The design philosophy behind Van der Pol's new baby goes back to the seventies. At that time wind energy was considered to be a good alternative for supplying electricity to isolated regions of the world, far from any power grid. Small wind generators were often a cheaper option than running electricity transmission lines for hundreds of miles. Yet much of this early thinking has been lost over the past 20 years, with wind turbines fulfilling an alternative role as an auxiliary source of power for national grids in rich countries looking to diversify into clean power generation.
Van der Pol wants to get back to basics. One of the main reasons wind energy failed to get off the ground in developing countries was technology failure because of remote operation in harsh climates -- dust and fine sand scour the blades, reducing their lifespan by one third; maintenance is a problem, not only because of the lack of skilled manpower, but also because a crane is hard to come by. Van der Pol has tried to take all these problems and others into account. He has not designed a small 'big' turbine, but started from scratch.
The Tocardo 4500, with a rotor diameter of 4.5 metres and able to produce up to 3.2 kW, has six blades made of stainless steel, which should make it resistant to the elements. The tip speed of the rotor has been kept to a low 70 kph to reduce wear and fatigue and the Tocardo is available with a synchronous or asynchronous generator or with a 24 V permanent magnet generator for use in combination with a battery. It can also be adapted to directly drive a water pump or other mechanical device.
A peculiar design feature is the hinged side vane, a Dutch invention, developed long ago at the Technical University of Eindhoven. The vane moves the rotor sideways out of the wind as wind speed rises above 10 m/s. Another design feature is the easy handling of the turbine. Weighing no more than a maximum of 125 kg, it can be transported on a pick-up truck and erected without a crane -- and lowered with its own winch for maintenance or in cases of extreme weather.