Nikola Tesla, wireless electricity, and the failure of Wardenclyffe Tower

Nikola Tesla 

Nikola Tesla (1856-1943) was a Serbian-American engineer and one of the most brilliant inventors of his time. His discoveries on how to utilise alternating current laid the foundation for the industrial revolution and today makes up the majority of power distribution systems globally. Finding inspiration from his mother Duka Mandic, whom he called a first-class inventor and credited for passing on her gift of discovery*, he went on to make significant contributions to the development of X-ray technology, radio, and robotics, as well as inventing the brushless AC motor, the rotating magnetic field, neon lights, and remote control. However, despite his many revolutionary inventions and around 300 patents to his name, Tesla died poor and ultimately failed in his greatest pursuit: to develop a free system of clean, wireless, electric power. Wardenclyffe Tower, also known as the Tesla Tower, was the first step in Tesla’s ‘World Wireless System’, a system designed to wirelessly broadcast electrical power across the globe, based on 20th century knowledge of resonance, the earth’s conductivity, and the Tesla coil. 

The Tesla coil: working principle

The Tesla coil, invented by Nikola Tesla in 1894, is an alternating current resonant transformer that produces a high voltage from a low current. The high voltage produces sparks of ‘lightning’ or electrical discharge which can power lightbulbs. This experiment was a key motivator for Tesla’s later works with Wardenclyffe, although today the main use of the Tesla coil is for filming, entertainment, and educational displays. 

In a typical transformer, the ratio of turns determines the output voltage. The resonant properties of the secondary coil in a Tesla coil allows the transformer to achieve much higher voltages. A high voltage power supply from the first transformer is applied to a small primary coil, creating a large magnetic field. Current flow through the primary coil charges up a capacitor until the voltage across it exceeds the breakdown voltage of the spark gap (air). The capacitor discharges through the secondary coil in the opposite direction. This reverse current flow induces a magnetic field around the primary coil in the opposite direction. The constant changing of field direction induces a current in the secondary coil and produces a voltage proportional to the winding ratio of the coils. The resulting high voltage produces arcs of electricity similar to lightning from the terminal (typically torus shaped to direct sparks outward and prevent interference). 

Despite the high voltage, these electric discharges only produce a very small current in people who interact with it because of the high impedance of the coil and are not dangerous unless a person has a pacemaker or other medical device that could be affected by the high voltages. The frequency of the current has little interaction with nerve cells.

Wardenclyffe Tower

Following the same principles as the small-scale Tesla coil, Tesla’s vision was to replicate this on a large scale to develop wireless power across the globe, so that information could be transmitted from one tower to another by resonance. His early design featured two towers placed next to each other, so that the gap between the two domes could act as a spark gap. After cost revisions, the tower was redesigned to feature the entire transmitter circuit in one tower (see Figure 2). 

Figure 3 shows Tesla’s plan for the World Wireless System. An oscillator tower stands at 187 feet with a large dome of conductive metals on top, and an iron root system 300 feet into the earth. When the tower and Tesla receivers are tuned to the same resonant frequency, Tesla theorised that energy could be efficiently transferred between them. 

After obtaining funding from financier J.P. Morgan, Wardenclyffe tower began construction in 1901 in Shoreham, New York. The 187-foot tower featured a large spherical terminal, which was intended to ionize the atmosphere and create a conductive path for the energy. Below ground, a network of metal rods and plates would transmit energy into the Earth, relying on the Earth’s conductivity to complete the circuit. The working of the tower fundamentally relied on two highly under-researched principles, which were:

1. Earth as a conductor: In 1899 before Tesla began work on Wardenclyffe, he studied the periodicity of lightning in Colorado Springs, USA, and discovered what he called earth resonance. He found that large electrical impulses travel longitudinally through the earth to the antipode and are reflected (i.e., ‘resonate’) creating terrestrial stationary waves. He planned to use the tower to send electrical energy through the ground, which would then be picked up by receivers located anywhere on the planet. 

2. Air as a conductor: Although air is normally a good insulator, at high altitudes (the earth’s ionosphere) it becomes an excellent conductor of high frequencies and voltages. The tower was designed to generate extremely high-frequency alternating currents, however reaching the earth’s ionosphere would require an antenna of at least 15 miles tall. Tesla apparently discovered a way to bypass this but did not make his methods public. 

There was very little knowledge about these phenomena at the time and even today are still not fully validated. 

Why Wardenclyffe failed

Tesla initially pitched the project to J.P. Morgan as a world system of wireless communication to send messages, reports, and secure military messages, and to broadcast news and music. Morgan invested around $150,000 which Tesla accepted and instead began working on wireless electricity transmission, despite the investment being far below a realistic sum for the cost of the project. As Wardenclyffe tower required frequent modifications to the tower’s design during construction as well as expensive materials, the project was very costly. At the same time, Guglielmo Marconi achieved his less ambitious and inexpensive aim of wirelessly communicating the letter ‘s’ in Morse code (using some of Tesla’s patents). Combined with the Panic of 1907 and realising Tesla’s primary aim was for electricity to be free worldwide, which would be difficult to monetise, J.P. Morgan withdrew financial support and Tesla was forced to abandon the project.

The scientific community and further potential investors were also sceptical about the feasibility of wireless energy transmission particularly considering energy losses over long distances, which made it difficult to obtain further funding. At the same time as Wardenclyffe Tower was being developed, Tesla’s AC power distribution system was being implemented rapidly. The established infrastructure of wired electricity transmission made it even more difficult for Tesla's wireless system to gain traction and funding, and the tower was demolished in 1917 to satisfy Tesla’s debts. 

Conclusion

Wardenclyffe tower was an ambitious and audacious project which ultimately was not financially feasible. Even with modern day technology, efficiency, safety, and economic considerations prevent the system being a practical reality. Nevertheless, Tesla was undeniably an ingenious inventor, and his futuristic and daring approach to engineering continues to inspire innovations as well as debate. Today the site of Wardenclyffe tower is home to the Tesla Science Centre, a memorial to Tesla’s life and work. 

Footnotes

* A highly skilled and intelligent woman despite no formal education, she invented various household tools and devices like the loom and egg whisk.

Written by Varuna Ganeshamoorthy

Related article: Electricity in the body

REFERENCES

Tesla, N., & Johnston, B. (1982). My inventions: the autobiography of Nikola Tesla.