From: Hannah Pell

On March 29, 2021, the Biden government announced another ambitious clean energy target: delivering 30 gigawatts of offshore wind by 2030. According to the Office for Energy Efficiency and Renewable Energy, the U.S. offshore wind capacity in 2019 was 28,521 megawatts (or 28.5 gigawatts) Using an additional 30 gigawatts over a decade would more than double the current capacity of US offshore wind energy.

How much power is 30 GW? It could be enough to supply 10 million households with electricity for a full year, offsetting 78 million tons of CO2 emissions (equivalent to the greenhouse gas emissions of 16,851,398 cars driven over a year and CO2 emissions of more than 8.7 billion gallons of gasoline consumed or 20 coal-fired power plants over the course of a year).

How does energy generation from offshore wind work and how does it differ from land wind? What role does offshore wind play in our national energy portfolio? And what special considerations need to be taken into account when planning offshore wind projects?

Current state of wind energy

Overall, onshore and offshore wind turbines contributed 7.2% to our country’s energy supply in 2019. According to a report by the National Renewable Energy Laboratory, there is an estimated 4,200 GW of potential new generation of electricity from offshore wind in the U.S. The cost per megawatt hour of wind power also fell to nearly a third of its price a decade ago, from about $ 85 to $ 90 / MWh to 30 USD / MWh due to significant advances in wind technology.

How do we decide where to build turbines as the wind varies depending on the season or even time of day? The US Energy Information Administration lists several preferred criteria: (1) the average wind speed is at least 4 m / s for small turbines or 5.9 m / s for utility-scale turbines, and (2) locations at higher elevations, open planes, or in Water and gaps between mountains that reinforce the wind blowing through.

The first supply-scale offshore wind farm in the US was built in 2016. The Block Island wind farm is located off the coast of Rhode Island and has five turbines that generate 30 MW of electricity for 17,000 households. Further offshore wind projects are currently being examined by the Bureau of Ocean Energy Management (BOEM). BOEM oversees the jurisdiction of the continental outer shelf region in which these projects may be built and is limited to 200 nautical miles “seaward of the baseline from which the breadth of the territorial sea is measured”.

Offshore versus land wind

Land turbines are much smaller than their offshore counterparts. The average land-based wind turbine is around 175 meters tall, while offshore wind turbines can reach 260 meters (around three times the height of the Statue of Liberty!). Despite the relative size differences, the turbines work the same way: wind turns the rotor blades, turns internal gears that turn the generator, and converts kinetic and rotational energy into electrical energy. In addition, onshore and offshore wind turbines have a mechanism that automatically shuts down when the wind speed exceeds 55 miles per hour, measured with an anemometer, and protects them from severe weather events such as hurricanes.

Offshore wind turbines are connected to the power grid by a series of cables laid under the seabed. More than half of our offshore wind turbines are so deep in the water that a variety of foundations have been built to secure the turbine to a stable platform, including monopile, twisted jacket and mono-bucket construction structures (pictures below) .

Image Credit: US Department of Energy.
Advantages and disadvantages
As with any energy source, there are distinct advantages and disadvantages, and balancing these is an important challenge in making a fair and large-scale transition to greener energy sources.

Wind is both a clean and a renewable source of energy. After the construction of a wind farm, the turbines no longer need fossil fuels. However, there are other environmental impacts including land use, noise and visual pollution, and disruption of natural habitats. The American Bird Conservatory estimates that wind turbines kill nearly 140,000 to 500,000 birds annually (but collisions with communication towers and power lines far exceed that number). As we build more wind turbines, migratory bird patterns are an important factor in determining the right locations.

Another benefit is that we don’t have to worry about the wind going out as it occurs naturally in the atmosphere. Although future supply is not a problem, the availability of wind is; Because of its interruption, the wind is not as reliable or steady as compared to nuclear power plants (which can run 24/7 and are used for base load supply). However, the exciting surge in investment, attention and resources focused on expanding wind power implies that the pros and cons outweigh the disadvantages.

Will all of these efforts bring us closer to net zero emissions? It seems like the answer is just blowing in the wind.


Please enter your comment!
Please enter your name here