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Tecnologies

Current technology allows to take advantage of the water power to generate electricity both in natural water courses (rivers…), as in artificially ones (channels, pipes…).

It is important to know that a mini hydraulic plant is not a big hydropower plant at reduced scale. An installation of some hundreds of kW has a completely different design from another of some hundreds of MW design and the equipment used in both cases is also different.

All mini hydraulic power plants have the following components:

1. Civil work installations

2. Electro mechanic equipment

Grafico tecnologia

Civil work installations scheme (Flowing water hydropower plant).

Grafico 2 tecnologias

Detail of an electro mechanic equipment (Foot of dam hydropower plant).

Civil works includes the infrastructure and facilities needed to derive, drive and restore the turbinate water as well as to accommodate the electromechanical equipment and the general power system and its control. These infrastructures are:

  • Weir (Azud). Work that is carried out to provoke retention on the riverbed and alter part of the course of the flow of the river to the hydropower faucet. In the case of the weir, it is a transverse wall to the river course, with low-altitude causing a backwater. In the case of the dam the wall that retains the water has a considerable height and causes a noticeable lifting of the level of the river through the creation of a reservoir.
  • Spillways. Devices that allow the return of the water from the reservoir to the river.
  • Faucet. Structure that is performed to facilitate the entry of water from the weir or the dam to the pipeline network. The faucet normally has a grille that prevents the entrance of solids to the canal and a safety gate.
  • Channels and pipes. Elements intended for the transport of water from the faucet to the hydropower plant. The first stretch, between the faucet water and the loading chamber is carried out through channels or pipes. The second, between the loading chamber and the turbine always use pipes.
  • Loading Chamber. Deposit located at the end of the channel. In some cases it is used as final regulation disposal, although normally it can only provide the volume needed for the start-up of the turbine without interruptions.
  • Penstock. It is the pipe that carries water from the loading chamber to the turbine, it means, driving the turbine power. It must be prepared to support the high pressures to which it is submit.

 

  • Mini hydraulic plant building. It is the place where is situated all the equipment: turbines, generators, alternators, electrical switchboards, control panels, etc. The building may be next to the weir or dam, located at the foot of this or be separated downstream.

Closing and adjustment elements. If the unit stops, the existence of devices that isolate the turbine or other working bodies is essential. Those are gates and valves.

The electromechanical equipment is composed by: turbine, generator and other electrical equipment necessary for the conversion of hydraulic energy into electricity and its disposal to the grid.

 

  • Turbine. Element that is responsible of using the kinetic and potential energy that contains the water, transforming it into a rotation movement, which transferred through a shaft to the generator produces electricity.
  • Generator. Machine that transforms the mechanical energy from the rotation of the turbine into electrical energy.
  • General electric equipment and power lines. Infrastructure responsible for the transformation of the voltage of the electricity generated to the distribution grid, for the measurement of the different parameters of electric current and for the connection of the hydropower plant to the distribution grid.
  • Elements of regulation, control and protection. The installation of these elements is necessary to regulate and control the good operation of the plant, including protection devices that must be applied to the control unit and the power line, and that act when there is any malfunction. Protection elements include mechanical, electrical generator, transformer and line protections.

The key element in any hydroelectric power station is the turbine. Hydraulic turbines are classified into two groups: impulse turbines and reaction turbines.

Impulse turbines are those that take advantage only of the speed of water flow to turn them. The most used is the so-called Pelton wheel. Basically consists of a wheel (or impeller) equipped with spoon-shaped buckets on its periphery. This turbine is very efficient when the available water source has relatively high hydraulic head at low flow rates. Other types of impulse turbines less-used are: the turbine Turgo and the cross-flow turbine, also known as Ossberger or Banki-Michell turbine. The first one has been developed from a modification of the Pelton turbine, resembling its impeller to a Pelton but split in half. This turbine is used in middle slope waterfalls and low flow. The Ossberger turbine impeller has a cylindrical shape, with multiple blades arranged as generators. This turbine is very well suited to all kinds of waterfalls and flows.

turbina pelton

Pelton Turbine. ECOFER company

turbina ossberger

Ossberger turbine

Reaction turbines have a rotor design that allows taking advantage of the pressure that the water still having at its entry to convert it into kinetic energy. The most commonly used reaction turbines are the Francis and the Kaplan. The Francis turbine is very well suited to all kinds of waterfalls and flows. It is the hydraulic turbine most widely used in the world. The Kaplan turbine is generally used for small falls and large or variable flows. Its appearance is similar to the propeller of a boat.

turbina francis

Francis turbine. Hydrotu company.

turbina kaplan

Kaplan turbine. Source: Atmosferis.com

Technological innovation has allowed appearing in the market substitute components of classic turbines, with different geometries. New patents for hydraulic plants with very low falls have been developed in order to make economically viable its energy use. Such is the case of Archimede’s screw or screw pump. This screw is a helical gravimetric machine used traditionally for water elevations, flour, cereals or excavated materials. This application is used in small waterfalls with low water flows that actually cannot be exploited with the turbine technology.

tornillo hidrodinamico

Hydrodinamic screw. Andritz company