River turbines: a new source of electricity

The expert: Jean-François Simon, PrésChairman and founder of Hydroquest in 2010. An engineer from the École Centrale and holder of an MBA from the University of California (UCLA).

Does a river current provide good energy?
Jean-François Simon: It has many advantages. It is renewable energy, but it is also highly predictable. There is always a current. It is the most regular of all sources. The power varies with the cube of the speed. A Hydroquest River 1.40 unit generates a nominal 40kW of power and the 2.80 model with two turbine stages generates 80 kW. So it is still necessary to install river turbines in farms like wind farms and solar farms.
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On the model installed at Orléans, the vanes (shown here in blue), rotate around vertical axes, penetrate 1.80 m underwater and are 5.9 m wide, as shown in the drawing on the left. They can be lifted up for maintenance or repairs (on the right). © Hydroquest
Why wasn’t the river turbine invented sooner?
It’s not that easy! We’re only just starting… For a river turbine to be usable, you have to make a machine that can withstand the effects of debris (there’s a lot of that in rivers!), that is easy to maintain (it would be very difficult for divers to work underwater to carry out maintenance or deal with a breakdown) and can be used in a farm arrangement.
Our turbines use two vertical rotating axes, which is a new approach because up until now existing models have used a horizontal axis, like wind turbines. We had to perfect an efficient deflection grille against everything that gets swept along by a river. To assist with maintenance, we chose equipment carried on a floating barge. The entire system can be pivoted upwards, so that you can work in the dry. Remote control tools with a control panel and cameras allow the installation to be monitored from a computer. Turbines can even be lifted up remotely.
Everything is now working correctly. We now have the first saleable machines. I dare say that we are the world leaders in river turbines.
The floating turbine at Orléans
Named Hydroquest River 1.40, since it comprises a stage with two turbines and generates 40 kW in a current flowing at 3.1 m per second, the Orléans turbine measures approximately ten metres in length. Since it only requires a depth of 2.2 m, it is suitable for shallow rivers. This turbine is the first to be connected to the French power grid and is mainly a demonstration unit for testing and confirming the viability of the machine and for showing to future clients. It is there in a real-life situation, except that there would be dozens of them or more in an operational installation. The idea was to test its ability to withstand the natural environment and also its acceptability and environmental impact on this Natura 2000 classified site. The project budget is 2.46 million euros over 3 years. In addition to Hydroquest, a Grenoble-based company, several others are involved, including EDF and the city of Orleans for installing it in the Loire.
The machine exists as a two-stage version (Hydroquest River 2.80, i.e.generating 80 kW) and the Grenoble-based company is also studying marine and estuarine turbines with the same vertical axis two runner stage principle. One of the advantages of these machines for marine use is that there is no need to turn the machine around when the tide changes. This is on a different scale and would involve mechanisms 20 m high, weighing several hundred tonnes.

What is the impact of such installations?
With these small units, the environmental impact is very limited. We can prove this with our demonstration unit installed at Orléans on the Loire, right in the middle of a Natura 2000 area. We studied the effect on the fish that pass through the turbines: they emerge unscathed. The barge is anchored to the bottom with small pilings. There is no civil engineering involved. The equipment is recyclable. Also everything can be containerised. I have lived in Africa and I fully understand the imperatives for those countries.

The turbine at Orléans, with its mechanism raised above the barge. You can see the deflectors for diverting large-sized debris carried along by the river. © Hydroquest
What is the extent of this source?
There are several possible sites in France and we do have projects. But essentially our development will take place in Africa, Latin America and Asia. There are possibilities for 3 to 4 MW installations which could replace diesel generators. Turbine installations in estuaries could be larger, of the order of 100 to 200 kW per unit. A marine turbine, like for example the one being prepared at Paimpol-Bréhat, which makes use of tidal currents, is a step up in power with units of 1 to 2 MW, weighing hundreds of tonnes. But you need strong tides and there are around fifteen major sites in the world.
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