Grassroots technology: Hydro power turbines start small to grow with proven concept

Underwater turbines are ready for commercial use. Tocardo has developed a turbine that runs in the tidal stream at the locks of the Afsluitdijk in the Netherlands, which is in use and connected to the power grid for four years already. The company is on the threshold of creating a new renewable energy market segment: underwater generators running on currents.

“We investigate a lot of sites that have names like ‘sound’ or ‘race’,” sales director Sander de Block of Tocardo mentions. These waters where sea flows along the shores through narrow passages, are the waters that have strong tidal currents. These kinds of waters attract the attention of tidal energy pioneers as the first places to install underwater turbines. “It is amazing to see the powers of nature in these places. The water bulges in and out of tidal lakes at speeds seven or eight knots. It is obvious that this energy can be utilised.”


After developing a trustworthy underwater turbine and testing it at a site near their office, Tocardo is ready for production. They offer standard models T100 and T200, producing one hundred or two hundred kiloWatts. Also in the company brochure are the T500 and T1000, yet these models are to be adapted to local circumstances. Big companies like crane manufacturer Huisman have taken a minority share in the company to help start up production. A factory hall is laid out and the first turbine has been delivered to a customer and has been paid: ”The first money is in the bank, we’re in business!”, De Block smiles. “From a scientist hobby, only interesting for inventors that want to experiment with the possibilities 

Experiment with the possibilities

hydro power, we have seen a transition towards viable business opportunities. Fact that bigger companies now invest in Tocardo is reassuring: it shows that they, too, believe in the potential of this company and the hydro power solution we offer.”

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From a scientist hobby to business opportunities


“It is all about the money”, De Block brings enthusiasm about innovative concepts and new markets down to reality. “The costs per kiloWatt hour of electricity is driving. If this price cannot compete with other resources, there is no business for us. That is why we are not focussing on enormous water energy plants in northern European seas, but provide small scale energy solutions to communities that live in remote areas. In Europe, it is not possible to compete with the electricity price on the grid. With gas and nuclear power plants all around, the production costs here are about four cents per kiloWatt hour. At remote places, where the village electricity network is not connected to the national grid but runs on generators for which diesel has to be flown in or transported from far away, the actual costs for electricity is high. In these early stages of power from underwater turbines, propelled by current, we must pick the fruit that hangs low and prove the concept while providing renewable energy in places where people actually save money by installing the turbines. It is much easier to be competitive in places where electricity prices are sky high.”

No 8 MbH December 2012 voor website.jpg 28 2“Part of my job is helping customers to keep perspective on their goal: generate electricity at lowest possible cost”, De Block reflects. “During an inspection visit in Canada, the clients looking to benefit the hydro power in their area took me to the inlet of a tidal lake. Water was really gushing through narrows. But it was very hard to install a turbine there. A concrete foundation needed to be put in place, several miles of electricity cable needed to be led through a nature reserve, costing a lot of money for installation and a lot of work getting all necessary permits. This would immensely effect the costs per kiloWatt hour. A few miles further on, there was a bridge over the sound leading to the narrow. I pointed there. There you can easily attach turbines to the bridges’ pillars, over the bridge runs a cable connected to the electricity grid. Yes, the current is not as strong there, but you will receive a much lower price for electricity if you accept the lower current. Instead of one fast rotating turbine in the narrow, one could install three slowly rotating turbines at the bridge with the same performance at a fraction of the cost.”

Formula 1

It all comes down to the typical way technological innovators think, De Block perceives: “Inventors are always looking for the best possible technological solution before introducing a new product. Turbines are designed to generate maximum kiloWatts given the current. Sites are chosen for maximum current. Everybody is designing Formula 1 race cars. But this will not get you up and down from Paris to Berlin. After the course of a race distance, some 300 kilometres, the engine needs to be overhauled. That is why we adopted a different way of thinking: we offer a simple diesel car that will take you the distance at moderate speeds a hundred times without problems. The result is substantial: electricity at moderate prices.”

Tocardo claims to be able to generate electricity at comparable cost as offshore wind turbines. Hydro power from tidal currents is not supported by governments, however. It took the wind energy industry about 35 years to come to the performance they have nowadays. Hydro power benefits for a part from these achievements but has to engineer for its own specifics. Suppliers are now looking into optimising bearings for the specific loads in underwater turbines. Tocardo turbines need four knots or two metres per second of current in at least five metres of water depth to reach their potential.


Like other experimenters in hydro power, Tocardo is gearing up to be able to realise large underwater electricity parks at the sea bed.

Starting with small scale projects

This is something for the future, though. The path of development chosen by Tocardo is to get to such complicated high-tech installations by starting with small scale projects, gaining experience and then scaling up. “Even then, it is much cheaper to install a large number of smaller turbines than to install one enormous machine”, De Block has calculated. “Installing five 200 kW turbines takes only 30% of the costs it takes to install one 1 MW turbine. Installing more small turbines has more benefits: failure does not mean the whole system is down. With a lot of turbines working together, everything still runs when one turbine fails or is out for maintenance. Downtime is very costly for parties that deliver to the grid.”

Some twelve years ago, a group of engineers started working on investigating the possibilities of generating energy from tidal currents as a side project, just to see if they could come up with a working concept. The project was named Tocardo as an anagram of names. The name remained throughout proceedings and is now a company name. In 2007, a first prototype was built. It looked like a simple two-bladed wind generator. The second type was built even simpler, without a gear box. A very simple direct drive generator with two wings, built to last instead of built to perform at extremely high electricity production. At a two-minute walk from the Tocardo offices, this second turbine is in place and connected tot the grid at the Afsluitdijk locks since 2008. Today, the business is taking off. De Block: “We opened offices in the UK and Canada. We expect to get orders for about 20 turbines the next few months. Delivery time is six to seven months. Next two years, we aim at passing the 100 turbine milestone.”

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