The German tower designer said the limit for turbine hub heights "should be around 180 metres" for the design to be cost effective.
Knitl told Windpower TV that hub heights of between 160 metres and 180 metres were feasible but also remained cost effective.
Knitl was speaking at the WindEnergy Hamburg 2014 event taking place in Germany this week.
"With the increasingly larger diameter rotors of the turbines, the tower also has to grow," Knitl said.
"The next generation we want to install will be a 160-metre hub height in the middle of next year."
Knitl also showcased the company's new energy storage system to be installed inside towers.
"We have developed with our hybrid tower system a combined system, water storage in the tower and a pump storage in a lake 200 metres downhil,l with a 20MW capacity in the turbines and also the pump storage," he added.