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Types of Renewable Energy
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Renewable energy refers to sources of energy that can be replenished in a short period of time. Some renewable sources are essentially infinite such as solar, wind and hydro power. Biomass and geothermal power can also be replenished, when properly managed. Renewable energy can be used as transportation fuels, to produce electricity, and for heating. Clean, renewable energy is not new, but a collection of economic, environmental and technological changes are leading to new and rapid development in the way these resources are used.
Biomass is plant material or animal waste. Examples include trees, corn, grass, and manure. The gases collected from the decomposition of these materials may also be used, such as landfill gas.
Biomass contains energy that can be used in a variety of different ways. Simply burning biomass can produce heat. It can be converted to transportation fuels. Ethanol is an example. Electricity can be produced from biomass when it is burned or gases are collected from it. Many items once created with petroleum, such as plastics, can now be produced with biomass. Research is continuing to find new ways to use biomass.
Whether burned or converted to gas, biomass does generate air pollution. Emissions vary by fuel and technology. These emissions can include NOx, CO, CO2, and particulates. Biomass power can have environmental benefits when it diverts waste from landfills or when gas from landfills is used. This gas, called methane, would otherwise be released into the environment. The collection and processing of biomass may contribute to environmental problems if it contains toxic contaminants or results in greater chemical use. If a source such as switchgrass is used, it can help the environment by reducing erosion and nitrogen runoff. The use of feces as a source of energy provides needed power and a way to safely dispose of the material.
Production of biomass is beneficial to farmers for a number of reasons. The product can be produced locally, keeping jobs and wealth in the area and reducing the need for foreign imports of oil. Diversifying crops allows for less concern if there are price fluctuations in other crops. Construction of the plants needed to convert crops or landfill gas creates jobs. One concern with biomass is that switching from food crops to fuel crops might drive-up food prices.
The burning of wood, a biomass, was probably the first use of energy by humans. Henry Ford originally designed his Model-T to be capable of operating with ethanol.1 Rudolf Diesel intended to use peanut oil to power his diesel engine.2 1 Clean Energy Alternatives: Ethanol. Environmental Protection Agency. [pdf] 2 Historical perspectives on vegetable oil-based diesel fuels. The National Biodiesel Board. [pdf]
Geothermal energy is heat in the ground. Volcanoes and geysers are two visible examples of this energy at the earth's surface. Although there may not be a visual indication of geothermal energy elsewhere on the planet, it is accessible in the ground. In these areas, geothermal can be used, with a system known as ground source heat pumps.
Geothermal energy can be used in several different ways. At its most basic, heated water from springs can be employed for cooking or warmth. In areas of high geothermal energy, such as the west coast of the United States, steam from the hot water can turn turbines to create electricity. Although Pennsylvania does not have great geothermal energy to produce electricity, we can still utilize the source with geothermal heat pumps. Underground, the temperature remains around 57 degrees throughout the year. A system of tubes pumps the energy above ground for use, providing warmth in the winter and cooling in the summer. Wells are dug and pipes buried in the ground. Fluid is circulated through the system. In winter it absorbs heat from the earth and warms the building. In summer it takes heat from the building and moves it to the earth.
Geothermal energy is produced quietly. Compared to fossil fuels, it results in the creation of little pollution and there is no danger of fire, asphyxiation, or explosion. The space needed for a system is typically small and underground, and therefore has minimal, if any, visual impact.
Initially, geothermal systems cost more than conventional heating and cooling systems. They have few moving parts. Because those parts are sheltered, they are durable and highly reliable. Proper design is vital to a carefree long-lived system. Homeowners and businesses must be particularly careful in screening their contractor.
Geothermal heat has been used for at least 10,000 years in the United States, beginning with Native Americans who went to hot springs for cleaning, warmth, and healing. In the 1880s, development of electricity generating power helped to provide lighting in some areas. Advances in technology have continued to today.
Hydro energy is created from the movement of water. Water is constantly moving around the earth in what is known as the water cycle. This involves the evaporation of water out of the ocean, forming clouds, and then falling to the ground as precipitation. This water may collect in lakes or rivers and may eventually reach an ocean before being evaporated to begin the cycle again.
Water can be used to produce electricity. A common way to harness this power is to dam a river or lake. At a dam, water is pulled downwards by gravity and past a turbine, which is spun in the process. The turbine generates electricity. Hydro can also be used on a small scale, even under 5 kw.
