EARTHDAY Explainers – IV

Blowin’ in the Wind

By Allen Huang
The whirlwind of change is sweeping across the global energy landscape, and one of the clean energy sources at the forefront of this transformative journey is the rapidly expanding wind energy sector.
As the most recent report from the Global Wind Energy Council (GWEC), an international trade association representing the wind energy industry indicates, the industry has achieved its second most successful year to date in 2023, with installations increasing by an impressive 50% year-on-year.

Many countries around the world have harnessed this energy source with incredible results. Denmark, for example, has supplied 57.7% of their electricity through wind energy in 2023, reaching an all-time high. In Spain, wind energy accounts for nearly a quarter of electricity generation, reflecting significant investments in wind farms across the country.
The United States, with its vast landscapes, harnesses wind power extensively, particularly in states like Texas and Iowa, where wind turbines generate a substantial portion of their energy. Currently, wind accounts for 10% of total energy output and 22% of new electricity capacity, which, along with existing infrastructure, has the ability to generate enough power to 43 million households.

Meanwhile, Germany’s robust wind energy sector contributes significantly to its ambitious climate goals, with wind farms playing a crucial role in reducing greenhouse gas emissions. It has overtaken coal, historically the most crucial source of energy, to be the largest source of electricity in 2023. These countries exemplify the global shift towards wind energy as a reliable and eco-friendly power source.
As nearly 200 countries set ambitious targets and pledge to triple renewable energy capacity by 2030, wind power is poised to play a critical role in reshaping our energy systems and paving the way for a net-zero future. Which is why EARTHDAY.ORG set the Earth Day Theme for 2025 as Our Power, Our Planet. With the specific aim of tripling renewable electricity generation by 2030.

How Do We Harness Wind Energy?

Wind energy harnesses the kinetic energy of moving air to generate electricity using large wind turbines. These turbines, which can have either horizontal or vertical axes, are equipped with blades that capture the wind’s energy. As the wind blows, it pushes against the blades, causing them to spin. This spinning motion turns the rotor, which converts the wind’s kinetic energy into mechanical energy.

The mechanical energy from the spinning rotor is then transferred to a generator through a direct-drive system. The direct-drive system connects the spinning blades directly to the generator, skipping the need for gears, so there is less chance of things breaking. This setup allows the turbine to work more smoothly and consequently requires less maintenance because it has fewer parts that can break.
The generator, housed within something called the nacelle—a protective casing at the top of the turbine—converts the mechanical energy into electrical energy. The nacelle safeguards the turbine’s crucial components and ensures efficient energy production.
A Wind turbine nacelle cross-section. (www.researchgate.net)

The Height Factor

The amount of power available in the wind, measured in watts, is proportional to the cube of the wind speed. This means that if the wind speed doubles at a constant rate, the amount of power available in the wind increases by eight times (because 2³ is 2 x 2 x 2 which is 8). So, even a small increase in wind speed can lead to a big increase in the amount of power you can get from the wind.

This consequently means that locations with high average wind speeds have significantly greater wind power potential than areas with lower average speeds.

Wind speed also typically increases with height above ground, so taller wind turbines can capture more energy. Why? Well because the air near the ground is slowed down by friction with surfaces like trees and buildings. As you go higher, this friction decreases as there’s essentially less to slow wind down and the wind flows more smoothly and quickly.
Therefore, taller wind turbines can capture these stronger, smoother and steadier winds at higher altitudes, allowing them to generate more energy compared to shorter turbines which are closer to the ground and the more obstructed wind.

Wind turbines are best situated in locations where the annual average wind speed reaches a minimum of 9 miles per hour (mph), equivalent to 4.0 meters per second (m/s), for small-scale wind turbines.

For utility-scale wind turbines, the ideal annual average wind speed should be at least 13 mph, or 5.8 m/s. In this context, “utility-scale” refers to large wind turbines used for generating electricity on a large scale, typically connected to the power grid and providing energy for widespread use. These are contrasted with “small-scale” wind turbines, which are used for local or individual applications, such as powering homes or small businesses.

Onshore Vs Offshore

There are two distinct ways that wind turbines have been used to generate electricity in large capacities, often referred to as “wind farms.”

Onshore wind farms are located on land, while offshore wind farms are situated in bodies of water, usually at sea. Both technologies have seen significant growth and advancement in recent years as countries go through their renewable energy transition.

Onshore wind energy has a longer history, with wind technology being installed on land for over a thousand years. In contrast, offshore wind energy is a more recent development, with the first offshore wind farm being built in 1991 in Denmark.

For onshore wind energy, once the electricity is produced, it is carried down through power cables inside the tower to a transformer at the base. The transformer increases the voltage of the electricity, ensuring that it can be transmitted efficiently over long distances to the power grid.
From the transformer, the electricity is fed into a switchyard, where it enters the broader electrical grid and is distributed to consumers. Onshore wind farms are often less expensive to build and maintain compared to offshore farms, making them a practical choice for certain places.

