Solar tracker
A motorised mounting structure that rotates PV modules or mirrors to follow the sun, raising the irradiance they receive over the day.
Trackers reduce the angle of incidence between sunlight and the module surface, increasing captured direct irradiance. Two main types exist:
- Single-axis horizontal trackers rotate rows east-west around a north-south axis, typically through ±50–60°. They add about 15–25% annual energy over fixed tilt in sunny, low-latitude sites and 8–15% in cloudier, higher-latitude ones (NREL, LBNL).
- Dual-axis trackers follow both azimuth and elevation, adding 30–40% over fixed tilt in high-DNI climates, but at much higher cost; they are now used mainly for concentrator PV and heliostats.
Single-axis tracking has become standard for utility PV: in the US more than 90% of new utility-scale capacity in recent years used it (LBNL Utility-Scale Solar, 2024 edition), and it is common in Spain, Chile, Australia, the Middle East and India. The added capital cost, roughly 0.05–0.10 USD/Wp, is usually repaid by the extra yield and the flatter, wider daily production profile, which is worth more in markets with an evening price peak.
Control features include backtracking, which flattens the rows in early morning and late afternoon to prevent row-to-row shading, and stow modes for high wind, hail or snow. Trackers combine well with bifacial modules. Their gain is smaller where the diffuse fraction (DHI/GHI) is high.
Related terms
All terms →- Bifacial module
A PV module that collects light on both its front and rear faces, using a transparent back sheet or glass to harvest ground-reflected and diffuse light.
- DNI (Direct Normal Irradiance)
Solar radiation arriving in a straight line from the sun disc, measured on a surface held perpendicular to the sun rays.
- DHI (Diffuse Horizontal Irradiance)
Solar radiation reaching a horizontal surface after being scattered by molecules, aerosols and clouds, excluding the direct beam from the sun disc.
- Specific yield
Annual energy produced per unit of installed PV capacity, expressed in kWh/kWp per year; combines solar resource and system performance.
- Concentrated solar power (CSP)
Power plants that use mirrors to concentrate direct sunlight onto a receiver, heating a fluid that drives a steam turbine, usually with built-in thermal storage.