I'm currently researching some mechanisms for a simulation game, which also covers several electrical power plant options. As part of this, I'm currently looking at a solar thermal power plant, which in the first phase is meant to use thermal oil for heat transfer and storage. Unfortunately I cannot find details on which exact thermal oils are usable in such a plant and how they are produced. I found that there are several options:

  • Mineral oil based
  • Synthetic silicon based
  • Biological

I checked several power plant pages, but they never go into that detail. So I'm looking for the kind of thermal oil that can be used in this context, the chemical composition and where/how it can be produced, so I can model a rough production chain. Also it would be nice to know if that oil has to be exchanged frequently or if it can stay inside the closed cycle for a long time.

Thanks in advance

  • 1
    $\begingroup$ Why don’t you check oil manufacturers and look for an oil with suitable characteristics? First thing common sense tells me is high temperature performance.... $\endgroup$
    – Solar Mike
    Dec 26 '20 at 11:51
  • $\begingroup$ I took a look at that, but only looked at the technical datasheets. I should have looked at the safety data sheet, which contains the chemical composition... Thanks for the hint and sorry for not looking close enough. $\endgroup$ Dec 26 '20 at 12:27

Solar heating systems have been designed with many different fluids depending on the ambient temperatures and max desired temperature.

The ambient temperature is because the night-time temperature or even no sun temperature will affect the performance of the fluid.

Some systems are designed to be above the boiling point of water so the system pressure is increased, others go higher than that so water is no longer viable.

To avoid fluid temperature problems some systems are designed as drainback, where the fluid is stored in a reservoir and can then be kept at a storage temperature. Drainback is a legal requirement in some countries as no antifreeze can be used to prevent leaks and subsequent or possible environmental pollution.

Here is a link to one site the lists several fluids that have or are in use: types of fluids


There are many ways to use the solar energy and depending on the scale they could use water in small home rooftop collectors to combination of sodium and molten salts in big solar towers.

See this link.

Quote from Wikipedia:

Early designs used these focused rays to heat water, and used the resulting steam to power a turbine. Newer designs using liquid sodium have been demonstrated, and systems using molten salts (40% potassium nitrate, 60% sodium nitrate) as the working fluids are now in operation. These working fluids have high heat capacity, which can be used to store the energy before using it to boil water to drive turbines. These designs also allow power to be generated when the sun is not shining.

  • $\begingroup$ OP asks about oil, and it has been used. I pointed it out to the op. $\endgroup$
    – Solar Mike
    Dec 27 '20 at 6:02
  • $\begingroup$ @Solar Mike, OP is asking about power plants. the oils in your answer are for household uses. My answer covers the molten salts for industrial scale solar power plants. $\endgroup$
    – kamran
    Dec 27 '20 at 7:34
  • $\begingroup$ Oils for household uses?? Either you mis-understood the question or have not worked on some solar thermal power systems which do use and have used, oils as the heat transfer fluid. Working on the real systems is much better in terms of experience than just a quick read of wikipedia... $\endgroup$
    – Solar Mike
    Dec 27 '20 at 8:18
  • $\begingroup$ Check out the Shell Durotherm series of oils - up to about 300 deg C , not really an oil for a household use... $\endgroup$
    – Solar Mike
    Dec 27 '20 at 8:37
  • $\begingroup$ i know but industrial plants use molten nitrate ranging from 450 to 550 degrees celsius. check this link, osti.gov/servlets/purl/5257229 $\endgroup$
    – kamran
    Dec 27 '20 at 15:38

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