Since the blades of the first power-generating wind turbine started turning in 1888, the industry has made incredible strides towards making wind one of the staples of today’s power economy.
This progress can be primarily attributed to massive advancements in electrical engineering, material design, electronics, the development of national power grids, and other factors that made wind power economically and technically efficient.
On top of that, green energy in general, and wind energy, in particular, received a solid boost during the fuel and energy crises of the 70s, which became an eye-opener for firm believers in fossil fuels. The signing of the Paris Agreement in 2016 became a turning point on the road to cleaner energy for many nations, turning their initiatives into legally binding commitments.
What happens today
Today, wind turbines come in a variety of designs and sizes, with different deployment options and power generation potential. All this variety can be generally split into two major categories: offshore and onshore turbines.
Offshore turbines have virtually no limitations on noise levels and the overall turbine size and can be installed in regions with strong and consistent winds. For example, today’s largest offshore turbine has just recently set a world record after generating a staggering 384 megawatts of power in just 24 hours — enough to power 170,000 households.
Their onshore counterparts, on the other hand, can be compact (to serve a single household or group of buildings) and allow installation near residential buildings or even on rooftops.
In this article, we will compare these two categories of wind turbines, weigh their pros and cons, and describe the current trends in the wind energy industry.
The evolution of onshore wind turbines
On the most general level, turbines differ by size (and the corresponding power output), design, and availability of additional systems that help optimize power generation or maintain its steady level in suboptimal weather conditions.
These land-based installations convert the kinetic energy of wind into electricity. The turbine’s blades capture wind energy and start rotating, which drives the generator to produce electricity. In terms of design, they typically feature either a horizontal axis, the most common type, with blades rotating like a fan, or a vertical axis, resembling a carousel.
ALT: The most popular wind turbine designs, horizontal and vertical
Source: ScienceDirect
In recent years, innovations have significantly improved onshore wind turbine materials and efficiency, as well as helped create completely new types of turbines still pending adoption. For instance, the use of stronger, lighter materials such as carbon fiber composites in blade construction allows for larger designs that capture more wind without compromising structural integrity.
Furthermore, advancements in aerodynamics and smart control systems are increasing turbine efficiency, even in low or variable wind conditions. These intelligent systems monitor wind conditions in real-time and constantly adjust the position of turbine blades to achieve the optimal angle of attack and capture as much wind as possible.
New turbine types include a variety of concepts and already existing designs based on unusual approaches to power generation. For example, a Spanish company called Vortex Bladeless proposed an innovative wind power harvesting mechanism based on the oscillation of a carbon-fiber rod with copper coils around it within a flexible plastic tube with magnets on its inner surface.
These oscillations and vibrations are caused by air vortices forming around the tube exposed to wind. Although visibly insignificant, they are sufficient for the device to start generating a steady flow of clean energy.
Challenges to overcome
Despite the growing popularity and ever-widening adoption of wind turbines, they are still facing certain challenges. Noise pollution, visual impact, wildlife disturbance, and a requirement for substantial land area often lead to resistance from local communities, limiting their deployment potential. Moreover, wind variability can result in inconsistent power generation.
To overcome these hurdles, manufacturers around the globe invest considerable money in noise reduction technologies, bird and bat deterrent systems, and improved predictive models for wind patterns. Only with these advancements will onshore wind energy be able to continue moving towards even higher efficiency, lesser environmental impact, and broader acceptance.
The present and future of offshore wind turbines
Offshore and onshore wind turbines are virtually identical in terms of how they harvest wind energy. Most offshore models, including the colossal, 853-foot-tall Haliade-X from General Electric, are HAWT (horizontal) turbines, but the vertical design is gradually making its way into the offshore segment, promising much higher power density and power generation efficiency in regions with unstable or alternating wind patterns.
ALT: Experimental wind farm comprised of vertical-axis turbines installed near each other
Source: New Atlas
The biggest difference lies in the methods of their installation and general turbine parameters. Since offshore turbines are installed in the sea and often at considerable depths, they require reliable foundations to rest on (in the case of fixed-base turbines) or mooring mechanisms (in the case of floating turbines).
