onshore vs. offshore wind

Onshore vs Offshore Wind: What Are the Differences and Facts?

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Onshore vs. Offshore wind, which one is better? Here is a comprehensive comparison of the two that will help you figure all this out.

Onshore vs. Offshore Wind: What Are the Differences and Facts?

The wind is a natural source of energy and, one of the most reliable ones. As long as there is wind, it means that we have a source of renewable power. Therefore, today, we will focus on onshore vs. offshore wind, to help us understand what their difference is and which one is best for wind power harvesting.

As more effort is being put to increase the use of renewable energy sources, as well as finding ways to preserve our environment, wind plays a major role. The wind energy industry has again and again proven to be a significant player in offering energy to many people.

Since the first onshore wind turbine was built in the late 1800s, up to the time when offshore harvesting was established in 1992, much development has taken place in this industry.

However, there is still much to do if we want to see this industry grow and to supply electricity to even more people.

But firstly, let see the definitions of onshore vs. offshore wind, to understand the distinction.

Onshore vs Offshore Wind

Onshore wind is the one that blows from the sea towards the land. On the other hand, offshore wind is the type of wind that blows from the land towards the sea.

The winds usually occur due to differences in pressure, in the atmosphere. For example, when there exists a difference in pressure within the atmosphere, air will shift from areas with higher pressure to areas with lower pressure. This, in return, results in the creation of winds at various speeds.

These effects are what takes place during the sea breeze and land breeze. For instance, if the atmospheric pressure is high, and with a clear sky, the land warms up in the daytime and gets cold by nighttime. The result of this is that wind will blow from the sea at daytime towards the land, while at night, it will blow from the land towards the sea.

Since our planet is also in constant rotation, the Coriolis effect also deflects the air. The deflection can take place in any part of the globe with the exception of places on the equator.

 


 

Wind Power Harvesting

For the longest time, onshore wind turbines have been dominant in the wind power harvesting process. This is because the offshore turbines were just introduced almost a century later in 1992, with the first offshore wind farm being set up in Denmark.

The introduction of offshore turbines was a result of necessity which was brought about by the effect we refer to as wind shadow. This occurs when turbines reduce the wind’s strength as it travels downstream. Therefore, there was a need to find an alternative source of stronger winds, and offshore winds became a target.

The winds out in the ocean are much stronger and consistent that the winds on land. This made it necessary to improve the wind turbines technology and use it in the ocean where they can produce more power. Many more countries now make use of offshore wind farms since its initial introduction in Denmark.

However, although numerous nations have embraced the use of offshore technology, most of the offshore farms are still found in Europe. Based on a report by Global Wind statistics in 2014, Europe holds around 90% of these offshore wind farms.

In the United States, onshore wind energy is more prevalent in the Midwest region of the US. On the other hand, offshore wind energy has become more dominant in the coastal states of the US.

Use our wind turbine calculator to determine the power of a each turbine and how many turbines you would need for a particular project.

And, although many may assume that when looking at onshore vs. offshore wind, the difference is only in where we set up the turbines, there is much more than that. The two types of wind power sources are different in multiple ways, with each having their own pros and cons.

Onshore Wind Overview

How Onshore Wind Energy Works

Just as the name goes, wind energy is energy that results from the transformation of air currents, into electricity. To utilize the wind that blows over the land, we must build wind farms that can extract optimum power from the wind. Wind farms found on the land are what we refer to as onshore wind farms.

To enable this, the wind farms consist of large wind turbines that will help to transform the wind’s kinetic energy into electricity. This is how an onshore wind turbine works to produce electricity.

  • The first step in this process is where the wind makes the blades of the turbine to rotate. These blades connect to the turbines through a hub.
  • The blades, together with the blades, rotate at a similar speed of seven to twelve turns every minute.
  • A gearbox, on the other hand, increases this speed to over 100 times. From there, it also transforms the speed into a high-speed shaft.
  • With a speed of over 1500 revolutions every minute, this high-speed shaft transmits the speed to a generator.
  • When this speed gets into the generator, the generator works to convert the mechanical power from the shaft into electrical power.
  • Since the power is in a direct current form, a converter then transforms this DC into AC.
  • From there, a transformer then increases the voltage to between 20 and 66 kV, which makes it possible to transmit this current through the onshore wind farm.
  • The next step is to transport the electricity through medium voltage cables and take it to a substation.
  • After reaching the substation, the energy is again transformed into a high-voltage current of +132 kV.
  • From here, an evacuation line transports the electricity to the distribution network, which in turn carries it to the consumption points (homes).

Pros of Onshore Wind Energy

  • Since onshore wind energy has been in use for the longest time, people have grown more familiar with it. For this reason, many nations still prefer to use onshore wind energy. For example, even Denmark, which established the first offshore turbines, still get the majority of their wind power from onshore farms (75% of their total wind energy).
  • In terms of cost, the infrastructure necessary for electricity transmission in onshore is significantly cheaper than that in offshore turbines. Due to the affordable cost, offering the power to the consumers is also cheap, which makes it a more popular source of renewable power.
  • Companies producing onshore turbines are located in the land, and therefore, if wind farms are set up near the companies, it can be economical. These companies will also boost the economies of the areas they are situated at.
  • There will be fewer emissions as a result of transporting the wind structures in onshore farms. This is because most farms can be set up near the manufacturing companies.
  • Onshore wind, in most cases, will attract investment in the area. This is because various projects will be started near the wind farm, which will, in turn, create a chain of other businesses.
  • Onshore wind is a source of renewable energy, and unlike many other power generation plants, this one doesn’t consume water.
  • The onshore wind turbines have minimal maintenance costs.

