Run-of-River Plants – A Reliable Power Supplier

Run-of-river plants supply electricity reliably and generally without major fluctuations. They are therefore utilised in to cover majority of electricity consumption, known as the base load.

How Does a Run-of-River Plant Work? 

A run-of-river plant utilises the natural decline of a flowing body of water and the speed of the current. The water is also accumulated in order to increase the difference in altitude between upstream water and downstream water (see animation), mostly six to 15 metres. The water thus "precipitates" into the abyss and is targeted towards a turbine, which then activates a generator, which, in turn, generates electricity. 

What advantages come with electricity generation from run-of-river plants? 

The capacity of our run-of-river plants ranges from but few kilowatts in small scale hydropower plants to more than 300 megawatts in the large Danube power plants. It depends on the number and the make of the turbines and indicates the speed at which electricity is generated. The quantity of electricity, on the other hand, is the task of the power plants and depends largely on the water level of the river. The more water flows through the turbines, the higher the quantity of energy generated. 

If you change the flow quantity in our model, you will see the effect on electricity generation. If the levels rise above a certain threshold value, for instance, due to flooding, electricity generation begins to decrease. At a certain point, the drop height is too low to drive the turbines and the power plant has to be turned off. 

Plant Safety and Floods 

Our task is to ensure the safety of the retaining walls and the proper operation of the power plants in the event of a flood.

What does a power plant do during flooding?

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Florian Seidl

Press spokesperson Eastern region

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Plant safety: Run-of-river power plants during flooding

Flooding are natural catastrophes upon which the power plants along the rivers hardly have any influence. While storage power plants can take in limited amounts of water, this option is not available to run-of-river power plants on the rivers. 

Run-of-river Power Plants during a Flood 

When approving run-of-river power plants, particular care is paid to keeping natural conditions, i.e. those present before the construction of the power plant, as unchanged as possible. Run-of-river power plants do not, however, constitute flood prevention. 

Should the water level downstream from a dam increase due to the large amount of water present, the power plant will cease to generate electricity: the gradient is no longer sufficient for the water to propel the turbines. 

In the case of a flood, the power plant control rooms, which are usually controlled from a distance, will be occupied by personnel round the clock in order to be able to react to any possible disruptions as quickly as possible. For every power plant there is an officially approved operating regulation. Therein, the water level in the backwater area is clearly regulated and is to be kept to. The upper water authorities at the Ministry of Life are responsible for this. 

Every power plant has a "discharge capacity"- until this capacity is reached the turbines can take in water and generate electricity. If the water capacity is exceeded, weir fields have to be opened in order to let off superfluous water from the backwater area. In this way, the water level in the vicinity of the dam can be decreased. The more the weir fields are opened, the more the water level sinks in the vicinity around the power plant. In the event of large floods, the river continues to flow unhindered, seeing as run-of-river power plants do not have reservoirs which can keep the water back. Thus the phenomenon occurs, where despite the flooding, the water level in the vicinity of the power plant sinks and boats find themselves on dry land. 

Hydrographic Services

In the event of a flood, the authorities in charge of crisis management jump into action: the hydrographic services of the state governments are in charge of issuing warnings and have automatic access to the water level data of all power plants.