- Single-axis tracker
- A structure that turns modules around one axis, usually from east to west along a north–south axis, so that they follow the sun during the day.
- Tracking angle and target angle
- The tracking angle is the actual tilt of the tracker, the target angle the tilt the controller sets. The deviation between the two shows whether a tracker follows correctly.
- Backtracking
- When the sun is low, steeply tilted rows would shade the next row. With backtracking the controller flattens the rows in the morning and evening so that no row shades the next.
- Astronomical control
- The controller computes the sun position from location, date and time instead of measuring it with a sensor.
- Wind stow
- A safety position the tracker moves to in strong wind to reduce the load on structure and modules. Which position that is, the manufacturer of the mechanics specifies.
- Hail stow
- A steep safety position for hail so that hailstones hit the modules at a flatter angle.
- Snow stow
- A tilted position for snow so that it slides off the modules and does not overload the structure.
- Farming position
- In Agri-PV, a position that allows work under the modules – vertical, for example, so that machines can pass.
- TCU (tracker control unit)
- The control unit on each tracker. It reads the tilt sensor, drives the motors and protects the tracker with limit switches and an emergency stop.
- NCU (network control unit)
- A network controller that coordinates many TCUs, distributes target angles and safety commands and passes data on to control systems.
- RSU (remote sensor unit)
- A sensor unit in the field, for wind or snow, for example, whose readings trigger safety positions.
- Inclinometer
- A tilt sensor that measures the actual angle of the tracker.
- Drive synchronisation
- On long trackers with two or more drives, all drives have to move together so that the structure does not twist.
- GCR (ground coverage ratio)
- The ratio of the module width to the row pitch. The higher the GCR, the closer the rows and the earlier backtracking is needed.
- Tracker availability
- The share of time in which a tracker follows its target angle. It is a metric of its own next to inverter availability.
- SCADA
- A plant's control system, which collects data from inverters, meters, weather stations and trackers and issues commands.
- Agri-PV (agrivoltaics)
- Using the same land for farming and photovoltaics at the same time.
- DIN SPEC 91434
- A German pre-standard with requirements for Agri-PV plants, including how much of the land must remain usable for farming.
- Retrofit and repowering
- Upgrading existing plants – for trackers, replacing controls, drives or sensors while the structure stays.
Solar tracker glossary
The main terms around single-axis trackers, their controls and Agri-PV – explained briefly and without advertising.