approximately current levels for the next 50 years, putting us on a potential path to stabilize around 500 ppm.

There are many possible wedges, including

1.Improvements to energy efficiency and vehicle fuel economy (so less energy has to be produced), and

2.increases in wind and solar power,

3.hydrogen produced from renewable sources,

4.bio fuels (produced from crops),

5.natural gas, and

6.nuclear power.

7.There is also the potential to capture the carbon dioxide emitted from fossil fuels and store it underground—a process called "carbon sequestration."

In addition to reducing the gases we emit to the atmosphere, we can also increase the amount of gases we take out of the atmosphere. Plants and trees absorb CO2 as they grow, "sequestering" carbon naturally. Increasing forestlands and making changes to the way we farm could increase the amount of carbon we're storing.

Some of these technologies have drawbacks, and different communities will make different decisions about how to power their lives, but the good news is that there are a variety of options to put us on a path toward a stable climate.

Electricity from Biomass

The term "biomass" encompasses diverse fuels derived from timber, agriculture and food processing wastes or from fuel crops that are specifically grown or reserved for electricity generation. Biomass fuel can also include sewage sludge and animal manure. Some biomass fuels are derived from trees. Given the capacity of trees to regenerate, these fuels are considered renewable. Burning crop residues, sewage or manure - all wastes that are continually generated by society -- to generate electricity may offer environmental benefits in the form of preserving precious landfill space OR may be grown and harvested in ways that cause environmental harm.

At present, most biomass power plants burn lumber, agricultural or construction/demolition wood wastes. Direct Combustion power plants burn the biomass fuel directly in boilers that supply steam for the same kind of steam-electric generators used to burn fossil fuels. With biomass gasification, biomass is converted into a gas - methane - that can then fuel steam generators, combustion turbines, combined cycle technologies or fuel cells. The primary benefit of biomass gasification, compared to direct combustion, is that extracted gasses can be used in a variety of power plant configurations.

In terms of capacity, biomass power plants represent the second largest amount of renewable energy in the nation.

Because biomass technologies use combustion processes to produce electricity, they can generate electricity at any time, unlike wind and most solar technologies, which only produce when the wind is blowing or sun is shining. Biomass power plants currently represent 11,000 MW - the second largest amount of renewable energy in the nation.

What are the environmental impacts?

Whether combusting directly or engaged in gasification, biomass resources do generate air emissions. These emissions vary depending upon the precise fuel and technology used. If wood is the primary biomass resource, very little SO2 comes out of the stack. NOx emissions vary significantly among combustion facilities depending on their design and controls. Some biomass power plants show a relatively high NOx emission rate per kilowatt hour generated if compared to other combustion technologies.

This high NOx rate, an effect of the high nitrogen content of many biomass fuels, is one of the top air quality concerns associated with biomass.

Carbon monoxide (CO) is also emitted - sometimes at levels higher than those for coal plants.

Biomass plants also release carbon dioxide (CO2), the primary greenhouse gas. However, the cycle of growing, processing and burning biomass recycles CO2 from the atmosphere. If this cycle is sustained, there is little or no net gain in atmospheric CO2. Given that short rotation woody crops (i.e., fast growing woody plant types) can be planted, matured and harvested in shorter periods of time than natural growth forests, the managed production of biomass fuels may recycle CO2 in one-third less time than natural processes.

Biomass power plants also divert wood waste from landfills, which reduces the productions and atmospheric release of methane, another potent greenhouse gas.

Another air quality concern associated with biomass plants is particulates. These emissions can be readily controlled through conventional technologies. To date, no biomass facilities have installed advanced particulate emission controls. Still, most particulate emissions are relatively large in size. Their impacts upon human health remain unclear.

The collection of biomass fuels can have significant environmental impacts. Harvesting timber and growing agricultural products for fuel requires large volumes to be collected, transported, processed and stored. Biomass fuels may be obtained from supplies of clean, uncontaminated wood that otherwise would be landfilled or from sustainable harvests. In both of these fuel collection examples, the net environmental plusses of biomass are significant when compared to fossil fuel collection alternatives. On the other hand, the collection, processing and combustion of biomass fuels may cause environmental problems if, for example, the fuel source contains toxic contaminants, agricultural waste handling pollutes local water resources, or burning biomass deprives local ecosystems of nutrients that forest or agricultural waste may otherwise provide.

volcanoes

Volcanoes are awesome manifestations of the fiery power contained deep within the Earth. These formations are essentially vents on the Earth's surface where molten rock, debris, and gases from the planet's interior are emitted.

