---
title: "Pelton turbine: System Erlach"
description: "Pelton turbine System Erlach: up to six nozzles on a horizontal shaft. More power per machine, smaller components, good operation at low discharge."
author: "Erlach & Erlach GmbH"
language: en
canonical: https://www.erlach-erlach.com/en/pelton-turbine/
translation:
  de: https://www.erlach-erlach.com/pelton-turbine/
license: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/)
source: Generated at build time from the HTML page; same text, same sources.
---

# Pelton turbine: System Erlach

The Pelton turbine System Erlach has up to six nozzles on a horizontal shaft. This gives more power per machine, smaller components and good operation even with little water. It was invented by Josef Erlach.

## The Pelton turbine: head becomes a fast jet

Nozzle, jet, runner

*[Pelton turbine, Nozzle, jet, runner: A runner with buckets on its rim. From the left, a nozzle with a needle directs a horizontal jet at the lower edge of the runner. An arrow shows the direction of rotation.]*

Bucket in section

*[Pelton turbine, Bucket in section: A bucket made of two halves, open towards the bottom, with a splitter in the middle. The jet comes from below, hits the splitter, divides and is turned by almost 180 degrees in both halves.]*

*The principle. Left, the runner seen from the front: the nozzle turns the pressure of the water into a fast jet that hits the buckets. Right, a bucket in section: the splitter divides the jet, and the two bucket halves turn the water almost fully around. Own schematic drawing.*

The Pelton turbine, also called the Pelton wheel, is a water turbine for high heads. The water comes from the mountain through a penstock. In the nozzle, its pressure is converted almost completely into velocity. The jet hits the buckets on the rim of a runner, is split and deflected, and gives up almost all of its energy. The turbine was invented by Lester Allan Pelton. His patent dates from 1880.

How nozzle, jet and bucket work together is explained under [Pelton turbine working principle](https://www.erlach-erlach.com/en/pelton-turbine/working-principle/). How to get from head and discharge to the machine is explained under [Pelton turbine design](https://www.erlach-erlach.com/en/pelton-turbine/design/).

## Pelton turbine and System Erlach: the difference

System Erlach is a particular Pelton turbine: the shaft is horizontal, and up to six nozzles sit around the runner. Nozzle, jet and bucket work as in any Pelton turbine. What differs is the housing and, depending on the choice, the inlet.

|     | Pelton turbine, conventional | Pelton turbine System Erlach |
| --- | --- | --- |
| Shaft position | horizontal with one or two nozzles, vertical with four to six | horizontal with two to six nozzles |
| Splash water | falls freely into the housing; with many nozzles on a horizontal shaft, part of it falls back onto the runner | two guide rings catch it and lead it to the outlet |
| Nozzle spacing | horizontal with three nozzles only 60 to 70 degrees | free to choose, 120 degrees with three nozzles |
| Inlet | ring distributor: each nozzle has a different inlet | ring distributor or axial inlet with identical pipes to all nozzles |
| Air in the housing | needs good ventilation | housing shields the runner and needs considerably less air |

**Source:** [J. M. Erlach, New Pelton Concept, Viennahydro 2012, full paper](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf), sections [1](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf#page=1) to [3](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf#page=7); [leaflet for Viennahydro, 22 November 2012](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach-und-Erlach_Faltblatt.pdf).

## Pelton turbine, conventional: splash water falls back onto the runner

The water that leaves the buckets still carries about two to four per cent of the energy of the jet. It sprays apart and carries a lot of air with it. The runner itself draws in air and can pull foam back into the buckets.

With one or two nozzles on a horizontal shaft, the water drains downwards. With more nozzles, part of it goes upwards, bounces off the housing and falls onto the runner. This is why machines with four to six nozzles have so far been built with a vertical shaft. More on this under [Horizontal Pelton turbine](https://www.erlach-erlach.com/en/pelton-turbine/design/horizontal/).

**Source:** [J. M. Erlach, New Pelton Concept, Viennahydro 2012, full paper](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf), sections [1](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf#page=1) and [2.2](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf#page=2).

## System Erlach, guide rings: two rings lead the water away

Josef Erlach started from the vertical machine with six nozzles and turned it by 90 degrees into the horizontal. So that the splash water no longer hits the runner, he placed a guide ring at a certain distance. This outer ring follows the main direction of the splash water. A second, inner ring bundles water and foam so that the runner stays protected.

