In this article, I will try my best to explain how a parabolic trough collector (PTC) works in details. So first it is important to know that this collector, is producing hot water or steam, so energy that is called thermal energy it has different usages in most industry sectors. It is important to know that PTCs works only with direct sunlight, so without any clouds in front of the sun (diffuse sunshine). Not like PV modules that works with both sunlights.
So let’s start the explanation, the PTC is 3m long and 1,25m wide, so an aperture area of 3,75m² of the mirrored surface. The PTC is build in strings of 5 to 10 PTCs, with one absorber tube of the appropriate length of the string. The PTCs are controlled by a programmable logic controller (PLC), so when the sun comes out a radiation sensor provides the necessary information, so that the PTCs will start tracking the sun. The whole string of PTCs are moved by one motor to track the sun. There are several control levels for the tracking, all controlled by the PLC, that gathers the necessary informations thanks to the different sensors (GPS, wind, position and radiation). By tracking the sun, the sun rays will fall horizontally on the mirrored parabolic surface, on that surface the rays are redirected to a focus line of 3,5mm radius, where an absorber tube captures the sun rays and transmits the focused energy to the thermal oil which flows through the absorber tube. Then thanks to a piping system, heat exchangers and pumps, the collected heat of the thermal oil will be exchanged with the water in an heat exchanger. The outlet temperature of the water can be controlled depending on the flow rate of the pumps. All these parameters are controlled by the PLC device.
It is an extremely interesting technology, especially for countries with a lot of direct sunshine, so in the southern hemisphere. In these country the global output is very high and this system can reaches temperatures until 400°C. They are also several variants of this technique, which have not been tested yet. For example Solar Cooling, desalination installation or direct steam generation, instead of going through an heat exchanger you would take water as an heat medium.
I hope I managed to explain it, in an easy way. It is much more easier to explain this technology when you can see the technology.