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Green Energy Sources
Much of the world's energy supply comes from natural gas and nonrenewable fossil fuels, such as petroleum, coal, methane and propane, which are being rapidly depleted. The burning of natural gas, fossil fuels and other hydrocarbon fuels is the largest source of CO2 emissions worldwide, and produces other pollutants such as nitrogen oxides, sulfur dioxide, VOCs (volatile organic compounds), and heavy metals. Many of the major fossil fuel sources are also found in foreign countries, which may take advantage of another country's dependence on them for oil and other fossil fuels. Over time, a lack of energy independence can lead to wars, monopolization, inflation, manipulation and oppression, both between and within nations. There are alternative energy sources however, which unlike fossil fuels, are renewable, sustainable, affordable, and globally available. Some of the most well known green energy sources include thermoelectric, solar, thermal, hydrogen, hydroelectric, wind, and biomass energy. Other, less common green energy sources still being developed include hygroelectric, piezoelectric and ambient RF energy, as well as a number of other emerging small-scale energy harvesting technologies.
Thermoelectric EnergyThermoelectric devices, such as thermocouples and thermopiles, thermoelectric generators, heat pumps, heaters, coolers, refrigerators and freezers, can convert temperature differences directly into electricity, or electricity into hot and cold temperatures. Thermoelectric devices are generally eco-friendly (depending on materials and production methods used), silent, long lasting, have no circulating fluids or moving parts, and relatively easy to find. The energy efficiency of such devices however, is only typically about 0.3-4%.
Solar EnergyThe earth recieves more solar energy from sunlight every minute than is used in fossil fuels worldwide every year. Solar energy can be eco-friendly, sustainable, energy efficient and affordable, depending on the materials and methods used. Solar energy can be used in a wide variety of applications, such as solar HVAC (space heating, ventilation and air conditioning), drying, cooking, lighting, PV (photovoltaic) and thermal electricity production, CHP (combined heat and power) systems, water heating, and water treatment systems, such as solar saltwater desalination, solar distillation and UV disinfection. Though solar energy is not available at night and less available in shady or overcast weather conditions, the electricity it can be used to produce can be stored for later use.
Thermal EnergyThermal heat energy may be used directly for such purposes as HVAC, drying, cooking, CHP systems, water heating, distillation and saltwater desalination, or indirectly for producing electricity or mechanical power via heat engines (such as steam or stirling engines) or thermoelectric devices. Though heat can be provided by burning something, such as wood, biomass or fuels, solar thermal energy (i.e., heat energy from the sun), heat storage or waste heat may be used as eco-friendly, renewable, affordable, energy efficient heat source alternatives. Solar heat collectors and solar concentrators may be used to collect solar heat energy, while heat storage mediums (such as hot water, sand, soil and/or PCMs) can be used to collect heat from any heat source, and store heat for later and extended use.
Hydrogen EnergyHydrogen energy is generally obtained from hydrogen fuel, which may be used in fuel cells to produce electricity, or burned directly for space and water heating, cooking, lighting, distillation, motive power (for motors and vehicles), or producing electricity from heat. Production of hydrogen fuel via the electrolysis of water is eco-friendly and sustainable, but not very energy efficient or affordable, as it generally takes more energy to produce hydrogen fuel than the energy it yields. The conversion of hydrogen fuel to electricity using fuel cells can be eco-friendly, sustainable and energy efficient, but fuel cells available to the general public typically use toxic chemicals as electrolytes and fuels other than hydrogen for power, which contribute to environmental pollution and may pose significant health risks. Burning hydrogen fuel directly produces water, but also nitrogen oxides, which contribute to pollution.
Hydroelectric EnergyHydroelectricity accounts for about 20% of all electricity produced and consumed worldwide. Hydroelectric systems can be on or off-grid and as small or as large as needed, but the water source is most often as close to the point of use as possible. Electricity is produced using dammed water or a running water source such as a river, creek, ocean tides or water falls to drive a water turbine and generator. Hydroelectricity can be green, energy efficient, affordable, and power an entire household, but is generally most suitable for land owners with sufficient space and water to drive the system.
