Farnham.+Fall+2010

= Solar Energy =



The Problem

Since fossil fuels where discovered, they have been the main source of energy for the world. Fossil fuels, such as coal and gasoline, make up 85 percent of the the world energy. The problem is that if we continue to burn through the fossil fuels at this rate we will eventually use up all the fossile fuels on the planet. The United States burns over 300 million gallons of gasoline a day and thats just the United States alone. The heavy use of the fossil fuels are also causing problems with the enviroment. Burning of these fossil fuels is considered to be the biggest contributing factor to the release of greenhouse gases into the atmosphere. It is said that energy providers are the largest source of atmospheric pollution today. There are many types of harmful outcomes which result from using fossil fuels to make energy. Some of these include air pollution, water pollution, formation of solid waste, and human illness. Not only is this effecting use physically it is also effecting us financially. Because there is a decline in the supply of fossil fuels there is a higher demand for these it. The high demand causes the prices of the fossil fuels to rise. The price of gasoline has more than tripled over the past thiry years and it is only going to keep increasing. So the real problem is that we doe not have any other reliable sources of enery that has taken the place of fossil fuels. Currently people have found many other ways that can provide alternate energy such as solar power, wind power, nuclear power, bio desiel and other forms of alternate fuels.

Solar Energy Intro

The sun has been used as a means of energy since the beginning of human civilization. The suns heat is used to warm and dry clothes. Its light is used to grow food and plants. It would only be a matter of time before a means was created that could harness the suns energy. In 1860 Auguste Mouchout became the first man to invent a machine that ran off solar power. The device was designed to use the suns energy and turn it into mechanical steam energy which was used to drive a steam engine. He used that steam engine to power a refrigeration system used to make ice (instead of melting it.) Almost 100 years later in 1956 the first solar cell was made available to the public for a payment of $300 dollars per watt. After the 1973 oil embargo, there was an increased interest in solar energy. Faced with a possibility of scarce oil resources, the United States government provided $400 million per year for solar energy research. Compared to other forms of energy like coal, oil, and nuclear, solar energy offers a clean renewable form of energy that will not harm the environment.

Benefits of Solar Energy

Energy from the sun is renewable. The sun will not run out of energy. Solar energy will have no negative effects on the environment. Solar panels used in the generation of solar energy are very reliable. They do not consist of many moving parts which leads to easier maintanence. They also produce very little to no noise It is cheaper in the long run. The money that is spent on the system is easily made back in not having to buy the power from power companies. Also if there is an excess of electricity produce, it can be sold to other to help make a profit.

Types of Solar Energy Systems

**Passive Solar Energy** Passive solar energy is able to use the suns energy without the use of mechanical devices. This will help cut down on the cost of heating and lighting to a home or building. Passive energy can be used to heat, cool, and light structures. It used buildings walls, floors, roofs, windows, exterior building elements and landscaping to control heat generated by sun. Lighting works by using the overall light of the surrounding sky and not just the daylight. This will cut down on cost of lighting and heat generated by the light bulbs. Heating works by passive solar heating when sunlight strikes an object and that object absorbs the heat. It can occur in a building effectively if windows are oriented correctly. The best window orientation is when the window is facing due south or at least 30 degrees from it. Once heat is inside structure methods such as installing high performance windows, making structure air tight from insulation, or insulated frames can help reduce heat loss by 50 to 75 percent


 * Active Solar Energy **

Active solar uses electrical or mechanical equipment such as pumps and fans, to increase the usable heat in a system. Active solar energy has three main components, collection, storage, and distribution. <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">Solar energy is collected using solar collectors. The most common collector that is used is the flat plate collector which is basically a glass covered insulated box. Inside the box there are black absorber plates which absorb the solar energy and convert it into heat. The heat energy is then transferred to a fluid which flows through the collector. The fluid can be either a liquid or air. This determines if the system is air based or liquid based. <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">Energy storage can be done in liquid base with water tanks or thermal mass which will store the heat in the liquid. In air-based systems, solar energy storage can be done with rock bins that hold in the heated air. <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">The Distribution of liquid-based systems will use pumps, radiant slabs, central forced air, or hot-water baseboards for distribution. Air-based systems will use fans and ducts to move the heated air.

