Role of Tilt Sensors in Solar Tracking

Tilt sensors significantly impact the output of solar power plants (CSP) and hence, are commonly used for solar tracking. Though the importance of solar tracking and the boost in production due to it is proven, there is a lot of confusion around how this systems works and what are the expected gains out of it. We often receive many queries and questions regarding effectiveness of tilt sensors for solar tracking and their advantage. This article tries to explain just that.

Importance of solar tracking

In case of solar power plants, the power output depends on the orientation of the panels with respect to sun. As the misalignment increases beyond a point, the output starts falling sharply. To be precise, the output of panels drops off with the cosine of the angle between the incident radiation and the panel.

It is a common misunderstanding that most of the solar power is available only in the noon times. In fact, several studies have demonstrated that the power available during early mornings and evenings are roughly half of the power available during noon time. In fact, the inclination angle at which maximum power may be expected also of function of location (latitude) and season. Absence of solar tracking means most of this energy is lost due to misalignment between sun rays and the collectors.

In countries like India, for most of the year solar energy is available abundantly. But in other parts of the globe, due to poor availability of solar power, not having solar tracking system leads to poor power output and hence long payback periods. Even in regions like India, use of solar tracking can significantly improve the power output resulting in fast recovery of the investments made.

Solar tracking can improve the output of solar power plants by 10-25% depending on the location and weather conditions. In case, if there is space constraint, more output can be achieved using solar tracking systems.

Types of solar tracking

Solar tracking can be done in two ways- single axis (only elevation) and dual axis(elevation and azimuthal).

Single Axis Solar Tracking

In single axis solar tracking, with the help of tilt sensors, the solar collectors are moved only to match the elevation of sun. This means, if the sun moves horizontally in the sky, the panels won’t be moved to face the sun.

The tilt sensors used for single axis tracking are generally single axis tilt sensors. The output achieved with single axis solar tracking is certainly more than output without any tracking system but is a bit lower than dual axis tracking system.

Dual Axis Solar Tracking

In dual axis solar tracking, the angle of elevation as well as azimuthal (horizontal) angle are controlled so that the collector always faces the sun accurately. The tilt sensors used for dual axis solar tracking are capable of detecting inclination in two dimensions. Though dual axis solar tracking systems are costlier than the single axis ones, the increase in output achieved justifies the extra expenses.

Role of tilt sensors in solar tracking

Though different techniques can be used for solar tracking, tilt sensors are probably the most widely used technology for solar tracking.

Another technology, which is used for solar tracking is optical encoders. Optical encoders have a disc with slits of different sizes and shapes on it at different angles. The light pulse coming through this slit is monitored to find out the angle of orientation. As the motor moves the shaft, the disc also rotates and as a result, the light pulse varies. This variation is used to find out the angle of rotation. In case of dual axis tracking, two separate motors are used and two optical encoders are installed to calculate elevation as well as azimuthal angle.

What makes tilt sensors a preferred choice for this application over the other technologies such as optical encoders? Following are a few of the features of tilt sensors that make them a perfect fit for this application.

  1. Tilt sensors are compact, easy to install and use and affordable. Their costs are significantly lower than the cost benefits one reaps out of them, justifying their use for this application. On the other hand, optical encoders are difficult to install and mis-alignments during the installation can produce a permanent error in the output unless corrected.
  2. Tilt sensors provide digital output which can be fed directly to controllers to actually control the orientation of the collectors. The output remains accurate over the period. In case of optical encoders, since they’re relative angle sensors, operation over the period can introduce a small error in the output which may gradually increase.
  3. Tilt sensors are rugged and hence, withstand heat, rains and other extreme weather conditions. When compared with tilt sensors, optical encoders having moving components and hence, are subject to wear and tear. Dust and dirt also affect their performance.