Turbotricity

Our new pinnacle wing and cowlings are finally in production after many delays. These mouldings give a superb finish to the appearance of the turbine, but they are more than a pretty face….

The cowling reduces wind drag at the hub, giving a free flow of air over the generator to the root of the blades. However, the important tweaking comes from the pinnacle wing.

Normally, downwind turbines suffer from tower shadow – when each blade passes by the tower, there is a brief moment when it gets turbulent wind caused by the tower which is a major obstacle located a few inches from the blade. On our Proven 2.5kw machine at home, the tower is quite wide at the point where the blade tip passes, and this gives the blade “dirty wind” for quite a few degrees of rotation.

Our pinnacle wing is designed to reduce this drag to an absolute minimum. It also helps to ensure that the turbine is steadily facing downwind. And it looks good….

We apologise to those who had expected us to sell turbines in the third week of April. We hit a technical hitch with vibration and some noise as a result. Because our turbines don’t have an iron core, they have much sharper pole changes as the magnet passes the coil, and this seems to cause a vibration.

On our experimental turbines, this was no problem because we weren’t using a tapered tower. However, when we put the turbine onto the tower we are actually using, the tower amplified the noise from the vibration like some sort of horn.

We could switch to a normal iron core turbine, but the turbine we are using has huge benefits – zero cogging at start-up, and very high efficiency – up to 94%. It is important that we get this right, and take the time to do so properly. We want to maintain a high level of efficiency with a turbine that will work in low wind speeds. Unnecessary noise from vibration is something that can be and must be eliminated.

So we are working on various ways of mounting the turbine with rugged vibration mounts to resolve this issue and expect to be back on track in another few weeks.

We believe it is essential to have a safe and simple way of raising and lowering the wind turbine. There are various systems used, the most popular one being to have an anchor point and winch using a “gin pole”. This requires an extra cubic meter of concrete for the anchor, and a fair bit of work with a tirfor winch.

We have seen other turbines that were lifted with a crane (OK first time, but what about the maintenance costs?) and in some cases turbines that had to be serviced by working aloft – again, reducing the cost of the hardware, but increasing the cost of maintenace.

The most dangerous suggestion we have seen is using a gin pole and attaching it to a car or tractor. The traction between tyres and grass is far too variable, and the forces are colossil when the turbine is nearly horizontal.

We are using a hydraulic ram and mobile hydraulic power pack to raise and lower our towers. This is simple and effective and the tower can be down within about ten minutes of arriving on-site. This method is used by many lampost companies to raise and lower their towers and works perfectly well.

The maximum load is when the tower is nearly horizontal, but the interesting part is when the tower is near vertical. At a certain point, it becomes almost balanced and you could push it into place with your little finger. Because there is a small amount of play in the hinge and at the connections for the hydraulics, this allows the turbine to swing by quite a few degrees at this point.

This is a problem for all lifting systems, particularly if you are behind the tower working a winch. At that point, the tower could swing like a pendulum and if any component failed, it would come down on top of you. Your hard hat would extend your lifespan by milliseconds….

While our hydraulic system can be operated remotely for safety reasons, we prefer not to allow the turbine to swing freely. To prevent this, we attach a rope about 3m from the base and a second person keeps this tight to take up the slack when the turbine is close to vertical. This way, the turbine falls gently onto its base and can be bolted down once in place.

This system is safe, simple and enable easy maintenance. For DIY enthusiasts, it would be possible to purchase a suitable hydraulc ram and operate this using a hydraulic take off from a tractor.