Without guide rings

*[Pelton turbine, Without guide rings: Section through a housing. Water sprays from the upper bucket diagonally upwards, bounces off the wall and the ceiling and falls back onto the runner.]*

With guide rings

*[Pelton turbine, With guide rings: Section through a housing. Next to the buckets there is an outer and an inner guide ring on each side. The water flows between the rings to the side and down the housing wall into the tailwater.]*

*Section through the shaft, runner with one bucket at the top and one at the bottom. Left, without guide rings: the splash water bounces off the housing and falls back onto the runner. Right, with guide rings: the outer and the inner ring lead the water away to the side and then downwards. Own schematic drawing after [J. M. Erlach, New Pelton Concept, Viennahydro 2012](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf), Fig. [3](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf#page=4), and [the 2012 leaflet](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach-und-Erlach_Faltblatt.pdf), Fig. [2](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach-und-Erlach_Faltblatt.pdf#page=2).*

The draining water still carries motion. It therefore needs little space, and the housing stays small. Additional plates against splash water and foam are not needed.

**Source:** [Viennahydro 2012, full paper](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf), sections [2.3](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf#page=4) and [3.1](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf#page=7), Fig. [3](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf#page=4); patent [EP 1 828 596 B1](https://www.erlach-erlach.com/en/pelton-turbine/patents/#ep1828596).

## System Erlach, six nozzles horizontal: the nozzles sit around the runner, also at the top

Because the water is guided, the nozzles can sit anywhere on the circumference, also at the top. Their spacing now follows only what the runner requires. A machine with three nozzles can have 120 degrees between the nozzles instead of 60 to 70. Horizontal machines with up to six nozzles become possible.

The housing has the same structure for all arrangements from two to six nozzles.

**Source:** [Viennahydro 2012, full paper](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf), sections [2.5](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf#page=6) and [3.2](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf#page=8); [leaflet for Viennahydro 2012](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach-und-Erlach_Faltblatt.pdf).

## System Erlach, shielded housing: less air, less foam

A conventional Pelton turbine needs good ventilation. The leaflet of 2012 describes the new housing as a closed system: the guide rings shield the runner, the machine needs considerably less air, and the draining water foams visibly less. Closed here means shielded, not pressure-tight.

**Source:** [Leaflet for Viennahydro, 22 November 2012](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach-und-Erlach_Faltblatt.pdf).

## System Erlach, axial inlet: a second invention, as an option

After the splash water had been mastered, a second idea was added: an inlet in the axis of the machine, with identical pipes to all nozzles. The housing with the guide rings works with both designs, with the conventional ring distributor and with the axial inlet. Both are shown on the page [Pelton turbine distributor](https://www.erlach-erlach.com/en/pelton-turbine/design/distributor/).

**Source:** [Viennahydro 2012, full paper](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf), sections [2.4](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf#page=4) and [3.2](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf#page=8); patent [EP 2 035 689 B1](https://www.erlach-erlach.com/en/pelton-turbine/patents/#ep2035689), inventors Josef Erlach and Thomas Staubli.

## Benefits of System Erlach: more power per machine, smaller components

-   **Power density.** Up to six jets per machine instead of two or three.
-   **Cost.** For the same head and discharge, a higher speed can be chosen. Runner and generator become smaller, and so does the building.
-   **Full load.** The model test shows a clear improvement at full load compared with the vertical machine.
-   **Part load.** The presentation of 2012 names a flat characteristic curve and good operation down to 5 per cent of the discharge. More under [Pelton turbine efficiency](https://www.erlach-erlach.com/en/pelton-turbine/design/efficiency/).
-   **Horizontal shaft.** All advantages of the horizontal design are retained.

**Source:** [Viennahydro 2012, full paper](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf), section [3.1](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf#page=7); [leaflet for Viennahydro 2012](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach-und-Erlach_Faltblatt.pdf).

## System Erlach in the model test: measured at Lucerne University of Applied Sciences and Arts

*[Photo: Josef Erlach in a checked shirt and Prof. Thomas Staubli in a black shirt stand at the test rig in front of a horizontal Pelton turbine with six feed pipes.]*

*Josef Erlach and Prof. Thomas Staubli at the test rig in Lucerne, 2009*

From 2008 the machine ran as a model on the test rig of Lucerne University of Applied Sciences and Arts, under Prof. Thomas Staubli. There had been preliminary tests at the University of Stuttgart. Who measured and who cites the work is listed under [Pelton turbine research](https://www.erlach-erlach.com/en/pelton-turbine/research/).

**Source:** [Lucerne University of Applied Sciences and Arts, Pelton turbine test rig (horizontal shaft)](https://www.hslu.ch/de-ch/technik-architektur/ueber-uns/organisation-und-themen/organisation/kompetenzzentren-und-forschungsgruppen/technik/fluidmechanik-numerische-methoden/experimentelle-analyse/pruefstaende-forschung-lehre/peltonturbinen-prufstand/).

## Origin of System Erlach: filed in 2004 and 2006, in a power plant since 2022

The principle that allows a horizontal Pelton turbine to take six nozzles goes back to Josef Erlach. He filed patent applications for it in 2004 and 2006. It was licensed, developed further and first built into a power plant in 2022. The individual steps with their sources are listed under [Pelton turbine history](https://www.erlach-erlach.com/en/pelton-turbine/history/).

