Offshore Wind Vs Onshore Wind Development: 7 Basis of Comparison
Offshore wind vs onshore wind comparison can be made on the basis of energy source, relative energy magnitude, energy systems, development locations, complexity, technological maturity, and acceptance.
These basis of comparison are used to analyze the difference between offshore and onshore wind development, as follows;
1). Energy Source (as a Basis of Comparison for Offshore Wind Vs Onshore Wind Development)
Basically, both offshore and onshore wind energy come from the same source; which is the convective cycling of air currents caused by natural solar heating.
This convective cycling is what creates air-pressure differentials and drives air masses to produce forceful aerodynamic streams that are described as wind.
However, the source of offshore and onshore winds can be differentiated based on their geographic circulation patterns.
Offshore winds come from the land, where air mass-convective cycling generates air streams that move toward the sea under the influence of combined factors like Earth's rotation, gravity, electromagnetism and pressure differences.
Onshore winds come from the sea, and move toward the land as a result of geographic and aerodynamic factors [10].
The differences pointed out above are also described in discussions of land and sea breezes, which are themselves equivalent to onshore and offshore winds respectively.
2). Relative Energy Magnitude
Offshore wind energy is generally greater in magnitude than onshore wind, and this can be explained by the interaction between air currents and the ocean surface, where wave energy dynamics develop a symbiotic or co-dependent relationship with air currents, and magnify the kinetic energy in offshore winds.
The kinetic energy of offshore wind is therefore higher than that for onshore wind, so that it is more common for a large portion offshore air currents to travel at speeds of 10 m/s and above [1].
For onshore winds, their magnitude or speed is diminished by energy losses through friction with rigid land surfaces, vegetation, geographic features and buildings among others. These winds also lose much of the kinetic energy induced by ocean wave interaction as they travel further away from the sea toward the land.
Higher energy magnitude is an advantage of offshore wind over onshore wind, especially in the context of electricity generation.
The capacity factor of onshore wind is a relative measure of its power output divided by its maximum capacity, and has an average of about 36%, as different from 50% for offshore wind.
Since capacity factor is indicative of power output, offshore wind farms and turbines can yield at least 10% more electricity than onshore wind farms and turbines respectively.
It is important to note this power output difference when considering that offshore wind development is more expensive than onshore, as it shows that the cost difference is compensated by power output; so that offshore wind systems will typically generate mote electricity than onshore systems within an equal amount of time [2] [3].
3). Energy Systems (as a Basis of Comparison for Offshore Wind Vs Onshore Wind Development)
Offshore and onshore wind energy systems are turbines and wind farms.
The only difference between the systems used to harness offshore and onshore wind, is deign considerations.
Basically, offshore wind energy systems are designed with consideration of the need for structural resilience and stability, due to the presence of powerful waves and wind energy in offshore locations.
With regards to such considerations, offshore systems may comprise of any of two main types of offshore wind turbines; namely floating and non-floating.
For non-floating systems, these are best suited for locations where the water depth is relatively shallow, and may use any of various types of offshore foundations like monopile, tripod, and suction caisson.
Offshore wind systems are also built to capture a maximum amount of wind energy efficiently.
Other factors considered when designing offshore wind systems include the need to be resistant to corrosion, and a means of effective transmission of generated power to the point(s) of use, which are usually onshore.
Lastly, both offshore and onshore wind energy systems can be designed as a hybrid of more than one renewable energy technology.
For offshore systems, the additional energy resources harnessed on a hybrid wind energy system may include solar and wave energy; so that solar panels and wave energy converters may be integrated into offshore wind systems [7].
Onshore wind energy systems can be combined with solar energy systems to increase space efficiency and maximize power generation.
4). Development Locations
One of the most prominent differences between offshore and onshore wind development is the possible locations for projects in each of these fields.
Onshore wind energy development is more versatile in terms of its geography, than offshore wind development. This is because land-based locations are more accessible than offshore locations for wind power system installations, than offshore locations.
For onshore wind energy development, suitable locations include those which occur in areas with access to wind energy and few obstructions. Such areas are generally remote, and unaffected by ecosystem-altering human activities like urbanization.
Suitable offshore locations are harder to access, in spite of the fact that oceans occupy a larger portion of the Earth's surface than land.
