Parabolic Trough


Parabolic trough solar technology is credited by being synonymous with “the very first application of solar energy.” Presently, it is the most advanced and lowest cost large scale solar power technology available. Considerable R&D has been done in last 3 decades and is also being currently conducted to enhance this technology.

Parabolic troughs are high performance solar reflectors capable of delivering high temperatures efficiently. When the parabolic shaped reflector is pointed towards the sun, parallel rays’ incident on it, are reflected onto the thermally efficient receiver tubes located at its focal point. In order to optimize solar energy generation, the troughs are designed to chase the Sun’s movement along a single axis.

A linear receiver tube placed along the focal point of the parabolic trough contains a thermal transfer fluid usually oil that gets heated to around 400oC. This superheated fluid is piped to the solar steam generator where it generates the steam which drives the turbine.

Parabolic trough technology as a solar power solution has matured over the time, ever since it was first developed in 1980’s. It has accumulated substantial experience by means of establishment of a small commercial industry to produce and market these systems. It is, therefore at the laser focus of Thermosol Glass.


Parabolic trough reflector:

The reflector is made of thick or thin glass with several layers of coating- a silver reflectivity layer, a protective copper layer and additional three layer coating. The multilayer glass construction ensures high optical accuracy, low heat losses, high resistance to corrosion.

Linear Receiver tube:

The receiver of a parabolic trough is a 70mm diameter metallic black tube for high absorptance for solar radiation and to minimize the energy loss. An evacuated glass tube envelopes the receiver tube to reduce heat loss due to convection, thereby considerably reducing the heat loss coefficient. The glass envelope is typically coated with an anti reflective coating to improve transmissivity. The linear receiver in order to further reduce the convective heat loss at high operating temperatures incorporates a vacuum tight enclosure between the glass jacket and metal tube.

Tracking Mechanism:

In order to optimize solar energy generation, the collector system is supplemented with a sun tracking system. These systems can either be mechanically or electronically controlled with electronic system generally providing higher reliability and tracking accuracy. Tracking of the collectors is controlled by a system that utilizes an optical system to focus radiation on two light sensitive sensors.

Support structure:

The collector support structure is the third core component of the solar collector. Its installation and mounting accuracy has high influence on the total plant performance. The support structure has to face the following structural requirements:

  • Stiffness-The structure has to be a robust, with a rigid frame, capable to maintain exact geometry (optical precision) at all times.
  • Weight – Low weight reduces cost of both material and transportation.
  • Motion – A high angular tolerance is necessary to enable one-axis tracking requirements. The tracking has to be accurate, robust and sufficiently strong to be capable to operate even under extreme weather conditions.