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Low head Hydroelectric Generator


Low-head hydropower refers to hydropower developments where the head is typically less than 20 meters, although the exact definition varies.

Head is the vertical height measured between the water inlet and outlet water levels. By using only small drops in rivers and tides to generate electricity, we can provide a renewable energy source with minimal environmental impact. Since the power produced is a function of the head, these systems are usually classified as small-scale hydro with installed capacity of less than 5 MW.

Low head Hydroelectric Generator

Types of low head hydroelectric generator

Run of Run (RoR)

It is possible to generate low head hydropower from rivers, so called river of run or run of river projects. Weirs, rivers, streams, locks and sewage discharges are suitable for this. Weirs are common along rivers throughout Europe. They are also common in canalized rivers and rivers with breakwaters.
Conventional technology typically requires large amounts of water to generate significant power at low head sites. In order to drive generators efficiently, gearboxes must be used, requiring expensive equipment and civil infrastructure. When using run-in water, head is usually provided by a canal, pipe or tunnel built upstream of the power plant. The steep descents such as waterfalls and rapids are attractive because upstream construction costs are required.
hydroelectric plants using run-of-river technology have little or no reservoirs. Depending on the power plant, the reservoir is called a pond because in run-of-river operations there is no reservoir or only a limited volume. These non-pond structures act as intermittent energy sources as they are subject to seasonal river flow patterns.
Water is stored in conventional reservoirs and serves as flood control, power source for transportation, and fresh water supply for agriculture.

Tidal Hydropower

Combined with dams and lagoons, the tidal ebb and flow creates height differences. Le Reims in France is where the tidal range first opened.
Tidal energy is not yet widely used, but it could become an important power source in the future. Tides are more predictable than the wind and the sun. Among renewable resources, the main drawbacks of tidal power are that it is relatively expensive and difficult to find locations with strong tidal current speeds or extents.
A number of technological developments have occurred in recent years as technology has improved, suggesting that the capacity of tidal power generation may be much greater than previously thought. Design improvements include dynamic tidal power and tidal lagoons with various configurations such as new axial and cross-flow turbines. As a result, economic and environmental costs can be lowered to competitive levels.
Low Head Pumped Seawater Storage
Currently these technologies are at very low TRL levels. However, it may become part of the energy system in the future. Load sharing is achieved with this form of energy storage from hydropower. Turbines release stored water to generate electricity during periods of high power demand.

Dynamic Tidal Power

Dynamic Tidal Power, a method of harnessing the power of tidal movement, is another promising type of low-head hydropower. A dam-like structure is required, but because the area is unenclosed, there remains "damless hydropower", while at the same time producing enormous amounts of electricity.

Low Head Turbine Types

Turbines suitable for low head service vary from Francis, Propeller, Kaplan and Pelton designs as compared to turbines used in more conventional large hydro applications.
There are various types of low head turbines.

Archimedes Screw Turbine

Archimedes screw turbines are relatively new in the world of small hydropower, having been introduced only ten years ago. However, as pumps they have been around for decades and have been installed tens of thousands of times around the world, especially in sewage treatment plants. The Archimedes screw turbine works in the same way as the Archimedes screw pump, but in reverse order. The weight of the water on the blades of the propeller causes the shaft to rotate as it enters the top of the shaft, causing the water to drop to the lower level. The
generator can be driven by a rotating shaft. Due to the slow speed, a gearbox is required. The screws are designed for low heads (1.5 to 5 meters) and medium to high flow rates (1 to 20 m^3/s). Multiple screws are used to increase flow. The turbine blade design and low speed rotation make for a large but friendly turbine for aquatic life.

Kaplan Turbine 

Kaplan Turbine is a propeller turbine that can generate electricity at different heads and flow rates. Kaplan pumps operate at low to medium head (1.5 to 20 meters) with flow ranges from 3 m3/s to 30 m3/s. It is possible to use multiple turbines at high flow rates. These turbines can be harmful to aquatic life. They usually require a full screen from the water.

Issues to Consider When Using Low Head Turbines

The environmental impact of river flow and tidal turbines raises several concerns.


Rotating knives pose a threat to aquatic life such as fish. Screening systems can be used within waterways to eliminate the risk of moving parts coming into contact with marine life. It has been extensively tested for safety and is certified safe for smolts, adult fish, eels, seabirds and marine ecosystems.

Seafloor Topography 

It is undeniable that devices alter wave patterns and currents, resulting in changes in sediment deposition. Studies to date have shown no significant impacts or even benefits such as slowing coastal erosion. This is especially important given that waves are steadily increasing in size. Downwind of the device, seas can be calmer than normal, but this is reported to free up more space for activities such as water sports and sailing. Considerations may make it difficult to obtain permits for hydroelectric plants on rivers and similar waterways. There may be resistance to major infrastructure and other visible infrastructure above water. B. Archimedes screw system and turbine house. Vibrations caused by the
gearbox can also raise environmental concerns that can affect nearby wildlife such as otters and birds. A major impact could be generated by the large transmission lines required to carry power from the shoreline to end users.

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