Barria.Fograshy.Fall.2009.energywiki

=Coal=

Coal is a fossil fuel. It is derived from plant material that was buried millions of years ago in a four step process: Lush vegetation grew in warm swampy areas that covered much of the United States (and the world) about 300 million years ago. The plants and trees absorbed the rays of the sun - used in photosynthesis - which was stored in the leaves and tissues. As the vegetation died, it fell into the swamps. As the amount of material accumulated in the presence of the water, it began to form a spongy, brown material which we know as peat or peat moss. Over time, geologic forces buried the peat bogs - sometimes hundreds of feet deep - where they were compacted by the pressure of the soil and rock on top of them. Coal was gradually formed from the buried peat. The greater the pressure under which the coal was formed, the harder the coal that was produced. There are four major types of coal. From the softest to the hardest they are: Lignite coal - The softest of the four types of coal. It is a brownish black in color, very crumbly and primarily used for the generation of electricity. Because of its color, it is often referred to as "brown coal." Lignite is the result of millions of tons of plants and trees that decayed in a swampy atmosphere about 50-70 million years ago. The material on top of the lignite deposits in North Dakota and Montana - called overburden - was deposited by runoff from the west as the Rocky Mountains formed. The heating content of lignite is approximately 4,000-8,000 Btu's per pound. The carbon content of lignite is 25%-35% and it has a very high water content - about 35 percent. For more information about lignite, visit the Lignite Energy Council website.  Sub-bituminous coal - This is a medium soft coal that contains much less moisture than lignite and is not nearly as crumbly. Like lignite, its primary use is in the generation of electricity. The carbon content of sub-bituminous coal runs from 35%-45% and its heat value generally ranges from 8,000-13,000 Btu's per pound. It is produced primarily along the east side of the Rocky Mountains from eastern Montana to the four corners area where the states of Arizona, Colorado, New Mexico and Utah join. Bituminous coal contains even less moisture than the sub-bituminous type. The carbon content of bituminous coal is generally from 45%-85%. Its heat value ranges from 10,500-15,000 Btu's per pound - greater than either lignite or the sub-bituminous types. In addition to being used for electrical generation, it is also used in making coke or coking coal, an essential ingredient in making steel. Most production of bituminous coal is from the east coast to the Midwest states and in Alaska. Anthracite coal - discovered in 1769 - is the hardest of the four types. It averages 85%-95% carbon content and has the highest heating value of the four types of coal. It is not uncommon to find anthracite that produces well in excess of 15,000 Btu's per pound. To put that in perspective, that is roughly one and one-half times as much heat as the same volume of oil and four times as much as seasoned hard-maple firewood. Anthracite makes excellent home heating fuel because it burns cleanly, does not produce volatile gases and does not deteriorate. It can be stored on the ground for long periods of time without creating environmental problems. Anthracite is mined in only a few areas, mostly in the eastern Pennsylvania region. It is used extensively in municipal water purification and treatment plants and for home heating.

When coal is used for electricity generation, it is usually pulverized and then combusted (burned) in a furnace with a boiler. The furnace heat converts boiler water to steam, which is then used to spin turbines which turn generators and create electricity. The thermodynamic efficiency of this process has been improved over time. "Standard" steam turbines have topped out with some of the most advanced reaching about 35% thermodynamic efficiency for the entire process, although newer combined cycle plants can reach efficiencies as high as 58%. Increasing the combustion temperature can boost this efficiency even further. Old coal power plants, especially "grandfathered" plants, are significantly less efficient and produce higher levels of waste heat. About 40% of the world's electricity comes from coal,[14 and approximately 49% of the United States electricity comes from coal. 6determine the amount of CO2 it produces or inhibits (THIS REQUIRES A STOICHIOMETRY EQUATION!) [[image:coal-fired-plant-jj-001.jpg]] Commercial coal has a carbon content of at least 70%. Coal with a heating value of 6.67 kWh per kilogram as quoted above has a carbon content of roughly 80%, which is

(0.8kg)/(12 x kg/kmol) = (2/30kmol)

 , where 1 mol equals to NA (//Avogadro Number//) atoms. Carbon combines with oxygen in the atmosphere during combustion, producing carbon dioxide, with an atomic weight of (12 + 16 × 2 = 44 kg/kmol). The CO2 released to air for each kilogram of incinerated coal is therefore

