Indirect heat exchange with an intermediate heat transfer fluid is currently the
standard when there is a continuous fluctuation in the heat source. This fluid will
stabilize the fluctuations and improves stability of the heat transfer to the working
fluid. Thermal oil, pressurized water and saturated steam are commonly used for this
intermediate loop. An intermediate heat transfer fluid (HTF) loop controls the fast
variations of the heat source allowing smoother cycle operation than is the case with
direct feeding. With this design it is also possible to couple different heat sources and
supplies their heat to single ORC.