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Home » Learning Center » Category 2 » Collector Balance of System

Collector Balance of System

A number of other key components make up the balance of system in the parabolic trough solar field, including:

• Pylons and foundations
• Drive
• Controls
• Collector interconnect

Pylons and Foundations

The pylons support the collector structure. They allow the collector to rotate and track the sun. The pylon is mounted on a concrete foundation that can support the weight and wind loading on the collector. Pylons also support the drive and controls at the center of the collector, and the bearings between each solar collector element (truss or torque tube) and at the end of the collector.

Drive

Each solar collector assembly includes one drive. The drive positions the collector to track the sun during the day. The sun’s beam radiation continuously reflects off the mirrors and onto the linear receiver.

The drive is located at the center of the collector. It can be either a standard motor and gear box configuration (LS-2) or can use a hydraulic drive system (LS-3, EuroTrough, Solargenix SGX-1). The drive must be able to accurately position the collector for tracking. It should also be able to handle the wind loads.

Controls

Each solar collector assembly has its own local controller (LOC) that controls its operation. The local controller controls the tracking of the collector. It also monitors for any alarm conditions, such as a high or low fluid temperature in the receiver.

The local controller communicates with a supervisory computer in the power plant control building. The supervisory computer sends commands to the local controller telling it when to start tracking the sun or when to stop tracking at the end of the day.
A photo of a double ball joint assembly on /between parabolic trough collectors.

The ball joint assembly at the Nevada Solar One project connects the receivers on two adjacent collectors and allows them to track independently.

Collector Interconnect

Each solar collector assembly operates independently from the adjacent collector. Luz installed insulated flexible hoses at the end of the collector for connecting the receiver to header piping and between two adjacent collectors.

The flex hose allows the collectors to rotate independently. The original flex hose designs proved to be inadequate for the service and suffered from high failure rates. KJC Operating Company developed a new ball joint assembly to replace the flex hose. The ball joint assemblies appear to be more reliable and have lower pumping losses.

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