index > Today's Earth, Our Future > 5. Clean energy > What is Energy?

What is Energy?

It is said that global warming has to do with energy. Do you know what energy is? Just like we say, "That person's full of energy," energy means the power to carry out an action, like move or carry things. In order to perform these different actions in our daily lives, like running, jumping and thinking, we need "food" as a source of our energy.

Similarly, we use energy to transport people by car, to supply power for lighting and heating buildings or to operate machinery. Now then, where does all this energy come from?

Common sources of energy that we use every day are taken from natural resources that come from the earth. There are two kinds of natural resources: unlimited and limited resources.

Here's one example of an unlimited resource. We all get warm when we sit in the sun, right? This heat comes from the sun's power, or "solar" energy. You can sit out in the sun every day, but this solar energy never runs out. Other unlimited energy sources, which in fact mean "sources that never run out," are those that are generated from the wind, water, the earth's heat (geothermal energy) and from waves in the ocean.

On the other hand, how about the energy we use for gas heaters? When we use them, we burn gas made from petroleum oil that is taken from underground. Petroleum oil and coal are natural resources that were made by the process of breaking down, or the "decomposition" of plants and animals over millions of years, and that's why they are called "fossil fuels." They are never restored naturally, so when we dig them out and use them up, they are lost for good.

We also should think about whether or not carbon dioxide (CO2) is produced when we use energy. When we burn fossil fuels such as petroleum, coal and natural gas, CO2 is released into the atmosphere. And CO2 is a major cause of global warming.

By contrast, other energy sources like solar, wind and water power do not make, or "emit," CO2. (But we should realize that in order to make the equipment to use these energies, we use fossil fuels that create CO2, or cause CO2 "emissions.")

Another thing we should think about is where your energy sources are coming from. Is it a resource that's available in your own country or does your country need to buy and import it from other countries? If your country depends on imported resources, in an emergency situation, there is likely to be an energy shortage.

In order to become "energy independent" without the need to rely on resources from other countries, it is important for every country to increase its "energy self-sufficiency ratio," or in other words, the amount of energy that can be provided from resources within the country, (which some people call these "domestic" resources).

Sometimes we change, or "convert" natural resources into other forms of energy. For example, we use water power, coal, petroleum or natural gas to produce electricity.

Electricity is our most commonly used form of energy. Since it's so convenient, we consume a great amount of it at home, at school and at work for many purposes such as lighting or to operate appliances and other electronic equipment.

As a result, 30% of the CO2 emissions that cause global warming come from making or using electricity. This means that global warming has to do with how much electricity we use.

Whenever you turn on a TV or a light at home, electricity is carried to your house through the power lines. If you trace these lines to their origin, you will reach an electric power generator, or "power plant" that produces the electricity. What is the source of energy used to generate electricity at this power plant? The key to solving global warming lies in the very answer to this question.

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