Energy 101 - an energy primer

This energy primer was created in an attempt to help you understand some complex processes that are happening all around you each day! Hopefully it is easy to follow and entertaining...

These are the questions that are answered!

(click on the question to skip down the page to the appropriate section)

1. What is energy?

2. What are some types of energy?

3. Is Power the same thing as Energy?

4. What is a kilowatt(kW)? What is a kilowatt-hour(kWh)?

5. How is electricity generated?

What is Energy?

We all have a basic concept of what energy is...

- When we are tired we might say that we have "no energy"

- We need electrical energy to power our appliances.

- When we leave the door open in the winter, we are losing heat energy.

An official definition is as follows:

Energy is the capacity of a physical system to perform work.

Now this definition is a little confusing. Work is performed when a force is exerted on a object and it moves a certain distance.

The important part of the definition is that energy is a capacity to do something; it is not a thing in itself.

For example you purchase electrical energy (the units are kilowatt-hours or kWh) which has the capacity to do something - like convert to light energy in a light bulb.

One more important concept:

Energy can not be destroyed or created, only transferred or converted.

Let's move on with the energy primer to discuss the types of energy to help clear things up...

What are the types of Energy?

  1. Energy Related to Motion. When we talk about the motion of objects, the forms of energy in the discussion are Kinetic Energy, Potential Energy, and Work

    • Kinetic Energy is the type of energy an object in motion possesses. For example, when a ball is thrown it has kinetic energy. If the ball hits the ground the energy is converted to work (the ground may dent).
    • Potential Energy is related to the distance an object is from the ground or other surface. I cup on the counter has potential energy. If it falls off the counter, the energy is converted to kinetic energy, and when it hits the ground it performs work (smashes).
    • Work is done when an object is moved a certain distance. For example, if I push a cup off the counter, work is done.
  2. Thermal (Heat) Energy. Some object that is a higher temperature has more thermal energy than one at a lower temperature. If object has more thermal energy, its molecules are moving and vibrating at a faster rate (higher kinetic energy and potential energy).

    Note: Your furnace actually converts chemical energy to heat energy as combustion is a chemical process.

  3. Electrical Energy. Some materials like copper are conductors. When electricity flows through copper, electrons are moved from one atom to another creating electrical current.

    The "force or pressure" required to move the electrons is from the voltage in the line. Voltage is like pressure in your water lines and current is like flow. Without pressure in your water line, your garden hose only trickles (no flow). The same is true for electric current; current can not "flow" without voltage.

  4. Chemical Energy. When two molecules react chemically energy is released or absorbed. An example is combustion in your home's furnace (as mentioned above). The methane in the natural gas reacts with oxygen and forms carbon dioxide and water, while releasing heat.

    In your body, certain molecules are stored (potential energy) and then broken down when the energy is required. The chemical energy is converted to both heat (to keep you warm) and kinetic energy (moving an arm for example).

  5. Light Energy. Light, electromagnetic radiation, is emitted and absorbed as tiny particles called photons. The spectrum of light includes a wide range of wavelengths. Only a small portion of the light spectrum is visible light.

    Some of the other areas are microwave, UV, infrared, x-rays, and radio waves. UV (ultra violet) light has a shorter wavelength than visible light and contains more energy. This is why UV light can burn your skin.

    An incandescent light bulb only converts approximately 10% of the electricity into visible light. The rest is converted to infrared light which we can't see but we feel it as heat.

  6. Sound Energy. Sound can be described as a pressure wave travelling through something like air or water. Something like a drum vibrates the air around it. This air compresses and then expands the air next to it and starts a chain reaction (a wave travelling through the air). Our ears then change the sound wave into a signal of nerves pulses sent to the brain.
  7. Nuclear Energy. There is a ton of energy contained within the nucleus of an atom (If you remember from your science class, the nucleus contains particles called protons and neutrons and is surrounded by a cloud of electrons).

    With nuclear energy, the matter is actually converted into energy. There are two types of nuclear processes: fission and fusion. The type used in current nuclear power plants is fission. The actual process is beyond the scope of this energy primer but a short description of the processes is below.

    Nuclear fission is the process where a large atomic nucleus (such as the nucleus of a uranium atom) is split releasing immense quantities of energy.

    Nuclear fusion is the process where multiple nuclei join together to form a larger nucleus also releasing large quantities of energy. Fusion is not yet used commercially.

Is Power the same thing as Energy?

No. Power is the rate at which energy is converted or "used".

For example, on your electrical bill, energy is measured in kilowatt-hours (kWh), which is the average rate at which you use energy x the number of hours in the month. The average rate you use energy is measure in kilowatts (kW).

An other example is a 800 W electric heater (W = watts of power). If you use it for 100 hours in a month, you will have used 80000 watt-hours or 80 kilowatt-hours (kWh) of energy.

The next section of the energy primer discusses this further.

What is a kilowatt(kW)? What is a kilowatt-hour(kWh)?

Typically, units of measurement can be confusing.

Units of energy include:

  • J = joules
  • Nm = newton-metres
  • kWh = kilowatt-hours
  • cal = calories
  • Btu = british thermal units
  • therms

All these units can be converted other units on the list (they are a measurement of the same thing = energy).

For electricity, it is standard to use kWh, while for thermal energy you would likely use Joules (metric) or Btu (imperial). You could say that you used 3414 Btu of electricity but this is not common (equivalent to 1 kWh or 3600000 J).

Units of power include:

  • W = watts
  • J/s = joules per second (same as a watt)
  • Btu / h = british thermal units per hour
  • hp = horsepower
  • cal / s = calories per second

How is Electricity Generated?

Electricity is generated through various energy conversion processes. The final step in each case is the conversion to electrical energy. In the power generation industry the final conversion to electrical energy is by one of the following three processes:

  1. Generators. The shaft of a generator is turned by some mechanical device like an engine, gas turbine, water turbine, water wheel, wind turbine or steam turbine. A generator converted kinetic energy to electricity through a electromagnetic induction process.
  2. Direct Chemical Conversion - Fuel Cells, Batteries, etc.
  3. Light Conversion - Solar Panels, Solar Cells.

Energy Primer

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