What chracterizes the axial flow turbine is its rotation axis. It could be placed vertically or horizontally to water surface. In this latter type the axis is parallel positioned to the incoming water stream. Also the generator can be submerged under water or non-submerged. This turbine is usually used as tidal energy converter. For small river use, the axis could be an angle inclined to the water stream. See figure \ref{Hydro_HorizontalAxis}.
Hydrokinetic converters with a vertical axis concept are uncommon, because they have similar problems to VAWTs such as a lower efficiency and self-starting issues. Their axis are usually installed perpendicularly to water surface and have a submerged Darrieus structure. See \ref{Hydro_VerticaAxis}. …show more content…
\subsubsection{Pico Hydro Turbines}
Pico Hydro is one of the lowest cost technologies that generate electricity. This type is at the forefront of existing micro hydro turbines because it can derive power from low head and flow streams, such as 1m and 1L/s. see `` Research and development aspects of pico-hydro power.
Most Pico hydro turbines working with a rated power output of 3kW are classical water wheels. As illustrated in the figure there three main groups of water wheels, that can be classified according to the water flow direction, namely:
Overshot design is more efficient that the latter two, since the head is quite high from 2 to 10m and 85\% of the hydropower could be caught in the turbine, even for really small $Q: 0.05-1,25 m³/s$. The Pitchback Water Wheel Design is a variation of the overshot design. In addition to the gravitational weight of the water, this turbine rotates also under the push of the water flowing below it. This increases the efficiency of the system on one hand but requires also the construction of a ``Pentrough'' nozzle jetting the water into the wheel\cite{AlternativeEnergy}.
\subsection{Hydropower
Hydrokinetic converters with a vertical axis concept are uncommon, because they have similar problems to VAWTs such as a lower efficiency and self-starting issues. Their axis are usually installed perpendicularly to water surface and have a submerged Darrieus structure. See \ref{Hydro_VerticaAxis}. …show more content…
\subsubsection{Pico Hydro Turbines}
Pico Hydro is one of the lowest cost technologies that generate electricity. This type is at the forefront of existing micro hydro turbines because it can derive power from low head and flow streams, such as 1m and 1L/s. see `` Research and development aspects of pico-hydro power.
Most Pico hydro turbines working with a rated power output of 3kW are classical water wheels. As illustrated in the figure there three main groups of water wheels, that can be classified according to the water flow direction, namely:
Overshot design is more efficient that the latter two, since the head is quite high from 2 to 10m and 85\% of the hydropower could be caught in the turbine, even for really small $Q: 0.05-1,25 m³/s$. The Pitchback Water Wheel Design is a variation of the overshot design. In addition to the gravitational weight of the water, this turbine rotates also under the push of the water flowing below it. This increases the efficiency of the system on one hand but requires also the construction of a ``Pentrough'' nozzle jetting the water into the wheel\cite{AlternativeEnergy}.
\subsection{Hydropower