Solar Energy – Turning Sunlight into Electricity

Solar energy could be used to generate electricity on a large scale if solutions were found for certain problems. At present it is too difficult to produce large amounts of solar energy and store it for times when the sun is not available such as overnight, on overcast days or at high latitudes. However let’s take a look at the way in which sunlight can be turned in a source of electrical power.

Solar energy keeps us all alive. The heat and light from the sun is what keeps the earth at the correct temperature. It is the sun’s energy that keeps almost all living organisms alive. It is the sun that determines natural systems and cycles. About 95% of the energy from the sun is given off as light that we can see. However the light that we can see is only a small amount of the sun’s total energy.

The "photovoltaic effect" is a process through which a PV cell changes sunlight into electricity. The light from the sun is made up of photons. These are particles of solar energy. Depending on their wavelengths, each photon contains different amounts of energy. When photons strike a PV cell they are reflected, absorbed, or pass right through.

So how does solar energy produce electricity? When a photon is absorbed it can generate electricity. Then the energy of the photon is transferred to an electron in the PV cell (a semiconductor). The electron escapes and becomes part of an electrical circuit. When it escapes it makes a tiny hole. The PV cell has a built-in electric field. This enables the cell to provide the voltage needed to drive the electrical current into a light bulb.

Link

All About Global Warming

Global warming is the term used to describe a gradual increase in the average temperature of the Earth's atmosphere and its oceans, a change that is believed to be permanently changing the Earth’s climate forever.

While many view the effects of global warming to be more substantial and more rapidly occurring than others do, the scientific consensus on climatic changes related to global warming is that the average temperature of the Earth has risen between 0.4 and 0.8 °C over the past 100 years. The increased volumes of carbon dioxide and other greenhouse gases released by the burning of fossil fuels, land clearing, agriculture, and other human activities, are believed to be the primary sources of the global warming that has occurred over the past 50 years.

Scientists from the Intergovernmental Panel on Climate carrying out global warming research have recently predicted that average global temperatures could increase between 1.4 and 5.8 °C by the year 2100. Changes resulting from global warming may include rising sea levels due to the melting of the polar ice caps, as well as an increase in occurrence and severity of storms and other severe weather events.

See More

Storing Solar Power Efficiently

Thermal-power plants that store heat for cloudy days could solve some of the problems with solar power.

Solar proponents love to boast that just a few hundred square kilometers' worth of photovoltaic solar panels installed in Southwestern deserts could power the United States. Their schemes come with a caveat, of course: without backup power plants or expensive investments in giant batteries, flywheels, or other energy-storage systems, this solar-power supply would fluctuate wildly with each passing cloud (not to mention with the sun's daily rise and fall and seasonal ebbs and flows). Solar-power startup Ausra, based in Palo Alto, thinks it has the solution: solar-thermal-power plants that turn sunlight into steam and efficiently store heat for cloudy days.

"Fossil-fuel proponents often say that solar can't do the job, that solar can't run at night, solar can't run the economy," says David Mills, Ausra's founder and chairman. "That's true if you don't have storage." He says that solar-thermal plants are the solution because storing heat is much easier than storing electricity. Mills estimates that, thanks to that advantage, solar-thermal plants capable of storing 16 hours' worth of heat could provide more than 90 percent of current U.S. power demand at prices competitive with coal and natural gas. "There's almost no limit to how much you can put into the grid," he says.

Major utilities are buying the idea. In July, the Pacific Gas and Electric Company (PG&E) signed a 25-year deal with Ausra competitor Solel Solar Systems of Beit Shemesh, Israel, to buy power from a 553-megawatt solar-thermal plant that Solel is developing in California's Mojave Desert. The plant will supply 400,000 homes in northern and central California when it is completed in 2011. Florida Power & Light, meanwhile, hired Solel to upgrade the 1980s-era solar-thermal plants it operates in the Mojave.

Ausra, meanwhile, is negotiating with PG&E to supply power from a 175-megawatt plant that it plans to build in California, for which it secured $40 million in venture financing this month.

