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**Solar Power:** //Harnessing The Sun//

__** Table Of Contents **__ II. Ways Of Capturing the Sun III. Transmission Across the Public and Industrial Grid** The 2020 Efficiency Plan for Clean Energy V. Solar Power As a Solution to Climate Change VI. Potential Technological Improvements for Solar Power**
 * I. Pros and Cons of Solar Energy
 * IV. Use Of Solar Power Today

 **I. Pros and Cons of Solar Energy**

**//__ Pros __//**

Solar panels obviously **do not produce any pollution**, themselves.

As some other alternative forms of energy (e.g. wind power) can be noisy, **solar energy methods are extremely quiet**.

To produce solar energy, **the cells do not have to be linked to an overall power grid. This enables solar energy to be harnessed in extremely remote locations.** Examples of this use are highly efficient satellites in outer space. **Individual homes can harness their own energy system**; they don't have to be connected to a grid.

As sun is very prevalent, **solar energy can be used over a wide range of the earth**; New technologies are now advocating for overcast skies and not-so-sunny conditions as well.

Many solar panel systems are installed on house rooftops, **eliminating the need for an un-intrusive operating space.**

Even though the initial setup cost for a solar panel system is a bit overwhelming, **solar energy is free**, and the cost will be made up in the money saved in later years.

The most obvious pro of solar energy would be **its ability do decrease reliance on fossil fuels**, thus decreasing the contributors to the greenhouse effect and climate change.

__**// Cons //**__

The **initial installation cost of solar energy is extremely expensive**; efficient solar cells can be $1,000.00 or much more. Also, more than one may be needed.

Solar panels are **only able to produce energy while there is daylight**. This means, for about half of the day, solar panels are not producing energy.

Dramatic, and even lesser **weather patterns** (e.g rainy, snowy conditions) **can affect the energy efficiency** of a solar panel system.


 * Pollution poses a major threat to the ability of solar cells to produce energy**. In high-pollution areas, where the sun is not as visible, solar power is more difficult to harness.

 []

** II. Ways Of Capturing the Sun **

**//__ Photovoltaic(PV) Solar Energy Systems __//** []

Many people who use PV systems to convert sunlight into electrical energy are independent users. They put the photovoltaic solar boxes on their rooftops and create their own energy. "In 1839, French scientist Edmund Becquerel discovered that certain materials would give off a spark of electricity when struck with sunlight (Grinning Planet)." Each individual solar cell is made of a silicon substrate. (silicon in its pure state is not a good conductor). This silicon substrate has a very weak grip on its electrons, making them vulnerable for use in energy. The first layer of silicon has too many electrons, while the next layer has too few. Light photons hit the first layer of silicon and knock the extra electrons loose. As these loose electrons flow towards the lower layer with too few electrons, they pass through an electrical circuit. Their natural inclination to flow towards the "too-few" layer is what brings them to the electrical circuit. The current produced from this circuit can be used to power equipment and devices used in heating and other household or industrial processes. 



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__//**Concentrated Solar Energy**//__ Very long metallic, parabolically shaped mirrors are designed to track the suns photons in the most direct path at any time. Mirrors are used, so that the sunlight can be concentrated on a long pipe full of heatable liquid, which runs parallel, along the entire expanse of the mirrors.

This pipe full of liquid usually runs alongside a pipe of water. As the water is heated with a heat exchanger it is converted to steam. At the end of the pipes lies a turbine that is driven by the steam power flowing out of the piping. As technology is advancing, future plants are being considered that would send the hot fluid through a large holding tank, which would heat a large mass of molten salt. This large holding reservoir would provide and retain heat at night, which could be tapped out of the reservoir for use when the sun is down.



Another form of concentrated solar energy uses large towers (as seen in the above picture) that are beamed with light reflection concentrated from many individual mirror units. These towers can be filled with many different substances which conduct heat well, and transfer the energy beyond. __
 * //Passive Solar Energy//**

[] __ <span style="font-family: 'Palatino Linotype', 'Book Antiqua', Palatino, serif;"> " Passive solar heating makes use of warmth moved by the natural processes of reflections, radiation, conduction and convection. " Passive solar energy directly utilizes the rays of sun to heat and light buildings, when the sun is still available. Passive solar energy does not make use of electric pumps, or generators to produce electricity for a building. All surfaces of the building directly exposed to the sun's rays play a part in collecting the solar energy of the sun. Any other surface inside or outside of the most common example, the residential house, are heated and affected by means of conduction, convection, and radiation, (the most common and useful). During the time of year where heating is essential, (winter) the sun makes a low arc in the southern sky. This means the sun hits the building's southern side pretty directly throughout the entire day, and the southern side of the house recieves the most solar energy than any other side. Southern facing windows work the best in capturing the sun's light and heat just like a greenhouse, or the "greenhouse effect." These windows allow the sun's energy to shine through and heat the interior of the house. Not only windows, but dark exteriors on a house help to better absorb light and heat, and light colored interior paints efficiently reflect light for better visibility. Interior surfaces made of substances like brick, or rock, are heated during the day and can become great radiators of heat, as they stay hot for a long time during the night hours. It has been said that in a very well insulated, energy efficient home, this passive form of utilizing solar energy can wipe out up to 30% of the heating load in winter months (UAF.edu), making this simple and easily-engineered form of passive energy quite worth it. Many houses do use passive forms of solar energy today.

