What are renewable (or green) sources of energy? They generally include solar, wind, and geothermal conversion to electricity. Other renewables, such as electrical energy derived from the movement of ocean currents, waves, and tides are also considered renewables.
They are considered to come from natural sources, and to be naturally replenished (renewable). They are considered to be 'environmental friendly' by some because they are perceived as not damaging the environment, and they are thought not to be consumed in the generation of energy (naturally replenished), therefore they go on forever without 'stealing' from the earth (reference: http://en.wikipedia.org/wiki/Renewable_energy).
Of course, both oil, natural gas, and nuclear are all from natural sources. However, you will NEVER hear of nuclear as a renewable energy source even though the "burning" of nuclear materials in a reactor can produce new nuclear fuel to produce more energy.
Much to do has been made by politicians about doing more research to make renewable energy more competitive by reducing their cost. This is all a distraction to keep supporters of renewable energy at bay because most politicians know renewables can not replace traditional energy sources. They just want you to think they are doing all they can to replace traditional sources of energy. Technology can always be tweaked, but at some point the hard decision has to be made to lock in the existing technology and move forward. So why haven't we done that?
Now why do I say that renewables can't replace traditional sources of energy?
Solar-uses photoelectric or photovoltaic cells to convert sunlight directly into electricity (reference http://en.wikipedia.org/wiki/Solar_energy). Technology to produce solar cells has improved dramatically over the last 20 years. There are no carbon emissions or other emissions from solar generated electricity.
However, there are concerns to be considered. (1) Some environmentalist in the western United States, and others have raise concerns about the large areas of land used for solar farms. They are also concerned about the potential environmental impact to plants and animals that live in those environs to the significant reduction of sunlight reaches those plants and animals over extremely large areas. No one has done a comprehensive Environmental Impact Statement (EIS) on these impacts as is required for a coal-fired power plant, a nuclear power plant, or a petroleum refinery. (2) The sun only shines half the time, which means no electricity is being generated at night. That means a solar farm has to be made 2x bigger than a conventional power plant so that enough energy can be produced and stored to meet energy demands. That requires more land area and compounds the issues in item (1) above. (3) Since electricity is not being produced half the time, excess energy must be produced and stored to provide a consistent supply of electricity. The excess energy is stored in batteries. The batteries require a storage area, like a warehouse, that uses more land (see item (1) above). In addition, batteries contain various hazardous materials such as lead, lithium, corrosives, etc. depending on the type of batteries used. These batteries will ultimately need disposal as hazardous waste and/or need expensive recycling with concomitant hazards. And they are expensive which will ultimately increase the cost of the electricity. (4) The photovoltaic cells contain various hazardous materials that will also have to be disposed of as hazardous wastes and/or expensive recycling. (5) A complicated, but potentially real issues that must be addressed in any EIS is the impact, if any, of sprawling solar farms on weather patterns. Yes, the impact on weather. The sun heats the earth, evaporates water, and creates winds. What happens when much of the suns energy is converted to electricity? That part that is converted cannot be used to heat the earth, evaporate water, and cause winds. This potential impact must be evaluated in an EIS before large land mass is dedicated to solar farms.
So how large of land mass is required for a solar farm. Well, if you build one to generate one million kilowatts of electrical power (the typical nuclear plant output, http://www.me.sc.edu/nuclear/NE-FAQs.pdf) you would need to build a solar farm at least the size of Rhode Island. Wow!
More on the other renewable energy sources next time.
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