Underutilized Tesla Turbines Show Promise for Niche Energy Applications

The Tesla turbine was invented and patented by its namesake, Nikola Tesla, whose contribution to widespread US adoption of Alternating Current is probably his most well-known feat. Unlike conventional turbines, which use aerodynamic (or hydrodynamic) surfaces to extract work from flows of gas (or water), Tesla turbines are bladeless. They consist of a series of circular disks that pick up energy from fluid shear as high-velocity flows travel past.

A Tesla turbine’s disks are spaced closely together, and they contain outlet holes near the center that let the fluid escape near the axis of the turbine. This feature likely promotes co-rotation of the fluid in the turbine housing with the disks, forming a kind of vortex. By contrast, so-called Thupp turbines let the high-velocity fluid in and out at the periphery of the disks, a configuration that does not promote vortex formation. In the Tesla turbine, the disks are connected directly to a shaft, which protrudes from the turbine housing. When fluid flows over the disks, they turn the shaft, which can then be tapped to perform useful work or be affixed to a generator to create electrical power.

Benefits of Tesla turbines compared to conventional turbines include 1) ease of fabrication, 2) “thin” aspect ratio, and 3) and robustness against multi-phase flow. A Tesla turbine drawback is high rotational velocity, which is known to warp the disks. Phoenix Navigation and Guidance, Inc. of Munising, MI seems to have made a start on use of advanced materials to mitigate warping, but the current state of their Web site suggests the company may be dormant. Also, since turbine output power is the product of rotational velocity and torque, high Tesla turbine rotation rate leads to low torque production. Thus, a gear-down (with inherent efficiency losses) is often required for a Tesla turbine to turn a generator.

Tesla turbines were seriously studied and evaluated by Professor Warren Rice of Arizona State University and found to approach 40% efficiency. While not comparable to axial turbines, this efficiency is high enough to suggest that Tesla turbines can be a viable solution in niche applications where axial turbines do not function well: tight spaces and when working fluids carry abrasive particles.

Somehow, despite their legitimate value in niche applications, Tesla turbines got lumped into the class of energy technologies that is outside the mainstream research and development community. So, it is difficult to find recent professional work on this energy technology, but amateur research is prolific. A YouTube post, “Tesla Turbine Concepts Explained“, gives a 10-minute presentation on Tesla turbine basics that is mostly technically sound, and from that post there are links to hundreds of other amateur Tesla turbine videos. Alan Swithenbank (who is a staff member at Stanford University) maintains an interesting sight highlighting his Tesla turbine creations, and the Tesla Engine Builders Association maintains a Web site with spirited discourse about advancing Tesla turbine development.

Seeing an opportunity to further extend Tesla turbine research to capitalize on niche applications in renewable energy, the Mechanical and Energy Engineering Department at the University of North Texas (UNT) purchased a small air-driven turbine from OBI Laser Projects, a job shop in Canton, CT.

UNT Students built the air inlet manifold pictured above and set up the turbine for measurements of maximum rotational velocity as a function of inlet pressure. In this configuration, the turbine spins with no external load, providing a data on how fast air is flowing in the housing and how much disk distortion is occurring.

Tamir Emran contributed to this post.