Hydrogen Cooling System in Electric Generators

It is undeniable that an electric generator must have an excellent cooling system to dissipate the heat created in it. If the heat inside the generator is not discharged immediately, it will directly damage the generator itself. Excessive heat can extreme damage the rotor coil, the stator, and will even burn the components of the generator.

Air becomes a popular medium used to cool generators. The abundant and inexpensive amount is a strong reason to continue using it. However, the air conditioning system used in the generator turned out to save weaknesses. The air is unable to cool the generator with a capacity above 425 Megawatts. In addition to its insufficient heat conductivity, its density is too heavy to be another disadvantage. For this reason, other types of gas are needed which are better in terms of thermal conductivity and other characteristics.

Hydrogen gas is the best choice to replace air as a generator cooling medium, especially for large generators. Hydrogen was chosen because of its excellent characteristics when used as a cooler, call it a high thermal conductivity (0.168 W / m · K), very light density, and also high specific heat. With these characteristics, making hydrogen 7-10 times better than air if used as a cooler. This can be likened, to generate the same electric power, air-cooled generators will be 7-10 times larger than hydrogen-cooled generators. Therefore, for large generators, hydrogen cooling systems will be more economical when compared to using air coolers. Actually helium gas has good thermal conductivity (0.142 W / m · K ), but because the price is much more expensive than hydrogen, it is not used.

But isn’t hydrogen a very flammable gas? Yes, hydrogen is indeed a very flammable or explosive gas. But do you remember about the fire triangle? Even though the hydrogen in the generator works at high temperatures, if we can keep hydrogen away from oxygen, the fire triangle will be broken, and the hydrogen will be safe from the risk of burning. For this problem there are already several support systems that are used to prevent hydrogen always in its pure state (maintained at about 99{206f867d40cce763e89ed637df575ac8333a3fb0bacfe4f95f2708eb87ae8002}), and will not be in direct contact with atmospheric air. A hydrogen purity sensor ( purity meter ) is used to always monitor it in real-timethe level of purity of hydrogen. With this tool, the slightest hydrogen mixed with other gases will be easily known. If the hydrogen purity reading drops, a purging system is always ready to be used to increase the hydrogen purity rate. Purging systems usually also include a hydrogen pressure control system so that it is always maintained at a certain number. On the other hand, there is a system called a hydrogen dryer which also serves to maintain the purity of hydrogen from moisture which if left potentially triggers a spark inside the generator. Another support system is called the Oil Seal systemwhich we will introduce further later, serves to prevent the leakage of hydrogen into free air considering the hydrogen cooling media is used on the rotor side of the generator which of course there is a potential side of contact (in the bearing generator) between air and hydrogen. We will discuss these supporting systems for hydrogen-cooled generators in more detail next time.

For hydrogen and water cooled generators, they share the task so that hydrogen becomes the cooling medium of the rotor while the water is tasked to cool the stator coil. Like the previous system, hydrogen circulates with the help of a fan that rotates with the rotor so that it can reach all parts of the rotor. At the end of the circulation system, the hydrogen enters the heat exchanger cooler  to dispose of its heat in the water media. While on the stator side, water becomes a cooler that is able to reach all parts of the coil that we did not get in the previous system. With a cooling system like this, it is recorded that the largest generator design is capable of producing 858 Megawatts of electricity.