For example, we have chemical energy in the form of fuels and can convert that chemical energy into electricity. How does that process work? How can we turn kinetic energy of wind mills to electricity? How does sunlight turn into heat energy? How come we can measure energy in Joules when there are so many forms of it?
In: Chemistry
>For example, we have chemical energy in the form of fuels and can convert that chemical energy into electricity.
Chemicals store energy in the form of chemical bonds between atoms. There are other chemicals and configurations that these atoms would prefer to bond with, but are unable to spontaneously. For example, lets take a gas made up of Hydrogen (H2) and Oxygen (O2). The ideal configuration for these atoms would be to form water, but the hydrogen and oxygen are stable enough that they aren’t just going to break their bonds for no reason.
Lets introduce a source of heat to the gas. This can be in the form of a flame, a spark, or just a really hot piece of metal. The heat adds energy to the molecules, giving them the strength to break their chemical bonds and reconfigure in their ideal form. The result is water + energy in the form of heat since the new molecule is in a more ideal state than just pure H2 and O2. This heat is enough to trigger the reaction in more molecules, and now you have a self sustaining reaction as long as you keep adding more H2 and O2 to replenish what is consumed. Your exhaust gas (H2O) is also now very hot compared to the initial temperature.
Hot things want to expand. We can exploit this by turning the heat energy into kinetic energy. In a car, this expanding gas pushes a piston which drives a crankshaft. In a power plant, the gas pushes through a turbine. As the gas expands, it loses its kinetic energy and cools down again.
If we want to extract electricity from this rotational energy, we need to use magnets. When a changing magnetic field passes over a conductor of electricity (copper wire), a current is conducted in that wire. We wrap wires around a hollow chamber, and then stick a magnet attached to our rotating crankshaft or turbine shaft into that chamber. As the magnet rotates, the orientation of its magnetic field changes. Because the wire experiences this changing magnetic field, a current is created inside of it. This is how an electrical generator works. Side note: Permanent magnets are not strong enough to generate a very strong electrical current, so we’ll actually siphon off a small portion of the electricity we generate to run a powerful electromagnet attached to our rotating shaft instead. Because the magnetic field is stronger, we generate even more electricity and are easily able to offset the loss required to run the electromagnet.
Keep in mind that this only follows a simple form of energy generation from chemical bonds. There are other more complex forms such as fuel cells which would turn our H2 and O2 into H2O with the generation of electricity more directly, but these are rather inefficient and we don’t use them as much. I used hydrogen and oxygen because they’re simple and only have one reaction product, but you can just as easily substitute the hydrogen for something like methane (CH4).
Nuclear reactors use the heat from their fuel decaying to heat water into steam and run turbines, and wind farms or hydroelectric plants get their kinetic energy from the force of the wind or water flow.
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