(2/30 kmol x (44kg/kmol))= (88/30 kg) a proximally 2.93kg

 . This can be used to calculate an emission factor for CO2 from the use of coal power. Since the useful energy output of coal is about 30% of the 6.67 kWh/kg(coal), the burning of 1 kg of coal produces about 2 kWh of electrical energy. Since 1 kg coal emits 2.93 kg CO2, the direct CO2 emissions from coal power are 1.47 kg/kWh, or about 0.407 kg/MJ. The U.S. Energy Information Agency's 1999 report on CO2 emissions for energy generation, quotes a lower emission factor of 0.963 kg CO2/kWh for coal power. The same source gives factor for oil power in the U.S. of 0.881 kg CO2/kWh, while natural gas has 0.569 kg CO2/kWh. Estimates for specific emission from nuclear power, hydro, and wind energy vary, but are about 100 times lower The energy density of coal, i.e. its heating value, is roughly 24 megajoules per kilogram. The energy density of coal can also be expressed in kilowatt-hours for some unit of mass, the units that electricity is most commonly sold in, to estimate how much coal is required to power electrical appliances. One kilowatt-hour is 3.6 MJ, so the energy density of coal is 6.67 kW·h/kg. The typical thermodynamic efficiency of coal power plants is about 30%, so of the 6.67 kW·h of energy per kilogram of coal, 30% of that—2.0 kW·h/kg—can successfully be turned into electricity; the rest is waste heat. So coal power plants obtain approximately 2.0 kW·h per kilogram of burned coal. As an example, running one 100 watt lightbulb for one year requires 876 kW·h (100 W × 24 h/day × 365 {days in a year} = 876000 W·h = 876 kW·h). Converting this power usage into physical coal consumption:  (876kW x h)/(2.0kW x h/kg)= 438 kg of coal = 966 pounds of coal It takes 438 kg (966 lb) of coal to power a computer for one full year. One should also take into account transmission and distribution losses caused by resistance and heating in the power lines, which is in the order of 5–10%, depending on distance from the power station and other factors.

 ** The Advantages of Coal ** Coal is one of the most abundant sources of energy, more so than oil and natural gas Coal is inexpensive when compared to other fossil fuels (or alternative energy sources) Coal is versatile enough to be used for recreational activities such as BBQ’s or simply for home fires Burning coal can produce useful by-products that can be used for other industries or products Electricity produced from coal is reliable Coal can be safely stored and can be drawn upon to create energy in time of emergency Coal based power is not dependent on weather which cannot be said for alternative forms of renewable energy such as wind or solar power Transporting coal does not require the upkeep of high-pressure pipelines and there is no requirement for extra security when transporting coal Using coal reduces the dependence on using oil, which is often found in nations where there is unstable political regimes ** The Disadvantages of Coal ** <span style="display: block; font-family: 'Times New Roman'; font-size: 12pt; msofareastfontfamily: 'Times New Roman'; text-align: left;">Burning coal emits harmful waste such as carbon dioxide, sulphur dioxide, nitrogen oxides, sulphuric acids, arsenic and ash. It also emits twice as much carbon dioxide when compared with natural gas to produce the same level of heat, which increased the levels of harmful greenhouse gases emitted into the earth’s atmosphere. Carbon dioxide emissions from the burning of fossil fuels now account for about 65 per cent of the extra carbon dioxide in our atmosphere. The burning of coal by large-scale factories to power industry has led to acid rain in some regions. Coal can be cleaned and/or turned into a liquid of gas but this technology has yet to be fully developed and adds to the expense of creating fuel via coal. Coal mining can scar the landscape and the equipment used for mining is large and noisy which may affect local wildlife. Transporting coal can be problematic because it requires an extensive transportation system and can also cause additional pollution in the form of emissions from transportation vehicles such as lorries, etc. There are limited stocks of coal remaining – they will be entirely depleted this millennium if we continue to burn coal in the future at the same rate we are today coal can be considered as a non-renewable energy source. The mining industry can cause health difficulties for miners and fatalities due to the potentially dangerous nature of the work. Burning dirty coal can create significant pollution problems.

**Background Information-- How is coal used?** Coal has four major markets: electric utilities, industrial/retail users, the steel industry and exports. Electric utilities use more than 86 percent of the coal produced in the United States. Upon close examination, it is clear that price has been a major deciding factor in coal's increased use. More than 57 percent of the electricity generated in the United States comes from coal. In an electric power plant, coal, like oil and natural gas, is burned to produce heat. The heat is used to change water into steam. The steam then turns the blades of a turbine, spinning the generator, producing electricity. Before the coal is burned it is crushed and pulverized to the consistency of face powder. Coal's second largest market is industrial and retail users. Among the industries using coal, the largest consumers are chemical manufacturers, users of stone, clay and glass, paper mills, primary metal industries and the food industry. Industry uses coal as a chemical feedstock to make dyes, insecticides, fertilizers, explosives, synthetic fibers, food preservatives, ammonia, synthetic rubber, fingernail polish, medicines, etc. The third largest market is the iron and steel industry, where coal is used to made into coke. Coke is derived from bituminous coal through heating in airtight ovens. The lack of air prevents the coal from burning and converts some of the solids to gases leaving coke. The fourth market segment is exports. The top five foreign markets are Canada, Japan, Italy, Netherlands and Brazil. U.S. coal distributed to foreign countries in 1988 totaled 95 million short tons (76 million to overseas destinations and 19 million to Canada). Major reasons for the decline in United State's coal exports from the all-time high of 112.5 million tons in 1981 are stiff competition in the international marketplace and worldwide economic conditions.

