This generates considerable amounts of heat due to friction and electrical losses – particularly in the stator and rotor. If this heat is not dissipated effectively, it can lead to overheating, which reduces the efficiency of the generator, shortens the service life of the components or can even cause serious damage.
Effective generator cooling is therefore essential to ensure reliable operation of the wind turbine, minimize downtimes and keep energy efficiency high in the long term.
Air cooling for generators
Air cooling for wind turbines is a widespread and comparatively simple cooling system that is used in particular for small to medium-sized turbines. From an ecological point of view, it has some advantages, but also certain limitations that are important when considering sustainability and environmental compatibility.
With air cooling, ambient air is fed through the generator or a separate cooling duct to dissipate the heat generated. This is done either directly by natural convection or more actively by fans that circulate the air. In closed systems, the air is circulated inside the system, often cooled by a heat exchanger, without allowing salts, dirt or moisture to penetrate from outside.
Air cooling does not require environmentally relevant coolants such as water-glycol mixtures or other chemical substances that could pollute the soil, ground or seawater in the event of a leak.
Air is available as a cooling medium indefinitely and does not need to be treated or refilled. This reduces operating costs and maintenance costs.
Compared to active water cooling systems, air cooling generally requires less energy, as no pumps need to be operated - only fans (if necessary), which often work efficiently.
Fewer components also mean less susceptibility to defects, which in turn reduces material consumption for repairs and replacements.
Air has a significantly lower heat capacity than water. This means that at very high outputs (such as those found in modern, large wind turbines), air cooling may reach its limits. This can result in lower efficiency or a shorter service life for the components, which indirectly requires more material and energy input.
Filters must be used to protect the system from dust, pollen or salty air (e.g. in offshore systems). These must be regularly maintained and replaced, which means additional consumption of resources.
Active air cooling by fans can cause additional noise, which - depending on the location - can be an environmental impact issue. ebm-papst fans are highly noise-reduced. We can offer solutions to further reduce noise emissions.
From an ecological point of view, air cooling is a resource-saving and environmentally friendly solution for wind turbines - especially for smaller or well-ventilated turbines. For large turbines with high output, however, it reaches its natural limits, meaning that more efficient, but also more complex and potentially more environmentally relevant cooling systems such as water cooling often have to be used. The choice of cooling system should therefore always be made taking into account the ecological impact, the size of the plant and the location.
Enclosed ventilation cooling systems
Structure and mode of operation
The air inside the encapsulated wind turbine circulates in a closed circuit. It absorbs the heat from the hot components (e.g. generator, converter) and transports it to the heat exchanger. It remains completely isolated from the outside environment, which is particularly advantageous for systems in dusty, salty or humid environments (e.g. offshore systems or desert regions).
The second air circuit is located outside the encapsulated system. A fan draws in outside air and guides it through the outer side of the air-to-air heat exchanger. There, this outside air absorbs the heat that was transferred to the heat exchanger surface via the inside air and releases it to the outside again. The two air flows never mix.
As the inside of the wind turbine is completely shielded, no particles, moisture, salts or insects can penetrate. This reduces maintenance costs and increases the service life of the system.
The system works purely with air and does not require any environmentally relevant substances such as glycol or other liquids.
The external air routing and the separation of the two circuits keep the level of contamination inside to a minimum, resulting in less filter use - an ecological advantage in the life cycle.
Because air movements are channeled internally, the system is often quieter in operation than open cooling solutions.
The use of an air-to-air heat exchanger and several fans requires precise control and regular maintenance of the components - which could easily have an impact in terms of energy and resources. With our solutions from ebm-papst, however, we offer energy-saving advantages in fan and control technology.
The heat exchanger and the air ducts take up more space than simple air cooling with open ventilation slots.
Even if the heat exchangers work efficiently, air as a medium remains physically limited in its heat capacity. For very large generators or hot climate zones, the system can reach its thermal limits.
A fully encapsulated active air cooling system with an air-to-air heat exchanger is a very clean and safe cooling method for wind turbines from an ecological point of view - especially where environmental influences are aggressive or where the least possible impact on nature and resources is desired. It combines the advantages of closed systems (protection, low maintenance, long service life) with an environmentally friendly cooling strategy, but can only be considered if the heat output can still be managed within an air-based framework.
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