Using What We Have: Hydrogen Energy
Hydrogen is the most abundant element on earth, always found combined with other elements to form chemical compounds. One example of this is water-H2O-which is a combination of hydrogen and oxygen. By harnessing the power of this element, we can create a natural form of energy that is not only renewable, but also healthy for the earth. This technology, which NASA has been using for years, is now being researched for possible use in everyday life.
Hydrogen energy is stored in the form of fuel cells. These fuel cells are what powers spaceships during takeoff. Because hydrogen is not found naturally by itself, the first step to building a fuel cell is to remove the hydrogen from a compound. Hydrogen is found not only in water, but also in natural gas, the substance most often used for this process, which is known as reforming and uses heat to separate the hydrogen from the natural gas. When water is used, a similar process, called electrolysis, is used to separate the hydrogen and oxygen with an electrical current. The result of each of these processes is more energy, in the form of hydrogen, than is used in the process itself.
Hydrogen energy is researched because it is such a pure from of power. An engine that uses hydrogen produces almost no pollution, making it much preferred over fossil fuels. In the space shuttle example, for instance, the byproduct of burning hydrogen to power lift-off is purified water, which the astronauts than can drink. Therefore, using hydrogen power is not only clean, but also useful. Fuel cells are often compared to batteries, and work in much of the same manner, but unlike batteries, which eventually lose their charges, a fuel cell continues to work until its source of hydrogen is cut off. Inside the cell, oxygen is combined with hydrogen, and the chemical process that produces water also gives off heat and electricity. The water can then be broken into hydrogen and oxygen once again, and the process starts all over again.
In the future, scientists have predicted that fuel cells will become more widely used. Currently, they are still working on more convenient storage methods since hydrogen, although very light, takes up a lot of space. When this process becomes more refined and cost effective, this could be a solution to the world’s energy problems, and since the process is not only renewable, but clean, it can help save our environment as well.
Clinical use
Vardenafil’s indications and contra-indications are the same as with other PDE5 inhibitors; it is closely related in function to sildenafil citrate (Viagra) and tadalafil (Cialis). Structurally, the difference between the vardenafil molecule and sildenafil citrate is a nitrogen atom’s position and the change of sildenafil’s piperazine ring methyl group to an ethyl group. Tadalafil is structurally different from both sildenafil and Levitra vardenafil. Vardenafil’s relatively short effective time is comparable to but somewhat longer than sildenafil’s.