Wind power is providing an increasingly large slice of the world’s power and its efficiency strengthens the case for investment in renewable energy. Key to ensuring that efficiency is the use of the latest pressure switches and transducers, says Mike Powers, Product Marketing Director for Gems Sensors and Controls
As a means of generating energy on a worldwide scale, wind power is still in its infancy and, despite an on-going global increase in capacity, operators of the technology and its supporters within and without government are still fighting to convince us that we should continue to invest in it. During February 2012, the BBC reported two wildly conflicting parliamentary views within the space of 24 hours, providing an enlightening illustration of the on-going debate: a proposed wind farm in Sussex – which, if given the go-ahead, will be seen from Brighton beach – was hailed by the local Liberal Democrat MP as a welcome provider of local jobs, carbon reduction and enough renewable electricity to power approximately 450,000 homes; meanwhile, over 100 Conservative MPs were petitioning the Prime Minister to cut wind farm subsidies for what they described in a letter to The Sunday Telegraph as, “inefficient and intermittent energy production.”
Clearly, the fight is very much on to defend the integrity of wind turbines and there is, therefore, a pressing need to support the industry with robust, reliable technology that minimises maintenance costs and maximises productivity.
A key element in any plan to optimise wind farms is to increase efficiency via preventative measures, thus maximising turbine availability and providing a steady supply of renewable, reliable energy. This requires engineers to specify components that are highly unlikely to cause failures and stoppages; this includes even the smallest components, the failure of which can cause as much downtime as that of larger parts, such as gearboxes or hydraulic systems. The need to reduce maintenance is especially acute where wind turbines are concerned because of the environment in which they are often situated. Consider the complications of accessing a high wind turbine nacelle in an offshore wind farm that cannot even be visited until a repair vessel has been organised, and it is easy to see how time and money can swiftly be swallowed up by maintenance costs, fuelling the arguments of those MPs and campaigners who would like to see a reduction in wind farm subsidy.
One area in which the need to supply devices that can function for extended periods under extreme operating conditions has been well addressed is in the provision of pressure switches and transducers. In a typical wind turbine, key actions are managed via a series of pressure sensors to ensure safe and efficient operation; for example, the management of the pitch control system. In order to optimise the productivity of a wind turbine its power output must be maximised at any given wind speed, and this is achieved by adjusting the angle at which the edge of the blade cuts into the wind.
Hydraulic pitch control
Pressure transducers play an important role in ensuring swift changes in the pitch of the blades, changes that can also prevent the turbine from damage; if the wind speed rises above the turbine’s rate capacity, the blades must be edged parallel with the wind, or ‘furled’, to avoid any potential damage. Hydraulic pitch control, a system that uses fewer components than a mechanical alternative and thus satisfies the need for reduced maintenance, is the most common method of protecting the blades as described above, since it responds more quickly and minimises the likelihood of overload. Hydraulic pitch control is typically accompanied by hydraulic yaw control, a system that maximises power output by positioning the rotor to face the wind and which is also controlled by pressure sensors.
With so much depending on the efficiency and productivity of wind turbines, the designers and manufacturers of sensors have worked hard, and succeeded, to provide sophisticated and reliable components that optimise the performance of wind farms. One particular factor that has recently been addressed is that of supplying sufficient overpressure capability. While it is the elemental force of the wind that makes the harvest of so much clean energy possible, it is an ungovernable force and therefore one that can threaten to damage machinery. Historically, a sudden gust of wind striking the blades has generated a pressure spike on the hydraulics that control the pitch and yaw, but Gems Sensors and Controls has now addressed this problem by providing custom pressure sensors that allow overpressure capacity to be raised beyond the limits of conventional components. The addition to the pressure port of a snubber, a restrictive orifice that smoothes out pressure spikes, can also protect the sensor itself.
One reason why today’s pressure sensors can provide exceptionally accurate performance in such challenging applications as wind turbines is the introduction of stainless steel casings that prevent the sensor from being subject to corrupting influences. The vast amount of electrical potential produced by the turbine can cause some sensors to provide an incorrect pressure reading, but stainless steel casings provide a high level of shielding from electromagnetic interference to minimise the likelihood of error. Stainless steel casings have therefore been a significant step towards preventing such possible scenarios as the indication of incorrect pressure levels within an accumulator, which can result in damage as the pitch of the blades is no longer under accurate control.
The ongoing improvements in pressure sensing technology offer huge potential to prevent costly maintenance within wind farms. By consulting with an established supplier that has experience of specifying equipment for demanding applications such as wind turbines, engineers can take advantage of some powerful components that are helping to support the viability of the wind power industry.
To find out more about pressure sensor technology in wind turbines, visit the Gems Sensors and Controls website at www.gemssensors.com/en-GB.