Although coal’s contribution to world primary energy consumption has declined markedly over recent decades, of the three main fossil fuels (coal, gas and oil) it still maintains a position, just behind oil and at parity with gas, of around 25% of the total. In North America (Canada, USA and Mexico) coal is a prime source of energy; half the electricity US consumers use is generated by coal. In Poland it contributes 95% of energy production. China and India use nearly half of the world’s coal; the expectation is (at least until recent months) that these two countries will take half as much again over the next two decades. It is indisputable that coal will remain abundant long after natural gas and oil have become scarce. Indeed, while the exploitable lifetimes of currently known natural gas and oil reserves can be measured in decades, those of coal are in centuries.

Coal-fired units produce electricity by burning coal in a boiler to heat water to produce steam. The steam, at tremendous pressure, flows into a turbine, which spins a generator to produce electricity. The steam is cooled, condensed back into water, and returned to the boiler to start the process over. For example, the coal-fired boilers at TVA’s Kingston Fossil Plant near Knoxville, Tennessee, heat water to about 1,000 degrees Fahrenheit (540 degrees Celsius) to create steam. The steam is piped to the turbines at pressures of more than 1,800 pounds per square inch (130 kilograms per square centimeter). The turbines are connected to the generators and spin them at 3600 revolutions per minute to make alternating current electricity at 20,000 volts. River water is pumped through tubes in a condenser to cool and condense the steam coming out of the turbines. The Kingston plant generates about 10 billion kilowatt-hours a year, or enough electricity to supply 700,000 homes. To meet this demand, Kingston burns about 14,000 tons of coal a day, an amount that would fill 140 railroad cars. In the United States, coal has been used for decades, the main natural resource for the production of electrical energy. As stated in the paragraphs above, coal has a lot of advantages and disadvantages. In today’s world we are worried about how coal is destroying the Earths ozone by producing massive amounts of green house gasses that are being released into the atmosphere. There are several other recourses that we could use to make electrical energy without releasing green house gasses into the atmosphere. These new recourses of energy are not as efficient as coal, but in near future they will be just as good as coal. Some examples of new renewable recourses are wind turbines, solar panels, hydroelectric, and biodiesels shown as below. Wind is a form of solar energy. Winds are caused by the uneven heating of the atmosphere by the sun, the irregularities of the earth's surface, and rotation of the earth. Wind flow patterns are modified by the earth's terrain, bodies of water, and vegetation. Humans use this wind flow, or motion energy, for many purposes: sailing, flying a kite, and even generating electricity. The terms wind energy or wind power describe the process by which the wind is used to generate mechanical power or electricity. Wind turbines convert the kinetic energy in the wind into mechanical power. This mechanical power can be used for specific tasks (such as grinding grain or pumping water) or a generator can convert this mechanical power into electricity. So how do wind turbines make electricity? Simply stated, a wind turbine works the opposite of a fan. Instead of using electricity to make wind, like a fan, wind turbines use wind to make electricity. The wind turns the blades, which spin a shaft, which connects to a generator and makes electricity. Take a look inside a wind turbine to see the various parts. View the wind turbine animation to see how a wind turbine works. This aerial view of a wind power plant shows how a group of wind turbines can make electricity for the utility grid. The electricity is sent through transmission and distribution lines to homes, businesses, schools, and so on.

Advantages of Wind Energy
1. Wind energy is nothing new. It's a well-known method of using kinetic energy (wind) to produce mechanical energy and has been around for thousands of years since the Persians and later Romans were using windmills to draw water and grind grain. 2. Wind energy is a renewable resource meaning that the Earth will continue to provide this and it's up to people to use it and harness it to best advantage. 3. Wind energy is cheap and is largely dependent upon the manufacturing, distribution and building of turbines for the initial costs. The U. S. DOE estimates wind energy can be produced for as low as 4 to 6 cents per kilowatt hour. 4. Wind energy replaces electricity from coal-fired power plants and thus reduces greenhouse gases that produce global warming. 5. Wind energy is available worldwide and though some countries may be "windier" than others, the product is not like oil that has to be transported on tankers to the far regions of the earth. 6. Wind farms on average have a smaller footprint than coal-fired power plants and even though some people don't like the appearance to wind turbines, they object more to having a coal-fired power plant in their backyards. 7. Wind turbines can also share space with other interests such as the farming of crops or cattle. 8. Wind energy is available in many remote locations where the electrical grid doesn't reach. Farms, mountain areas and third world nations can take advantage of wind energy. 9. Wind energy is creating jobs that are far outpacing other sectors of the economy. 10. Wind energy doesn't have to be used solely on a commercial scale as residential wind turbines are now gaining ground in many communities.

