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Temperature difference drives electricity? Why can thermal energy be converted into electricity?
As the world's demand for renewable energy grows, scientists and engineers are increasingly exploring how to harness heat found in nature to generate electricity. Among them, the thermoelectric effect, as a technology that directly converts temperature difference into voltage, is receiving widespread attention and research.
Thermoelectric effect consists of three fascinating effects: Seebeck effect, Peltier effect and Thomson effect, which together demonstrate the principle of how thermal energy is converted into electrical energy.
Overview of Thermoelectric Effect
Thermoelectric effect can be simply defined as the phenomenon that voltage is generated when there is a temperature difference between the two ends of a substance. In this process, thermal energy can be effectively converted into electrical energy. How does this happen? When a temperature gradient exists, charge carriers within a substance diffuse from areas of higher temperature to areas of lower temperature, creating a voltage. This property allows thermoelectric devices to be used in areas such as power generation, temperature measurement, and fine-tuning of temperature.
Seebeck effect
The Seebeck effect refers to the electromotive force generated across a conductor when there is a temperature difference between two points on the conductor. This electromotive force is proportional to the temperature difference and is described by the Seebeck coefficient. In 1821, physicist Seebeck rediscovered the phenomenon, giving it its name.
The Seebeck effect is not only the generation of an EMF, it also induces a measurable current or voltage, just like any other form of EMF.
How thermoelectric devices work
Although the basic principle of the thermoelectric effect seems simple, it is full of challenges in actual operation. Take a thermocouple as an example. It consists of two wires of different materials that form a hot junction at the bimetallic junction. The temperature difference at this hot junction drives the flow of electric current. When the Seebeck coefficients of these materials differ, a measurable voltage is generated at their free ends, enabling them to be used as thermometers.
Peltier effect
The Peltier effect is another key thermoelectric phenomenon, which occurs when an electric current passes through the junction of two conductors, causing heating or cooling. The inverse relationship of these effects allows thermoelectric devices to be used for both cooling and heating, making them ideal for a variety of active cooling applications, such as heat dissipation in electronic devices.
From small thermoelectric coolers to complex heat pump systems, the Peltier effect plays an integral role in modern technology.
The impact of Thomson effect
The Thomson effect goes a step further and examines the heating or cooling behavior of a current conductor under a temperature gradient. In other words, the effect involves the interaction between the current and temperature changes within a conductor, making the design of any thermoelectric device require taking this complex energy transfer mechanism into account.
Applications of thermoelectric devices
As the demand for energy efficiency increases, the potential applications of thermoelectric devices continue to expand. From medical devices to wearable technology, from aerospace to industrial process control, thermoelectric devices can be used in a wide range of applications.
While these devices currently operate at relatively low efficiency, their irreplaceable nature with no moving parts opens up entirely new possibilities for their future.
Future Outlook
Thermoelectric technology is experiencing rapid development, and ongoing research is dedicated to finding new materials to increase the efficiency of this technology. In addition, how to combine thermal power systems with other renewable energy technologies will become an important direction for future research. Could widespread adoption of thermoelectric devices one day change our understanding of energy efficiency?
