Coal: Where It Comes From Coal comes from energy stored by plants living millions of years ago. These dead plants were covered by many layers of dirt and water that trapped the energy. Top layers put pressure on the dead plant layer and turned it into coal. Giant machines remove coal from the ground using surface mining (remove topsoil from the ground, mine shallow coal, replace soil) or underground mining (build mine shafts underground, ride elevator down and use machine to mine coal). Surface mining is cheaper and more common. Coal is then cleaned on-site (dirt, rock, ash, and sulfur are removed), and usually shipped by train to electric power plants.
Coal: How It’s Used Coal is the most abundant fossil fuel in the U.S. 92% of power plants use coal to generate electricity by burning it to make steam, which turns electricity-generating turbines. Some industries, like concrete and paper, burn coal for its heat. Coal can be super-heated and smelted into steel. 4%, or 4.6 million tons, of all coal produced in the U.S. is exported.
Coal: Characteristics There are four types of coal: lignite, subbituminous, bituminous, and anthracite. Lignite is the youngest and uncommon, subbituminous and bituminous are million years old and most common, and anthracite is the oldest and rarest in the U.S. A sample of bituminous coal
Coal: Advantages and Disadvantages Coal is a nonrenewable resource. Coal is cheap to mine and will be available for 225 more years at today’s rate of use. Mining can destroy land and pollute the air. Burning coal gives off carbon dioxide, nitrogen oxide, and mercury. The use of coal contributes to acid rain levels; mercury kills fish and the animals that eat them. Scientists are working on removing some harmful parts of coal.
Oil: Explanation and Usages Oil, much like coal, is a liquid found deep underground that is made of decomposed organic matter. Oil is the most used source of energy in the U.S.; it accounts for almost 40% of the nation’s energy. It can be refined into gasoline, kerosene, liquefied petroleum gas (like propane), diesel, and jet fuels. Oil is mostly burned for transportation or home heating, but some is used as fuel in electricity- generating plants.
Oil: Advantages and Disadvantages Burning oil produces much air pollution, including nitrogen oxides, sulfur dioxides, carbon dioxide, methane, mercury, and volatile organic compounds. Oil-fired steam plants use significant amounts of water to generate electricity. Oil wastes are toxic and hazardous. Drilling produces air pollutants, toxic waste, and destroys huge habitats. Refineries pollute the air, water, and land. Oil transportation accidents can kill thousands of birds, fish, plants, wildlife, etc.
Natural Gas: Explanation and Usages Natural gas is made from decayed organic matter trapped under layers of earth. Some of this matter turns into coal, some into oil, and some into natural gas. First, seismic surveys locate where to drill wells. Then, they begin drilling for the gas. It flows up the well to the surface and into large pipes that ship it to gas processing plants. After it is refined, the natural gas is stored in empty oil/gas wells or caverns and distributed by pipeline when people need it. About 50% of the homes in the U.S. use natural gas for heating; it is also used as a raw material in products like paint, fertilizer, plastic, antifreeze, etc.
Natural Gas: Advantages and Disadvantages 22% of the energy in the U.S. comes from natural gas. Industry relies on it to produce steel, glass, paper, clothing, electricity, and more. 62.5% of homes use it to fuel appliances. Though natural gas produces fewer emissions than other fossil fuels, it still generates a large amount of CO 2. Gas leaks can cause explosions. This is why foul- smelling mercaptan is added to natural gas to make leaks detectable. A natural gas well
Propane: Explanation and Usages Propane is a gas that is found mixed with natural gas and oil; processing plants separate them at refineries. It then goes by underground pipe to terminals that further ship it to distributors. Propane is transported as a liquid in a compact pressurized container, which turns it back into a gas when the valve is opened. Uses include: heating barns and fueling farm equipment, heating homes, fueling grills, appliances, machinery (like forklifts), and making products like nylon and plastic. Propane makes up less than 2% of U.S. energy. 45% of propane is used to make plastic.
Propane: Advantages and Disadvantages Propane is a nonrenewable fuel. It is generally a clean- burning fossil fuel; it emits less carbon monoxide and hydrocarbons than gasoline. Propane does produce considerable amounts of water vapor and carbon dioxide. A propane tank used to fuel a grill
Nuclear Energy: Explanation and Usages Nuclear power comes from energy stored in the nucleus of an atom. The atoms most commonly used are from the U-235 found in uranium. Two ways to release energy: fusion (combining atoms) and fission (splitting an atom apart). During fission, neutrons hit the uranium atom and split it apart, causing a chain reaction. The heat given off from fission is used to make electricity.
Nuclear Energy: How It’s Processed Nuclear reactors- machines that contain a chain reaction and release heat. Inside a nuclear power plant: - First, fission generates heat in a reactor. - The heat boils water into steam. - The steam turns turbine blades, which drive electricity-creating generators. - The steam is changed back into water and cooled in a separate cooling tower to be used again.
Nuclear Energy: Advantages and Disadvantages Nuclear energy is generally considered nonrenewable because there is only a small amount of uranium on earth. Nuclear power produces no air pollution, though there are some emissions from processing uranium. By-products include used fuels, radioactive waste, and heat. Radioactive waste must be disposed of properly; otherwise it can be very harmful to the environment. The U.S. Department of Energy has plans to put spent fuel in a deep, underground repository in Nevada.
