The Organic Rankine Cycle: Harnessing Low-Grade Heat for Power Generation

What is the Organic Rankine Cycle?

The Organic Rankine Cycle (ORC) is an efficient process for generating electricity from waste heat, which can be sourced from various industrial processes or renewable energy systems. It operates similarly to the traditional steam Rankine cycle but uses organic fluids with lower boiling points and higher specific heats.

In this cycle, a working fluid is heated by low-grade thermal energy, undergoes phase changes (evaporation and condensation), and drives a turbine to produce electricity.

How Does the ORC Work?

The ORC begins with heating an organic working fluid in an evaporator. As the fluid absorbs heat, it vaporizes at a lower temperature than water, allowing for efficient operation with waste heat sources that are not hot enough to boil water.

The resulting high-pressure vapor then expands through a turbine, converting thermal energy into mechanical work, which is subsequently converted into electrical power by a generator.

Key Components and Their Functions

In the ORC, each component plays a crucial role: the evaporator heats the working fluid to its boiling point, the turbine converts thermal energy into mechanical work, and the condenser cools the vapor back into a liquid for reuse.

The pump recirculates the working fluid through the cycle by pressurizing it before it enters the evaporator.

Factors Affecting Efficiency

Efficiency in the ORC is significantly influenced by factors such as the choice of organic working fluid, heat-source temperature, condenser/cooling temperature, and turbine efficiency. Each parameter affects the cycle's thermal efficiency and net power output.

For instance, a higher heat-source temperature can increase the thermal efficiency but may require more robust materials for the components to withstand high temperatures.

Frequently asked questions

Try it live

Everything above runs in your browser — open Organic Rankine Cycle: 2D Loop Diagram and change the parameters while it is running. Nothing is installed, nothing is uploaded, the whole model lives in one tab.