Water, unlike fossil fuels, does not produce pollution when generating power. Damming a river will cause the water level to rise behind it, creating recreational opportunities with the water. At the same time, however, the backup of water will cover any low lying areas, forcing people and businesses to relocate and natural resources to disappear. Dams can also impede the movement of animals, such as fish, from moving freely upstream. Organisms moving downstream may become caught in the turbines. If the flow of water is properly controlled, areas below the dam should not be adversely effected, but if the water is too high or low, it can cause flooding or drought. Dams can also disrupt the chemical and nutrient content of the water. Micro-hydro, or small scale projects will not have nearly the impact that a larger project would have.
Hydropower is typically the cheapest way to produce electricity. Once the equipment is installed, maintenance is the only cost, because the water will flow for free. The equipment will generally last longer than that of other energy sources. Hydropower can be produced in the United States, so resources do not need to be imported. Getting licensing to complete a project can be time consuming.
Hydropower has been used by people for thousands of years. Projects to provide lighting from the power of water began in the 1880s. Since then, a number of large scale projects have developed across the country, with the west coasts states producing the most energy from hydropower.
Solar energy is the rays of light that reach the earth from the sun. The rays also can turn into heat.
Solar energy can be used to produce heat or electricity. Heat (or thermal) energy can collect passively. Passive solar design lets houses collect solar heat in winter through southern-facing windows and rock or brick to capture and radiate the heat. In summer, an overhang will protect the home from too much sun. No mechanical system is involved. Active solar heating also gathers sunlight and converts it to heat, but involves a fan or pump to move the heat to a chosen destination. Solar energy can be used to generate electricity. By concentrating light into a central area where it becomes heat, water can be turned into steam and used to turn turbines. Photovoltaic (PV) cells or panels can be placed in sunlight, converting the rays directly into electricity.
Solar energy is collected quietly. It does not release emissions into the air or hazardous chemicals onto the land or water. While construction of the system does involve the use of hazardous materials, it is less than those that would result from the use of fossil fuels. Because sunlight is not concentrated at any one point, large areas must be covered to collect an adequate supply of it, although constructing them on preexisting buildings reduces this impact.
Solar energy creates jobs that can be located in the United States. Initial costs are very high, but once the project is completed, the production of energy can begin recouping those costs. Because it uses no fuel, solar panels are not subject to fuel price spikes. Using the energy near the site of production reduces the chance of a transmission failure. Solar projects allow for great flexibility in terms of the size of project.
Solar energy has been used for thousands of years. At first, the sunlight was used to burn things to create fire. Later on, people learned to build their homes facing south, to maximize the amount of sunlight reaching them. In the 20th century, photovoltaic cells were developed and used to generate electricity from the sun. PV panels became an important part of space travel, powering satellites in space. Today the technology continues to develop.
Wind is the movement of air. It is created by sunlight shining on the earth. The light does not reach the planet evenly (such as part of the planet being dark at night), which causes differences between warmer air and cooler air and forms wind. Shorelines and the tops of mountains are two good areas to find this resource.
Wind is kinetic energy that can be used to do work. Humans can collect wind energy by using windmills and wind turbines. When the blades of a windmill turn, the device converts the energy into power to do work. A wind turbine has blades that spin and convert the wind into electrical power.
Wind turbines, like all electricity sources, can have both positive and negative impacts on the environment. On the positive side, wind turbines emit no pollution, generate no waste, require no mining for fuel, and use negligible amounts of water. They have a small footprint and the land around them can still be used for farming or forests. On the negative side, turbines and their access roads can fragment habitat. Unless carefully constructed and maintained, the roads can lead to erosion. The turbines must be properly sited to avoid avian migratory paths and bats. Turbines are also sometimes noted for producing sound and causing a shadow flicker. Some people enjoy seeing wind turbines, viewing them as kinetic sculpture and some find them aesthetically unpleasing.
Wind energy generates jobs, increases the local tax base, and provides income for landowners. Initial costs are very high, but once it is completed, the production of energy can begin recouping those costs. Because it uses no fuel, wind turbines are not subject to fuel price spikes. Wind is renewable, so we will never run out!
Wind has been used by humans for centuries. It allowed people to sail the oceans and explore the world. We used windmills to grind grain. In the late 1800s, millions of windmills could be found in the United States pumping water. Commercial wind farms have developed over the past fifty years and can now produce large amounts of power.
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