Onshore vs Offshore Wind Power

Exploring the main differences between land & sea based wind farms.

Wind power is one of the most naturally abundant, affordable, and reliable sources of energy in the entire renewable energy sector. It was also one of the first renewable energy sources to be harnessed, given that transforming kinetic energy (movement) into consumable energy (electricity) has played a part in engineering since ancient times. The UK, Denmark, Germany, Sweden and Holland were the initial pioneers of wind power generation, but in the last decade countries like the US have joined them, and are now at the forefront of the movement. Currently, there is 650.8GW (650.8 billion watts) of wind power technology installed around the world. Almost 10% of this was installed in just the last year.

Wind power provides the USA with clean, renewable energy. Both onshore and offshore wind power helps to reduce our carbon footprint dramatically, and whilst onshore wind farms are currently favored as the cheaper option, the future seems to favor offshore, due to a lack of space constraints, and a more consistent generation of energy.

When considering wind power, there is one question which springs to mind: which is better, onshore or offshore wind turbines? There are many different factors to consider in the debate between these two modes of wind power, and determining which is superior in fields such as productivity and cost effectiveness is crucial to the future of wind installations. Onshore wind farms call for turbines to be installed on land, whilst offshore farms require that turbines be installed over open seawater, where the wind is more consistently powerful.

Similarities Between Onshore and Offshore Wind Power

Whilst offshore wind turbines differ in many respects from their onshore cousins, both operate via the same mechanical principle. Wind turbines consist of rotor blades, spinning around a horizontal hub which contains a gearbox and generator. As wind hits the blades of a turbine, forcing them to spin, the kinetic energy is passed into a gearbox, housed inside the turbine. From here, the gearbox serves to intensify the kinetic rotation, in turn powering a generator which converts this kinetic energy into electricity. Finally, the electricity is delivered from the turbine to the grid.

Materials used in the construction of wind turbines are basically the same, whether those turbines are installed offshore or onshore. In theory, were onshore and offshore turbines the same size, and exposed to identical wind speeds, they would generate identical amounts of energy.

Differences Between Onshore and Offshore Wind Power

Despite sharing materials and mechanic principles, there are some stark differences between these two modes of wind power. The most obvious difference between onshore and offshore wind turbines is the location of the farms. In fact, it is largely due to the vast geographical and geological differences between land and sea that there exists any differences between the turbines and their construction.

The cost of installing onshore wind farms are significantly lower to those involved in offshore farms, as you might expect. Offshore wind farms require platforms, underwater cables, interconnection, and other factors such as additional safety features, all of which increase installation costs. Furthermore, maintenance of offshore farms must be conducted via helicopters and ocean-faring vessels, which by nature is more expensive than using land-based transport alternatives.

On the other hand, onshore wind power can be slightly less predictable and reliable than offshore. To properly install onshore farms and provide clean energy generation, the terrain and wind currents which that terrain is exposed to must first be carefully studied, and the land then bought or leased (which in itself can pose problems). Of course, land must first be available, too, and with a burgeoning global population demanding increasing space for housing and agriculture, the ideal locations for wind farms are often already taken.

Compared to onshore farms, offshore farms enjoy a less troublesome inconsistency of wind power and availability, providing in turn a more reliable and efficient power generation.

Onshore Wind Review

Cost

Onshore wind energy is relatively inexpensive. Thanks to the existing infrastructure (for energy transmission), lower maintenance costs, and availability of installation materials, they are significantly less expensive to install than offshore farms. Today, the price of installing 1MWh of onshore wind in the US can be as little as $20, which is $50 per MWh cheaper than it was in 2012. It is estimated that these costs will drop even further by 2030, a year in which the number of wind farms in the US may have tripled compared to 2018 numbers.

Space

A notable disadvantage of onshore wind is simply that it requires land. To provide an uninterrupted flow of wind for power generation, onshore wind turbines must be placed at a minimum distance of 150m from any obstructions, with and a turbine-to-turbine separation of seven times the diameter of the rotor. In a world where space is at a premium, this can cause real problems for wind energy investors.

