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Energy cannot be neither created nor destroyed, only changed from one form to another.
Energy cannot be neither created nor destroyed, only changed from one form to another.
Energy cannot be created nor destroyed, but it can be converted into other forms. Potential energy to kinetic energy, chemical energy to heat energy, and so forth. Chemistry and engineering allow us to transform energy into forms that are beneficial to us. Let's look at some forms of energy and how it can be converted into other forms.
Potential and Kinetic Energy
Riding a bike uphill stores energy from your body as potential energy. You convert the chemical energy from the food you eat into motion, which is then stored and waiting to be released.
Potential energy is like stored energy, something you can change into kinetic energy. Potential energy is ready to go, to make something move by releasing what you have put into it.
Kinetic energy is the energy of motion. It is energy being stored or released. It is the energy of motion.
Potential energy can be converted to kinetic energy slowly or quickly. When potential energy is released it makes things move. Sometimes this isn't good!
Chemical Energy
What we know as "fire" is an exothermic reaction that releases energy that has been stored as chemicals.
Chemical reactions can be classified in two major ways; Exothermic and Endothermic. "Exo" means "out," and is a type of chemical reaction that releases energy. "Endo" means "in," and is a reaction that absorbs, or takes in, energy. A fire is an example of an exothermic reaction, and when an ice cube melts in a glass of liquid heat is taken in from the liquid and is an example of an endothermic reaction. Both are chemical reactions where energy is moved from one substance to another.
We can use these reactions to change the form of energy and convert it to more useful purposes. The carbon bonds in fossil fuels and organic materials can be broken and the energy released to produce heat, which can then be used for propulsion, to generate electricity, or control the temperature of things.
The exothermic reaction from burning gasoline or diesel fuel moves pistons and shafts in our vehicles to move us and our things around more easily than if we had to depend on manual labor. Endothermic reactions allow us to cool things and maintain low temperatures to keep things from getting too hot.
Melting ice is an endothermic reaction that we can use to keep things cold.
Electricity and Magnetism
Magnets are made from many, many molecules or atoms that align end to end, each with a positive and negative side. Positive sticks to negative, and not to other positive items. When these all line up, end to end, a magnetic field is formed. When we rotate a conductor (such as iron) in a magnetic field, some of the magnetic energy is converted to electricity. Electricity also flows from negative to positive, and we can easily convert this back into magnetic energy and use it to power some of our devices. Electricity can also be used to light our homes and work spaces, to heat and cool us, and to power machines, phones, radios, computers and many other things that make our lives easier.
Green Energy
"Green Energy" is simply environmentally friendly energy, that is to say that it puts less strain on our resources and doesn't pollute as much. Examples of Green Energy are wind, solar, and clean burning fuels such as hydrogen.
Harnessing the wind to turn electrical generators or water pumps is pretty clean. However, it takes lots of energy to make a wind turbine, or a solar panel for that matter. This energy takes a while to recover and it has been estimated that a large wind turbine has a 15 year life span, and it takes half of that to make up the energy that it takes to build the machine.
Large numbers of wind turbines can be put together in "wind farms," but unless they run long enough to offset the energy needed to produce them, they aren't as clean as people have been led to believe.
Solar power is harnessing the light and heat energy of the sun. Of course, plants already do this, but it's much harder for us. Solar panels use different materials that react with light to produce electrical current that can be stored in batteries. Like wind power, the manufacture of these panels takes a lot of energy, which must be paid back in order for them to be truly clean and pollution free. So, when we think of "clean" or "green" energy, we need to also think of what it takes to harvest these natural resources and the pollution that is produced in the manufacture of the equipment that allows us to do it.
For instance, a man puts solar panels on his roof and runs his house off the electricity they generate. It might cost many thousands of dollars to install these panels, and if the savings in electricity charges are only slight it may take many, many years to pay off the "carbon debt" of the manufacture and installation of the system.
Electric cars are another type of green machine that has a large carbon "footprint," that must be "paid back" before they are truly clean. It takes a lot of energy to make the car, and then unless you get your electricity through wind or solar systems that are already clean, the energy they use from the "plug" is made by generators that use coal or other fossil fuels to produce the electricity. Currently it is much more efficient and generates less pollution to simply use a car that is either a hybrid or gets really good gas mileage.
Electric cars aren't as clean as you'd expect! Remember, energy cannot be created nor destroyed, only changed in form. If fossil fuels are burned to produce electricity used in a vehicle, it doesn't matter much if you have an electric car or not. Carbon is carbon.
"Mom? Have you seen my matches?" Oops.
Hydrogen fuel has it's own problems. Although when combined with oxygen and burned, the byproduct is water, the hydrogen and the engines that burn it are expensive to produce, and the hydrogen gas is highly flammable and extreme caution must be used for safety.
Nuclear Energy
Radioactive elements such as Uranium can be used to generate heat and therefore electricity, but besides the huge cost of a nuclear reactor necessary for this to work, they leave dangerous waste products that will be toxic for thousands of years. Failures of these plants can cause widespread disaster.
Alternative Fuels
We already talked about hydrogen, but other fuels that are clean burning, such as alcohol (which is usually produced from corn, and must be grown using water, fertilizer, pesticides, and then harvested, fermented, and distilled), also consume a great deal of energy during their production. Burning waste material (garbage) to get rid of it is a great idea, but this process usually results in pollution in the form of smoke and cinders that are both toxic and hard to get rid of.
Recently good news comes from Berlin. A German company has found a way to recycle coffee grounds and use them to make reusable coffee cups and dishes. They can be used over and over for up to 5 years, and then, since they are biodegradable, you just throw them away with no guilt about polluting the environment. Cool, eh? Now, that's green!
In summary, green energy is a great idea, but much more work needs to be done to make it truly efficient.
Questions to think about:
Questions to think about:
- How can we successfully harvest solar, wind, or tidal power without having to spend more energy making the machines that enable us to do that?
- What does it mean to be "green?"
- How green is what we consider to be "green," or clean energy?
- What are some alternatives? Could we just simply cut back on our energy consumption? Why or why not?
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