Why TCU price alone does not tell you what you are buying

A tracker control quotation can look simple. There is a price for the tracker control unit, or TCU, and a number of rows.

That is not enough to compare two control systems properly.

The TCU sits at row level and controls tracker movement, but it is only one part of the system. A complete control package can also include a network control unit (NCU), environmental sensors, communications hardware, motor connections, software, monitoring, commissioning tools and technical support.

Two suppliers can therefore quote a similar TCU price while offering materially different systems.

Start with the motor and drive system

The first question is whether the TCU is actually compatible with the tracker it will control.

Voltage, rated current, starting current, motor power and control logic have to match the selected actuator and drive system, including the slew drive where applicable. A controller that appears suitable from a datasheet still has to be checked against the motor and mechanical architecture it will operate.

Protection functions depend on the same relationship.

A TCU may monitor motor current, enforce movement limits or command the tracker into a defined protective position. Those functions only work properly when the controller, motor, sensors and tracker operating logic have been considered together.

This is why Truaxis evaluates controller compatibility against the selected drive system rather than treating the TCU as an isolated component.

What sits above the TCU?

A multi-row tracker plant also needs the individual controllers to communicate with the rest of the system.

The NCU provides that higher control and communications layer, coordinating information between the row-level TCUs, environmental sensors and the wider plant monitoring architecture.

Wind is a straightforward example.

Detecting a wind-speed threshold is only the first step. The information has to reach the relevant control layer, the correct command has to reach the affected trackers and the rows have to move into the intended protective position.

The same architecture may also handle other environmental inputs depending on the project and control strategy.

A control-system quotation therefore needs to show how the whole hierarchy works, not simply how many TCUs are supplied.

Small items can change the scope

Cables, connectors, antennas, communications adapters and commissioning tools are small compared with the tracker structure itself.

Across a project, they are still part of the control system.

The same applies to software.

A buyer should know whether monitoring is included, what interface is available to the plant SCADA, whether cloud access or software licences carry recurring charges and what hardware or software is needed to diagnose a controller in the field.

A lower TCU price is of limited value if important parts of the operating architecture appear later as additional scope.

Commissioning belongs in the comparison

The system also has to work on site.

Commissioning can include controller configuration, communications checks, sensor integration, tracker calibration, functional testing and training. The scope differs between suppliers, as does the balance between remote and on-site support.

Travel, accommodation, engineering time and the condition of the installation before the commissioning team arrives can all influence cost and programme.

The same issue continues after handover. Remote support, field intervention, diagnostic tools, spare controllers and replacement procedures affect how quickly a tracker can be returned to service.

These items should be understood before the control-system supplier is selected, not after commissioning begins.

What should an EPC compare?

• whether the TCU is compatible with the selected motor and drive system;
• the required NCU or central-control architecture;
• which environmental sensors are included;
• communications equipment, cables and connectors;
• monitoring, SCADA and software interfaces;
• cloud, licence or other recurring charges;
• commissioning scope and required tools;
• recommended spares;
• remote and on-site technical support;
• warranty coverage.

Once those items are aligned, the commercial comparison becomes much more meaningful.

The controls have their own lifecycle

Truaxis treats the structure, drive and control systems as distinct warranty categories, with the applicable terms defined at project level rather than assumed to be identical across every site.

The structure, drive and controls work as one tracker system, but they do not have identical service requirements, failure modes or support needs. The commercial comparison should reflect that from the start.

The same distinction matters after commissioning. A control system may remain in service for many years, so an EPC should also ask who will provide remote diagnostics, software and firmware support, replacement controllers, spare parts and field intervention when they are needed. Long-term access to technical knowledge and replacement components is part of the control-system decision, not an issue to discover after handover.

A technically sound controller has more value when the supplier can continue supporting the system through its operating life.