Overall Pros

Onshore wind is one of the most popular renewable energy sectors today.

• Onshore wind has lower installation costs than offshore, with investors seeing a return on their initial investment in as little as two years.
• Energy generated can be easily fed to the grid via existing infrastructures.
• A greater proportion of wind power companies specialize in onshore farm installation.
• Maintenance costs are relatively low.

Overall Cons

On the other hand, there do still exist some drawbacks to the onshore wind sector.

• Onshore wind farms require a more careful analysis of wind current and speeds than offshore wind, which can mean longer lead times in construction.
• Space on land is undoubtedly more limited due to the cost of leasing land, pre-existing obstruction, and the potential for future urban expansion.
• Public resistance to the installation of onshore wind farms can be high, especially when construction is planned near residential areas, due to perceived levels of visual and noise pollution.

Offshore Wind Review

Cost

The price of offshore wind installation can be up to 20% higher than that onshore. This is largely due to the lack of existing energy transmission infrastructure at sea, the extra materials required for safety purposes, and other technical challenges, including the maintenance of machinery out at sea. Nevertheless, as of 2019, offshore wind power costs fell 32% when compared with those in 2018, with per MWh costs estimated at around $78. By the year 2038, it is projected that offshore wind power will be as affordable as fossil fuel.

Space

One of the major benefits of offshore wind farms is that there is almost no limit to the space in which they can be installed. Provided they are installed at least 200 nautical miles from land, and built 50ft into the ocean floor, they can be erected almost anywhere, with no issues. Moreover, their exposure to wind is both more consistent and generally stronger than the relatively unreliable wind speeds found on land.

Overall Pros

Whilst onshore wind farms are more popular in the emerging renewable energy construction industry, offshore wind continues to enjoy some major benefits, when compared with onshore.

• With no constraints to space, offshore wind farms require far less legislative planning, and little time spent determining wind speeds and exposure, since wind on the open ocean is reliably consistent and present.
• Offshore wind farms have the potential to generate much higher amounts of electricity, thanks to their exposure to faster and more consistent winds.
• There are no visual or noise pollution complaints associated with offshore wind farms.
• Offshore wind turbines can be made two or three times larger than those onshore, thanks to the near limitless space and lack of public pushback. Larger turbines tend to mean greater cost efficiency in construction, and an overall greater production of energy.

Overall Cons

Whilst offshore wind power enjoys its fair share of advantages, there are of course disadvantages, too.

• The costs of energy-transmission and installation can be up to 20% higher than those associated with onshore wind.
• There is evidence to suggest that offshore wind farms can negatively impact both flying and underwater flora and fauna.
• Offshore wind farms require maintenance which is both harder to perform and more expensive than the maintenance of onshore farms.
• Following a potential malfunction, energy restoration times are likely higher for offshore than onshore wind farms.

Conclusion

As it stands, onshore wind power seems a more cost-efficient choice than offshore, thanks to maintenance, installation, and materials costs all being lower. As of 2020, the price per MWh is as low as $20 for onshore wind farms, whilst for the same energy generation in an offshore farm, investors might expect to pay nearly quadruple the price. Nevertheless, projections suggest that within the next couple of decades, the price of offshore wind may drop below that of fossil fuels.

Despite the trend toward onshore wind in today’s market, there are several limiting (potentially severely limiting) factors associated with onshore farms. For one, wind on land is far less reliable, strong, and consistent than it is offshore. There is of course also the issue of space and land leasing, as well as the noise and visual pollution complaints from nearby communities, which can pose a problem in the planning and development of onshore farms.

As the world’s population continues to increase, and available space on land decreases, it would seem that once the costs of installing offshore wind farms decrease, they will overtake onshore wind as the most viable, efficient, and cost effective version of wind power generation.

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