AdvancedTopic 105 of 105Thermodynamics & Fluids
Organic Rankine cycle
Uses organic fluids to generate power from low-temperature heat sources.
In depth
ORC uses an organic working fluid (R245fa, pentane, toluene) with low boiling point in a Rankine cycle to generate power from heat sources of 80–350 °C: geothermal, industrial waste heat, biomass, solar. Efficiencies 10–25%. Fluid selection (dry, isentropic, wet) affects turbine design.
Key points
- Closed loop with condenser and pump
- Recuperator
- Small scale 10 kW–10 MW
ExampleA cement plant recovers kiln exhaust heat with an ORC to generate electricity.
What is Organic Rankine cycle?
Uses organic fluids to generate power from low-temperature heat sources.
Why is it important to understand organic Rankine cycle?
The organic Rankine cycle uses fluids with low boiling points to produce power from low-temperature heat, which opens up waste heat and geothermal sources.
Why use an organic fluid instead of water?
Organic fluids boil at lower temperatures and pressures, so they suit low-temperature heat sources better than water.
What limits an ORC plant?
Its efficiency is low because the heat source temperature is low, so the economics depend on cheap or waste heat.
How is Organic Rankine cycle used in practice?
Typical applications include generating electricity from waste heat of an industrial process at about 120 degrees Celsius, using a geothermal source at moderate temperature for a small power plant and recovering heat from a biomass boiler exhaust to make electricity.
What should I learn before Organic Rankine cycle?
Study "Large eddy simulation" first (topic 104 of 105 in Thermodynamics & Fluids). It covers the groundwork this topic builds on.
What are the key points of Organic Rankine cycle?
Closed loop with condenser and pump. Recuperator. Small scale 10 kW–10 MW.
Can you give an example of Organic Rankine cycle?
A cement plant recovers kiln exhaust heat with an ORC to generate electricity.
What comes after Organic Rankine cycle?
This is the final topic in Thermodynamics & Fluids.
How difficult is Organic Rankine cycle?
It is classed as Advanced in Thermodynamics & Fluids (topic 105 of 105). It is an advanced topic. It assumes you are comfortable with the intermediate topics in Thermodynamics & Fluids.