Dream on the road of wireless charging
Since Austrian and American physicist Nikolay Tesla proposed the idea of wireless power transmission a hundred years ago, wireless charging technology has made great progress, but its application has made slow progress. Until the popularity of mobile phone wireless charging in recent years, wireless charging was well known to the public. The popularity of electric vehicles has also aroused people's curiosity: can wireless charging be applied to electric vehicles?
Tesla coil and its wireless charging system
Nikola Tesla obtained the Tesla coil circuit patent on April 25, 1891 and first publicly displayed it in a speech by the American Society of electrical engineers at Columbia University in New York a month later. Although Tesla has obtained many patents for similar circuits before, this is the first circuit containing all components of Tesla coil: high voltage primary transformer, capacitor, spark gap and hollow oscillation transformer.
From 1891 to 1893, Tesla began to lecture and display Tesla coils everywhere, showing its new scientific discoveries in high-voltage and high-frequency power transmission. Unlike the DC or low-frequency AC that scientists were familiar with at that time, the RF AC generated by Tesla coil. He used spectacular brush discharge and streamer to heat iron through induction, indicating that RF current can be transmitted through insulator and single line without return path. There is no need for wires to power bulbs and motors, which impressed the audience. He also applied hundreds of thousands of volts to his body, so that his body was illuminated by luminous corona discharge in a dark room, which proved that high-frequency current would not cause electric shock. These speeches and performances made the scientific community know Tesla oscillator at that time, and his reputation enjoyed a high reputation in the world.
Tesla's lifelong dream is to use Tesla coil to realize wireless power transmission. From 1891 to 1900, he tried to conduct some wireless charging experiments to transmit RF power over a short distance through inductive coupling between coils. In 1893, at the Chicago Columbia fair, he lit a light bulb from another room. By tuning to resonate with Tesla coil LC circuit, he found that the receiving LC circuit can increase the transmission distance and transmit energy through resonant inductive coupling. From 1899 to 1900, in his Colorado Springs laboratory, he used a huge transmitting coil to generate a high voltage of 10 million volts, and lit three incandescent lamps at a distance of about 100 feet (30 meters). Today, the resonant inductive coupling discovered by Tesla has become a very common concept in electronics, which is widely used in intermediate frequency transformers and short-range wireless power transmission systems, such as mobile phone charging boards.
We know that inductive and capacitive coupling is a near-field effect, so it can not be used for long-distance transmission. But Tesla is convinced that he can develop a remote wireless power transmission system to transmit power directly from power plants to homes and factories without wires. He claims to be able to transmit electricity around the world, including through the earth and the atmosphere. Tesla believes that the whole earth can be used as an electric resonator. By driving the current pulse from the grounded Tesla coil to the resonance frequency of the earth, the potential of the earth can be oscillated, so as to create the global status wave. The AC can be received through the capacitive antenna, which can resonate with any point on the earth. Another idea is that the transmitting and receiving terminals can be suspended by balloon at an altitude of 30000 feet (9100 meters), where the air pressure is very low. He believes that this thin air with high conductivity can transmit power to high voltage (hundreds of millions of volts) over a long distance.
Tesla wants to build a global wireless power network, which is called the world wireless system, which can transmit information and power to everyone on earth. 100 years later, although his dream did not come true, the wireless charging of mobile phones and even electric vehicles has become a reality. His lofty dreams, bold ideas and adventurous spirit have laid a solid foundation for the development of modern electronic technology.
