What are the different types of Micro-Hydro systems?
Micro Hydro systems typically produce under 100 kW and can be used to power single properties or small communities, depending on the size of the installation. The construction of a micro hydro system is normally pretty site specific and will depend on the type of landscape and other considerations. For example, you might have a ready-made dam area or pond that can be adapted or you may be next to free flowing river.
All micro hydro systems have the same basic construction, with a turbine leading to a generator that is then connected to the home, providing AC that can provide all electricity needs. There are a variety of turbine designs that create the mechanical energy to drive a generator, including:
- Reverse Archimedes Screw: Water going into the top of the device makes the screw rotate and this can be used to feed a generator. It is an ideal system to handle dirty water with variable flow rates and can operate at high efficiencies.
- Gorlov Helical Turbine: Helical blades or foils can create mechanical power independent of the water flow and have been used in tidal hydro systems.
- Kaplan Turbine: This is a propeller based system and provides efficient mechanical turn in low head situations and are the most widely used technology for energy production that uses turbines.
- Water Wheel: Harking back to the days when we used them for grinding wheat and corn, water wheels are still in use today, with the more advanced hydraulic wheel-part reaction turbine having efficiencies of over 80%.
- Gravitation Water Vortex: This is a simple design where the water from something like a weir or water fall is diverted into a basin that causes a vortex at the exit (much like water going down a plug hole) which drives a simple fan arrangement connected to a generator.
For the purposes of micro hydro, the types of turbine available can be split into two different types: impulse and reaction.
Impulse Turbines for Micro Hydro
These are more commonly used than reaction turbines because they are essentially simpler in design and therefore have less maintenance issues associated with them. All impulse turbines rely on the force of the water striking them and have two main types:
- Pelton Wheel: Water is pushed through a gradually narrowing pipe, increasing the pressure as it reaches the turbine. The wheel has cup shaped buckets that the water strikes and this causes it to move and turn the generator. It operates most efficiently at high head, low flow situations.
- Turgo Impulse Wheel: This is a slightly more efficient version of the Pelton Wheel and is angled so that the water hits more of the cup shaped buckets at the same time, creating a faster revolution.
For small amounts of electricity you can also get a Jack Rabbit turbine that can be dropped into shallow water and is capable of producing about 100 watts of power.
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Reaction Turbines for Micro Hydro
These are highly efficient but depend on the pressure created by the water rather than the speed with which it hits the turbine. In this respect, it is highly site specific and not suited to all projects. They are more complex in design which is why they are rarely used for micro hydro unless it is a specially designed project.
Off Grid vs On Grid
The other difference between types of micro hydro system is whether they feed just one property that is off grid or connect to the grid and benefit from something like the Feed in Tariff. Off grid is normally suitable for those properties that are in remote places and just need a power supply. Connecting to the grid is useful if you produce excess electricity as you can then earn extra money be selling that back to the energy companies which can give you a faster return on investment.
Is Micro Hydro Right for your Property?
There’s no doubt that a renewable energy source such as micro hydro can produce quite large benefits for a property. The problem lies in the planning and construction stages and choosing the right system for your needs. In truth most homes do not have access to the right resources to undertake a project of this kind, but if you do then the factors you need to consider are the flow and the head.
- Flow is the speed of water passing, which is how much is going by each second. People often distinguish between low flow and high flow.
- Head is the difference in height over a reasonable difference.
It is also important to think about what happens to the river over a year. Does the water flow slow considerably? Often the minimum flow in drought conditions is the deciding factor as to whether your site is suitable for a micro hydro system.
Find out more about the suitability of your property for micro hydro.
Installers of Micro Hydro
Hydroelectricity on a smaller scale is a growing industry and there are a number of manufacturers and installers available who can advise on the right kind of system for your property. Find out more about installers of micro hydro here.
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