An Organic Rankine Cycle running on a low-enthalpy geothermal source has far less thermal energy to work with than a conventional high-temperature plant, which makes working-fluid selection one of the highest-leverage decisions in the whole system. These are early framing notes, not final conclusions.
Why low-enthalpy sources are harder to exploit
High-temperature geothermal or industrial waste-heat sources have enough thermal margin that fluid selection matters, but isn't usually the deciding factor in whether a system is viable. Low-enthalpy sources remove that margin — a poorly matched working fluid can be the difference between a system that's thermodynamically worthwhile and one that isn't.
The trade-offs actually in play
- Boiling point relative to the available source and sink temperatures
- Thermal stability of the fluid across the cycle's operating range
- Environmental and safety profile of the candidate fluid
- Practical availability and cost at the scale the system requires
None of these can be optimized in isolation — a fluid that's thermodynamically ideal but impractical to source or handle safely isn't a usable answer. The optimization problem is as much about constraints as it is about peak theoretical performance.
“In a low-enthalpy system, the working fluid isn't a component choice — it's most of the design.”
Where this research actually stands
This framing sits ahead of any modelling results — the underlying research is at an early, conceptual stage, and no performance figures are claimed here. The expertise page linked below gives the accurate current scope of this thread of work.