One of the reasons for this is the relatively-recent nature of offshore energy technology and maritime development.
Offshore wind energy locations include only areas with access to the sea, such as coastal zones. Examples of offshore wind energy locations in the world as of 2023 are; China, Denmark, Germany, Netherlands, Portugal, United Kingdom and United States.
Each of these locations can harness offshore wind energy because they have access to the sea.
Also, the effectiveness of offshore wind energy development depends on specific offshore location, which could be close to the coast in shallow seawater, or at greater depth and distance away from the coast.
The best offshore wind energy locations are those far from the coast or shallow water zones [4]. While these deep-sea locations are home to surplus amounts of wind, they are also difficult to access for such projects.
After offshore wind energy has been used to generate electricity, it is often challenging to distribute such power to the point(s) of use, due to the complexity of trans-ocean electricity transmission using underwater cables.
5). Complexity (as a Basis of Comparison for Offshore Wind Vs Onshore Wind Development)
Offshore wind energy systems and development projects are more complex than their onshore counterparts.
The higher complexity of offshore wind is due to issues of marine navigation, site selection, design and maintenance.
Structural design of offshore wind systems includes considerations of resilient foundation, anchorage, and energy efficiency.
The scale of offshore wind energy systems tends to be larger than that of onshore systems, mainly due to the prospect of harnessing larger amounts of energy. This can increase the complexity factor.
Other sources of complexity for offshore wind energy development include electricity transmission, and trans-boundary ownership agreements [6].
6). Technological Maturity
Offshore wind represents one of the advances in technology that are being pursued for wind energy.
This means that the technological maturity of offshore wind is low compared to that of onshore wind.
There are both positive and negative prospects associated with this fact.
Being a more mature technology, it is likely that the coming years will see a decline in the rate of development of onshore wind energy.
Offshore wind energy is relatively immature, meaning that there is still a chance of positive discoveries in the near future, which could play a major role in sustainable development and energy transition.
However, the technological immaturity of offshore wind energy can explain some of its limitation and complexities, since these issues are likely to be resolved with technological modifications and optimization.
This is proven by the fact that so far (as of 2023), there is a gap in the availability of detailed analyses of offshore wind energy technology [8]. Such detailed analysis are derived from research and development efforts, and crucial to the growth, advancement and subsidization of offshore wind energy.
7). Acceptance (as a Basis of Comparison for Offshore Wind Vs Onshore Wind Development)
Acceptance by sectors of society, and the general public, is also an important factor to be used for comparison and evaluation of offshore and onshore wind energy development.
Criteria that determine the acceptability of wind energy technology include site selection factors, cost, complexity, and environmental impact.
Factors taken into consideration for site selection of wind energy development locations are accessibility, wind speed, regional population density, industrial facilitation and energy management infrastructure [9].
Generally, wind energy deployment is recommendable in areas that are unaffected by overpopulation or even significant human presence, and which are economically and geographically equipped to harness wind as a reliable energy resource.
Site selection and technical complexity are both higher for offshore wind energy than onshore, and this can be influential toward the perception of this option as a feasible one.
Acceptability of wind energy development is also linked to the cost of deployment [5]. For offshore wind, cost is generally higher, although it goes along with the prospect of higher power gains.
In terms of environmental impact, both offshore and onshore wind energy development can have environmental effects, although wind is a green energy resource with no greenhouse emissions.
Environmental impacts of wind energy development include aesthetic pollution and problems of expired/damaged component recycling.
Summary of Difference between Offshore and Onshore Wind Energy Development
The following table summarizes the difference between offshore and onshore wind energy development, based on factors discusses in this article;
Comparison Criteria | Offshore Wind | Onshore Wind |
Energy Source | Land air currents | Sea air currents |
Relative Energy Magnitude | High | Low |
Development Locations | Remote land areas | Deep or shallow sea locations |
Complexity | High | Low |
Technological Maturity | Low | High |
Conclusion
The areas of comparison for offshore wind vs onshore wind development are;
1. Energy Source
2. Relative Energy Magnitude
3. Energy Systems
4. Development Locations
5. Complexity
6. Technological Maturity
7. Acceptance
References
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