Questões de Vestibular

    As we all know, electricity is a fundamental need. On a daily basis, we consume electricity even without us knowing it. Just a simple task such as listening to your music player consumes electricity. Today, most of our electric generators and power plants are fed with fossil fuels such as petroleum and coal. However, due to the exponential increase of power demand, fossil fuel supplies are slowly being depleted. Not only that, but also burning fossil fuels has given off greenhouse gases and other unwanted byproducts. Because of this, the search for alternative energy sources is now a necessity. One of the most promising alternative energy sources today is Wind Powered Generators. So, what is a wind-powered generator? Basically it is the use of wind as a mechanical force needed to power an electric generator. Utilizing wind as an energy source is not exactly a new idea. The ancient Persians were the first to use wind to pump water, cut wood, and grind food and others by building windmills. Even today you can find windmills still being used on some farms. It was the use of wind as an electric source that came into existence much later. The first practical wind powered generators were built in 1970, but yet we rarely see them in widespread use today, why? Let’s look at the advantages and disadvantages of the wind powered generator.

    The main advantage of wind powered generators is that they have, ideally, zero gas emissions – unlike fossil-fueled power generators. Because of the alarming effects of greenhouse gases and global warming, we want our power generators to be as clean and as environmentally friendly as possible. Since there is no burning process in a wind powered generator that produces toxic gases, it is very safe to build one in residential areas. Also, with proper engineering and enough wind, these generators can provide a high rate of wattage that can go as high as the Megawatt range. Another advantage is that it can be implemented using several small turbines connected together. This is a good thing when there is not enough space for huge structures.

     The major disadvantage of wind powered generators is that wind power varies greatly from one place to another and from day to day and season to season. Sometimes wind may be strong enough to supply energy, but that strength cannot be maintained due to changes in weather patterns. Needing strong, constant wind to most effectively power wind generators is one reason they are often built in coastal areas. Another disadvantage is that the structure of most practical wind powered generators is huge and bulky. Commonly, its size is proportional to the wind power it can collect.

    Research in wind power has now intensified because of its innate advantages over other power generators. With this increase in interest in wind energy and alternative energy sources as a whole, our future will become brighter and more and more remote areas will eventually enjoy the benefits of clean electric energy. In an electricity-dependent world, power supplies must provide the required electricity for communities and businesses. Wind powered generators might just be the solution for power shortages.

Disponível em: http://mysolarcellhome.org/articles/pros-and-cons-of-wind-powered-generators. 

Strategic Spending on Organic Foods

Sweet bell peppers are among the vegetables high in pesticides. (Richard Drew/Associated Press)

(Extraído de http://well.blogs.nytimes.com/2008/04/18/strategic-spending-on-organic-foods. Acesso em 14/09/2008.)