Hydro electric power generation with low Hydraulic head
Extending pressure pipeline in to the water source from the intake point of penstock will boost hydro power in a hydro electric power plant
The low head hydro power generator illustrated here is intended to use for river current of 15-20 fts hydraulic head and mini hydro power plants to produce electricity. This method is also applicable to hydro power plants at any capacity. An existing power generator can be easily modified to optimize its power using this method. To facilitate the pressure pipeline inside the reservoir, a channel or trench is excavated to extend the pressure pipe line in horizontal direction, if the reservoir bed is steep and intake level is dropped near the dam. This way existing hydro power generators having short penstock lengths can be improved by providing additional pipe length inwards to the reservoir from intake.
Many dam based hydro power generators were built without providing sufficient length in penstock, between intake and turbine. Even these hydro power stations can be modified to boost power with the improvement described here. This type of power plant is suitable for lowland rivers with sufficient flow. Most low head, low flow hydro power sources are not exploited since standard hydro power generation techniques cannot be employed in such conditions.
Most current hydroelectric projects require a large hydraulic head to drive power turbines. Required hydraulic head usually created by constructing a dam in a river bed, creating a reservoir. A hydraulic control tower is constructed towards the opposite end of the reservoir and a pressure pipe line (penstock) is drawn to the power house at the other end.
An experiment was carried out at our laboratories to investigate the flow through two pipes of same diameter fitted at the same height from water level inside of a water tank as shown. It is found the longer pipe line inside the water tank generates a higher speed resulting more powerful flow. Flow in this pressure pipe develops due to gravitational acceleration on a horizontally flowing water column also, when it is an enclosed stream of flow. If this length is short it is not possible to develop the speed of an stream line.
Extending the pipeline to outside, also having same effect.
A second experiment carried out with a coiled pipe line instead of a straight length. We found the similar effect for the same length. Accordingly we can device a hydro power booster pipe connected at sluice gate end without extending the pipe to a distant location.
This method can be diversified further to minimize the extending distance from hydropower dam, by giving a spiral shape to the pressure pipe as shown below.
Water entering at intake is having zero velocity and it has to accelerate to gain certain velocity when it reaches turbine blades. If the intake pipe is extended sufficiently the streamline flow can accelerate the flow speed inside the pipe line. Therefore, by extending the pipe line in to intake water source, flow speed increases.
Let us consider the flow of fluid through a pipe having inlet and outlet sectional area are A1, and A2 consecutively. Velocity at two points will be v1 and v2. According to Continuity Equation A1.v1 = A2.v2= Constant
This method is applicable to reservoirs constructed to use Pelton wheel as well.
This type of built in pressure pipe is capable of generating a streamline of flow. The sum of dynamic pressure and kinetic pressure will be same at section A-A and section B-B of the streamline flow inside enclosed pipe. Section A-A having a larger area than section B-B. Therefore in this energy system design the speed of flow will increase when it reaches the turbine blades, generating an additional kinetic energy.
Optimization of hydro power for low head turbine
According to present invention, an enclosed penstock (pressure pipe line) is constructed up to the power house, form a suitable distance to generate hydraulic pressure. This hydro power development based on the fact that the flow through closed conduit (pipe) will be greater than flow through an open channel. Water flowing though a closed conduit (pipe) is a lamina flow in a river is a turbulent flow.
Thus, the new technology can be employed to utilize hydro power from rivers having consistency of flow. This technology is inexpensive compared to hydro power projects built with massive hydraulic retaining structures. Sites for this purpose are available in many countries to double the power generating capability of the nation. Therefore this is an affordable and green alternative for small scale waterway sites as well as rivers having large flow without sufficient water head. Also this pressure pipe line optimization technique can be used in existing dams, weirs, waterways and irrigation canals.
Run-off river hydro-electric plants without pond
An application of Pressure pipe optimization technique is illustrated in the run-off river type of hydroelectric power plants is shown below. This construction method based on the fact that water flow though a pipe line will be greater than the free flow of water in a river. Construction of pipe lines to a long distance is highly practical in our times. Thus water of rivers also can be utilize to generate electricity where there is no facility for storing the water. Bringing a part of river flow through the pipeline laid along the river bed would not do any harm to biological inhabitant, chemical characteristics or physical layout of the environment.
Shown above is a longitudinal section and cross section of a river with a consistency of flow where the gradient, conventional hydro power generation methods cannot adopt due the little pressure difference at higher location and the lower location point of the river flow. The water surface pressure at point A and point E are same and equal to atmospheric pressure. River water flow is having some velocity at point "A". Although the point D is a location lower than point "A", velocity of water flow increase by a small value, since it is open channel flow with frictional losses due to uneven surface of river bed and embankments. But the pressure pipe (closed conduit) laid on river bed from point A to point D having reduced in pipe cross section and pressure accumulate at point D that can be applied to generation hydro electric power. The bulb type reaction turbine of Kaplan type is most suitable in such low heads.
Such hydro power generator can be installed at Peradeniya- Sri lanka along Mahaweli River basin without disturbing the environment and without interrupting the natural water flow of the river at the location shown in this picture where 1: Intake point; 3- Pressure pipe line; 2-Bulb type turbine.There's an uninterupted continues flow along this river though out the year.
The power generator is Shaft-extension type tubular unit.
It requires less space with smaller powerhouse and free discharge without flow interruption due to power house construction. Adjustable Wicket gates are placed at the intake. Runner blades are made adjustable to provide the flexibility to adapt changing head and demand of different power output.
At intake point at "A" trash track, flow control gate and fish screen are introduced. In this typical example the turbine and the generator house are separated constructions. Details shown in Figure. 6 are: 1. Water flow coming through penstock, 2. River water flow, 3. Turbine 4. Electricity Generator & Power house.
Preferably the generator and turbine are housed inside separate chambers while the elongated turbine shaft drives the generator in the power house. The water flow passes in a radial and axial direction through turbine blades to generate power.
This hydro power generation process result no river flow decrease. Therefore, no impact on aquatic life and water quality: No water impoundment and no flow changes are done. So that, no embankment erosion and loss of land space for storage tanks and reservoirs consuming land space. Such hydro power systems can be installed in association of a bridge across the river.
The designer suggests that maximum of half the river flow to use at any instance.The turbine can be a pit turbine which is a variation of the bulb turbine well suitable for hydropower plants with water head ranging from 2 m to 10 m and unit capacity in the range of 15MW to 30 MW. Also it cab be a fixed blade type since expected flow does not vary.
They are suitable for exploitation of tidal power and hydraulic power with low heads such as 2Meters and large flow rates, therefore suitable for generating tidal power as well.
Besides, sending river flow through pressure pipes can prevent flooding in low laying regions.
Pressure pipe optimization technique doubles the hydro power generating capability of the nation.
This technology differs from existing hydro power generation techniques for having a closed conduit (an extension of pipe line) projected in to the water source (head waters) from the turbine generator to improve the stream of water flow. This technology provides a hydraulic express-way from untapped water streams.
For more information contact: Leelananda Jayasuriya : E-mail : email@example.com Phone : 0094 112915390
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