Applications
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Chapter 17: Electric Potential and Electric Energy; Capacitance Applications |
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"A Work Week"
We have been studying capacitors, devices that allow the temporary storage of energy in an electric circuit. This is another thing that physics is good for: understanding what energy is allows us to improve the ways in which we obtain energy, store it, and use it. 
Why is important to be able to store energy? There are several reasons.
Power companies need to store large quantities of energy because they generate energy all night at the same rate that they do during the day. However, there is much less demand at night. Thus, some of the energy generated at night must be stored and released during the day. This process is known as "load shifting."
Another reason to store energy is to use it at a remote location. For instance, it takes electricity to start your car, but you don't want to have to plug it in to do so. Thus, you use an energy storage device (battery!) to carry a small amount of electrical energy around in your car. This suggests another reason to store energy. In order to use it while in motion. Your car's gas tank enables you to store a large amount of chemical energy for use while moving.
| An aside: sometimes, it is the lack of energythat is precious. Later in the course we will study thermodynamics and learn a great deal about the relationship between heat and other forms of energy. For now, consider this. If a company needs to operate large cooling systems, it may be economically favorable to keep them running all night. In this case, the company can load shift by making ice at night and using it to cool things during the day. |
What are the important characteristics of an energy storage system? Here are a few:
Power companies use several strategies to store energy during the day. A common example is "pumped hydroelectric power". In these systems, the power company pumps water up hill to a reservoir during low load periods (night and weekend) and runs the water back down through the turbines during peak load hours. These systems can store a lot of energy, and they can be started up quite quickly. However, they occupy a lot of land and they require a considerable change in height (usually at least 100 meters) between the upper and lower reservoirs.
A second way that the power company can shift loads to off peak hours is to get each customer to shift their use of electricity a bit. Many power companies offer discount rates for nighttime power usage. Of course, consumers can take advantage of these discounts by changing their habits (doing the was at night for example. However, there are also systems that the consumer can buy that shift significant amounts of energy usage to the evening hours. An example is a thermal storage system which heats ceramic bricks, masonry, or water during the night then releases this energy to heat the house during the day. Systems like this are best used as a backup for a heat pump or in homes that rely on electric baseboard heat.
One of the largest forms of energy storage is the dam. In this case, water is stored at high elevation, and turns a turbine/generator on its way to low elevation. We may think of this as storing energy in the gravitational field, just as a capacitor stores charge at high voltage, keeping energy in the electrical field.
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| From the US Dept. of the Interior, Bureau of Reclamation |
Other examples of energy storage include:
More links about energy storage...
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