Where the design runs today and where it is planned is listed under [Pelton turbine power plants](https://www.erlach-erlach.com/en/pelton-turbine/power-plants/). Who builds it is listed under [Pelton turbine manufacturers](https://www.erlach-erlach.com/en/pelton-turbine/manufacturers/).

## Pelton turbine System Erlach: all pages in three branches

**01 Pelton basics.** How a Pelton turbine works: nozzle, jet, bucket, housing.

- **[Pelton turbine working principle](https://www.erlach-erlach.com/en/pelton-turbine/working-principle/)**: Nozzle, jet, bucket: how head becomes rotation.

**02 Pelton design.** Designing a Pelton turbine: from head and discharge to the machine in thirteen steps, with calculator.

- **[Pelton turbine design](https://www.erlach-erlach.com/en/pelton-turbine/design/)**: From head and discharge to the Pelton turbine in thirteen steps: jet, runner, speed, generator, buckets, housing. With calculator.
- **[Pelton turbine nozzle](https://www.erlach-erlach.com/en/pelton-turbine/design/nozzle/)**: The head sets the speed of the jet. The discharge sets its diameter.
- **[Pelton turbine specific speed](https://www.erlach-erlach.com/en/pelton-turbine/design/specific-speed/)**: The figure that says how thick a jet may be in relation to the runner.
- **[Horizontal Pelton turbine](https://www.erlach-erlach.com/en/pelton-turbine/design/horizontal/)**: Up to six nozzles on a horizontal shaft: why the water is split and why a Pelton turbine with many nozzles is otherwise vertical.
- **[Pelton turbine distributor](https://www.erlach-erlach.com/en/pelton-turbine/design/distributor/)**: One pipe in the centre, equal paths to all nozzles. What a distributor does and which two types exist.
- **[Pelton turbine efficiency](https://www.erlach-erlach.com/en/pelton-turbine/design/efficiency/)**: Six nozzles to switch off on a horizontal shaft: why efficiency falls more slowly at low discharge.

**03 Pelton turbine System Erlach.** The horizontal Pelton turbine with up to six nozzles: power plants, manufacturers, history, patents and research.

- **[Pelton turbine power plants](https://www.erlach-erlach.com/en/pelton-turbine/power-plants/)**: Where the horizontal Pelton turbine with six nozzles runs today and where it is planned.
- **[Pelton turbine manufacturers](https://www.erlach-erlach.com/en/pelton-turbine/manufacturers/)**: Who has worked with Josef Erlach on the horizontal Pelton turbine with up to six nozzles, and who does today.
- **[Pelton turbine history](https://www.erlach-erlach.com/en/pelton-turbine/history/)**: From the first filing in 2004 to the first machine in a power plant in 2022, with a source for each step.
- **[Pelton turbine patents](https://www.erlach-erlach.com/en/pelton-turbine/patents/)**: Each patent family with number, inventors, priority and present legal status.
- **[Pelton turbine research](https://www.erlach-erlach.com/en/pelton-turbine/research/)**: Model test, university studies and the works that refer to Erlach.
- **[System Erlach in the press](https://www.erlach-erlach.com/en/pelton-turbine/press/)**: What daily papers, trade journals and research have written about System Erlach since 2011.
- **[Josef Erlach](https://www.erlach-erlach.com/en/pelton-turbine/inventor/)**: Career, works and awards of Josef Erlach, and Philipp Erlach.

## Josef Erlach and Philipp Erlach: inventor and managing director

**Josef Erlach** is a mechanical engineering technician specialising in Pelton turbines. After posts at Escher Wyss, Sulzer Escher Wyss, VA Tech Escher Wyss and Andritz Hydro and around 25 years of work on the standards for water turbines, he developed the Pelton turbine System Erlach. Six patent families on the Pelton turbine go back to him, five of them on the System Erlach. IEC 1906 Award 2010, Hidroenergia 2014 Innovation Award. The curriculum vitae is under [Josef Erlach](https://www.erlach-erlach.com/en/pelton-turbine/inventor/).

[ORCID](https://orcid.org/0009-0009-9550-0772) · [Google Scholar](https://scholar.google.com/citations?user=HomeaoMAAAAJ) · [LinkedIn](https://www.linkedin.com/in/joseferlach)

**Philipp Erlach** is managing director of Erlach & Erlach GmbH, co-inventor of the Pelton turbine with suction inlets and co-author of the publications of 2014, 2016 and 2026.