Disadvantages of Wind Energy
1. Wind is an intermittent source of energy and when connected to the electrical grid provides an uneven power supply. Some places such as the Gulf Coast region of the U. S. have too strong of winds during hurricane season that may damage wind turbines. 2. Some people object to the visual site of wind turbines disrupting the local landscape. 3. The wind doesn't blow well at all locations on Earth. Wind maps are needed to identify the optimal locations. 4. The initial cost of a wind turbine can be substantial, though government subsidies, tax breaks and long-term costs may alleviate much of this. 5. Transmission of electricity from remote wind farms can be a major hurdle for utilities since many time turbines are not located around urban centers. 6. The storage of excess energy from wind turbines in the form of batteries, hydrogen or other forms still needs research and development to become commercially viable. 7. Some environmentalists have complained that large utility wind turbines have a detrimental effect to migratory bird flight paths. 8. Depending upon the type of wind turbine, noise pollution may be a factor for those living or working nearby. 9. Even though costs of wind energy have come down dramatically it still has to compete with the ultra low price for fossil fuel power plants. 10. Utility scale wind turbines can interfere with television signals of those living within a mile or two of the installation, which can be frustrating for homeowners.

**Background Information-- How is coal used?** Coal has four major markets: electric utilities, industrial/retail users, the steel industry and exports. Electric utilities use more than 86 percent of the coal produced in the United States. Upon close examination, it is clear that price has been a major deciding factor in coal's increased use. More than 57 percent of the electricity generated in the United States comes from coal. In an electric power plant, coal, like oil and natural gas, is burned to produce heat. The heat is used to change water into steam. The steam then turns the blades of a turbine, spinning the generator, producing electricity. Before the coal is burned it is crushed and pulverized to the consistency of face powder. Coal's second largest market is industrial and retail users. Among the industries using coal, the largest consumers are chemical manufacturers, users of stone, clay and glass, paper mills, primary metal industries and the food industry. Industry uses coal as a chemical feedstock to make dyes, insecticides, fertilizers, explosives, synthetic fibers, food preservatives, ammonia, synthetic rubber, fingernail polish, medicines, etc. The third largest market is the iron and steel industry, where coal is used to made into coke. Coke is derived from bituminous coal through heating in airtight ovens. The lack of air prevents the coal from burning and converts some of the solids to gases leaving coke. The fourth market segment is exports. The top five foreign markets are Canada, Japan, Italy, Netherlands and Brazil. U.S. coal distributed to foreign countries in 1988 totaled 95 million short tons (76 million to overseas destinations and 19 million to Canada). Major reasons for the decline in United State's coal exports from the all-time high of 112.5 million tons in 1981 are stiff competition in the international marketplace and worldwide economic conditions. Although coal’s contribution to world primary energy consumption has declined markedly over recent decades, of the three main fossil fuels (coal, gas and oil) it still maintains a position, just behind oil and at parity with gas, of around 25% of the total. In North America (Canada, USA and Mexico) coal is a prime source of energy; half the electricity US consumers use is generated by coal. In Poland it contributes 95% of energy production. China and India use nearly half of the world’s coal; the expectation is (at least until recent months) that these two countries will take half as much again over the next two decades. It is indisputable that coal will remain abundant long after natural gas and oil have become scarce. Indeed, while the exploitable lifetimes of currently known natural gas and oil reserves can be measured in decades, those of coal are in centuries.

Coal-fired units produce electricity by burning coal in a boiler to heat water to produce steam. The steam, at tremendous pressure, flows into a turbine, which spins a generator to produce electricity. The steam is cooled, condensed back into water, and returned to the boiler to start the process over. For example, the coal-fired boilers at TVA’s Kingston Fossil Plant near Knoxville, Tennessee, heat water to about 1,000 degrees Fahrenheit (540 degrees Celsius) to create steam. The steam is piped to the turbines at pressures of more than 1,800 pounds per square inch (130 kilograms per square centimeter). The turbines are connected to the generators and spin them at 3600 revolutions per minute to make alternating current electricity at 20,000 volts. River water is pumped through tubes in a condenser to cool and condense the steam coming out of the turbines. The Kingston plant generates about 10 billion kilowatt-hours a year, or enough electricity to supply 700,000 homes. To meet this demand, Kingston burns about 14,000 tons of coal a day, an amount that would fill 140 railroad cars. In the United States, coal has been used for decades, the main natural resource for the production of electrical energy. As stated in the paragraphs above, coal has a lot of advantages and disadvantages. In today’s world we are worried about how coal is destroying the Earths ozone by producing massive amounts of green house gasses that are being released into the atmosphere. There are several other recourses that we could use to make electrical energy without releasing green house gasses into the atmosphere. These new recourses of energy are not as efficient as coal, but in near future they will be just as good as coal. Some examples of new renewable recourses are wind turbines, solar panels, hydroelectric, and biodiesels shown as below.