Cons of Onshore Wind

  • The speeds of onshore wind are unpredictable, more than in offshore. The inconsistencies in the wind speeds will cause inefficiency with the turbines, especially when the speeds are too low, or even too fast.
  • Not only does onshore wind differ in speeds, but the directions also vary more often. For the turbines to function efficiently, they should face the direction of the wind. If the direction keeps on changing, it will negatively affect the efficiency of the turbines.
  • Some people work against the growth of onshore wind farms claiming they are a danger to birds, or that they are a noise nuisance. However, there is little or no evidence to support these claims.
  • They generate lesser energy than their offshore counterparts. For example, an average onshore wind turbine produces around 2.5 to 3 megawatts while an offshore one produces an average of 3.6 megawatts.


 

Offshore Wind Overview

This type of wind harvesting came into existence nearly 100 years after the invention of onshore wind energy. For this reason, technology is yet to gain as much popularity as its predecessor.

However, after their first establishment in Denmark, multiple other nations have made significant strides towards its development.

How Offshore Wind Energy Works

Wind harvesting here is done through erecting offshore wind turbines deep into the ocean. The process is as follows:

The initials steps of offshore wind energy, are similar to the ones of the onshore wind energy. The differences arise almost in the middle of the process.

  • The first step in this process is where the wind makes the blades of the turbine to rotate. These blades connect to the turbines through a hub.
  • The blades, together with the blades, rotate at a similar speed of seven to twelve turns every minute.
  • A gearbox, on the other hand, increases this speed to over 100 times. From there, it also transforms the speed into a high-speed shaft.
  • With a speed of over 1500 revolutions every minute, this high-speed shaft transmits the speed to a generator.
  • When this speed gets into the generator, the generator works to convert the mechanical power into electrical power.
  • From here, the electricity generated is taken down using the interior of the tower.
  • Since the power is in a direct current form, a converter then transforms this DC into AC.
  • After the conversion into alternating current, a transformer increases the voltage to between 33 kV and 66 kV, to enable transportation across the offshore wind farm.
  • The electricity is then carried to a substation, by the use of underwater cables.
  • After it reaches the substation, this electricity is again transformed into a high-voltage current of over 150 kV.
  • The last step is to transport the electricity through a distribution network up to the consumers’ homes.

To better comprehend the topic on onshore vs. offshore wind turbines, here are some advantages and disadvantages of offshore wind.

Pros of Offshore Wind

  • Offshore wind turbines have proven to be more efficient as compared to the onshore turbines. This is because the speed of these winds is high, and they are consistent in terms of direction. For this reason, you will require fewer turbines to produce the same capacity of energy than through onshore turbines.
  • Offshore wind turbines are far away into the ocean. This means that they don’t cause any disruption in human activities. They are miles away from the coast, such that you can’t see them, leave alone feel their existence.
  • They don’t interfere in any way with the land as they are set up far away from coastlines.
  • The offshore wind farms can, in some instances, help to protect the inhabitants of that area (marine life). Since they restrict access to areas where they are set up, they tend to protect the marine ecosystem around.
  • Just like with the onshore wind farms, they are a source of renewable energy. Also, they do not use up water like other power plants, and they provide job opportunities.

Cons of Offshore Wind

  • Although the turbines are more efficient, the process through which the electricity reaches the land and to the public is expensive. The necessary technology for the transportation of electricity from the turbines is way costly than in onshore turbines.
  • Due to strong winds and waves, the offshore turbines have to endure more wear and tear. The result of this is a high cost of maintenance which continues to increase the gap between offshore and onshore wind costs.
  • Because offshore turbines are harder to get to, it could take longer to fix problems and restore them to function properly.
  • Unlike in other new energy developments which through Renewable energy cooperatives, minor-town citizens can invest in, offshore farms don’t allow.
  • Although not necessarily a disadvantage, the effects the offshore wind farms have on marine life, as well as birds are not comprehensively understood. This brings uncertainty on whether the project is the better option.
  • When we build offshore wind farms near to the coastline even up to 26 miles, they might be visible from the coast. This may affect tourism and other activities. They may be unpopular to investors which may affect the property prices of the area.

These pros and cons helps to bring more clarity on the issue of onshore vs. offshore wind. we cannot understand the two concepts without looking at their strong points, as well as their weak points.

Conclusion On Onshore Vs. Offshore Wind

From the much research done to come up with this article, it’s evident that onshore wind energy is still widely used than the offshore wind. Even with the numerous advantages that come with offshore wind, onshore is still the preferred choice. I hope that from this article about onshore vs. offshore wind, you can clearly see the distinction between the two.

Which of the two methods of harnessing wind power do you think is best?

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