Wednesday, June 16, 2010

Guest Blogger Today

We have a guest blogger today. Barbara Young has a lot of interesting and informative things to tell us about solar energy: how it works, some history, and a really thorough list of solar power pros and cons.

Warning from Dave -- she knows way more about solar power than I do -- get ready to learn!

Barbara writes regularly here on her very lively site that I plan to keep up with:

Her efforts are focused entirely on helping people save energy using solar powered energy to reduce CO2 emissions and energy dependency.

After you read this I’m betting that you bookmark that site – it’s that good!


Here’s an instant approach to learn the way solar panels work

What's solar energy ?

Solar energy is radiant energy that's produced by the sun. Each day the sun radiates, or sends out, an enormous amount of energy. The sun radiates more energy in one second than people have used since the beginning of time!

The energy of the Sun derives from within the sun itself. Like other stars, the sun is mostly a big ball of gases––mostly hydrogen and helium atoms.

The hydrogen atoms in the sun’s core combine to create helium and generate energy in a process called nuclear fusion.

During nuclear fusion, the sun’s extremely high pressure and temperature cause hydrogen atoms to come apart and their nuclei (the central cores of the atoms) to fuse or combine. Four hydrogen nuclei fuse to become one helium atom. However the helium atom contains less mass compared to four hydrogen atoms that fused. Some matter is lost during nuclear fusion. The lost matter is emitted into space as radiant energy.

It requires millions of years for the energy in the sun’s core to make its way to the solar surface, and then slightly over eight minutes to travel the 93 million miles to earth. The solar energy travels to the earth at a speed of 186,000 miles per second, the speed of sunshine.

Only a small part of the energy radiated by the sun into space strikes the earth, one part in two billion. Yet this quantity of energy is enormous. On a daily basis enough energy strikes the united states to supply the nation’s energy needs for one and a half years!

Where does all this energy go?

About 15 percent of the sun’s energy that hits the planet earth is reflected back to space. Another 30 percent is used to evaporate water, which, lifted in to the atmosphere, produces rainfall. Solar energy is also absorbed by plants, the land, and the oceans. The remaining could be employed to supply our energy needs.

Who invented solar power ?

People have harnessed solar technology for hundreds of years. Since the 7th century B.C., people used simple magnifying glasses to concentrate the light of the sun into beams so hot they would cause wood to catch fire. Over 100 years ago in France, a scientist used heat from a solar collector to produce steam to drive a steam engine. In the beginning of this century, scientists and engineers began researching ways to use solar energy in earnest. One important development was obviously a remarkably efficient solar boiler invented by Charles Greeley Abbott, an American astrophysicist, in 1936.

The solar hot water heater gained popularity at this time in Florida, California, and the Southwest. The industry started in the early 1920s and was in full swing prior to The second world war. This growth lasted before mid-1950s when low-cost natural gas took over as primary fuel for heating American homes.

People and world governments remained largely indifferent to the possibilities of solar energy before oil shortages of the1970s. Today, people use solar technology to heat buildings and water and also to generate electricity.

How do we use solar power today ?

Solar energy is employed in several different ways, of course. There are two very basic kinds of solar energy:

* Solar thermal energy collects the sun's warmth through 1 of 2 means: in water or in an anti-freeze (glycol) mixture.
* Solar photovoltaic energy converts the sun's radiation to usable electricity.
Listed here are the five most practical and popular ways that solar energy is employed:

1. Small portable solar photovoltaic systems. We have seen these used everywhere, from calculators to solar garden tools. Portable units can be utilised for everything from RV appliances while single panel systems are used for traffic signs and remote monitoring stations.

2. Solar pool heating. Running water in direct circulation systems via a solar collector is an extremely practical method to heat water for your pool or hot tub.

3. Thermal glycol energy to heat water. In this method (indirect circulation), glycol is heated by natural sunlight and the heat is then transferred to water in a warm water tank. Using this method of collecting the sun's energy is more practical now than ever. In areas as far north as Edmonton, Alberta, solar thermal to heat water is economically sound. It can pay for itself in three years or less.

4. Integrating solar photovoltaic energy into your home or business power. In many parts on the planet, solar photovoltaics is an economically feasible method to supplement the power of your home. In Japan, photovoltaics are competitive with other types of power. In the USA, new incentive programs make this form of solar technology ever more viable in many states. An increasingly popular and practical way of integrating solar energy into the power of your home or business is through the usage of building integrated solar photovoltaics.

5. Large independent photovoltaic systems. For those who have enough sun power at your site, you might be able to go off grid. You may also integrate or hybridize your solar energy system with wind power or other forms of renewable energy to stay 'off the grid.'

How can Photovoltaic panels work ?

Silicon is mounted beneath non-reflective glass to produce photovoltaic panels. These panels collect photons from the sun, converting them into DC electrical energy. The power created then flows into an inverter. The inverter transforms the power into basic voltage and AC electrical energy.

Solar cells are prepared with particular materials called semiconductors for example silicon, which is presently the most generally used. When light hits the Photovoltaic cell, a certain share of it is absorbed inside the semiconductor material. This means that the energy of the absorbed light is given to the semiconductor.

The power unfastens the electrons, permitting them to run freely. Photovoltaic cells also have one or more electric fields that act to compel electrons unfastened by light absorption to flow in a specific direction. This flow of electrons is a current, and by introducing metal links on the top and bottom of the -Photovoltaic cell, the current can be drawn to use it externally.

What are the positives and negatives of solar energy ?

Solar Pro Arguments

- Heating our homes with oil or natural gas or using electricity from power plants running with oil and coal is a reason for global warming and climate disruption. Solar power, on the other hand, is clean and environmentally-friendly.
- Solar hot-water heaters require little maintenance, and their initial investment can be recovered within a relatively short time.
- Solar hot-water heaters can work in nearly every climate, even in very cold ones. Simply choose the best system for your climate: drainback, thermosyphon, batch-ICS, etc.
- Maintenance costs of solar powered systems are minimal and the warranties large.
- Financial incentives (USA, Canada, European states…) can aid in eliminating the cost of the first investment in solar technologies. The U.S. government, for instance, offers tax credits for solar systems certified by by the SRCC (Solar Rating and Certification Corporation), which amount to 30 percent of the investment (2009-2016 period).

Solar Cons Arguments

- The initial investment in Solar Hot water heaters or in Solar PV Electric Systems is higher than that required by conventional electric and gas heaters systems.
- The payback period of solar PV-electric systems is high, as well as those of solar space heating or solar cooling (only the solar warm water heating payback is short or relatively short).
- Solar water heating do not support a direct in conjunction with radiators (including baseboard ones).
- Some air conditioning (solar space heating and the solar cooling systems) are costly, and rather untested technologies: solar ac isn't, till now, a truly economical option.
- The efficiency of solar powered systems is rather influenced by sunlight resources. It's in colder climates, where heating or electricity needs are higher, that the efficiency is smaller.

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