Wind is a form of solar energy. Winds are caused by the uneven heating of the atmosphere by the sun, the irregularities of the earth's surface, and rotation of the earth. Wind flow patterns are modified by the earth's terrain, bodies of water, and vegetation. Humans use this wind flow, or motion energy, for many purposes: sailing, flying a kite, and even generating electricity. The terms wind energy or wind power describe the process by which the wind is used to generate mechanical power or electricity. Wind turbines convert the kinetic energy in the wind into mechanical power. This mechanical power can be used for specific tasks (such as grinding grain or pumping water) or a generator can convert this mechanical power into electricity. So how do wind turbines make electricity? Simply stated, a wind turbine works the opposite of a fan. Instead of using electricity to make wind, like a fan, wind turbines use wind to make electricity. The wind turns the blades, which spin a shaft, which connects to a generator and makes electricity. Take a look inside a wind turbine to see the various parts. View the wind turbine animation to see how a wind turbine works. This aerial view of a wind power plant shows how a group of wind turbines can make electricity for the utility grid. The electricity is sent through transmission and distribution lines to homes, businesses, schools, and so on.

Advantages of Wind Energy
1. Wind energy is nothing new. It's a well-known method of using kinetic energy (wind) to produce mechanical energy and has been around for thousands of years since the Persians and later Romans were using windmills to draw water and grind grain. 2. Wind energy is a renewable resource meaning that the Earth will continue to provide this and it's up to people to use it and harness it to best advantage. 3. Wind energy is cheap and is largely dependent upon the manufacturing, distribution and building of turbines for the initial costs. The U. S. DOE estimates wind energy can be produced for as low as 4 to 6 cents per kilowatt hour. 4. Wind energy replaces electricity from coal-fired power plants and thus reduces greenhouse gases that produce global warming. 5. Wind energy is available worldwide and though some countries may be "windier" than others, the product is not like oil that has to be transported on tankers to the far regions of the earth. 6. Wind farms on average have a smaller footprint than coal-fired power plants and even though some people don't like the appearance to wind turbines, they object more to having a coal-fired power plant in their backyards. 7. Wind turbines can also share space with other interests such as the farming of crops or cattle. 8. Wind energy is available in many remote locations where the electrical grid doesn't reach. Farms, mountain areas and third world nations can take advantage of wind energy. 9. Wind energy is creating jobs that are far outpacing other sectors of the economy. 10. Wind energy doesn't have to be used solely on a commercial scale as residential wind turbines are now gaining ground in many communities.

Disadvantages of Wind Energy
1. Wind is an intermittent source of energy and when connected to the electrical grid provides an uneven power supply. Some places such as the Gulf Coast region of the U. S. have too strong of winds during hurricane season that may damage wind turbines. 2. Some people object to the visual site of wind turbines disrupting the local landscape. 3. The wind doesn't blow well at all locations on Earth. Wind maps are needed to identify the optimal locations. 4. The initial cost of a wind turbine can be substantial, though government subsidies, tax breaks and long-term costs may alleviate much of this. 5. Transmission of electricity from remote wind farms can be a major hurdle for utilities since many time turbines are not located around urban centers. 6. The storage of excess energy from wind turbines in the form of batteries, hydrogen or other forms still needs research and development to become commercially viable. 7. Some environmentalists have complained that large utility wind turbines have a detrimental effect to migratory bird flight paths. 8. Depending upon the type of wind turbine, noise pollution may be a factor for those living or working nearby. 9. Even though costs of wind energy have come down dramatically it still has to compete with the ultra low price for fossil fuel power plants. 10. Utility scale wind turbines can interfere with television signals of those living within a mile or two of the installation, which can be frustrating for homeowners. Solar powered electrical generation relies on heat engines and photovoltaics. Solar energy's uses are limited only by human ingenuity. A partial list of solar applications includes space heating and cooling through solar architecture, potable water via distillation and disinfection, daylighting, solar hot water, solar cooking, and high temperature process heat for industrial purposes.
 * Solar energy **, radiant light and heat from the Sun, has been harnessed by humans since ancient times using a range of ever-evolving technologies. Solar radiation, along with secondary solar-powered resources such as wind and wave power, hydroelectricity and biomass, account for most of the available renewable energy on Earth. Only a minuscule fraction of the available solar energy is used.

Solar technologies are broadly characterized as either passive solar or active solar depending on the way they capture, convert and distribute solar energy. Active solar techniques include the use of photovoltaic panels and solar thermal collectors to harness the energy. Passive solar techniques include orienting a building to the Sun, selecting materials with favorable thermal mass or light dispersing properties, and designing spaces that naturally circulate air.

