I’m not sure I understand the question. Thermodyamic systems convert energy from one form to another – a very common one, used in power plants is called the Rankine cycle.
This is where water is pumped (at pressure) into a boiler where it is heated to form steam. The heat can come from anywhere btw – (burning oil/gas or even solar!). The high pressure steam is then used to turn a turbine and generate electricity. It returns to be a low pressure water after the turbine and the cycle can start again.
So this whole cycle is thermodynamic – using fluids to convert heat energy into electricity.
Let me know if I answered you Question – or I totally missed the point ? 🙂