What distinguishes Ausra's design is its relative simplicity. In conventional solar-thermal plants such as Solel's, a long trough of parabolic mirrors focuses sunlight on a tube filled with a heat-transfer fluid, often some sort of oil or brine. The fluid, in turn, produces steam to drive a turbine and produce electricity. Ausra's solar collectors employ mass-produced and thus cheaper flat mirrors, and they focus light onto tubes filled with water, thus directly producing steam. Ausra's collectors produce less power, but that power costs less to produce.

One megawatt's worth of Ausra's solar collectors has been producing steam in New South Wales, Australia, since 2004; the steam is fed into the turbines of a primarily coal-fired power plant. The final piece of the system--a proprietary heat-energy-storage system--should be ready by 2009.

cubic mile of oil (CMO)

I just ran across an interesting article about renewable energy over at the Green Tech weblog. In it, they break down the type of investment that would be required to replace the energy provided by a cubic mile of oil (CMO).

In case you’re not aware (as I wasn’t), a CMO is a measure of energy consumption. Apparently the world consumes slightly more than one CMO worth of energy from oil per year, and the equivalent of three CMOs from all energy sources. Over 80% of this total energy usage comes from fossil fuels, including oil, coal, and natural gas (see graph, below).

So… What would it require to replace just one CMO of fossil energy per year?

Solar panels

Assuming annual electricity capture of 2.1 megawatts per solar panel, we’d have to place them on 4.2 billion rooftops. In other words, we’d have to install on them on 250,000 roofs per day for the next 50 years to have enough solar panels to offset our current annual oil usage (and this ignores things like coal; see below).

Wind power

What about wind power generators? You’d need 3 million to equal one CMO. That would require the installation of 1,200 per week for the next 50 years.

Hydroelectric power

A large hydroelectric dam can generate roughly 18 gigawatts of power per year. Thus, to offset one CMO of energy, we’d have to build 200 major hydroelectric dams. The problem? There aren’t enough rivers left in the world to dam up.

Solar thermal power

It would require 7,700 solar thermal plants to offset one CMO. That would require the construction of 150 plants per year for 50 years. Unfortunately, just one has been built in the past 15 years.

Nuclear power plants

It would take 2,500 nuclear power plants producing 900 megawatts to produce the equivalent of one CMO worth of energy. In other words, we’d have to build one a week for 50 years. It’s also worth noting that nuclear power isn’t exactly renewable.

The future of demand

Even if we decided to pursue one of the above options, it’s important to keep in mind that energy demand is continually increasing. According to Ripudaman Malhotra, a fossil fuels researcher at SRI International, world energy demand is expected to double to six CMOs within the next 30 years.

The good news here is that we still have time. Current estimates show oil reserves of roughly 46 CMOs, natural gas reserves totalling 42 CMOs, and coal reserves of 121 CMOs. These numbers increase further when you add in difficult to extract sources such as tar sands.

The bad news is that, beyond being non-renewable, these sources of energy also have a number of adverse environmental impacts, and burning more of them at a faster rate is just going to create more problems.

The way forward

Clearly, if we’re ever going to come anywhere near freeing ourselves from fossil fuels — an eventual necessity, as we’ll ultimately run out — it will require a tremendous investment, a variety of different technologies (likely including some that haven’t been invented yet), and an awful lot of conservation.

Unfortunately, we’re dealing with a problem on such a massive scale that minor changes won’t be enough. Consider, for example, that replacing 1 billion incandescent bulbs with compact fluorescent bulbs only saves 0.01 CMOs per year. Yes, it’s important to cut back wherever we can. In this case, however, baby steps won’t be enough.

It’s also important to keep in mind that all of the technologies listed above result in electricity production. Given that a large fraction of our energy consumption is currently non-electric, we’ll need a lot of other infrastructure changes to go along with this.

Ten facts about renewable energy

As the impact of fossil fuels on our environment becomes ever more stark, renewable energy - with its non-polluting qualities and infinite capacity - is just what we need to save our fragile planet. It's thanks to the work of engineers and scientists that we are able to harness the renewable energy available to us and make it useful. Prepare yourself for our top 10 must-know renewable energy facts...