Darmstadt University of Technology in Germany won the 2007 Solar Decathlon in Washington, D.C. with this passive house designed specifically for the humid and hot subtropical climate. Sunlight has influenced building design since the beginning of architectural history. Advanced solar architecture and urban planning methods were first employed by the Greeks and Chinese, who oriented their buildings toward the south to provide light and warmth. The common features of passive solar architecture are orientation relative to the Sun, compact proportion (a low surface area to volume ratio), selective shading (overhangs) and thermal mass. When these features are tailored to the local climate and environment they can produce well-lit spaces that stay in a comfortable temperature range. Socrates' Megaron House is a classic example of passive solar design. The most recent approaches to solar design use computer modeling tying together solar lighting, heating and ventilation systems in an integrated solar design package. Active solar equipment such as pumps, fans and switchable windows can complement passive design and improve system performance. Urban heat islands (UHI) are metropolitan areas with higher temperatures than that of the surrounding environment. The higher temperatures are a result of increased absorption of the Solar light by urban materials such as asphalt and concrete, which have lower albedos and higher heat capacities than those in the natural environment. A straightforward method of counteracting the UHI effect is to paint buildings and roads white and plant trees. Using these methods, a hypothetical "cool communities" program in Los Angeles has projected that urban temperatures could be reduced by approximately 3 °C at an estimated cost of US$1 billion, giving estimated total annual benefits of US$530 million from reduced air-conditioning costs and healthcare savings.

Greenhouses like these in the Westland municipality of the Netherlands grow vegetables, fruits and flowers. Agriculture seeks to optimize the capture of solar energy in order to optimize the productivity of plants. Techniques such as timed planting cycles, tailored row orientation, staggered heights between rows and the mixing of plant varieties can improve crop yields. While sunlight is generally considered a plentiful resource, the exceptions highlight the importance of solar energy to agriculture. During the short growing seasons of the Little Ice Age, French and English farmers employed fruit walls to maximize the collection of solar energy. These walls acted as thermal masses and accelerated ripening by keeping plants warm. Early fruit walls were built perpendicular to the ground and facing south, but over time, sloping walls were developed to make better use of sunlight. In 1699, Nicolas Fatio de Duillier even suggested using a tracking mechanism which could pivot to follow the Sun. Applications of solar energy in agriculture aside from growing crops include pumping water, drying crops, brooding chicks and drying chicken manure. More recently the technology has been embraced by vinters, who use the energy generated by solar panels to power grape presses. Greenhouses convert solar light to heat, enabling year-round production and the growth (in enclosed environments) of specialty crops and other plants not naturally suited to the local climate. Primitive greenhouses were first used during Roman times to produce cucumbers year-round for the Roman emperor Tiberius. The first modern greenhouses were built in Europe in the 16th century to keep exotic plants brought back from explorations abroad. Greenhouses remain an important part of horticulture today, and plastic transparent materials have also been used to similar effect in polytunnels and row covers.

**__ Solar Energy Advantages __** ** 2. Environmentally friendly ** ** 3. Independent/ semi-independent ** ** 4. Low/ no maintenance **
 * 1. Saves you money **
 * After the initial investment has been recovered, the energy from the sun is practically FREE.
 * The recovery/ payback period for this investment can be very short depending on how much electricity your household uses.
 * Financial incentives are available form the government that will reduce your cost.
 * If your system produce more energy than you use, your utility company can buy it from you, building up a credit on your account! This is called net metering.
 * It will save you money on your electricity bill if you have one at all.
 * Solar energy does not require any fuel.
 * It's not affected by the supply and demand of fuel and is therefore not subjected to the ever-increasing price of gasoline.
 * The savings are immediate and for many years to come.
 * The use of solar energy indirectly reduces health costs.
 * Solar Energy is clean, renewable (unlike gas, oil and coal) and sustainable, helping to protect our environment.
 * It does not pollute our air by releasing carbon dioxide, nitrogen oxide, sulphur dioxide or mercury into the atmosphere like many traditional forms of electrical generations does.
 * Therefore Solar Energy does not contribute to global warming, acid rain or smog.
 * It actively contributes to the decrease of harmful green house gas emissions.
 * It's generated where it is needed.
 * By not using any fuel, Solar Energy does not contribute to the cost and problems of the recovery and transportation of fuel or the storage of radioactive waste.
 * Solar Energy can be utilized to offset utility-supplied energy consumption. It does not only reduce your electricity bill, but will also continue to supply your home/ business with electricity in the event of a power outage.
 * A Solar Energy system can operate entirely independent, not requiring a connection to a power or gas grid at all. Systems can therefore be installed in remote locations (like holiday log cabins), making it more practical and cost-effective than the supply of utility electricity to a new site.
 * The use of Solar Energy reduces our dependence on foreign and/or centralized sources of energy, influenced by natural disasters or international events and so contributes to a sustainable future.
 * Solar Energy supports local job and wealth creation, fuelling local economies.
 * Solar Energy systems are virtually maintenance free and will last for decades.
 * Once installed, there are no recurring costs.
 * They operate silently, have no moving parts, do not release offensive smells and do not require you to add any fuel.
 * More solar panels can easily be added in the future when your family's needs grow.

