The turbine: The heart of the hydropower plant
First developed in the 19th century, the hydro turbine is
the machine that fueled the Indutrial Age. Today, the hydro
turbine harvests energy from today's cleanest, most
renewable energy source: water.
The hydro turbine is based on a simple concept. It converts the potential energy of water flowing against it into mechanical (rotational) energy. The turbine is connected to the generator, converting this rotational energy into electric power. As such, the turbine is the heart of the hydropower plant.
BFL has access to the world's most advanced, environmentally friendly hydro turbine technologies, which have no adverse effect on the environment.
A hydro turbine for every application
Hydropower turbines are classified based on head height, or the height of the fall of water. There are low-, medium- and high-head turbines. They are also classified as having a vertical or horizontal orientation. BFL incorporates state-of-the-art turbine technology into every small hydro plant we produce—four-, five- and six-bladed Kaplan machines, Francis machines, and two-through-six-jet Pelton machines. These applications range from 1-2 megawatt run-of-river schemes to 60 megawatts in a single powerhouse with tunneling and large water conductor systems. Our turnkey hydropower solutions leverage several designs:
Kaplan and propeller turbine are axial-flow turbines, generally used for low heads.The Kaplan turbine has adjustable runner blades and may or may not have adjustable guide-vanes.
If both blades and guide-vanes are adjustable, the turbine is a "full Kaplan" and double-regulated.
"Semi-Kaplan" features fixed guide-vanes and are single-regulated.
Unregulated propeller turbines, in which both the guide-vanes and runner blades are fixed, are used when both flow and head remain essentially constant. Conversely, the double-regulated Kaplan, is a vertical/horizontal axis machine with a spiral casing and inlet casing, and a radial wicket-gate configuration.
With Kaplan turbines, the water flows in axially (horizontally) or radially (vertically) inward, enters the runner in an axial direction. The control system is designed such that the variation in blade angle is coupled with the guide-vanes setting, in order to obtain the best efficiency over a wide range of flows. The blades can rotate with the turbine in operation, through links connected to a control tube inside the hollow turbine axis.
A horizontal Kaplan turbine (S-type), used for heads of up to 25 meters. The turbine size is limited to 3200mm and, since its speed is very low, is usually paired with speed-increasing gearbox.
A vertical Kaplan turbine, used for heads up to 50 meters. The vertical Kaplan turbine is also usually combined with speed-increasing gearbox for power ratings up to 4 megawatts. Above 4 megawatts, a vertical Kaplan turbine is directly connected to generator.
Diagram of a vertical Kaplan turbine. View Larger »
Francis turbines are radial flow turbines used for medium heads.They have fixed runner vanes and adjustable guide-vanes. With a Francis turbine, the water moves through the turbine as if it were in a closed conduit pipe; the water flows from a fixed component (the distributor) to a moving one (the runner) without any contact with the atmosphere. The guide-vanes, which control the discharge going into the runner, rotate around their axes via connecting rods attached to a large ring that synchronizes the movement off all vanes.
Diagram of a horizontal Francis turbine. View Larger »
Pelton turbines are used only for relatively high heads.They are impulse turbines in which one or more jets impinge on a wheel that has, on its periphery, a large number of buckets. Each jet issues through a nozzle with a needle (or spear) valve to control the flow.
The runner is mounted directly on the generator shaft, affording the most compact arrangement. Any kinetic energy leaving the runner is lost, so the buckets are designed to keep exit velocities to a minimum. The turbine casing only needs to protect the surroundings against water splashing and therefore can be very light.
The Pelton wheels are horizontal shaft in design, with one or two jets or vertical multi-jets. Choosing a one, two or multi-jet configuration depends on the hydraulic conditions of head and discharge. The turbines are simple in construction and require little space. Maintenance of Pelton turbines is easy, as they are set above the maximum tail water level.
Diagram of a vertical 6-jet Pelton turbine. View Larger »