The ORC unit is a system based on a closed-loop thermodynamic cycle for the generation of electric and thermal power, especially suitable for distributed generation. In this section the key points of ORC technology compared to steam technology are explained.


  • Large range of sizes from small to medium sizes (up to 20 MW per single shaft)
  • Different primary energy sources, from renewable energy (geothermal, solar, biomass) to energy efficiency (i.e. waste heat from idustrial processes) to conventional fuels (natural gas, flare gas)
  • Different kind of heat-carrier fluids: intermediate fluid (thermal oil, saturated steam, water) or directly from industrial smoke through a direct exchange
  • Large rangeability: different temperatures of the source (even below 100°C through selection of proper working fluid); partial load (the ORC system keeps high electrical efficiency even when operating with lower thermal power input, even 10% of the nominal one)

* The efficiency of the ORC system is always optimized: on average at 50% load, electrical efficiency is still 90% of the nominal electrical efficiency.

  • Cogeneration mode or power only mode. In cogeneration, the thermal output can be hot water or steam
  • Ease of integration into pre-existing systems (i.e. in waste heat recovery from industrial processes).
  • Island mode capability


  • Simple technical features: low pressures involved, low speed turbine, limited number of stages of the turbine (≤6), self-lubricating fluids, no water required, low refiling of fluid required
  • Ease and cost-effective operation & maintenance: automatic operation (no qualified operator required), minimal maintenance activities, no major overhaul (turbine not subject to erosion and corrosion), fast start-stop procedures, no chemical treatments of water, compactness
  • Possibility to install the ORC unit in remote places, working efficiently


  • High availability (98% +)
  • Long life


  • Core system for renewable energy and energy efficiency
  • Clean generation of power and heat
  • Reduction of CO2 emissions (e.g. in heat recovery or in geothermal where the ORC system operates with zero emissions thanks to the reinjection)