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How Efficient is Wind Power

How Efficient is Wind Power

A short write-up on wind energy efficiency that will help you understand the intricacies of power generation by harnessing wind, with reference to maximum output possible.
Abhijit Naik
We have obviously come a long way from the traditional windmills of the yesteryears, which were primarily used to grind corn, to the state-of-the-art wind turbines - with the sole purpose of generating electricity, that have been introduced of late. Amidst all the chaos surrounding the use of fossil fuels and pollution that they cause, wind energy come up as one of the apt alternative source of energy today. In fact, many people are of the opinion that wind power has the ability of replacing fossil fuels for electricity generation in the future.

How Efficient is Wind Energy in terms of Productivity?

Back in 1919, Albert Betz, a German physicist, revealed that the maximum possible output for wind turbines is 59 percent. In what is referred to as the Betz's law, he states that the maximum possible energy that can be derived from a hydraulic wind engine or a wind turbine is 16/27 i.e. 59 percent of the total kinetic energy of wind. However, any wind farm which boasts of an efficiency of 30 percent is considered efficient today. You may also come across sources - most of which happen to be wind turbine companies, which state that the modern wind turbines have the capacity of generation 70-80 percent electricity. The fact is that ideally even modern wind turbines can only produce 20-40 percent electricity - depending on several underlying factors, at the max. The fact that a power source with an efficiency of mere 30 percent is being pitched as a power source of the future will no doubt come as a surprise for many. In order to understand the intricacies of the entire matter, we need to go through the basics of wind power generation - right from how wind energy is converted into electricity.

The Efficiency of Wind Turbines

Basically, a wind turbine is a device which converts the kinetic energy of wind into mechanical energy, which is eventually converted to electricity by a generator attached to it. Is it feasible to convert all the kinetic energy of wind into mechanical energy using wind turbines? To put it in one word, the answer will be 'no'. As with all the other sources of energy, even wind energy has some limitations. In order to convert 100 percent of kinetic energy into mechanical energy, the wind turbines will have to harness all the wind that it is subjected to. If stalwarts of the field are to be believed, these wind turbines can only convert 50 percent of the kinetic energy of the wind and convert it to mechanical energy, while the remaining 50 percent escapes the turbines. In other words, only half of the energy that the wind has is harnessed by wind turbines, while the remaining half passes through the rotating turbines in form of wind.

In order to score a perfect 100 percent on the efficiency chart, the wind turbine will have to harness the entire kinetic energy of the wind that is coming its way. However, harnessing all the kinetic energy will result in zero velocity or no wind on the other side of the turbine. At the same time, we need to take into consideration the fact that these wind turbines are designed to work at a particular speed at which the output is maximum. Say the wind turbine is designed to give best possible output at the speed of 20 mph, the highest amount of energy produced will be 20 mph - while the amount will be less when the speed is less. Considering that the wind speed is never constant, it is difficult to predict that the wind turbine will produce certain amount of electricity in course of a year. At the same time, the efficiency of generator is not 100 percent, and that - along with the loss in conversion of current, will also bring down the total output by a small extent.

What about the claim of 70-80 percent electricity generation. Well, these machines do have the capacity of generating so much power, but as we said earlier several underlying factors come into play here. For instance, the chances of wind speed being constant is next to impossible, which means the turbine will not be able to generate same amount of power every day. The 30 percent that the experts claim is the theoretical maximum output, which is also referred to as the load factor. For the purpose of comparison, the theoretical maximum output or load factor for conventional power stations in around 50 percent on an average. Even though the same is lower in case of wind power, the fact that it is environment friendly and renewable source of energy give it the required boost.

Other than all these facts on the efficiency of wind power in terms of productivity, one also has to take into consideration its efficiency in terms of cost incurred. The entire concept which puts forth wind power as the best power source of the future relies on the idea of maximizing output whilst keeping a check on the expenses incurred. If you evaluate the initial cost incurred on the development of infrastructure and payback time, it is safe to say that wind power is cost-effective in a long term. However, we also need to take into consideration the fact that we are yet to solve some issues about the efficient use of this energy source, and thus a safe option will be to pump in some more money in research and development to ensure that we get the best possible deal - even if it means waiting for some more time.