There is almost always more than one solution to any given problem. One of society’s compounding problems is the waste of energy and the fact that traditional energy is not being recycled. Thermoelectricity could be considered a clean energy source capable of turning waste heat into electricity. The Stirling engine is definitely an interesting way to power mechanical work. A peltier junction is also an interesting way of achieving this goal in a not so traditional way. Both the Peltier junction and the Stirling engine use the thermoelectric effect to allow work to be done.
The thermoelectric effect works by temperature conversion via p/n junction to electricity. It is often most seen in Peltier junctions. The thermoelectric effect has three main properties in which enables us to understand how it works.
1. Seebeck Effect
When heated or cooled on one side, the p/n junction will produce voltage which can be used. The greater the difference in heat between the two sides of the junction, the greater voltage output will be produced. The temperature difference makes the metals react differently which creates a magnetic field.
2. Peltier Effect
When a current is passed through the junctions then one side will get hot, and the other will become cold. This is often used in refrigeration.
3. Thompson Effect
The Thompson effect is the third effect in which heat is proportional to both the electric current and temperature gradient. This further enables calculation of the first two effects voltage potentials.
As much as 60% of total energy produced in the United States, is wasted. The majority of the wasted energy is in heat or thermal energy. We can utilize waste heat by employing Stirling engines, Peltier junctions, and thermocouples. The water that is heated for your showers can be put through a heat exchange to produce electricity as well as be recycled. Automobiles that use combustion lose as much as 75% or more of the energy produced to function. Using waste heat recovery will enable electricity to be produced from that heat which could be used for charging batteries. The less work you put on the engine the more horsepower you will achieve. This could lead to an engine being smaller but having the same performance as a larger engine.
Stirling engines are not a new concept. In fact, one of the first Stirling engines appeared in 1816. There are many DIY Stirling engines on the internet. NASA even finds the concept of the Stirling engine practical enough to help power the curiosity mission on Mars. Another use for a Stirling engine is to pump water. They work by using an external heat source. Once you have the external heat source, then the Stirling Cycle can take place. Heat expands the gas inside the cylinder, and doesn’t leave the cylinder. The left cylinder will heat up, causing the gas to move to the right cylinder which is being cooled. The right cylinder’s piston will then compress the gas by moving upward and transferring the gas back to the left cylinder. The process is repeated indefinitely, given there is a constant heat source. There are many variations of the engine with different applications for each. The beauty of a Stirling engine is that the source of heat can come from anything.
Feature Image: Telus Company plans to reuse waste heat from its existing data cener in Vancouver, BC to power its new Telus Garden development. Image via TelusGarden.com.