When thick magma and large amounts of gas build up under the surface, eruptions can be explosive, expelling lava, rocks and ash into the air. Less gas and more viscous magma usually mean a less dramatic eruption, often causing streams of lava to ooze from the vent.

The mountain-like mounds that we associate with volcanoes are what remain after the material spewed during eruptions has collected and hardened around the vent. This can happen over a period of weeks or many millions of years.

A large eruption can be extremely dangerous for people living near a volcano. Flows of searing lava, which can reach 2,000 degrees Fahrenheit (1,250 degrees Celsius) or more, can be released, burning everything in its path, including whole towns. Boulders of hardening lava can rain down on villages. Mud flows from rapidly melting snow can strip mountains and valleys bare and bury towns. Ash and toxic gases can cause lung damage and other problems, particularly for infants and the elderly. Scientists estimate that more than 260,000 people have died in the past 300 years from volcanic eruptions and their aftermath.

Volcanoes tend to exist along the edges between tectonic plates, massive rock slabs that make up Earth's surface. About 90 percent of all volcanoes exist within the Ring of Fire along the edges of the Pacific Ocean.

About 1,900 volcanoes on Earth are considered active, meaning they show some level of activity and are likely to explode again. Many other volcanoes are dormant, showing no current signs of exploding but likely to become active at some point in the future. Others are considered extinct.

Wildfire Saftey Tips

Unlike many natural disasters, most wildfires are caused by people—and can be prevented by people, too. Meteorologists are not yet able to forecast wildfire outbreaks, so people in fire-prone areas should plan ahead and prepare to evacuate with little notice. Here are some tips on how to prevent wildfires and what to do if you're caught in the middle of one.
How to Prevent a Wildfire
• Contact 911, your local fire department, or the park service if you notice an unattended or out-of-control fire.
• Never leave a campfire unattended. Completely extinguish the fire—by dousing it with water and stirring the ashes until cold—before sleeping or leaving the campsite.
• When camping, take care when using and fueling lanterns, stoves, and heaters. Make sure lighting and heating devices are cool before refueling. Avoid spilling flammable liquids and store fuel away from appliances.
• Do not discard cigarettes, matches, and smoking materials from moving vehicles, or anywhere on park grounds. Be certain to completely extinguish cigarettes before disposing of them.
• Follow local ordinances when burning yard waste. Avoid backyard burning in windy conditions, and keep a shovel, water, and fire retardant nearby to keep fires in check. Remove all flammables from yard when burning.
Evacuation Tips
• If advised to evacuate, do so immediately.
• Know your evacuation route ahead of time and prepare an evacuation checklist and emergency supplies.
• Wear protective clothing and footwear to protect yourself from flying sparks and ashes.
Before You Leave, Prepare Your House
• Remove combustibles, including firewood, yard waste, barbecue grills, and fuel cans, from your yard.
• Close all windows, vents, and doors to prevent a draft.
• Shut off natural gas, propane, or fuel oil supplies.
• Fill any large vessels—pools, hot tubs, garbage cans, or tubs—with water to slow or discourage fire.
If Caught in a Wildfire
• Don't try to outrun the blaze. Instead, look for a body of water such as a pond or river to crouch in.
• If there is no water nearby, find a depressed, cleared area with little vegetation, lie low to the ground, and cover your body with wet clothing, a blanket, or soil. Stay low and covered until the fire passes.
• Protect your lungs by breathing air closest to the ground, through a moist cloth, if possible, to avoid inhaling smoke.
timerCount('article_body');

Wildfires Dry, Cold, and Windy

Uncontrolled blazes fueled by weather, wind, and dry underbrush, wildfires can burn acres of land—and consume everything in their paths—in mere minutes.
On average, more than 100,000 wildfires, also called wildland fires or forest fires, clear 4 million to 5 million acres (1.6 million to 2 million hectares) of land in the U.S. every year. In recent years, wildfires have burned up to 9 million acres (3.6 million hectares) of land. A wildfire moves at speeds of up to 14 miles an hour (23 kilometers an hour), consuming everything—trees, brush, homes, even humans—in its path.
There are three conditions that need to be present in order for a wildfire to burn, which firefighters refer to as the fire triangle:

1. fuel,


2. oxygen,


3. and a heat source.

• Fuel is any flammable material surrounding a fire, including trees, grasses, brush, even homes. The greater an area's fuel load, the more intense the fire.


