Horizontally revolutionary

HP3+, which stands for a horizontal Pelton turbine with three or more nozzles, is the name given to this innovation by Voith Hydro. An increase in the number of nozzles results in an increase in power density and thus also in speed. As a result, both the generator and the turbine can be made smaller.

Mack sees another major advantage: “Servicing a horizontal machine is much easier than a vertical shaft because everything is on one level in a horizontal arrangement.” The maintenance team can stay on one floor and in the power­house environment when servicing the turbine and has a direct view of the overhead crane. When installing vertical arrangements, the installation team often has to work across several floors under makeshift lighting conditions using chain hoists. Accordingly, this requires much more effort to create a safe working environment. “Our colleagues from St. Pölten came up with a lot of ideas during the mechanical design work for the HP3+ in order to be able to service the turbine quickly and safely,” says Mössinger. “The result has likewise been innovative solutions that didn’t exist before.”

In addition, about 20 years ago, companies started to completely gut old powerhouses that were equipped with horizontal machines in order to then use vertical machines. This required dismantling the underwater channels and the entire infrastructure on site. Because the powerhouse is too low to properly perform maintenance on a vertical machine, however, this solution always remained a compromise. “When performing general maintenance, it is often necessary to tilt the entire generator and then dismantle the rotor in a horizontal position. This obviously involves a considerable amount of work,” explains Mack. When utilizing horizontal units, this effort is, of course, no longer required. Construction measures are also much more modest, as the new horizontal machines can, ideally, be placed on top of the existing foundations.

The candidate that met these requirements is none other than Austria’s leading energy transition company Verbund. It operates the Gerlos 1 storage power plant in the Zillertal valley in Tyrol. This plant was brought into operation in 1949 and now has an annual capacity of 326 GWh. As a result, the power plant supplies over 70,000 four­person households with renewable energy, as the first six­-nozzle horizontal Pelton turbine has been successfully in operation here since October 2022. It replaced the four two­-nozzle vertical machines previously installed.

Although the equipment itself is more expensive with the horizontal solution, customers save that much more when it comes to construction costs. This is because the turbine can be replaced without major construction work, which saves a massive amount of time and money. And the fact that fewer machines are in operation also reduces maintenance costs in the future.

The specification originally envisaged a conventional twin unit with one generator and two two­-nozzle turbines each. There simply wasn’t enough installation space for this solution, however. “For our HP3+ solution, we were able to gain valuable space by developing the inlet numerically,” Mössinger adds. “This ensured that the unit would be well positioned in the powerhouse for all maintenance operations.”

These advantages are also proving their merits in a second pilot project at the Vermuntwerk plant in Vorarlberg, which is operated by Illwerke. Here, five two­-nozzle units are being replaced by two turbines with six nozzles – while total plant capacity will remain the same. “Two turbines means you only have to maintain two runners and two generators and also only two transformers, instead of five like before. This will significantly reduce maintenance costs.”

Mack has been involved in the development of this innovative solution from the very beginning. “It was great seeing the first prototype of an HP3+ installed and then in operation.” To him, one thing is abundantly clear: “On the one hand, developing a solution like this requires members of management at Voith who have the necessary vision to see that such an idea will be successful. On the other hand, confidence in our solution on the part of customers, which has grown over many years of continuous collaboration, is also necessary. At the end of the day, we want our customers to be satisfied with our turbines, that’s the main thing.”

Innovative turbine developers at Voith: Reiner Mack, Dr. Peter Mössinger and Dr. Jörg Necker.