30 metres below ground, the air is thick with the smell of machine lubricant. Some water gurgles through the pipes, though other than that all is quiet. When the world’s largest tap in the Koepchenwerk facility is opened however, the ground trembles. The equivalent of 785 bathtubs of water shoots into the turbine every second, as the Herdecke pumped-storage plant goes online, providing power for around 380,000 homes within 70 seconds.
The koepchenwerk facility – an intelligent waterworld
(Only available in German)
The Koepchenwerk facility: the idea to build the power station came from former RWE technical chairman Arthur Koepchen, and the plant was later named after him. For peak times when energy requirements were at their highest – during the daytime in that era – an additional power station was built alongside the lignite-fired power plants in the Rhine region. When the turbines of the old Koepchenwerk facility became irreparably damaged in the 1980s, a new pumped-storage plant was built on the same site.
The Koepchenwerk facility: a symbol of the region
The hydroelectric power station is located in an idyllic setting: the dammed-up Ruhr river flows slowly by, while the facility nestles on the side of the Ardey Hills near the town of Herdecke. From the air, the facility does not seem particularly remarkable, with four pipes visible that connect the upper reservoir to the listed old plant. These are no longer in use, and the pipes that connect the new facility run below ground. Around 150 metres beneath the reservoir, two buildings stand on the banks of the dammed-up Ruhr. Just beneath the reservoir, white RWE lettering measuring several metres greets drivers on the Autobahn 1. These have become emblematic of the region – in the past they were also illuminated, until the lights got stolen.
The secrets of the pumped-storage power plant, however, are concealed deep within the hill. Beneath the building, a large shaft plunges over 50 metres straight into the ground. Staff wishing to carry out monitoring and maintenance work must take a lift eight storeys down, and then a further staircase to the bottom. In regular operation, nobody enters this area, where huge pipes, metal bridges and staircases are illuminated by pale neon light. This is the location of the world’s largest tap, as well as the turbine and generator, which are the centrepieces of the facility that was modernised again in 2007. Connected by a steel shaft, they are about the same height as a four-storey building.
Energy requirements change every second
It is this technology that enables a pumped-storage power station to do what a standard power plant cannot –not only generating electricity but storing it too. Several times a day, water flows through the shaft – sometimes in one direction, sometimes in the other. If electricity is being produced, water passes from the upper reservoir through the turbine into Lake Hengstey. If electricity is being stored, the generator turns the turbine in the other direction. In this case, water is pumped into the upper reservoir, so it is again available for energy generation. The reservoir holds a little more than 1.5 million cubic metres of water, ensuring the power plant can operate for four consecutive hours before water must be pumped back up again.
Only pumped-storage power stations enable energy to be stored in significant quantities. For intelligent power grids, this is essential, as renewable sources often produce more power than is required at any given time. Excess energy can be stored in the reservoirs, and any future power shortages can be compensated for. In summer, when renewable energies provide a regular supply of energy, electricity is drawn from the Herdecke plant between one and five times a day. In wintertime, this figure can rise to nine. Alongside fluctuations in energy production, there are also fluctuations in energy consumption – in the morning, when people turn their kettles on, energy requirements increase sharply. Towards the end of the working day at around 4 or 5 pm, demand drops considerably. Energy requirements change every second, however, depending on how much electricity is being used by industry and private homes.
The output of 270 Formula 1 cars
In Herdecke, a click of a mouse is all that is needed to release the power of the elements. The turbine is set in motion from a control centre which oversees all run-of-the-river hydroelectric plants on the Ruhr. If energy needs to be produced, hydraulic motors open the huge tap. This “tap” is actually known as the ball valve, and, at about 500 tons, is an imposing sight. It takes around 20 seconds to open completely, then water flows through the pipe from the reservoir 150 metres higher up. This is also incredibly impressive – 110 cubic metres of water flow into the turbine every second, through a pipe with a diameter of 4.5 metres. When the powerful wheel drives the turbine, it sounds like a jumbo jet taking off. Just 70 seconds have passed since the clicking of the mouse, and the plant feeds the equivalent output of 270 F1 cars into the power grid.
The fast start-up time and ability to store energy make pumped-storage power plants important components in the intelligent power grids of the future. After all, storing renewable energy is one of the biggest problems. Pumped-storage facilities can quickly and flexibly counteract fluctuations, whether too much or too little energy is being produced. Furthermore, no other power station can reach full capacity from a standing start so quickly. In addition, the Herdecke facility also represents an important emergency resource within the grid – in the case of a complete power outage, it can be started up without any external assistance, and then provide other power stations with the energy required to get going again.
After over 80 years of history, the Herdecke pumped-storage power stage is now part of a modern power grid for the next millennium – something Arthur Koepchen would barely have dreamed of back in 1930.Image: Claudia Kempf/www.claudiakempf.com