STEAM POWER PLANT (PART 2: RANKINE CYCLE TURBINE)

Rankine cycle is one of the thermodynamic cycles which convert from heat into power (kinetic energy). We say it is a cycle because the process in this cycle always repeat and repeat again. To convert from heat energy into kinetic energy, it has several processes  and needs several components to support those processes. Those are: Boiling, expansion, condensation, and pumping. Figure 1. Is schema of those processes.

               Figure 1. Schema Rankine Cycle

At figure 1 there are two kinds of lines, ref and blue. Red is sign for high pressure and blue is sign for low pressure. Processes from 1 to 4 will be repeated again and again, so the rotor of turbine will be rotated continuously.

1 to 2, pumping  the water into boiler. At point 1 the pressure of water is low and at point 2 the pressure is high. The phase at point 1 and 2 is water (liquid).

2 to 3, Boiling. This Process needs energy especially heat energy, it can be from kerosene, coal, etc. Water will be boiled and water phase changes from water (liquid) into steam (gas). This steam (at point 3) has high pressure and temperature, so it has high energy (enthalpy).

3 to 4, Turbine Expansion. In this process occur the conversion into work (kinetic energy).  The high energy whose steam at point 3 is used to produce work (kinetic energy). This process causes drop pressure and temperature of steam (steam at point 4).

4 to 1, Condensation. To change phase from steam (gas) into water (liquid) need remove heat or in other word it has to be cooled. This process usually need heat exchanger, so that it can remove heat then the steam phase will change.

Those processes from 1 to 4 will be repeated again and again, so the rotor of turbine will be rotated continuously. 

STEAM POWER PLANT (PART 1: TURBINE)

Steam power plant  maybe is the most common power plant in the world. This technology converts from heat into electricity. Steam Power Plant has at least two parts, Turbine and Generator. Turbine is the system which converts from heat energy into kinetic energy (Rotation) and Generator is the system which use kinetic energy to produce electricity.

TURBINE

To produce rotation, turbine needs heat source. It can be coal, gasoline, kerosene, etc. This heat energy is used to boil the water. Because of that, phase of water will be changed from water (liquid) to vapor (gas/steam). This steam is used to rotate the rotor of the turbine. The figure.1 bellow explain about that.

Figure 1. (a) Schema of turbine; (b) Illustration from heat into rotation

If the system  is like that figure,  it will needs water more and more because after the steam rotate the rotor, steam is thrown away. The solution of this problem is Rankin cycle.

In rankine cycle, steam will be used again. Figure 2 is explanation about that.

Figure. 2

After rotate the rotor, steam enter to condenser. In condenser steam phase will be changed from steam (gas) into water (liquid) and all the water will be collected in a tank. From tank, water is pumped to boiler again, and the process is repeat again and again.    

That is the principle of simple turbine system which allow convert from heat into rotation.