**__ Solar Energy Disadvantages __** <span style="color: #4f81bd; font-family: Times New Roman; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; msofareastfontfamily: 'Times New Roman';"> = Hydroelectric power: How it works = <span style="color: #4f81bd; font-family: Times New Roman; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; msofareastfontfamily: 'Times New Roman';">
 * The initial cost is the main disadvantage of installing a solar energy system, largely because of the high cost of the semi-conducting materials used in building one.
 * The cost of solar energy is also high compared to non-renewable utility-supplied electricity. As energy shortages are becoming more common, solar energy is becoming more price-competitive.
 * Solar panels require quite a large area for installation to achieve a good level of efficiency.
 * The efficiency of the system also relies on the location of the sun, although this problem can be overcome with the installation of certain components.
 * The production of solar energy is influenced by the presence of clouds or pollution in the air.
 * As far as solar powered cars go - their slower speed might not appeal to everyone caught up in today's rat race.

So just how do we get electricity from water? Actually, hydroelectric and coal-fired power plants produce electricity in a similar way. In both cases a power source is used to turn a propeller-like piece called a turbine, which then turns a metal shaft in an electric generator, which is the motor that produces electricity. A coal-fired power plant uses steam to turn the turbine blades; whereas a hydroelectric plant uses falling water to turn the turbine. The results are the same. Take a look at this diagram (courtesy of the Tennessee Valley Authority) of a hydroelectric power plant to see the details: The theory is to build a dam on a large river that has a large drop in elevation (there are not many hydroelectric plants in Kansas or Florida). The dam stores lots of water behind it in the reservoir. Near the bottom of the dam wall there is the water intake. Gravity causes it to fall through the penstock inside the dam. At the end of the penstock there is a turbine propeller, which is turned by the moving water. The shaft from the turbine goes up into the generator, which produces the power. Power lines are connected to the generator that carry electricity to your home and mine. The water continues past the propeller through the tailrace into the river past the dam. By the way, it is not a good idea to be playing in the water right below a dam when water is released! This diagram of a hydroelectric generator is courtesy of U.S. Army Corps of Engineers. As to how this generator works, the Corps of Engineers explains it this way: "A hydraulic turbine converts the energy of flowing water into mechanical energy. A hydroelectric generator converts this mechanical energy into electricity. The operation of a generator is based on the principles discovered by Faraday. He found that when a magnet is moved past a conductor, it causes electricity to flow. In a large generator, electromagnets are made by circulating direct current through loops of wire wound around stacks of magnetic steel laminations. These are called field poles, and are mounted on the perimeter of the rotor. The rotor is attached to the turbine shaft, and rotates at a fixed speed. When the rotor turns, it causes the field poles (the electromagnets) to move past the conductors mounted in the stator. This, in turn, causes electricity to flow and a voltage to develop at the generator output terminals."

<span style="color: black; font-family: Arial; font-size: 18pt; mso-fareast-font-family: 'Times New Roman';">Advantages and Disadvantages <span style="color: black; font-family: 'Times New Roman'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman';"> **<span style="color: black; font-family: 'Times New Roman'; font-size: 13.5pt; mso-fareast-font-family: 'Times New Roman';">Advantages **<span style="color: black; font-family: 'Times New Roman'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman';"> **<span style="color: black; font-family: 'Times New Roman'; font-size: 13.5pt; mso-fareast-font-family: 'Times New Roman';">Disadvantages **<span style="color: black; font-family: 'Times New Roman'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman';">
 * Inexhaustible fuel source
 * Minimal environmental impact
 * Viable source--relatively useful levels of energy production
 * Can be used throughout the world
 * Smaller models depend on availability of fast flowing streams or rivers
 * Run-of-the-River plants can impact the mobility of fish and other riverlife. NOTE: Building a fish ladder can lessen this negative aspect of hydroelectric power

