The Ottenbach Small Hydro is a 1920 electrified small hydroelectric power station of the former Silk Weaving Mill A. F. Haas & Co. in the Swiss village of Ottenbach. It is preserved in its original condition of 1920, still able to operate, aimed to be an historical witness of the industrial archaeology. The ensemble of factory, power plant and hydraulic structures is a cultural asset under preservation order.
From 1645 onwards, the millers of Ottenbach and Rickenbach used in addition to the ditches in the village the water of the river Reuss to grind the grain, because those did not supply enough water during the summer months. In 1833, the Canton of Zürich granted the license to use the water to operate a grain mill. In 1836 the miller Jakob Beerli built a canal with a dam in order to bring the water of the Reuss to the millwheel in a more regulated manner.
In 1869, the Zurich Mechanical Silk Weaving Mill (owned by Bodmer & Hürlimann) bought the former mill from Heinrich Schmid, who had bought it from his cousin Jakob Beerli and converted it into a textile factory. On November 9, 1871, Bodmer & Hürlimann received the water rights concession No. 19 from the Canton of Zurich, signed by the Town Clerk and Swiss poet Gottfried Keller. It was based on the old water rights concession of 1833 with minor modifications, and water power was used as a direct mechanical drive of the looms via the still existing bevel shaft and the transmission system. The mill wheel was replaced by a Jonval turbine (Bell Maschinenfabrik) in 1881. In 1909, the old turbine house was replaced by a new building according to the plans of the Hickel Engineering Office in Lucerne, and the bottom of the discharge channel was lowered so that a new Francis turbine (Uzwil Machine Factory) could be inserted into the former idling channel. At low water-levels in winter, a coal-fired locomotive was coupled to the transmissions instead of the turbine system. Two horse-drawn carts had to travel back and forth between Ottenbach and Affoltern am Albis railway station to bring the required amount of coal. In 1920, today's plant components were built in and the looms were electrically powered by a new, more powerful Francis turbine and a generator. During the global economic crisis, the company was overtaken by the Silk and Decorative Fabric Weaving mill A.F. Haas & Co., which produced until 1970 and since then has been running a textile trading business, today named Haas Shopping.
In 1977, the canton of Zurich purchased the adjacent nature reserve of Bibelaas, including the small power station, canal and dam, as a measure to protect the banks of the Reuss. In 2011/12, the headrace canal and the dam had to be repaired due to the damage caused by the floods of 2005 and 2007.
Turbine house
The machines and drives in the turbine house date back to 1920, when the looms were converted to electric operation. In the basement there is the turbine, guide vanes and water chamber. In the engine room, the large bevel gear wheel, which sits on the turbine axis and is equipped with original wooden teeth from 1920, is set in motion by the rotational force of the turbine. With the small bevel gear wheel and the transmissions, the rotational force is transmitted to the bevel shaft, which drives the generator at 1000 revolutions per minute. The regulator measures the speed and then regulates the flow of water to the turbine in order to adapt the output to the water supply. In island operation mode it maintains the main frequency of 50 Hz.