Today’s offshore turbines use a variety of foundation types depending on the installation depth, seabed characteristics, typical wind speeds, and expected weather conditions.
As a rule, the choice of the type of foundation for a particular turbine would depend on the depth of installation:
- Monopiles for nearshore areas with depths under 30m
- Suction buckets or pile foundations for depths between 30 and 60 meters
- Tension leg, spar, or semi-submersible platforms for floating turbine operations at depths exceeding 60 meters
ALT: The most common types of offshore turbine foundations
Source: Virtuosity
On top of that, offshore turbines do not have the size- and noise-related limitations that are typically imposed on their onshore counterparts, which allows manufacturers to build truly impressive models with record power-generating capacities.
The latest trends in offshore turbine design
Experts predict that the next decade will be characterized by a steady growth of the size of offshore turbines that will be averaging 17+ MW of rated power capacity and an increased deployment distance (around 70 km from the shore) with depth exceeding 40 meters.
Rotor size is likely to eventually become the limiting factor both on land and at sea, which will force the industry to focus on grid optimization, connectivity between individual units, or generating additional value on-site. One of the possible scenarios that has already been implemented is the production of hydrogen on offshore platforms equipped with wind turbines.
ALT: The future of onshore and offshore wind turbines – 2035 forecast
Source: Berkeley Lab
Another visible trend in offshore wind energy is the development of unconventional turbine designs. For example, a Norwegian startup called World Wide Wind (WWW) is developing counter-rotating vertical turbines — highly stable, power-efficient, floating turbines to be used in deep waters and regions with consistently strong winds.
Typical challenges of offshore wind farm operators
Unlike onshore turbines whose deployment is often hampered by the need to obtain multiple permissions from local authorities and communities, address complex environmental concerns, and secure large plots of land, the growth and development of offshore wind farms are mostly limited to the availability of vessels, cranes, and ports capable of handling large-scale turbine deployment operations.
A comparative analysis: onshore vs. offshore
One crucial consideration when comparing onshore and offshore wind turbines lies in their overall efficiency. Typically, offshore wind turbines demonstrate superior efficiency, as they can harness stronger, steadier winds occurring over the sea free from topographic obstacles.
In terms of cost, offshore wind turbines have higher initial setup and maintenance expenses due primarily to the complex maritime installations and harsher operating conditions. However, these costs can be offset over time due to better energy production, making them comparable to their onshore counterparts in long-term economic feasibility.
Environmental and logistical issues also present considerable differences. Onshore wind farms may face local opposition due to noise and aesthetic considerations, while offshore turbines might impact marine ecosystems. Logistically, offshore turbines require specialized vessels for installation and thorough maintenance planning to combat harsher sea conditions.
Both onshore and offshore wind turbines contribute significantly to the global renewable energy landscape. However, the higher efficiency and tremendous untapped offshore wind resource potential signal a likely shift towards increased offshore wind infrastructure.
This analysis highlights the need for continued innovation to optimize wind power generation across diverse geographic and economic landscapes, thus securing the sustainability and consistent growth of the global renewable energy sector.
Conclusion
The exploration of onshore and offshore wind turbines reveals both differences and unique advantages of both turbine types. Onshore turbines offer lower installation costs and easy maintenance access, while offshore turbines, although more expensive, provide significantly higher productivity due to strong and consistent sea winds.
Despite challenges such as environmental impacts and community acceptance, advancements in materials, design, and turbine deployment methods are steadily making both types more efficient, cost-effective, and environmentally sensitive.
As global awareness and acceptance of renewable energy grow, so does the promise of wind power. Today, its substantial contribution to the renewable energy sector cannot be overlooked. The future of wind power, both onshore and offshore, appears bright and backed by continuous innovations and the collective global effort towards sustainable power. Our continued investment and research in this area will ensure the ongoing improvement and greater effectiveness of wind turbines, compact and gigantic alike, making them an increasingly viable solution for worldwide energy needs.
The author of the article is Simo Eiert, CEO of Freen OÜ, a rapidly growing European manufacturer of small wind turbines with record power generation efficiency and patented hardware design.