Hydraulic turbines are bulky by their own nature. Indeed, to generate even relatively moderate output, on the order of some hundred of kW, under 2/3 m heads, turbine flow rates can exceed 10 m3/s. This results, for water supply works in large civil engineering structures, proportioned to the collected flow rates.
In order to make their equipments more competitive, hydraulic turbine constructors have always tried to optimize their products by increasing their performances, in particular by decreasing the runner diameters. This runner diameter decrease has led, in case of low heads, to the increase of civil works necessary to execute water intake and outlet structures such as that their economical implementation results as not profitable.
The basic idea of the VLH concept goes against this tendency by aiming at the significant decrease of the civil works required for low and very low heads plants by increasing the size of the turbine runner diameter and by integrating therein a self-supporting structure which guarantees all the functions of a conventional facility.
The VLH turbogenerator allows to incorporate the following functions:
- Standardized Kaplan turbine with 8 blades adjustable according to the level and to the flow rate.
- Self-supporting structure enabling complete factory assembly, very fast mounting or deposit.
- Slow direct-drive variable-speed permanent-magnet generator incorporated and submerged together with the turbine.
- Device for stopping and cutting off the flow by closing the blades on themselves with no power from the system.
- Distributor used as a protection grid.
- Embarked rotating trash rake cleaner.
- Electronic speed variator.
- Integrated electronic control equipments managing the turbogenerator unit and the power electronics equipments.
- Withdrawal device enabling taking the unit out of the water for maintenance or for withdrawal in case of a flood.
The VLH Range:
- 5 diameters (3150, 3550, 4000, 4500, 5000 mm)
- Head range: from 1,4 to 3,2 m (up to 4,0 m optional non standard solution)
- Flow range: from 10 to 30 m3/s
- Power range: from 100 to 500 kW – the studies carried out and the experience on projects and installations performed demonstrate that with powers higher than 500 kW it results as more profitable from the point of view of the expected returns on investment to install several smaller machines rather than a single large one.