Wind: Explanation and Usages Wind power is mainly used to generate electricity. Earliest examples of use: sails on a ship, windmills. Modern wind machines (turbines) use blades to collect the wind’s kinetic energy, slowing down its speed. The wind flows over the blades causing lift, and the blades turn. This drives a shaft that turns an electric generator to produce electricity. Horizontal-axis turbines are most common and have 3 airplane propeller-like blades. Vertical-axis turbines are uncommon and have blades that go from top to bottom like an egg-beater.
Wind: Advantages and Disadvantages Wind power is renewable and makes up a little more than 1% of U.S. energy. Other types of plants must be used when the wind isn’t blowing. It creates no pollutants. Though the wind is free, wind turbines can be expensive. Turbines may be ugly to look at and affect wild bird populations. A horizontal-axis wind turbine
Solar Power: Explanation and Usages Converted into Heat Solar-thermal energy can be passive or active. passive- no machines needed, like your car heating up on a summer day. active- requires a collector to absorb and collect solar radiation, then fans or pumps circulate the heated air/fluid throughout the area being heated (such as a building). Converted into Electricity Solar energy can be converted into electricity using Photovoltaic (PV devices) or solar power plants. PV devices- AKA “solar cells”; change sunlight directly into electricity by absorbing the sun’s photons. This causes the front and back of the cell to be negatively and positively charged, creating electricity. solar power plant- heat from solar-thermal collectors is used to heat a fluid that creates steam. The steam turns turbines, powering a generator that produces electricity.
Solar Power: Advantages and Disadvantages Solar power is renewable. Though sunlight is free, solar panels can be expensive. The amount of sunlight is not constant, depending on location, time of day, and weather. Since the sun doesn’t deliver much energy at one place and at one time, a large surface area of solar cells is needed to collect enough. Solar power does not create air pollutants, however it consumes silicon and produces some waste. Photovoltaic “solar cells”
Hydropower: Explanation and Usages Hydropower is energy from moving water. Hydroelectric power is one type that provides 1/3 of the world’s electricity. Early example of use: water wheels powered mills. There are three types of hydropower, but in each plant is built upon this basic system: flowing water pushes against turbine blades, which spin a generator and produce electricity. The more water there is, the more electricity is generated.
Hydropower: Types of Plants Impoundment uses a dam to store river water in a reservoir, then releases it to generate electricity as needed. Diversion, or “run-of-river”, channels part of the river through a canal or penstock (a pipe used to carry water to a wheel or turbine). Pumped Storage works in two ways: - low electricity demand: the plants store energy by pumping water from a lower reservoir to an upper reservoir. - high electricity demand: the water is released from the upper reservoir into the lower reservoir to generate electricity.
Hydropower: Advantages and Disadvantages Hydropower is the cheapest form of energy- once the plant has been installed, the water is free. Damming rivers could destroy or disrupt wildlife and other natural resources. Fish, like salmon, are prevented from swimming upstream to spawn. Special “fish ladders” can be installed to help fish swim over the dam.
Geothermal: Explanation and Usages Geothermal is Greek for “earth heat”. It’s created by earth’s water and heat and is used either directly for heating buildings or indirectly for creating electricity. Naturally occurring examples are volcanoes, hot springs, and geysers. Most geothermal reservoirs rim the Pacific Ocean. Some geothermal energy plants use the temperatures near the surface, while others drill miles into the earth.
Geothermal: Types of Plants Geothermal plants use high-temperature hydrothermal resources from dry-steam wells or hot water wells to generate electricity. There are three types of plants: - Dry-steam plants use steam from reservoirs to directly turn generator turbines. - Flash-steam plants are the most common and take high-pressure hot water from deep inside the earth and convert it into steam to drive turbines. The steam is then cooled, condensed, and injected back into the ground to use again. - Binary plants transfer heat from the water to a liquid, which makes steam and turns turbines.
Geothermal: Advantages and Disadvantages Geothermal energy is renewable. The U.S. generates the most geothermal electricity, however it only accounts for less than ½% of total U.S. electricity. Geothermal energy has almost no negative impact on the environment; the emission levels are lower than other resources. A geyser
Biomass: Explanation and Usages Biomass involves burning fuel for electricity. Fuels include: timber, agricultural and food processing waste, specifically grown fuel crops, sewage sludge, and manure. Two types of plants: direct combustion and biomass gasification. - Direct combustion plants burn biomass in boilers that supply steam that turns turbines and generate electricity. - Biomass gasification plants convert biomass into methane that can fuel steam generators, combustion turbines, or combined technologies. One benefit is that gasification can be used with different plant technologies.
Biomass: Advantages and Disadvantages Biomass is renewable and can generate electricity at any time. Biomass fuels are made of materials that might be otherwise put in landfills. All biomass plants generate various levels of air emissions; including high NO x emissions, and carbon monoxide levels that can be higher than in coal plants. Its impact on human health is unclear. Harvesting wood and agricultural products can be expensive- large volumes must be collected, transported, processed, and stored. Burning fuels might create toxic contaminants, pollute water, or deprive ecosystems of nutrients.
Bibliography “Energy Kid’s Page.” Energy Information Administration. 30 Nov “Hydropower.” National Geographic. 2 Dec “Electricity Generating Technologies: Where does our electricity come from?.” Power Scorecard. 1 Dec “Types of Hydropower.” Fuel from the Water. 2 Dec