1. There are five main forms of renewable energy: solar, wind, water, biofuel and geothermal (heat from the earth).

2. If it could be properly harnessed, enough sunlight falls on the earth in just one hour to meet world energy demands for a whole year!

3. Ever the innovator, Albert Einstein (left) won the Nobel Prize in Physics 1921 for his ground-breaking experiments with solar power and photovoltaics.

4. The geothermal energy from the core of the Earth is closer to the surface in some areas than in others. Where hot underground steam or water can be tapped and brought to the surface it can be used to generate electricity.

5. A world record was set in 1990 when a solar-powered aircraft flew across the USA in 21 stages, using no fuel at all.

6. One wind turbine can produce enough electricity to power up to 300 homes.

7. The largest wind turbine in the world, located in Hawaii, stands 20 storeys tall and has blades the length of a football pitch.

8. An average wind speed of just 14mph is needed to convert wind energy into electricity; that shouldn't be too hard to come by in breezy Britain!

9. Water is the most commonly used renewable energy resource, providing enough power to meet the needs of 28.3 million people.

10. Those clever old Romans not only gave us the modern drainage system and many of our roads, they were also among the first to use geothermal energy to heat houses.

Fun Facts about Renewable Energy

Fun facts about wind power

In 200 B.C., people in China and the Middle East used windmills to pump water and grind grain. The first modern wind turbine was built in Vermont in the early 1940s. Wind farms currently produce enough electricity to meet the needs of more than 600,000 families in the United States. The largest wind turbine in the world, located in Hawaii, stands 20 stories tall and has blades the length of a football field. An average wind speed of 14 miles per hour is needed to convert wind energy into electricity.

One wind turbine can produce enough electricity to power up to 300 homes.

Learn more about wind power

Make your own wind power toys

Fun facts about biomass energy

Almost half of the renewable energy produced in the United States comes from biomass sources, li ke wood and paper products. In Iowa and Wisconsin, biomass energy from landfills and dairy farms is being used to make electricity. In southern Iowa, a power plant is using a crop called switchgrass to make electricity. Learn more about biomass energy Fun facts about hydro power Water power has been used for grinding grain for more than 2,000 years. The first U.S. hydroelectric power plant opened on the Fox River near Appleton, Wisconsin, on September 30, 1882. Worldwide, water is the most commonly used renewable energy resource, providing enough power to meet the needs of 28.3 million consumers. Hydro power currently provides about 10 percent of the electricity in the United States. Learn more about hydro power Fun facts about geothermal energy Volcanoes and geysers are examples of geothermal energy. In 1864, a hotel in Oregon heated rooms using geothermal energy from underground hot springs. The first geothermal power plant opened in California in 1921. A professor at Ohio State University invented the first geothermal heating system in 1948. Learn more about geothermal power Fun facts about solar power More than 10,000 homes in the United States are powered entirely by solar energy. Enough sunlight falls on the earth's surface every hour to meet world energy demand for an entire year. Silicon from just one ton of sand, used in photovoltaic cells, could produce as much electricity as burning 500,000 tons of coal. In the 1830s, the British astronomer John Herschel used a solar collector box to cook food during an expedition to Africa. Albert Einstein won the Nobel Prize in 1921 for his experiments with solar power and photovoltaics. The first big solar power plant opened in California in 1982. Learn more about solar power Make your own solar oven

Renewable Energy - Facts

What Is Renewable Energy?

By definition, renewable energy is "clean" - producing few or no hazardous emissions or pollutants, and having minimal impact on fragile ecosystems.

There are five main types of renewable energy: hydro, biomass, geothermal, solar and wind.

While each of these can be used to generate electricity, only hydro and biomass currently provide a significant amount of power [see chart below] - but that fact will change in the coming decades.

In addition to the obvious environmental benefits, green power could have major economic advantages as well:

• It decreases our dependence on foreign oil imports and the resulting price fluctuations.

• It reduces the need for costly emissions controls.

• It provides new energy markets and creates new jobs.

The financial impact could be significant in the Midwest. Switchgrass and other biomass materials provide an alternative crop option, animal waste and crop residues can be sold and reused, and the construction of wind farms or other green power facilities creates jobs and local rural economies.

Sources of Renewable Energy: