Viktor Kaplan: The inventor of the turbine that transformed hydropower

He wasn’t even ten years old when he built his first motor. As a child, he also created a working model of a steam engine and experimented with a small water wheel on the Mürz River. Viktor Kaplan was born in 1876 in Mürzzuschlag, Austria, as the son of a railway official, but his talent and passion for technology were undeniable.

It’s no surprise, then, that he pursued technology and engineering in his studies at the Vienna Technical University, where he focused on diesel engine construction. He continued working with engines in his first job at the Ganz and Comp machine factory in Löbensdorf near Vienna, where he spent two years developing an internal combustion engine. 

Kaplan’s Path to Revolutionizing Hydropower 

However, it didn’t take long before, at the age of 33 (in 1903), he relocated to Brno at the invitation of his superior, Professor Alfred Musil, to join the German Technical University. There, as a designer in the Department of Mechanical Engineering and Kinematics, he began to focus on the economic use of water streams—an issue that was significant at the time.

For generating electricity from water streams, the Francis and Pelton turbines were used, but by the early 20th century, they no longer met the demands of the industrial revolution. Thus, Kaplan built on Francis’s work, aiming to find ways to utilize water streams more efficiently. 

The Birth of the Kaplan Turbine 

Kaplan’s theoretical knowledge was impeccable, but he didn’t stop at theory. In his experiments, he sought the most suitable parameters for the traditional Francis turbine and was the first in the world to take water viscosity into account in his calculations. He knew that reducing the energy loss caused by water friction was essential, so he experimented with the number of blades, their angle, and thickness.

He soon realized that an efficient turbine should function similarly to a ship's propeller, leading him, in 1913, to be the first to conceive of installing adjustable blades in the runner to adapt the shape of the runner to the current water flow. This significantly improved the turbine’s regulation capabilities, resulting in a highly efficient turbine that could also be used with low water flow. As a result, even less predictable or fluctuating water flows could remain profitable. 

From Basement Laboratory to Worldwide Success 

Let’s go back to the beginning of Kaplan’s time in Brno. Upon his arrival, Kaplan lacked a laboratory where he could verify his theoretical knowledge. His first experiments were conducted not with water, but with air, using household items—such as heating with an iron stove to create the necessary upward airflow, and a wheel with paper blades.

It wasn’t until 1909, when Kaplan also became an associate professor, that he requested the university to establish a laboratory in the school’s basement. Unfortunately, his efforts were met with indifference and meager financial support from the Austrian government, so Kaplan had to secure all the equipment on his own. In the small basement room, he worked alone or with his assistant, Jaroslav Slavík, with equipment far smaller than required.
 

At the right time, he met his benefactor—Brno businessman Heinrich Stork, who invested in Kaplan’s research. This smart move paid off for Stork a few years later when his father’s company, Ignaz Storek, made history by producing the first Kaplan turbine. The first turbine, manufactured in 1919, was installed in a spinning mill in Velm, Austria. It achieved an impressive efficiency of 86%, confirming the accuracy of Kaplan’s research. This pilot prototype remained in operation for an incredible 33 years.

Soon, more successful installations followed, but Kaplan was fully satisfied only after his 8,243-kW turbine (with a 5.8-meter diameter runner, the largest in the world at the time) was installed in 1925 at the Lilla Edet hydropower plant in Sweden. 

Exhausting Legal Battles 

Although the first Kaplan turbine was manufactured after World War II, its invention dates to 1912. Between 1912 and 1914, Kaplan applied for patents for his main inventions (radial Pelton wheel, adjustable blades, bladeless space arrangement between the guide and radial wheel, and chamberless blades), but it took nearly a decade before the patents were recognized. The process was complicated by World War I, but the main obstacle was the manufacturers of the Francis turbine, who saw Kaplan’s invention as a threat to their investments. Efforts to tarnish Kaplan’s reputation led to a nervous breakdown, but he eventually succeeded in completing the patent process in 1920.

 

The most challenging moment in Kaplan’s career came in 1922 when a problem with the turbine material arose. During the installation of turbines on large rivers, their blades broke, and concrete walls cracked. The issue was caused by cavitation, the release of air absorbed from the water. However, this obstacle was also overcome (thanks to solutions from Kaplan’s assistants), and the situation soon improved even further when Kaplan won all his legal battles. With duly accepted patents, his turbine could embark on its victorious journey around the world. 

The Ignaz Storek company manufactured over 500 turbines over several decades, which were installed in many European countries. 

A Peaceful Retirement on a Farm 

Kaplan spent nearly 30 years in Brno (1903–1931). At the age of 55, he ended his university career and moved to Rochuspoint, Austria, where he built his own workshop and a small hydroelectric power plant. Just a few years later, on August 23, 1934, he passed away at the age of 57, shortly after receiving an honorary doctorate in technical sciences from Brno University.

For his work, he was also honored 20 years after his death with the Rudolf Diesel Medal, Europe’s oldest award for scientific work, inventions, and innovations with direct economic impact and significance.

Viktor Kaplan left behind dozens of theoretical works and applied for over 280 patents in 27 countries during his lifetime.