Position sensors for better energy yields with solar trackers

Solar plants are becoming an integral part of our infrastructure – in the face of rising energy prices and diminishing resources of fossil fuels, they are a popular alternative. And they are not only the photovoltaics panels that can be seen on many housetops all over the world but come in various shapes and kinds. Parabolic trough solar farms, for instance, are being installed on uninhabited land in sunny regions – they transform solar energy into heat to power a turbine that generates energy. The efficiency factor of this kind of solar plant can be improved by solar tracking systems which orient the panels or collectors to the changing position of the sun. This function, which is available both for photovoltaic and solar thermal applications, requires precise position data and a measuring solution working reliably even under highly demanding outdoor conditions.  POSITAL, a developer and manufacturer of absolute rotary encoders and tilt sensors, offers different solutions.

Solar tracking is performed in one or two axes. Single-axis systems require less mechanical effort and fewer sensors – for example, they can be equipped with a single-turn absolute rotary encoder or a tilt sensor with a measuring range of ±50° or more. If a gear unit is used, a multi-turn encoder will be necessary. Two-axes tracking systems enable higher efficiency but are also more mechanically demanding. In addition to horizontal (azimuth) orientation, the panels are also oriented along the vertical axis. This requires either two encoders (single or multi-turn, depending on the mechanical requirements) or one encoder and one tilt sensor with a measurement range of at least ±60°.

Rotary encoders and tilt sensors for solar tracking systems

Optical IXARC encoders from POSITAL use a proven opto-electronic scanning method and are especially suited for high-precision applications. The single-turn sensor provides a resolution of 16 bits per revolution. In addition, a maximum of 16,384 revolutions (14 bits) can be registered in multi-turn mode, thereby covering a 30 bit measuring range. The optical encoders do not require backup batteries or referencing – they instantly provide current, absolute position and revolution values even after power loss. All models are optionally available as stainless steel versions and with protection ratings up to IP68.

Magnetic IXARC encoders are a cost-efficient alternative. Featuring robust and contact-free magnet technology, which provides a maximum resolution of 12 bits; these encoders easily withstand the most rugged environmental conditions such as humidity, extreme temperatures, and vibrations. The devices can cover up to 20 bits for revolution measurement. They are optionally available with a radial or axial cable output and as hollow shaft or solid shaft versions. Heavy duty models reach protection ratings up to IP69K. The encoders operate without gear units or batteries and can therefore be manufactured very cost-efficiently. Since the Wiegand and Hall sensing technology requires only one permanent magnet, the components take up a minimum of space – this further reduces material costs.

An alternative to rotary encoders, TILTIX inclinometers from POSITAL enable easy and low-cost mechanical integration combined with high-precision position data. Mounting fixtures and couplings are not required. They are particularly well-suited for tracking in the elevation axis. TILTIX inclinometers are available as two-axes versions with a ±80° measurement range and as a one-axis version for 360°. They provide a 0.01° resolution at a 0.1° measuring accuracy. The sensors feature capacitive cells based on MEMS technology (micro-electro-mechanical systems), and allow users to measure inclination values directly, without being mechanically coupled to drive elements. A high sampling rate of up to 100 measurements per second enables an efficient filtering of vibrations and shocks and minimizes the settling time. The highly robust devices feature IP68 or IP69K protection ratings. They are available with SSI, CANopen, DeviceNet, or fieldbus interfaces, or with analog voltage or current signal outputs. “Industrial” and “Heavy Duty” models are available with plastic or aluminum enclosures.