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Biodiesel is a form of diesel fuel manufactured from vegetable oils, animal fats, or recycled restaurant greases. It is safe, biodegradable, and produces less air pollutants than petroleum-based diesel. Biodiesel can be used in its pure form (B100) or blended with petroleum diesel. Common blends include B2 (2% biodiesel), B5, and B20. B2 and B5 can be used safely in most diesel engines. However, most vehicle manufacturers do not recommend using blends greater than B5, and engine damage caused by higher blends is not covered by some manufacturer warranties. Check with your owner’s manual or vehicle manufacturer to determine the right blend for your vehicle. Broadly speaking, biofuel refers to any solid, liquid or gas fuel that has been derived from biomass. It can be produced from any carbon source that is easy to replenish - such as plants. One of the main challenges when producing biofuel is to develop energy that can be used specifically in liquid fuels for transportation. The most common strategies used to achieve this are: What are the different types of biofuel? There are many different biofuels available in the UK. One of the most common worldwide is E10 fuel, which is actually a mixture of 10% ethanol and 90% petroleum. This formula has been improved in recent years with the introduction of E15 fuel (15% ethanol, 85% petroleum); E20 fuel (20% ethanol, 80% petroleum); E85 fuel (85% ethanol, 15% petroleum); E95 fuel (95% ethanol, 15% petroleum) and E100 fuel which is ethanol with up to 4% water. In Europe, biodiesel is the most popular form of biofuel - it can be used in any diesel engine when mixed with mineral diesel. This is produced from oils and fats and is now readily available at many petrol stations. There are many other types of biofuel available including vegetable oil, which is used in many older diesel engines; butanol, which is seen as a replacement for petroleum; and biogas which is produced from biodegradable waste materials. This technology has been expanded with the introduction of 'second generation' biofuels - which use biomass to liquid technology. Examples include biohydrogen, biomethanol and mixed alcohols. Third generation biofuels are also known as algae fuels. They have many advantages including have a low input and a high yield level – they produce 30 times more energy per acre than land – and are also biodegradable. As a result, they are relatively harmless to the environment if spilled. Where are biofuels used? Biodiesel can, in theory, be used in all diesel engines. However, due to the parts attached to the diesel engine, some manufacturers do not approve engines running on 100% biodiesel. Volkswagen, SEAT, Audi and Skoda all approved their cars built from 1996-2004 running on 100% RME biodiesel - that is biodiesel made from rapeseed - on the condition that it meets specification EN14214. Generally speaking, it is recommended that you use a combination of biodiesel blended with regular diesel. Indeed at the majority of petrol stations, a 5% biodiesel mix is used. It is also worth bearing in mind that biodiesel made from waste cooking oil can freeze in the winter - and so no more than a 50% blend is recommended. Between 2000 and 2005 ethanol production doubled, and biodiesel production quadrupled, so biofuels are clearly on the rise. The British Government's Renewable Transport Fuel Obligation currently requires 2.5% of fuels sold at the pump to be biofuels. This will increase to 5% by 2010, while the EU has a target of 5.75% of all transport fuels to be from biological sources, also by 2010. What are the advantages of biofuels? The aim of all biofuels is to be carbon neutral. They reduce greenhouse gas emissions when compared to conventional transport fuels. In reality, biofuels are not carbon neutral simply because it requires energy to grow the crops and convert them into fuel. The amount of fuel used during this production (to power machinery, to transport crops, etc) does have a large impact on the overall savings achieved by biofuels. However, biofuels still prove to be substantially more environmentally friendly than their alternatives. In fact, according to a technique called Life Cycle Analysis (LCA) first generation biofuels can save up to 60% of carbon emissions compared to fossil fuels. Second generation biofuels offer carbon emission savings up to 80%. This was backed by a recent UK Government publication which stated biofuels can reduce emissions by 50-60%. Another advantage of biofuels is that they save drivers money. The UK Government in particular has introduced many incentives to drivers of 'green cars' based on emissions - with reduced taxation dependent on how environmentally friendly your vehicle is. With petrol prices on the rise, replacing petroleum with a renewable energy source should also offer significant savings at the pump in the long term, particularly when biofuels are more readily available. There are arguments too that biofuels are helping to tackle poverty around the world. For example, the Overseas Development Institute has pointed to wider economic growth and increased employment opportunities along with the positive effect on energy prices, as reasons to back biofuel production. This is debated due to the pressures it places on agricultural resources but biodiesel could be a long term solution as it uses simpler technology and lower transportation costs alongside increased labour. What are the disadvantages of biofuels? There are several concerns about biofuels - and particularly including. The production of non-sustainable biofuels has been criticised in reports by the UN, the IPCC and many other environmental and social groups. As a result many governments have switched their support towards sustainable biofuels, and alternatives such as hydrogen and compressed air. During 2008, the Roundtable of Sustainable Biofuels is developing principles for sustainable biofuel production.
 * Grow plants – Plants that naturally produce oils include oil palm, jatropha, soybean and algae. When heated resistance (viscosity) is reduced they can be burned within a diesel engine or they can be processed to form biodiesel.
 * Grow sugar crops or starch – These include sugar cane, sugar beet, corn and maize which are then turned into ethanol through the process of yeast fermentation.
 * Woods – By-products from woods can be converted into biofuels including methanol, ethanol and woodgas.
 * Biodiversity - A fear among environmentalists is that by adapting more land to produce crops for biofuels, more habitats will be lost for animals and wild plants. It is feared for example, that some Asian countries will sacrifice their rainforests to build more oil plantations.
 * The food V fuel debate - Another concern is that if biofuels become lucrative for farmers, they may grow crops for biofuel production instead of food production. Less food production will increase prices and cause a rise in inflation. It is hoped that this can be countered by second generation biofuels which use waste biomass - though again, this will impact the habitat of many organisms. The impact is particularly high in developing countries and it is estimated that around 100million people are at risk due to the food price increases.
 * Carbon emissions – Most LCA investigations show that the burning of biofuels substantially reduces greenhouse gas emissions when compared to petroleum and diesel. However, in 2007 a study was published by scientists from Britain, the USA, Germany and Austria which reported the burning of rapeseed or corn can contribute as much to nitrous oxide emissions than cooling through fossil fuel savings.
 * Non-sustainable biofuel production – Many first generation biofuels are not sustainable. It is necessary to create sustainable biofuel production that does not effect food production, and that doesn’t cause environmental problems.