• Air supplies the oxygen a fire needs to burn. Heat sources help spark the wildfire and bring fuel to temperatures hot enough to ignite.


• Lightning, burning campfires or cigarettes, hot winds, and even the sun can all provide sufficient heat to spark a wildfire.
  Although four out of five wildfires are started by people, nature is usually more than happy to help fan the flames. Dry weather and drought convert green vegetation into bone-dry, flammable fuel; strong winds spread fire quickly over land; and warm temperatures encourage combustion. When these factors come together all that's needed is a spark—in the form of lightning, arson, a downed power line, or a burning campfire or cigarette—to ignite a blaze that could last for weeks and consume tens of thousands of acres.
  These violent infernos occur around the world and in most of the 50 states, but they are most common in the U.S. West, where heat, drought, and frequent thunderstorms create perfect wildfire conditions. Montana, Idaho, Wyoming, Washington, Colorado, Oregon, and California experience some of the worst conflagrations in the U.S. In California wildfires are often made worse by the hot, dry Santa Ana winds, which can carry a spark for miles.
  Firefighters fight wildfires by depriving them of one or more of the fire triangle fundamentals. Traditional methods include water dousing and spraying fire retardants to extinguish existing fires. Clearing vegetation to create firebreaks starves a fire of fuel and can help slow or contain it. Firefighters also fight wildfires by deliberately starting fires in a process called controlled burning. These prescribed fires remove undergrowth, brush, and ground litter from a forest, depriving a wildfire of fuel.
  Although often harmful and destructive to humans, naturally occurring wildfires play an integral role in nature. They return nutrients to the soil by burning dead or decaying matter. They also act as a disinfectant, removing disease-ridden plants and harmful insects from a forest ecosystem. And by burning through thick canopies and brushy undergrowth, wildfires allow sunlight to reach the forest floor, enabling a new generation of seedlings to grow.
  

Benefits of Glass Recycling: Why Recycle Glass? Glass Recycling is Efficient and Sustainable; Saves Energy and Natural Resources

Glass recycling is good for the environment.. A glass bottle that is sent to a landfill can take up to a million years to break down. By contrast, it takes as little as 30 days for a recycled glass bottle to leave your kitchen recycling bin and appear on a store shelf as a new glass container.

Glass recycling is sustainableGlass containers are 100-percent recyclable, which means they can be recycled repeatedly, again and again, with no loss of purity or quality in the glass.

Glass recycling is efficient.. Recovered glass from glass recycling is the primary ingredient in all new glass containers. A typical glass container is made of as much as 70 percent recycled glass. According to industry estimates, 80 percent of all recycled glass eventually ends up as new glass containers.

Glass recycling conserves natural resources. Every ton of glass that is recycled saves more than a ton of the raw materials needed to create new glass, including: 1,300 pounds of sand; 410 pounds of soda ash; and 380 pounds of limestone.

Glass recycling saves energy. Making new glass means heating sand and other substances to a temperature of 2,600 degrees Fahrenheit, which requires a lot of energy and creates a lot of industrial pollution. One of the first steps in glass recycling is to crush the glass and create a product called “cullet.” Making recycled glass products from cullet consumes 40 percent less energy than making new glass from raw materials, because cullet melts at a much lower temperature.

Recycled glass is useful. Because glass is made from natural materials such as sand and limestone, it glass containers have a low rate of chemical interaction with their contents. As a result, glass can be safely reused. Besides serving as the primary ingredient in new glass containers, recycled glass also has many other commercial uses—from creating decorative tiles and landscaping material to rebuilding eroded beaches.

Glass recycling is also simple, as I pointed out at the beginning of this article. It’s simple because glass is one of the easiest materials to recycle. For one thing, glass is accepted by almost all curbside recycling programs and municipal recycling centers. About all most people have to do to recycle glass bottles and jars is to carry their recycling bin to the curb, or maybe drop off their empty glass containers at a nearby collection point.

If you need an extra incentive to recycle glass, how about this: Several U.S. states offer cash refunds for most glass bottles, so in some areas glass recycling can actually put a little extra money in your pocket.

Ozone and Traffic Pollution Increase Asthma-Related Hospitalizations in Children

Both ozone and primary pollutants from traffic substantially increase asthma-related emergency department visits in children, especially during the warm season, according to researchers from the Department of Environmental Health at the Rollins School of Public Health at Emory University in Atlanta.

