Industry Focus Renewable Energy Sustainably increasing efficiency


As Bryan Hall of Balluff UK explains, there is a need for the availability and efficiency of energy generating systems to constantly improve to become safer and more energy efficient - and this is where sensors and precision distance measurement technology comes in


lisecond cycles. This accurate and reli- able detection is an indispensable pre- requisite to be able to turn the rotor blades quickly into a safe position in an emergency, for example. In order to increase efficiency, extend maintenance intervals and lower down-times, gear- free systems operating without contact are a must in today’s applications. Characteristic data is rated measuring lengths up to 7,600mm and a resolution of 1µm.


Monitoring tower tilt


he call for energy efficiency and safety among electricity users means a constant improvement in energy generating systems. There are various approaches to achieving these goals - examples of which include weight reduction in wind power sys- tems through alternative materials, a gearless drive train, quick starting gas turbines, exact regulation of the guide vanes in hydroelectric power plants, and accurate regulated actuating drives for valves, flaps and sliders. These mea- sures to improve efficiency and safety make the implementation of intelligent, reliable sensors and precision distance measurement technology necessary. An example of where magnetostric- tive position measuring systems are used is in hydraulically actuated pitch adjustment units for wind power plants. With a quick reacting and exact adjust- ment of the setting angle of the rotor blades, they help not only to increase the energy efficiency and safety of the wind power plant, but also to guarantee an optimal and stable operating state for a wind power plant, regardless of what the prevailing wind conditions are. It goes without saying that these posi- tion measuring systems have to be extremely robust, vibration and shock resistant, and insensitive to temperature changes and moisture. All of these requirements are fulfilled by Balluff’s micropulse position measuring systems. They measure the current pitch set- ting continuously to exact µm in mil-


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Constantly changing wind conditions cause abrupt load changes in wind tur- bines. Particularly during strong gusts of wind, storms or a wind energy system’s start-up phase, towers can tilt so much that the overall system lifetime is affected. An inclination sensor can reduce this stress on the system. It reli- ably measures the absolute angle of inclination and ensures that limit values are not exceeded.


For this application the inclination sensors use a capacitive measuring prin- ciple and are equipped with a liquid- based measuring cell. These consist of four capacitors filled with a liquid dielectric. The capacitive measuring system allows for a higher accuracy than simple inclination sensors using the MEMS-Chip and functions in tem- peratures down to -40°C making it well suited for wind turbine applications.


Directing the sun’s energy Another typical example for the use of sensors in increasing efficiency is in concentrated solar power thermal power plants. Here, in order to achieve the highest possible degree of


Left: BML


magnetic tape measuring systems from Balluff measure the


current azimuth and evaluation position directly on the axes of rotation of the heliostats


performance, the mirrors (also called heliostats) are highly exact, individual and, very importantly, repositioned with repetition accuracy. Aside from that, in an emergency, such as in the event of a storm, they must be brought into a secure position.


BML magnetic tape measuring sys- tems from Balluff measure the current azimuth and evaluation position directly on the axes of rotation of the heliostats. With a resolution of 1µm up to 10µm, and a system accuracy of up to +/- 10µm, the BML systems are well suited for this purpose. And, because they work without contact, are com- pletely wear-free and nearly mainte- nance-free, they are guarantors of optimal energy yield.


BML magnetic tape systems, which have already been used for years on a number of systems, fulfill not only these stringent requirements for accuracy and reliability, but also those of the extremely inhospitable environments in which they are used. These are usually locations with strong, continuous and stable direct sunlight, such as deserts or steppe-like sites characterised by high and changing temperatures, moisture, condensation, UV radiation and mechanical strain due to sand abrasion.


Below: inclination sensors used for monitoring tower tilt on a wind turbine - reliably measuring the absolute angle of inclination and ensuring that limit values are not exceeded


HALT tested components Safety and reliability are the critical quality criteria for wind energy and solar installations. Only systems that work with little maintenance and offer a high availability can achieve the desired energy efficiency objectives. Balluff routinely relies on HALT tests (Highly Accelerated Life Tests) in its in-house testing facility for its sen- sors and position measuring systems. In it, the components are subjected to an accelerated ‘aging process’ of from three to five days and, in this manner, the total of all strain within the life of a sensor is simulated by time lapse. In this manner, possible weak points can already be reliably detected and corrected in the development phase. The results are position mea- suring systems of particular quality and reliability that fulfill their tasks over the course of years with the same reliability and precision. With them, the system availability increases for the long term, service and repair costs are prevented and a significantly higher efficiency is achieved.


Balluff www.balluff.com T: 0161 282 4740


Enter 207 NOVEMBER/DECEMBER 2013 Automation


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