Utilizing the Steam Rankine Cycle for Industrial Decarbonization

November 27, 2024

A Rankine cycle is a thermodynamic cycle that converts thermal energy into mechanical work by the constant evaporation and condensation of a circulating working fluid, which is water for the case of a Steam Rankine Cycle. In this application, the cycle is composed of four main components, boiler (evaporator), expansion device (turbine), condenser, and the feed-pump.

Steam Rankine Cycle Steps

The steps needed for a Steam Rankine Cycle (SRC) are similar to an Organic Rankine Cycle (ORC) with a few key differences including working fluid and heat source temperature.

Working Fluid: a SRC uses water which has a higher boiling point than the organic fluids, namely refrigerants or hydrocarbons, that an ORC would use.
Heat Source Temperature: an ORC is well suited for lower temperature heat sources, while the SRC is better suited for high-temperature waste heat streams, typically above 570∘F or 300∘ C.

Both cycles can be used for industrial decarbonization applications.

To explain the overall SRC process, we begin with the heat source, such as the combustion of fossil fuels or a high-temperature industrial process. This heat source is used to boil (evaporate) water into high-pressure steam. The high-pressure steam is then expanded through a turbine, generating mechanical energy. This mechanical energy is converted into electricity by a generator. After passing through the turbine, the steam is condensed back into water in a condenser. This releases the remaining heat energy, which is typically dissipated in a cooling tower. The condensed water is then pumped back into the boiler to repeat the cycle. By continuously heating, expanding, condensing, and pumping water, the SRC efficiently converts thermal energy into electrical energy. To prevent excessive corrosion of equipment, additional processes are required for an SRC to treat the incoming water stream, such as a deaerator to remove dissolved oxygen and a water treatment program to remove solids and dissolved minerals.

Efficiency of a Steam Rankine Cycle

Similar to an Organic Rankine Cycle, the efficiency of a Steam Rankine Cycle (SRC) is determined by its ability to convert low-temperature heat into mechanical work and can be analyzed through thermal, cycle, and system efficiency.

Thermal efficiency is the ratio of useful work output to heat input, affected by the heat source temperature and the organic working fluid’s properties.
Cycle efficiency depends on the effectiveness of key components, including the evaporator, turbine, condenser, and regenerator.
System efficiency encompasses the performance of ancillary components like pumps and heat exchangers encompasses the performance of ancillary components like pumps and heat exchangers

About the Author

This blog post was written by Savini Jayasinghe and Tyson Migadel. Kanin Energy is a clean energy developer that helps heavy industry decarbonize their operations. If you have any questions about this post or Kanin Energy, contact us at hello@kaninenergy.com.

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About Kanin Energy

Kanin Energy is a clean energy developer based in Calgary and Houston that focuses on decarbonizing heavy industry through waste heat recovery. In doing so, Kanin contributes carbon-free baseload electricity generation, thereby offsetting power produced from fossil fuels. Kanin has a technology agnostic approach and successfully de-risks projects by providing expertise in carbon markets, project finance, and energy policy, as well as providing an innovative energy-as-a-service third-party financing model and turnkey approach that enables industrial facility partners to decarbonize their operations.

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Kanin Energy

This article was authored by a member of the Kanin team. To discover more about our team, please visit our team page.