Effects of Global Warming Signs Are Everywhere

The planet is warming, from North Pole to South Pole, and everywhere in between. Globally, the mercury is already up more than 1 degree Fahrenheit (0.8 degree Celsius), and even more in sensitive polar regions. And the effects of rising temperatures aren’t waiting for some far-flung future. They’re happening right now. Signs are appearing all over, and some of them are surprising. The heat is not only melting glaciers and sea ice, it’s also shifting precipitation patterns and setting animals on the move.

Some impacts from increasing temperatures are already happening.

• Ice is melting worldwide, especially at the Earth’s poles. This includes mountain glaciers, ice sheets covering West Antarctica and Greenland, and Arctic sea ice.
• Researcher Bill Fraser has tracked the decline of the Adélie penguins on Antarctica, where their numbers have fallen from 32,000 breeding pairs to 11,000 in 30 years.
• Sea level rise became faster over the last century.
• Some butterflies, foxes, and alpine plants have moved farther north or to higher, cooler areas.
• Precipitation (rain and snowfall) has increased across the globe, on average.
• Spruce bark beetles have boomed in Alaska thanks to 20 years of warm summers. The insects have chewed up 4 million acres of spruce trees.

Other effects could happen later this century, if warming continues.

• Sea levels are expected to rise between 7 and 23 inches (18 and 59 centimeters) by the end of the century, and continued melting at the poles could add between 4 and 8 inches (10 to 20 centimeters).
• Hurricanes and other storms are likely to become stronger.
• Species that depend on one another may become out of sync. For example, plants could bloom earlier than their pollinating insects become active.
• Floods and droughts will become more common. Rainfall in Ethiopia, where droughts are already common, could decline by 10 percent over the next 50 years.
• Less fresh water will be available. If the Quelccaya ice cap in Peru continues to melt at its current rate, it will be gone by 2100, leaving thousands of people who rely on it for drinking water and electricity without a source of either.
• Some diseases will spread, such as malaria carried by mosquitoes.
• Ecosystems will change—some species will move farther north or become more successful; others won’t be able to move and could become extinct. Wildlife research scientist Martyn Obbard has found that since the mid-1980s, with less ice on which to live and fish for food, polar bears have gotten considerably skinnier. Polar bear biologist Ian Stirling has found a similar pattern in Hudson Bay. He fears that if sea ice disappears, the polar bears will as well.

Source for climate information: IPCC, 2007

Solar Energy

Every hour the sun beams onto Earth more than enough energy to satisfy global energy needs for an entire year. Solar energy is the technology used to harness the sun's energy and make it useable. Today, the technology produces less than one tenth of one percent of global energy demand.

Many people are familiar with so-called photovoltaic cells, or solar panels, found on things like spacecraft, rooftops, and handheld calculators. The cells are made of semiconductor materials like those found in computer chips. When sunlight hits the cells, it knocks electrons loose from their atoms. As the electrons flow through the cell, they generate electricity.

On a much larger scale, solar thermal power plants employ various techniques to concentrate the sun's energy as a heat source. The heat is then used to boil water to drive a steam turbine that generates electricity in much the same fashion as coal and nuclear power plants, supplying electricity for thousands of people.

In one technique, long troughs of U-shaped mirrors focus sunlight on a pipe of oil that runs through the middle. The hot oil then boils water for electricity generation. Another technique uses moveable mirrors to focus the sun's rays on a collector tower, where a receiver sits. Molten salt flowing through the receiver is heated to run a generator.

Other solar technologies are passive. For example, big windows placed on the sunny side of a building allow sunlight to heat-absorbent materials on the floor and walls. These surfaces then release the heat at night to keep the building warm. Similarly, absorbent plates on a roof can heat liquid in tubes that supply a house with hot water.

Solar energy is lauded as an inexhaustible fuel source that is pollution and often noise free. The technology is also versatile. For example, solar cells generate energy for far-out places like satellites in Earth orbit and cabins deep in the Rocky Mountains as easily as they can power downtown buildings and futuristic cars.

But solar energy doesn't work at night without a storage device such as a battery, and cloudy weather can make the technology unreliable during the day. Solar technologies are also very expensive and require a lot of land area to collect the sun's energy at rates useful to lots of people.

Despite the drawbacks, solar energy use has surged at about 20 percent a year over the past 15 years, thanks to rapidly falling prices and gains in efficiency. Japan, Germany, and the United States are major markets for solar cells. With tax incentives, solar electricity can often pay for itself in five to ten years.