<span style="font-size: 110%; font-family: 'Palatino Linotype', 'Book Antiqua', Palatino, serif;">**<span style="display: block; font-size: 140%; font-family: Tahoma, Geneva, sans-serif; text-align: center;">III. Transmission of Solar Energy Across the Country and the Grid ** []

Currently, solar energy from photovoltaic farms or concentrated solar farms are wired to an inverter, which converts the "direct" current made by the moving electrons to "alternating" current or (AC), the standard voltage used by the utility grids. With a solar electric system connected to the grid, a single user doesn't have to rely solely on solar power. Solar power, however, in some cases, still provides about half of the power required for a user, and still works to offset fossil fuel use and consumption. The big inverter sends the AC energy into electric power lines, most of which can only carry electricity efficiently for a limited mileage. Usually unused solar energy is stored for use in lead-acid "batteries" during cloudy days or nighttime. In some cases however, as now in Wisconsin, a process called "net metering" allows individual owners of grid-connected solar systems to "sell" their extra power back to the grid when they are producing more than needed. Likewise, if more energy is needed, this system allows owners to tap energy out of the grid. <span style="display: block; font-family: 'Palatino Linotype', 'Book Antiqua', Palatino, serif; text-align: left;">

<span style="font-size: 150%; font-family: Tahoma, Geneva, sans-serif;"> <span style="display: block; font-size: 170%; font-family: Tahoma, Geneva, sans-serif; text-align: center;">**The 2020 Efficiency Plan for Clean Energy** <span style="font-family: 'Palatino Linotype', 'Book Antiqua', Palatino, serif;">But what matters even more than the current grid method, is the method that scientists, and clean energy proponents are developing. The system could almost deplete our reliance on fossil fuels completely. To start, energy from large photovoltaic farms, out in undeveloped and sunny regions of the southwest could be used to compress air and force in in underground caverns like aquifers, or old oil reservoirs. This pressurized air could be released on demand to turn a turbine which would generate electricity. This would only need a little aid from natural gas. In the future, electricity from the large-scale photovoltaic, or even concentrated solar farms from the southwest, could be sent, directly as DC current over high voltage DC lines, to compressed air storage sites. Year round, turbines could generate electricity. However, the current AC lines that supply power to metropolitan areas cannot withstand or carry energy over such long hauls, and the energy would be lost and wasted. The new HVDC (High voltage Direct Current) "backbone" would have to be constructed that would run from the southwest and diverge eastward. Then, these DC lines would end at DC converting stations, which could convert DC to the normal AC. This converted AC power could then be transmitted along the existing AC lines that supply energy and electricity to consumers nationally. A national HVDC backbone could carry energy without losing it, over much longer distances than existing AC lines can. The new DC lines would even be cheaper to build, and require less surface area than existing AC lines do. This way, large solar farms in remote locations could provide power for a national grid.

<span style="display: block; font-family: 'Palatino Linotype', 'Book Antiqua', Palatino, serif; text-align: left;">[]

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<span style="display: block; font-size: 140%; font-family: Tahoma, Geneva, sans-serif; text-align: center;">**IV. Use Of Solar Power Today** <span style="font-family: 'Palatino Linotype', 'Book Antiqua', Palatino, serif;"> - Over 10,000 homes in the United States are powered 100% by solar energy

- 200,000 homes in the United States use at least some photovoltaic technology

- #1 current home use: for heating over 300,000 swimming pools in the United States alone

- Used to heat water, accounting for 1/4 of the energy used in the household [|www.solarpowertoday.net]

[]
 * -** On Earth Day 2009, WalMart announced that within the next 18 months, it will double its solar power initiative, **cutting 22,500 metric tons of CO2 emissions per year.**

<span style="display: block; font-size: 150%; font-family: Tahoma, Geneva, sans-serif; text-align: center;">**V. Solar Power as a Solution to Climate Change**

<span style="display: block; font-family: 'Palatino Linotype', 'Book Antiqua', Palatino, serif; text-align: left;">-Solar power will be a reliable sorce for the forseeable future

-Sunlight would meet our energy demand thousands fold.