[philipp-erlach.com](https://philipp-erlach.com) · [ORCID](https://orcid.org/0009-0005-3167-7481) · [Google Scholar](https://scholar.google.com/citations?user=737GpU4AAAAJ)

## System Erlach, publications: presentations 2012 and 2014, article 2016, paper 2026

- **2026**: *Engineering with AI: Making Errors, Keeping the Lessons* (Source: Josef Erlach, Philipp Erlach · Viennahydro 2026 · Paper 157, presentation on 20 November 2026)
- **2016**: *Neues Pelton-Konzept — bis zu sechs Düsen in horizontaler Anordnung* (Source: Josef Erlach, Philipp Erlach · WasserWirtschaft · Vol. 106 (2016), no. 10, pp. 18–24 · [DOI 10.1007/s35147-016-0148-z](https://doi.org/10.1007/s35147-016-0148-z))
- **2014**: *We proudly present the first up to Six Jets Horizontal Pelton Turbine* (Source: Erlach & Erlach · Hidroenergia 2014 (ESHA), Istanbul · 21–23 May 2014)
- **2012**: *New Pelton Concept — up to six nozzles horizontal* (Source: Josef Martin Erlach · [Viennahydro 2012](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf), Wien · Full paper, presented to the professional community on 22 November 2012 · [Original PDF](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf) · [Full text as Markdown](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.md))
- **2012**: *Grüß Gott, we’re Erlach & Erlach. We proudly present the first ever up to Six Jets Horizontal Pelton Turbine.* (Source: Erlach & Erlach · [Viennahydro 2012](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach_New-Pelton-Concept_Full-Paper.pdf), Laxenburg · Leaflet for the presentation, four pages, 22 November 2012 · [Original PDF](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach-und-Erlach_Faltblatt.pdf) · [Full text as Markdown](https://www.erlach-erlach.com/downloads/2012_Viennahydro_Erlach-und-Erlach_Faltblatt.md))

Who cites these works is listed under [Pelton turbine research](https://www.erlach-erlach.com/en/pelton-turbine/research/).

## System Erlach, patents: six documents, legal status as of 27 September 2026

- **2004**: EP 1 828 596 B1, “Peltonturbine mit einem Wasserabfuhrsystem” (Inventors: Josef Erlach · priority 17 December 2004 · granted 23 September 2009; lapsed 2019 and 2020)
- **2004**: EP 2 278 155 B1, “Peltonturbine mit einem Wasserabfuhrsystem (Teilanmeldung)” (Inventors: Josef Erlach · priority 17 December 2004 · granted 21 March 2012; lapsed 2019 and 2020)
- **2006**: EP 2 035 689 B1, “Peltonturbine mit einem Zulaufsystem” (Inventors: Josef Erlach, Thomas Staubli · priority 03 July 2006 · granted 21 September 2011; in force in Germany, Austria and France until 14 June 2027 at the latest; lapsed in the other countries and in China)
- **2006**: EP 2 035 690 B1, “Düse mit Absperrelement” (Inventors: Josef Erlach · priority 03 July 2006 · granted 23 December 2009; lapsed 2013 and 2014)
- **2011**: EP 2 715 106 B1, “Peltonturbine mit Saugstutzen” (Inventors: Josef Erlach, Philipp Erlach · priority 12 July 2011 · granted 28 October 2015; lapsed 2017 and 2018)
- **2022**: AT 526 022 B1, “Peltonturbine” (Inventors: Josef Erlach · priority 17 March 2022; Austria: granted 2023, in force. Germany: application pending, not granted)

What each patent family protects is explained under [Pelton turbine patents](https://www.erlach-erlach.com/en/pelton-turbine/patents/).

## System Erlach, echo: daily press, trade press, research

In 2011 the Frankfurter Allgemeine Zeitung and the Zeitung für kommunale Wirtschaft presented the invention. In 2023 TU Wien names the design approach by Erlach and Staubli, Voith lists Erlach’s patents as prior art in its own patent documents, and in 2025 the trade journal zek reports on the “Pelton Turbine System Erlach” by Troyer.

[Frankfurter Allgemeine Zeitung, no. 213, 13 September 2011](https://fazarchiv.faz.net/document?id=FAZ__931046366f4a970c29a07b32caef7e0151fa0fe9), p. T 10; Zeitung für kommunale Wirtschaft, issue 10/2011, p. 43; Hahn et al., Energies 16 (2023) 2737; [EP 2 582 963 B1](https://patents.google.com/patent/EP2582963B1/); [zek Hydro, October 2025](https://hydro.zek.at/technik/troyer-praesentiert-neue-peltonturbine-system-erlach-in-flums/), pp. 66–67

All reports are listed under [System Erlach in the press](https://www.erlach-erlach.com/en/pelton-turbine/press/).

---

Erlach & Erlach GmbH, Ravensburg. Web page: https://www.erlach-erlach.com/en/pelton-turbine/ · License for this text: CC BY 4.0 · Overview for assistants: https://www.erlach-erlach.com/llms.txt