Brunel Blog| Onshore vs Offshore Wind - Pros & Cons

Introduction

Both onshore and offshore wind will see explosive growth in the coming decade. Learn more about the pros and cons of onshore and offshore wind power, including how each works, their usage in the global energy marketplace, and why both will play an important role in the global energy transition.

According to Statista, global wind power capacity reached 743 GW in 2020, up from 650 GW in 2019 despite delays on projects due to COVID-19. The exponential rise of wind power installations demonstrates its growing popularity around the world.

Driven by advances in technology and global policies fighting climate change, wind power is becoming more financially sustainable. China and the USA remain the world’s largest wind power markets, with countries in the UK and Europe, North America, and India also driving the trend at a rapid pace.

For an overview of the global wind power market, take a look at this video from the Global Wind Energy Council:

The Global Wind Market

How does wind power work?

Wind turbines work when air turns the carbon-fiber blades attached to the units. The blades are connected to a motor, which turns kinetic energy into electricity. The energy is transferred to a gearbox, which converts the slow spinning of the blades into a high-speed rotary motion. This then turns a drive shaft quickly enough to power an electric generator.

Traditionally, onshore wind turbines dominated the market, however, in recent years, advances in technology have led to the development of offshore wind farms.

For more information on the history of wind power, take a look at our post on how wind turbines have evolved.

What is onshore wind?

Onshore wind power refers to turbines located on land rather than over water. They are typically located in sparsely-populated areas with low conservation value. According to the International Energy Association, onshore wind electricity generation increased by 12% in 2019. Capacity additions also grew by 22% after stagnating for a couple of years.

Take a look at this video on how onshore wind farms work:

How Do Onshore Wind Farms Work?

Advantages of Onshore Wind

Besides the obvious advantages of sustainability, what else is advantageous about onshore wind?

Less expensive

The infrastructure required for onshore wind power is significantly less expensive than what’s required for offshore wind. In some cases, it’s half the cost and can provide investment payback as quickly as two years. It’s also the least expensive form of renewable energy compared to solar and nuclear power sources, which means it’s more affordable to consumers. Because they’re cost-effective, onshore wind farms tend to be larger, producing more energy per site.

Shorter cables

With less distance between the turbines and the consumer, there’s less voltage drop-off in the cabling

Quick installation

Onshore wind turbines are quick to install and can be constructed within a few months, unlike other energy sources like nuclear power stations, which can take over two decades to build. When in operation, onshore wind turbines also have low maintenance costs.

Low impact on surroundings

Onshore wind farms have less physical impact on their surrounding areas. Toxins aren’t released, the site can be farmed around, and there’s very little impact to wildlife.

Disadvantages of Onshore Wind

Varying wind speeds

The speed of onshore wind turbines is somewhat unpredictable. Because wind speed and direction vary on land, achieving consistent power generation can be challenging. As a result, wind speed and direction need to be carefully monitored to plan for energy generation.

Potential wind blockages

Physical blockages from buildings and surrounding landscape like hills or mountains can also cause production inconsistencies. For this reason, onshore wind can’t produce energy year-round and can only achieve around 2.5 MW, compared to offshore wind’s approximate 3.6 MW.

Intermittent energy

Because onshore turbines don’t run year-round, they require fossil-fuel backups when the wind speed is slow. As we come to rely more heavily on wind farms for our energy, increasing amounts of fossil fuels will also be required.

Visual and sound factors

Onshore wind farms can be an eyesore on the landscape. Wind turbines that are built on high ground to generate more power can be imposing on surrounding residential areas. Wind turbines also aren’t silent, meaning they cause noise pollution if located near a residential area. To illustrate, up close, a wind turbine sounds like a lawnmower.

Overall, the advantages of onshore wind and the sustainable energy it can create outweighs the potential disadvantages.

What is offshore wind?

Offshore wind power refers to wind farms that are located over shallow open water, usually in the ocean, where there are higher wind speeds.The term ‘offshore wind’ can also refer to inshore water areas like lakes and fjords. Most offshore wind farms use fixed-foundation wind turbines in shallow water. However, as technology advances, wind farms will be able to be built over deeper waters. According to the Global Wind Energy Council, offshore wind will surge to over 234 GW by 2030, led by Asia-Pacific.

Check out this video for an overview of how offshore wind power works:

How Does Offshore Wind Work?

Advantages of offshore wind

More energy generated

Offshore wind speeds are typically faster than on land, and even small increases in speed can produce large increases in energy generation. As such, fewer turbines are needed to produce the same amount of energy as an onshore turbine.

More wind consistency

Wind speeds offshore don’t vary as much and the wind direction doesn’t change as often, so offshore turbines are more consistent (meaning more reliable power generation).

Less visual impact

Offshore turbines don’t have as much visual impact as those on land. They don’t interfere with land usage, and there are no physical obstacles that can interrupt the wind flow. For this reason, offshore wind farms can be made larger and generate more energy than those onshore, with less physical impact.

Bigger turbines

Offshore turbines can also be built taller than those onshore, which means they can harness more wind energy and produce more electricity.

Disadvantages of offshore wind

Higher cost

Creating the infrastructure for offshore wind farms can be expensive and complex, especially over deeper waters.

Maintenance & repairs

Sea waves and very high winds can damage turbines, so they need more maintenance than their onshore counterparts. Offshore wind farms are also difficult to access, which means longer wait times for repairs.

Noise & visibility

The underwater noises from turbines can impact fauna and other marine life. Further, not all offshore wind farms are built out of public view. Some are built within 26 miles of the coastline, so can still be an eyesore for local residents.

Less local jobs

Unlike onshore wind farms, those offshore have a limited capacity to benefit local economies. As the manufacturers’ offices are situated inland and often far away from the offshore site, jobs aren’t created in the local community and other investments aren’t made.