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Next-Generation Small Hydro: Very Low Head Turbines

7 April 2011 Elisabeth Fischer




Bigger financial and ecological benefits are driving demand for small hydro projects. Elisabeth Fischer spoke to Claude O'Neil, co-inventor of the very low head turbine, an affordable and green alternative for small-scale waterway sites.


Growing social, financial and environmental benefits in comparison to large units have boosted interest in small hydro projects across the world in recent years. R&D in the field has intensified and new projects and technologies have hit the market.

The third Arena International Small Hydro, taking place on the 13-14 April 2011 in Vancouver, Canada, will shed light on some of the latest developments, present new and innovative tools, identify changing government policies in North America and Europe, and show an increasingly influential sector of the world's hydropower industry.

Working on the development of very low head (VLH) turbines from day one, the director of the Canadian company Novatech-Lowatt Turbines, Claude O'Neil, will talk about a new generation of small hydro projects at the event. Ahead of the conference, he gives an insight into some of the recent research achievements of VLH turbines.

Elisabeth Fischer: Very low turbines (VLH) are a relatively new concept. How has the technology developed?

Claude O'Neil: The development of VLH turbines started in 2002-2003 in France as a cooperation of Canadian and French university laboratories. It's a concept completely different to what we are used to in hydroelectric power. Traditionally, the R&D efforts on turbines are done by large companies and they work towards large sites. Small hydro turbines have always been on a scale down. However, if you use these large turbines for small head sites, the cost for the civil work required to feed the turbines and to recuperate the kinetic energy at the exit, is simply too large to be feasible.

"It's a concept completely different to what we are used to in hydroelectric power."

Our objectives were to develop a unit that requires very little civil work, is easy to install, and offers a high degree of reliability at a reasonable cost per installed kW. To achieve these goals, the VLH concept takes a completely different approach from the traditional design, using large Kaplan runners to practically eliminate the expensive civil structures of the traditional concept.

Generally speaking, the VLH unit is an integrated generating set incorporating a large Kaplan runner with eight adjustable and self closing blades, a fixed distributor composed of 18 wicket gates with flat bars inserted in between as trash rack, a permanent magnet generator directly coupled to the runner and an automatic trash rack cleaner mounted on the distributor.

EF: Which waterway sites are suitable for VLH turbines?

CON: Our concept was to try and use existing dams, weirs, waterways and irrigation canals. Before we started work on the project, I visited a few Canadian sites with a delegate from the French team. Most of the existing dams with a head lower than 3.5m were untapped, with no turbine installed. I wasn't surprised to hear that they had the same problem in Europe. We thought that this would be a great niche to target and so we've developed a turbine especially for very low head sites, which range from 1.4m-3.2m.

The largest machine we manufacture is 500kW and therefore a lot of the machines installed in the US are multiunits with 20-30 machines installed side by side. In Canada and Europe the sites are smaller and we have 4-5 machines side by side.

"The protection of the environment and especially the fish-friendliness of the machine was an important factor in the development of the turbine."

EF: Where have you installed these turbines?

CON: We installed a first prototype of the machine in 2007 in Millau in France. It ran for a year and after that period we did some small modifications, resulting from several tests. We'd realised that the machine would be more affordable if we used different materials and elements.

Presently, 15 VLH units are operating in Europe and 26 more are being fabricated for projects in France, Belgium, Italy and Poland. In North America, Novatech has recently completed a cold-climate adaptation study and eight units will be installed within the next two years.

EF: Aside from the size, what other advantages do VLH turbines hold over bigger units?

CON: One particular advantage of the machine is that one single unit contains the turbine, the generator and the blades with the trash rack cleaner. It all comes in one piece and a crane can easily lift the turbine from the delivery truck into the waterway. That means the VLH can be installed in less than one week. The waterway owner doesn't need a large machine hall or power unit to house the machine; a container-sized building will accommodate all the electronic gear needed.

Due to the compact size of the unit, the VLH turbines can be removed very easily from the dam, for example in spring during high flow. We've invented a system that can lift the machine off the water passageway and the original evacuation capacity of the dam can be recuperated.

As I mentioned before, we also conducted a cold-climate adaptation study. This basically means that we can install the machines in the very cold climate and icy conditions that we have for example in parts of the US and Canada.

EF: What are the environmental impacts of VLH turbines?

CON: The protection of the environment and especially the fish-friendliness of the machine was an important factor in the development of the turbine. We wanted to build a fish-friendly turbine and to reach this goal we conducted some tests in Europe in 2007 and 2008 with baby salmons and eels. The small salmons all survived the downstream migration and the survival rate of the eels was 92.3%, which was an outstanding result. Everybody was really excited. The testing was done by an independent biologist firm under the supervision of the French government.

After the tests, we identified where the few eels were killed and modified the turbine again. We conducted new tests at the end of 2010 and all the eels that migrated downstream the turbine survived. So we really do have a fish-friendly turbine and we are extremely pleased with that.

"The licensing is still a real problem in the States."

Another very important factor of the VLH is that it is a submerged machine, which means there is no noise or vibration. Standing only 2ft from the turbine you couldn't tell if it was in operation or not; it is very discrete. A lot of the currently installed units are placed in regional or national parks and we haven't had any problems with the acceptance of the local community.

EF: How does the licensing process of VLH turbines work?

CON: The licensing is still a real problem in the States. There is not a lot of difference between the licensing process of a 500kW and 500MW machine, which means that we can expect 4-5 years waiting time just to obtain a permit for a small-scale project. A lot of developers will opt for 1MW-2MW projects just of the long waiting times. Fortunately, the Congress is about to modify this approach and small project at existing dams will have a shortcut process. This is great news for us and will bring us much closer to Europe, where the process of obtaining a permit is much shorter.

The Small Hydro 2011 Conference will take place in Vancouver BC, Canada, on 13-14 April 2011.

The first ever installed very low head (VLH) turbine in Millau, France.
The top two figures show classic installations (vertical / horizontal Kaplan), whereas the bottom figure shows a VLH turbogenerator on the same scale.
The runner of the VLH turbine.