ENERGY IN THE RIVER A Huge Potential for Growth in Output
Since fl owing water, as a renewable energy source, doesn’t fl uctuate much − in contrast to wind or sun − it therefore fi ts extremely well into the energy grid landscape, with many hydroelectric power plants currently being modernized. These include the Böfi nger Halde on the Danube River.
The generators inside the Böfi nger Halde run-of-river power plant have been humming along smoothly since 1953. It is the most powerful of a total of eight hydropower plants operated by Stadtwerke Ulm/Neu-Ulm on the Danube, Iller and Blaukanal. Approximately half of the electricity that the municipal utility company obtains from water every year is generated here. It uses the natural gradient and the fl ow velocity of the Danube, as well as storing a certain amount of water. The difference in height between the upper and lower water, which is currently 7 meters, is what determines the amount of electricity that the operators can generate with this structure. As things stand today, the Böfi nger Halde delivers up to 52 million kWh of electricity per year. After the weir system has been raised by 50 cm, as part of the ongoing modernisation program, an additional 4.4 million kWh per year, i.e. almost one tenth more, will be added to the electricity yield.
Safety is the top priority
Safety will remain the top priority around the dam even after the weir has been raised. Precise and reliable measuring equipment makes even the smallest change visible here. Because the amount of water in the Danube fl uctuates over the seasons and even throughout the day, the current water levels and system data are continuously transmitted to the control centre to ensure smooth operation of the power plant. There, huge quantities of data are collected and evaluated. In addition, the technicians responsible for the hydropower facility carry out regular visual checks and on-site inspection rounds. One important piece of information for operating the power plant as effi ciently as possible, is the water level directly in front of the inlet into the weir. The water should fl ow in a controlled manner and drain quickly, in order to optimize plant utilization and reduce the load on the structure. This is especially important in the event of fl ooding. If the level exceeds a certain threshold value, power generation begins to decline. At a certain point, the head becomes too low to drive the turbines: the power plant then has to be shut down.
Redundant technology
A dual redundancy measuring system helps predict the electricity yield reliably. It continuously records the water level in front of the intake structure before the water is fed into the headrace channel. The operating team working with deputy plant manager Jochen Schneider measures the same level twice here: at spatially separate locations, using two different measuring principles. One system can replace the other at any time should deviations or errors occur. This allows the technicians to rule out, with very high
certainty, the possibility of both measuring instruments outputting the same error at the same time. To ensure comprehensive data acquisition and transmission at all times, they call up both measuring points at regular intervals from the control centre, even during normal monitoring mode.
The important measurement results are delivered contactlessly and continuously by an 80-GHz radar sensor, VEGAPULS 64.
Protection against fl otsam and ice
The robust sensor is encased in a specially manufactured, stilling tube that provides additional mechanical protection against fl otsam or other “events”. “During fl oods, huge tree trunks drift past, blocking the rake below the measuring point,” says Schneider, explaining the stresses to which the measurement technology is exposed. And last but not least, the tube structure also offers protection from animal visitors. “During the breeding season, swans expend a lot of energy and fl y around at high speeds – sometimes colliding with unexpected objects!” he recalls from experience. And because in the winter, deep snow and ice is almost always expected on the Danube in the Böfi nger Halde area, the protective tube can even be heated if necessary. Measurement errors caused by ice sheets are thus a thing of the past.
Long-term stable all-rounder
A few metres downstream, a VEGAWELL 52 immersible pressure probe measures the level a second time. With its wear-free ceramic measuring cell, it is an extremely long-term stable all- rounder for water applications and requires little effort on the part of the maintenance team. VEGAWELL 52 optimises and improves not only the accuracy of the measurement results, but also the costs of level monitoring at the weir.
Measured values with long-term value
Apart from providing information for the everyday operation of the plant, the data on the water levels form the basis for hydrological changes that directly affect stakeholders in the waterway. The values are used in a variety of ways, be it to plan the expansion or deconstruction of the river course or to regulate the barrages.
River navigation and local residents also depend on this information, for scheduling trips on the basis of current fairway conditions and taking protective measures against high water in good time.
AET ANNUAL BUYERS’ GUIDE 2021
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Flotsam is no problem here: A sturdy pipe provides additional mechanical protection for the level measurement system.
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