Home-spun power

A wind turbine that can be roof-mounted to provide homes with electricity is poised to enter commercial production after months of fine-tuning by the UK engineering team developing it.

Edinburgh-based Renewable Devices claims its Swift system is the first turbine in the world to be practical for use on roofs thanks to the elimination of noise and vibration, the traditional barriers to attaching wind energy devices directly to buildings.

‘Conventional wisdom says you don’t put turbines on roofs. We thought to hell with conventional wisdom, let’s design one,’ said Renewable Devices co-founder Dr. David Anderson.

The turbine can be connected to the grid for embedded power generation or linked to an immersion water heating system. The Swift has a rated power output of 1.5kw and will generate up to 4,000kwh per year depending on wind conditions, which its developers claim would cut up to £440 off annual energy bills.

Renewable Devices is about to begin full-scale production of the Swift after signing a sales and distribution deal with Scottish and Southern Energy. The utility will market the device across the UK at a cost of around £1,500 per unit, and hopes to install several thousand over the next two years.

‘We don’t know of any other company in the world that has reached this stage,’ said Anderson.

Renewable Devices has filed five international patents on the turbine’s underlying technology, which combines advanced mechanical engineering design with electronic control systems.

To keep turbine-to-building oscillations to a minimum, the Swift’s mounting brackets use damping systems designed to absorb a wide range of frequencies.

Its ring diffuser keeps turbine noise low by preventing the creation of turbulent vortices at the blade tip. The system’s five-bladed design acts as an additional constraint on noise by allowing a slower speed of rotation.

Both the rotation speed and system integrity are controlled by a custom-developed, over-power regulation mechanism. This consists of a twin-vane progressive mechanical furling system linked to an advanced electronic control system.

According to Renewable Devices, the regulator allows the optimum amount of power to be extracted from the turbine under all wind and loading conditions without stalling.

The company’s engineers worked with bearings giant SKF on the development of the rotor and furling mechanism. The carbon fibre rotor is supported by two stainless steel ball bearings designed to cope with the huge gyroscopic and thrust loads imposed by the turbine in high winds.