The advantages and disadvantages of solar trackers

What is a solar tracker?

A solar tracker is a device that moves solar panels to follow the sun's path across the sky. Tracking the sun allows solar equipment to absorb more sunlight during the day. More absorbed sunlight means more solar power generation.

Solar trackers tilt on one or two axes to keep angled toward the sun as light conditions change with weather and seasons. 

How do solar trackers work?

Solar trackers have turning mount-holding panels that follow sunlight using motors and sensors to find efficient angles. This effect keeps panels continuously facing the sun as conditions change.

Sensors detect the direction of incoming sunlight based on shadows and light intensity. They then send this information to a small attached computer. The computer calculates the ideal angle needed to have panels directly face the sunlight source. It angles the mount slightly ahead of the sun's movement to lead its path.

Electric gear motors tilt the panel mount left/right and up/down based on directions from the computer. Sometimes, solar installers use hydraulics for extra power when moving heavy loads.

This automated adjustment happens smoothly throughout the day, turning arrays toward the east in the morning and west in the evening. Software models even account for seasonal changes in sun positions.

Source: Solar Power World and Array Technologies.

Single-axis vs dual-axis solar tracking systems

Solar trackers come in two main varieties — single-axis and dual-axis models.

Variants of single-axis trackers include: 

Horizontal single-axis solar tracker (HSAT)

HSATs rotate panels on a horizontal axis, tilting them east-west over a day to follow the sun. The axis of rotation is aligned parallel to the ground.

Horizontal tilted single-axis solar tracker (HTSAT)

HTSATs work just like HSATs, except the axis of rotation is angled with one end raised higher off the ground instead of being parallel. This axis tilt optimizes angles for a site's latitude to increase exposure.

Vertical single-axis solar tracker (VSAT)

Unlike horizontal trackers, VSATs move panels on a vertical axis, angling them up or down to adjust for seasonal changes in the sun's height throughout the year. 

Vertical-tilted single-axis solar tracker (VTSAT)

VTSATs combine the tilting concept from HTSATs with the vertical rotation of VSATs. The vertical axis is angled 90 degrees vertically to target a location's latitude. This tilt improves tracking of seasonal sun paths.

The dual axis solar tracking system

Dual-axis trackers have rotational ability on both a horizontal and vertical axis, allowing solar panel positioning in almost any direction. They enable even more precise tracking of the sun's movement than single-axis options.

Dual-axis trackers tilt panels horizontally over each day as the sun rises in the east and sets in the west. This east-west adjustment over a daily solar cycle is powered by motors and gearing linked to a rotational axis. At the same time, dual-axis trackers pivot panels on a vertical axis at different inclines over the year, depending on the sun's height. This feature compensates for the higher-angled summer sun versus the lower-angled winter sun.

By combining horizontal daily rotation and vertical seasonal tilting, dual-axis tracking aims to keep panels aimed perpendicular to sunlight from any angle. The solar solution maximizes sunlight capturing and solar electricity generation across all conditions.

The advanced motion controls and equipment make dual-axis trackers more complex and costly than single-axis. However, their superior angle optimization provides even greater annual energy yield over fixed tilt or simpler single-axis trackers.

Pros and cons of single and dual-axis solar trackers 

Both single-axis and dual-axis solar tracking systems have their own unique strengths and weaknesses when considering maximizing solar panel productivity. 

Single axis trackers

Advantages

• More reliable and longer-lasting 

• Lower complexity so fewer maintenance issues

• Cheaper to purchase and operate vs dual-axis

• More efficient than stationary mounts: generate 15-16% more annual power than fixed panels

Disadvantages

• Produce less energy than dual-axis models during peak sunny times

• Limited technology upgrade capabilities

Dual axis trackers

Advantages

• Maximize power output by continually following the sun

• Help manage grid power limitations

• Require less land area to produce more total energy

• Generate 45-50% more annual power than fixed panels

• Quicker payback on investment costs

Disadvantages

• More prone to technical glitches due to complexity

• Shorter lifespan and lower reliability

• Higher maintenance costs

Choosing between single-axis and dual-axis solar tracking comes down to balancing reliability and output against complexity and costs. For many sites, single-axis trackers may provide the optimal tradeoff, more generation and lower cost. 

However, solar farms looking to maximize every kilowatt hour out of valuable land investments may prefer dual-axis tracking despite higher risks. The right conditions can enable even greater energy yields from perpetual sun following.