The heritage-protected Forbach run-of-river power plant, dating back to 1914, played a crucial role in electrification in the north of the Black Forest. Its conversion into a pumped storage power plant is expected to significantly improve its efficiency. Previously, water from the Schwarzenbach and Murg dams would flow into an equalization basin and then into the Murg after passing through the turbine wheels. However, the conversion plan includes the construction of an underground sub-basin, serving as an indirect power reservoir, allowing the water to be circulated as desired for electricity generation.
Excited about the project, Thorsten Weiner, Technical Division Manager at Porr Tunnelling Germany, acknowledged the inherent challenges of underground construction. "Even with 3D forecast modelling, BIM planning and exploratory drilling, underground construction work always remains challenging. Having an experienced team that can master these challenges with flying colours is essential. Taking a proactive role in the energy transition gives us additional motivation. It will be a pleasure for us to work on delivering the Forbach pumped storage power plant," he said.
The construction is scheduled to commence in autumn 2023, with Lot 2 encompassing the construction of caverns, water reservoirs, and tunnels using the mining method. Additionally, Porr will be responsible for the shell construction of the power plant cavern, the construction of two pressure shafts, and foundation engineering work. Before the new power plant can go into operation in 2027, the Porr team will undertake the challenging task of blasting and excavating significant cavities and tunnels in the rock, estimated to yield around 450,000m3 of rock excavation material.
The tunnel system within the project will have a total length of 5200m, and approximately 510m of shafts will be constructed using the raise-boring method. The underground water reservoirs will have a combined volume of 200 million liters. The main tunnel alone will stretch 946m in length and have a cross-section of up to 71.72m2. Additionally, the project involves the construction of six side tunnels, access tunnels, supply tunnels, and tunnels for energy transmission.
The Rudolf Fettweis hydropower plant (Rudolf-Fettweis-Werk) in Forbach (northern Black Forest) currently has a total capacity of approximately 71MW. It consists of four individual hydroelectric power plants built between 1914 and 1926. The main elements are the Schwarzenbach dam (Schwarzenbachtalsperre) with a capacity of 14 million cubic meters of water, and the Forbach and Kirschbaumwasen impoundments. Image courtesy of EnBW Energie Baden-Württemberg AG