<span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">**Solar Thermal Energy**

<span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%; margin: 0in 0in 10pt;">Solar thermal energy is the process of turning the suns solar energy into thermal energy used to heat a building. The solar energy is collected by the solar energy collectors. Solar energy is converted into heat by the greenhouse effect. The greenhouse effect works when // solar energy // passes through a layer of glazed glass where it is absorbed by the underlying material. The solar energy excites the molecules in the underlying material resulting in heat. The glazing of the glass prevents the heat from escaping, thereby effectively capturing the heat. <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;">The heat is then transferred to a heat transfer fluid which is typically made up of a <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;">glycol and water mixture to prevent freezing. The heat-transfer fluid is then pumped into a heat exchanger located inside the water storage tank where it heats the water. After the heat transfer fluid releases its heat it is circulated back to the solar energy collector to be reheated. <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">Photovoltaic Solar Power

<span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;"> <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">**Photovoltaic Solar Energy**

<span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%; margin: 0in 0in 10pt;">Photovoltaic solar energy is when solar energy is converted to electricity used to power a house or building.The electricity is generated from the solar power by solar cells. A solar cell converts sunlight directly into solar power electricity using a process known as the photovoltaic effect. Solar cells are made of materials called semiconductors. A semiconductor has the properties of an insulator, but when exposed to light or heat is capable of conducting electricity. The silicon used for the semiconductor needs to be treated by a process known as "doping" in order for it to generate electricity. The process of doping mixes an additional chemical element with the silicon to create either a positively charged or negatively charged layer of silicon. A solar power cell consists of two layers of this treated silicon. The bottom layer is positively charged (P-type) and the top layer is negatively charged (N-type). The two layers form an electric field between them which only allows the electrons to flow from the P-type silicon to the N-type silicon. When the solar power cell is part of an external circuit, this will allow it to generate solar electricity when light strikes the top silicon surface. There are three different types of photovoltaic cells, monocrystalline photovoltaic cells, polycrystalline photovoltaic, and amorphous silicon.

<span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%; margin: 0in 0in 10pt;"> <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%; margin: 0in 0in 10pt;">**Monocrystalline cells** - these solar cells are made by slicing thin wafers from a single long silicon crystal rod. They have the highest efficiency of 15%-18% but are also the most expensive.

<span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%; margin: 0in 0in 10pt;"> <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%; margin: 0in 0in 10pt;">**Polycrystalline cells** - are made from more than one silicon crystal. They are formed when molten silicon is poured into a mold and cooled to form an ingot. The ingot is then cut into smaller sections, each of which is then sliced into thin wafers. These cells have an efficiency of 12%-14% but are cheaper than the monocrystalline cells.

<span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%; margin: 0in 0in 10pt;">**Amorphous Silicon cells** – these are the oldest of the solar cells and are only 5%-6% efficient. They are made of silicon alloy that is deposited directly onto the backing material, usually either glass or metal.

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<span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%; margin: 0in 0in 10pt;">Voltage is generated when a P-type semiconductor and an N-type semiconductor. The P-type will make up the bottom layer of the solar cell and the N-type will make up the top layer. The two layers form an electric field between them which only allows electrons to flow from the P-type semiconductor to the N-type semiconductor.

<span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%; margin: 0in 0in 10pt;">Current is generated by creating a circuit between the P-type and the N-type. When light hits the solar cell current will flow from the N-type layer to the source and then to the P-type layer. This is how to get electricity from solar power.

<span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">**Solar Water Purification**

<span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">In solar power water purification systems the ultraviolet rays of the sun are used to kill harmful bacteria and germs that can be found in drinking water. <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">Heat from the sun passes through special panels that absorb the heat. The heat is then transfered to a container of water. The heat heats up the water killing the harmful bacteria allowing for safe drinking water. <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">Solar water purification systems are used all around the work to help places that have unsafe drinking water. Portable systems have been invented that can fit in a briefcase. Solar water purification is also used by emergency agency that go to the aid of people that have gone through a natural disaster. For instance they where used just recently in the Hati earthquake to help provide clean water the people of Hati whose water was contaminated.

<span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">Work Cited <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">[] <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">[] <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">[] <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">[|http://www.solar-energy-at-home.com] <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">[] <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">[|http://www.solar-is-future.com] <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">[] <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">[] <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">[] <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">[]