Downwind Turbines – Reducing Tower Shadow

Turbine cowlings and pinnacle

One problem with many downwind turbines is that because the tower is upwind of the blades, as each blade swings past its lowest point it suffers a shadow effect from the tower.

We are getting around this by setting the turbine on a lighter tubular pinnacle, and using cowlings to minimise the wind disturbance caused by this.

Despite costing about €20K, our old turbine at home has a crude cowling made from plastic sheeting held on with cable ties. The whole lot blew off last winter, and the cowling is shorter than the blades, so the tip of the blade has to pass through the shadow of a huge flange.

So today, we have settled on a design for the cowling and are starting on getting the mouldings done for this. We will have to get an original machined from CAD drawings and get a mould made from this. It’s a costly process, but a solid, well made cowling is essential to the smooth and quiet working of a downwind turbine, and without it, we would suffer a helicoptering sound as the blade passes the tower. Here’s hoping it all works out OK!