Energy and How We Use It

Energy is "the ability to do work." For everyone and everything, that means being able to grow and move. For babies, it means eating healthy food to develop, and for plants it means converting sunlight and water into energy to grow. Food is stored energy. When you eat it, your body uses it to do all kinds of work from running and jumping to thinking.

We usually think of energy as doing other kinds of work. For instance, energy is used to move people from one place to another in cars or to provide light and heat in buildings. Like your body using the energy in food, we often use fuels to give us stored energy. Gasoline used to power cars is one example. Car engines transform the energy in the fuel—gasoline—into work—turning the wheels to move the car and its passengers. While gasoline isn't the only fuel we use to transport ourselves, it is certainly the most widely used and the greatest source of pollution in our society today. Other fuels that help transport people include natural gas and ethanol.

The energy we use every day comes from resources. Resources are broken up into two categories — renewable and nonrenewable. Renewable resources are those that can be used or made over and over again from other resources — they are unlimited. Wood is a renewable resource because more trees can be grown to make more wood. Nonrenewable resources cannot be created over again and our supply of them is limited; once they run out, the resource is gone forever. Coal is an example of a nonrenewable resource because there is only so much of it on earth. Once we have mined it all, we will need to reuse it in order to have more for other uses.

Sometimes resources are converted from one form to another to get the energy we need. For example, we turn crude oil into gasoline to power most of our cars. Gasoline a fuel which contains stored energy. Like other resources, fuels can also be renewable or nonrenewable. Examples of renewable fuels include solar energy from the sun, wind energy, hydro energy from water, and biogas, which is a fuel made from plants. Fossil fuels—coal, oil, and natural gas which come from the remains of plants and animals that decomposed millions of years ago—are examples of nonrenewable fuels. Once we run out of these resources, we will have to find something else to fuel our society.

Electricity is one form of energy that we use everyday to light our homes and schools and run our appliances. It can be created by burning fossil fuels, or by using renewable energy from water, wind, the sun, and plants. When electricity is generated from fossil fuels, it is usually made at large power plants and creates pollution. Electricity from renewable sources is usually made on a smaller scale and does not pollute.

All of our current methods for generating electricity have their problems. Burning fossil fuels creates the majority of today's air pollution. This negatively affects our air, water, and land, which in turn affects our own health. Fossil fuel pollution can cause asthma and lung problems, especially for children and the elderly. Using large dams to create energy from water (called hydro-electricity), destroys ecosystems and kills wildlife. Generating power from the wind and sun only works when the sun is out or the wind is blowing. In order to have a constant power supply from these sources, we must find ways, such as batteries, to store the energy when the power cannot be generated.

An exciting way to generate electricity is from fuel cells. These devices generate electricity by combining oxygen and hydrogen in a chemical reaction that creates electricity. The only waste created from the process is water and heat. That means a building's hot water and heating needs can be met at the same time without any pollution. Fuel cells can work not only in the home, but car manufacturers are also trying to design a small fuel cell to replace the gasoline engine. They are a great way to produce electricity, but they are still very expensive and not yet widely available. Keep an eye out for them over the next few years.

Solar energy is the renewable energy we get from the sun. When the sun's rays are transformed into electricity, it is called photovoltaic (PV) energy. This is a simple and earth-friendly way to get electricity. PV panels can be put on the roof of a house to provide electricity or can be used in remote places where there is not electricity from other sources. A common example of PV electricity is the calculator. Nearly all calculators made today have a small PV panel that converts light into electricity to power the device. The next time you use your calculator, notice what happens when you cover the small panel with your hand. The calculator stops working. That is because it needs light to make electricity.

When the sun shines on an object like a rock or your skin, what happens? That object gets warm, right? Well, this concept can be used to heat water and buildings so that less other energy needs to be used. If buildings are designed with large windows that allow the sun's rays to heat surfaces inside the building, then it costs less to heat the building because the sun's energy is free and renewable. This type of building is called "passive solar" because it is not an active, mechanical system that heats the inside, but instead uses the natural heat from the sun's rays to heat the building.