Physical Science: Energy How Energy Can Be

Physical Science: Energy

How Energy Can be Converted from one Form to Another, With Examples

"Energy" is defined as the capacity to produce changes within a system. Within a system, energy can be changed to a different state in order to perform work in natural processes or machines (Shipman, Wilson, & Todd, 2009, pp. 88-89). Plants, animals and machines all convert energy to perform work in their processes. Through Photosynthesis, green plants use Chlorophyll, composed of miniature energy factories called Chloroplasts, to convert solar energy into storable chemical energy as a sugar called Glucose (Nave, Pigments for photosynthesis, n.d.). In the body of an animal or human, the cells' energy factories, called Mitochondria, contain Organelles, which convert chemical energy stored in food into Adenosine Triphosphate (ATP), which is the energy used in life processes (Nave, Mitochondria, n.d.). An internal combustion engine, such as a car's engine, converts the potential chemical energy in gasoline and oxygen into heat, then into kinetic (here, mechanical) energy, which propels the car (Cromer & Proctor II, 2012).

2. The Meaning of Fossil Fuels, Why They are an Attractive Energy Source, and Why They are an Unattractive Energy Source

Fossil fuels are hydrocarbons formed from the remains of dead plants and animals. The most prevalent forms of fossil fuels are coal, fuel oil and natural gas (Science Daily, 2010). They are an attractive energy source for several reasons: initially, they were easy to extract, plentiful, easy to transport and profitable for the suppliers (e.g. oil companies); now they are more scarce and harder to extract but they are still easily transported and profitable for the suppliers. Fossil fuels are an "unattractive" energy source because they are finite and nonrenewable. The following table shows estimate world reserves of fossil fuels as of 2007:

(Consortium on Energy Restructuring, Virginia Tech, 2007)

Fossil fuels are also an unattractive source of fuel because they are inefficient and result in considerable pollution. Since no conversion process can convert all the energy of one form into the new form and since the conversion of fossil fuels into electricity takes several steps, fossil fuels are an inefficient source of electric power, hovering around 40% efficiency. Fossil fuels also pollute the environment with fly ash, and "greenhouse gases" such as carbon monoxide, carbon dioxide, sulfur dioxide, and nitrous oxides gases. These "greenhouse gases" contribute to acid rain and global warming effects (Consortium on Energy Restructuring, Virginia Tech, 2007; PhysicsnScience, 2011).

3. Two Energy Alternatives to Fossil Fuels

Two energy alternatives to fossil fuels are hydroelectric power and wind power, both of which are indirect types of solar power. Hydroelectric power is an indirect source of solar power because it uses the "stream-flow" portion of the hydrological cycle. In hydroelectric power plants, a mass of water flows through hydraulic turbines, converting the water's potential energy into kinetic energy within the turbines and driving electric generators, thereby creating electrical energy that can be stored and used. Hydroelectric power is a more attractive than fossil fuels because it is renewable, non-polluting and highly efficient, as large turbines can capture up to 90% of the water stream's power. Hydroelectric power does have significant disadvantages because it can disrupt the environment's normal ecology by changing the water's natural flow and using a considerable amount of surrounding land.

Wind power, which is another form of solar power because wind is created by solar radiation, uses turbine-like wind generators: wind propels the generators, which convert the wind's kinetic energy into rotary-shaft motion, which is then converted into electrical energy that can be stored and used. Unlike fossil fuels, wind power is renewable and nonpolluting, with a maximum efficiency of 59.3% but a common efficiency of 40%; however, it does cause environmental problems such as creating noise, disrupting the natural aesthetics of their locations on mountains, mountain passes and coastlines, and they are apparently harmful to birds (Consortium on Energy Restructuring, Virginia Tech, 2007).