Selection of Micro Hydropower System and Turbine
There are numerous micro power systems operating in all parts of the world, the popular ones are listed below:
- High and Medium head systems
These include canal and penstock systems
Mill leaf systems
Small Barrage Systems
In this article we will use a run of river system as it is much easier to get planning permission for a simple system, such as a run of river system. This does not require a section of the river to be diverted across the land to run your system and will have the least effect on the river and surrounding ecosystem, only requiring a small barrage to one side of the river.
Typical Run of River Build Method
A temporary barricade is placed across the area where the device is going to be installed.
This will divert the water long enough for you to scoop away the sediment from the bottom of this part of the river, allowing a concrete plinth to be installed. Once the plinth has hardened, the permanent barrage in the form of an L shape can be fitted behind the temporary barrage and the turbine and generator bolted to the concrete plinth.
This L shape barrage can be fabricated from steel plate, the rear plate incorporating the turbine and the generator. This plate can be held in place using vertical steel guides to facilitate removal of the whole unit for maintenance. The device is then connected to the transformer/ voltage regulator which should include an isolation breaker.
A mesh screen is now fixed across the inlet channel to your turbine, preventing fish being drawn into the turbine as well as collecting any debris brought down by the river.
If the river is a salmon run, then a very fine mesh with than 12mm spacing is required by law to prevent smolts (young salmon) being caught up in the system.
The temporary barrage can then be removed to supply the turbine with water.
The turbines best suited to a run of river system are reaction turbines which are totally submerged in the river. These include various propeller types and Francis turbines.
We shall use an open flume type of Francis turbine, which is one of the oldest but reliable water turbines with many still in use after fifty or more years of trouble free operation. It consists of an open wheel which is fully submerged in the water current which causes it to rotate, driving a power generator.
The water leaves the turbine through a conical outlet pipe connected to the tailrace which returns the water back to the river.