Rankine Cycle

Definition

The Rankine cycle is a thermodynamic cycle that converts heat energy into mechanical work, commonly used in power generation systems. It operates by heating a working fluid to produce steam, which then expands through a turbine, generating electricity. This cycle is fundamental in concentrated solar power systems, as it efficiently converts solar heat into usable energy, while also being applicable in combined cycle applications that enhance overall efficiency by utilizing waste heat.

5 Must Know Facts For Your Next Test

1. The Rankine cycle typically uses water as the working fluid, which undergoes phase changes from liquid to vapor and back during the cycle.
2. The cycle consists of four main processes: isentropic expansion in the turbine, isobaric heat addition in the boiler, isentropic compression in the pump, and isobaric heat rejection in the condenser.
3. Efficiency improvements can be achieved by using reheat cycles or regenerative cycles that preheat the working fluid before it enters the boiler.
4. In concentrated solar power systems, solar collectors focus sunlight to heat the working fluid, which then drives the Rankine cycle to generate electricity.
5. Combined cycle applications often integrate the Rankine cycle with a Brayton cycle to enhance overall system efficiency by capturing and utilizing exhaust heat.

Review Questions

• Explain how the Rankine cycle operates and its significance in power generation.
  • The Rankine cycle operates through four processes: heating a working fluid in a boiler to create steam, expanding this steam through a turbine to produce work, condensing the steam back into liquid form, and pumping it back into the boiler. This cycle is significant in power generation as it efficiently converts thermal energy into mechanical work, making it ideal for various power plants including those using concentrated solar power. The ability to utilize phase changes enhances the efficiency of energy conversion.
• Discuss how integrating the Rankine cycle with a Brayton cycle can improve overall efficiency in power systems.
  • Integrating the Rankine cycle with a Brayton cycle creates a combined cycle power system that maximizes efficiency. In this setup, the Brayton cycle generates electricity using gas turbines powered by combustion or other means, while the waste heat from this process is then captured and utilized to drive the Rankine cycle. This dual approach allows for better use of fuel and energy resources by converting waste heat into additional electrical energy, significantly enhancing overall system performance.
• Evaluate the impact of using concentrated solar power with the Rankine cycle on renewable energy generation.
  • Using concentrated solar power (CSP) with the Rankine cycle has a significant impact on renewable energy generation by converting solar radiation directly into electricity. CSP systems harness sunlight through mirrors or lenses to concentrate light onto a receiver that heats a working fluid. This fluid then drives the Rankine cycle to generate electricity. The implementation of this technology promotes sustainability by reducing dependence on fossil fuels and lowering greenhouse gas emissions, while also providing a reliable source of energy during peak demand times when solar irradiation is at its highest.

Related terms

Thermodynamics: The branch of physics that deals with the relationships between heat and other forms of energy, crucial for understanding cycles like Rankine.

Turbine:

A mechanical device that converts kinetic energy from fluid flow into rotational energy, essential for generating power in the Rankine cycle.

Heat Exchanger:

A device that transfers heat between two or more fluids, playing a key role in optimizing the efficiency of the Rankine cycle.