Wind EnergyWind energy can be environmentally friendly, renewable, energy efficient and affordable. Wind energy can be converted to mechanical power and used directly for such purposes as pumping water, grinding grains, or running a small saw mill. Wind power can also be used to drive a wind turbine and electrical generator to produce electricity. Mechanical or electrical output from wind energy is generally unpredictable due to the unpredictable nature of wind, but the electricity it can be used to produce can be stored for later use.
Biomass EnergyBiomass includes organic matter such as trees, wood, plants, leaves, grasses, agricultural crops, animals, human and animal waste. Biomass can be burned directly for space and water heating, cooking, lighting, producing electricity or mechanical power via heat engines (such as steam or stirling engines) or thermoelectric devices. Biomass can also be used for the production of biofuels, such as methanol, ethanol, methane, biodiesel and syngas, which can be burned for similar purposes as burning biomass directly, as well as for motive power in motors and vehicles. Methanol, ethanol and methane are produced from the anaerobic decay of biomass, while biodiesel is produced from vegetable oils, and syngas is a mixture of carbon monoxide, hydrogen and other hydrocarbons produced by the partial combustion of biomass.
Biomass energy is renewable and earth friendly, and the burning of biomass and biofuels can be energy efficient and carbon neutral. When biomass is burned however, previously stored carbon dioxide is released, along with carbon monoxide, sulfur, hydrocarbons and particulates, which contribute to pollution and pose significant health risks. Production of biofuels via the anaerobic decay of biomass releases methane and other environmental pollutants, depending on the biomass and methods used. The burning of biofuels also releases previously stored CO2, as well as additional CO2, carbon monoxide, methane, sulfur oxides, hydrocarbons, particulate matter and/or other emissions that contribute to pollution and likewise pose significant health risks. Use of biomass energy and the production of biofuels from biomass also requires a significant amount of land, water, work and energy (typically more energy than it produces). Likely the best, most environmentally friendly use of biomass would be as compost, which is produced from the aerobic decay of biomass.
Combining Green Energy SourcesNearly all green energy sources work best under certain conditions, such as temperature, light, heat, water, space, general weather conditions, and so on. Solar energy for example, is best collected during the day and summer, while hydroelectric energy is most abundant during the spring, and wind energy is most abundant during the fall and winter. Multiple green energy sources can be combined and electricity produced can be stored for later use however, so as to provide a constant, reliable source of green energy under most or all conditions.
Green Energy Storage and ConversionWhile combining green energy sources can help to provide a continuous, reliable source of electrical power under most conditions, any energy system can still exceed or fail to meet energy requirements, depending on a number of additional factors. Such factors include energy sources, energy storage or conversion methods if any, energy efficiency, peak and off-peak hours, minimum and maximum energy requirements. Therefore, most green energy systems use some form of energy storage and conversion method to store excess energy when available, reduce additional electricity production requirements during peak hours, convert stored energy to another usable form (such as hot or cold temperatures, mechanical or electrical energy, DC or AC power) if necessary, regulate energy use and/or electrical output, continuously and reliably distribute stored energy, in desired forms and amounts, under all or nearly all normal operating conditions.
Energy is usually stored in the form of thermal heat energy, biofuels, chemical energy, in flywheels, pumped water, compressed air, electric or magnetic fields, or fuel cells.
Environmental and Financial BenefitsCollecting, storing, converting and distributing your own energy reduces your contribution to pollution, saves money by reducing or eliminating your energy costs, and increases self-sufficiency by reducing or eliminating the need to pay for others to provide energy for you. Excess renewable energy can be stored for later use, or can be sold to electric companies through the power grid. In addition, there are state and federal tax incentives (such as credits and deductions on income taxes) available for purchasing and using earth friendly, clean energy systems, renewable energy products and equipment.
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