-CO2 emissions will be reduced by 92%, putting an end to global warming

- Forty minutes of collected sunlight has as much energy as is consumed globally in a year

- Greenhouse gas emissions would be reduced by 1.7 billion tons from power plants and 1.9 billion tons from gas vehicles (replaced by hybrid vehichles) in a year

- U.S carbon emissions would be reduced by 62% from 2005 levels

With the success of the 2050 Plan,

<span style="font-family: 'Palatino Linotype', 'Book Antiqua', Palatino, serif;"><span style="font-family: 'Palatino Linotype', 'Book Antiqua', Palatino, serif;"><span style="font-family: 'Palatino Linotype', 'Book Antiqua', Palatino, serif;">- S<span style="font-family: Frutiger-BoldCn; mso-bidi-font-family: Frutiger-BoldCn; mso-bidi-font-weight: bold;"><span style="font-family: 'Palatino Linotype', 'Book Antiqua', Palatino, serif;">olar power could put an end dependency of the U.S on foreign countries for oil

- By 2050 switching c<span style="font-family: 'Palatino Linotype', 'Book Antiqua', Palatino, serif;">oal, oil, natural gas and nuclear power plants to solar power plants could supply **69% of the electricity** and **35% of total energy** in the world <span style="font-family: 'Arial', 'sans-serif';"><span style="font-family: 'Palatino Linotype', 'Book Antiqua', Palatino, serif;">[]

-Reliance on solar power could potentially increase job oportunities and the current state of the economy []

<span style="font-family: 'Palatino Linotype', 'Book Antiqua', Palatino, serif;">**The technology necessary for switching over to solar power is all ready, however:**
 * <span style="display: block; font-size: 140%; font-family: Tahoma, Geneva, sans-serif; text-align: center;">VI. Potential Technological Improvements for Solar Power **

- There is a lack of awareness of the opportunity solar power has to offer. The word must be spread!

- Optimum mass manufacturing must be utilized to make solar energy more affordable

- Preparations are under way to make electric/hybrid vehicles rely on solar power, which would further cut the current necessary fossil fuel use

-Wind, biomass, and geothermal sources must be further developed as well, so that by 2100 renewable energies would provide 100% of the electricity and 90% of the energy of the nation

- Modules could and should be made more efficient, a process which is already in progress

- Currently, $420 billion between 2011 and 2050 would be needed in subsidies to make solar power resources cost competitive. However, solar energy could be sold to consumers for the same price, 5 cents per kilowatt-hour, as current energy sources.

- 250,000 square miles of Southwest land would need to be used for solar power plants, where 4,500 British thermal units of solar power would be received annually. 2.5 % of this energy would be the equivalent of the electricity used in the United States in 2006.

[]

<span style="display: block; font-size: 160%; font-family: Tahoma, Geneva, sans-serif; text-align: center;">**Works Cited** <span style="display: block; font-family: 'Palatino Linotype', 'Book Antiqua', Palatino, serif; text-align: left;"> <span style="font-family: 'Palatino Linotype', 'Book Antiqua', Palatino, serif;"> Davidson, Paul. "Walmart to Double Amount of Solar Energy Use." //USA Today//. 22 Apr 2009. Gannett Co. Inc. 14 May 2009 <http://www.solarplan.org/Research/Z-M-F_A%20Solar%20Grand%20Plan_Scientific%20American_January%202008.pdf >.

"How Solar Energy Works | Union of Concerned Scientists." __Homepage | Union of Concerned Scientists__. 4 May 2004. Union of Concerned Scientists. 14 May 2009 <http://www.ucsusa.org/clean_energy/technology_and_impacts/energy_technologies/how-solar-

"Grid-connected solar electric systems." __Welcome to Wisconsin; Focus on Energy__. July 2005. Wisconsin Focus on Energy. 14 May 2009 <http://www.focusonenergy.com/files/Document_Management_System/Renewables/gridconnectedsolarelectricsystem

"Passive Solar Heating: An Energy Factsheet." __Cooperative Extension Service__. Nov. 2006. University of Alaska Fairbanks. 14 May 2009 <http://www.uaf.edu/coop-ext/publications/freepubs/EEM-01258.pdf>.

"Pros and Cons of Solar Energy." Apr. 2008. Clean Energy Ideas. 14 May 2009 <http://www.clean-energy-ideas.com/articles/pros_and_cons_of_solar_energy.html>.

"Solar Energy / How Solar Power Systems Work (environmental issue)." __Clean Funny Cartoons / Environmental Issues ... on Grinning Planet__. 4 May 2004. Grinning Planet. 14 May 2009 <http://www.grinningplanet.com/2004/05-04/solar-energy-power-systems-article.htm>.

Thomas, David. "American Solar Activity Program." //American Solar Activity Program//. 2008. American Solar Activity Organization. 14 May 2009 <http://www.solarplan.org/>.

"What is Solar Power?." //Solar Power Today//. 2009. 14 May 2009 <http://www.solarpowertoday.net>.

<span style="display: block; font-family: 'Palatino Linotype', 'Book Antiqua', Palatino, serif; text-align: left;">Zweibel, Ken, James Mason, and Vasilis Fthenakis. "Solar Grand Plan." __American Solar Action Plan__. Jan. 2008. Scientific American. 14 May 2009 [].