Hydropower technology
The perfect energy source should be renewable and constantly available. It should be converted into electricity effectively and without great losses, while being emission-free and resource-saving. Hydropower can meet all these requirements.
Hydropower plants have a wide range of services, they can be used flexibly, and they often do not require grid support to start. Not least because of their quick start and storage capacity, hydropower plants are the key element of the entire range of clean, carbon-free renewable energy sources.
from the existing Sellrain-Silz power plant group
Power plant types
Storage power plant
Pumped storage power plants
Run-of-river power plant
Storage power plants adapt to demand in their electricity production. Water is stored in large reservoirs, so electricity can be generated even in winter with little water flow.
Storage power plants are usually not intended for continuous operation, otherwise their reservoir would soon be empty. Rather, their purpose is to store the water quantities that occur differently over weeks and months and as the seasons change and to retrieve them flexibly in time if electricity needs are increased Pelton turbines are often used in storage power plants due to drop heights, which are usually high.
Pumped storage power plants are a special form of storage power plants. If there is an oversupply of electricity in the grid, it can be used to pump water from a lower reservoir to a higher one. If the consumption in the grid increases and a higher demand for electricity arises as a result, the water now flowing back down can generate flexible control and peak energy. Supply bottlenecks can be avoided this way. If they do occur, for example, because there are faults in the grid or other power plants fail, it is precisely this property that can ensure rapid compensation and prevent the spread of faults. In pumped storage power plants, Francis pump turbines are often used, which operate as a pump or turbine.
Run-of-river power plants produce electricity continuously according to the water flow in streams and rivers, as the water inflow constantly drives the turbines. Run-of-river power plants are therefore in operation around the clock, generating the basic electricity requirements. Some plants also have smaller reservoirs that allow some of the electricity to be produced according to fluctuating demand. Pelton turbines, Francis turbines and Kaplan turbines are used in runner power plants depending on the available drop height and flow rate. Due to the often low drop height and large amounts of water in run-of-river power plants, as shown in the picture on the left, Kaplan turbines or Kaplan tube turbines are usually used there.
Turbine types
Pelton turbine
The Pelton turbine (open jet turbine) is a constant-pressure turbine whose runner rotates in the air. The energy at the inlet side of the turbine is completely converted into kinetic energy with the aid of one or more nozzles before the water jet strikes the runner. The Pelton runner is a disk with buckets arranged on its outer circumference. Because the water flows through the buckets and is deflected almost 180°, the disk rotates and converts the energy in the process.
The water flowing out of the buckets enters the tailwater at a very low speed in free fall or along the walls of the turbine housing. The Pelton turbine is used at high drop heights and relatively low flow rates.
Francis turbine
The Francis turbine is a radial overpressure turbine, as the pressure upstream of the runner is greater than the ambient pressure. The energy at the inlet side of the turbine is only partially converted into kinetic energy in the distributor. The runner of the Francis turbine consists of a disk (bottom or hub) connected to the turbine shaft, the profiled blades and the ring placed over the blades. The inflow is radial, the outflow is axial. In the runner, the relative flow is accelerated and deflected, which generates a rotational movement. The direction and amount of the inlet velocity are predetermined by the position of the guide vanes. This allows the required flow to be set. Relatively high speeds still prevail at the outlet of the turbine. Therefore, a suction pipe is necessary for good turbine efficiency, where speed is converted into pressure. Maximum efficiency is achieved with a swirl-free exit. The Francis turbine is used for medium drop heights and medium to higher flow rates.
Kaplan turbine
The Kaplan turbine is an axial overpressure turbine that consists of a turbine housing with adjustable guide vanes. The associated runner consists of the hub in which rotatable blades are inserted. The adjusting mechanism is accommodated in the hub. With a narrow gap between the rotating runner and the stationary runner jacket, the losses are kept small. The inflow and outflow take place axially. In the runner, the relative flow is accelerated and deflected, which generates a rotational movement. Due to the double regulation – the adjustment of the rotating impeller blades and also of the guide vanes standing in the turbine housing – the turbines can be adapted to large flow fluctuations in order to achieve optimum efficiency. Relatively high speeds still prevail at the outlet of the turbine. Therefore, a suction pipe is necessary for good turbine efficiency, where speed is converted into pressure. The Kaplan turbine is best suited for large quantities of water and low gradients.