Despite its shorter history, offshore wind has seen rapid growth due to several advantages it offers over onshore wind. Offshore wind speeds tend to be higher and more consistent than on land, and the vast open spaces of the ocean allow for the installation of larger turbines and wind farms.

One of the key advantages of offshore wind energy is the size and scale of the turbines. With fewer space constraints compared to land-based wind farms, offshore installations can support larger rotor diameters and taller towers. This allows them to capture more wind energy, maximizing the potential output.

These turbines are anchored to the seabed by foundations, which vary depending on the water’s depth and environmental conditions. Typically, offshore wind farms are located several miles from shore, taking advantage of stronger wind patterns while minimizing their visual and noise impact on nearby communities.

The electricity generated by offshore wind turbines is transmitted to shore through a network of connecting cables. These cables run along the seabed and link the turbines to an offshore substation, and from there, the electricity is sent to an onshore substation, where it is fed into the national power grid.

Energy Storage

However, only a portion of the total power in the wind can actually be captured by a wind turbine. The theoretical maximum, known as the Betz limit, is 59.3% of the wind’s power. Actual wind turbines operate at lower efficiencies, typically 27-44% offshore and 30-35% onshore, due to various aerodynamic and mechanical losses.

Modern utility-scale wind turbines are usually horizontal axis machines with three blades. The blades use airfoil shapes to generate lift forces that cause the rotor to spin. Careful design of the blade shape and materials is critical for maximizing power output while minimizing loads and noise.

While wind is an abundant resource globally, it is intermittent. Wind speeds fluctuate over multiple time scales, so wind farms do not provide steady power output like conventional fossil fuel or nuclear plants.
To address this challenge, excess electricity generated during periods of high wind can be captured and stored in batteries. These batteries, such as lithium-ion or flow batteries, store the surplus energy as chemical energy.

When wind production drops or stops, the stored energy is released from the batteries and supplied to the grid, providing a more consistent and reliable power source. This method of energy storage helps to smooth out the fluctuations in wind power and ensures a steady electricity supply, even when the wind isn’t blowing.

Lithium-ion batteries are the most popular choice due to their high energy density and efficiency, making them suitable for both residential solar storage and large-scale grid applications.
For larger projects, flow batteries are often used; these store energy in liquid electrolytes and can be scaled up easily, offering long cycle life and robust performance.
In some cases, lead-acid batteries, though less efficient and with shorter lifespans, are still used due to their lower cost and established technology.

Sodium-sulfur batteries are another option, known for their high energy density and durability, making them ideal for stabilizing the grid in large-scale storage systems.

Emerging zinc-air batteries are also being explored for their high energy density and potential cost benefits, though they are still under development for large-scale use. Each type of battery helps address the variability of wind energy by storing excess power and providing a steady supply when wind conditions are less favorable.

Batteries are an essential component of the wind energy business but there are several challenges. They can be costly, with advanced technologies like lithium-ion batteries requiring significant investment, though prices are gradually decreasing.
Additionally, batteries have a limited lifespan, with their performance degrading after a certain number of charge and discharge cycles, necessitating eventual replacement.

Energy density refers to the amount of energy that can be stored in a given system or material per unit of volume or mass. Higher energy density means that more energy can be stored in a smaller or lighter space. The energy density of batteries, although improving, may still fall short compared to other storage methods, limiting their effectiveness for large-scale applications. Scaling up the density of the batteries, while appealing in theory, run amok to the issue of high cost and short lifespans.

There are other energy storage methods that are better suited for large-scale use. These methods include pumped hydroelectric storage, which stores energy by pumping water uphill to a reservoir and releasing it to generate electricity when needed, and compressed air energy storage, which stores energy by compressing air in underground caverns and releasing it to drive turbines.
Environmental concerns also arise from the production and disposal of batteries, including the impact of mining raw materials and recycling challenges.

Temperature sensitivity affects battery performance, as extreme conditions can degrade efficiency and longevity. Moreover, the rate at which batteries can be charged or discharged may not always meet the rapid demands of the energy grid, and large-scale systems require substantial physical space. Addressing these issues is crucial for enhancing the viability and sustainability of battery storage for wind energy.

The US Industry Blows Hard

According to the U.S. Energy Information Administration (EIA), the majority of U.S. wind electricity generation capacity is located in the middle of the country in states such as Texas and Oklahoma.

In 2023, The five states that produced the most electricity from wind in 2023 were Texas, Iowa, Oklahoma, Kansas, and Illinois. Together, these states accounted for approximately 59% of the total U.S. wind electricity generation that year.
In the U.S., the average household uses about 10,600 kWh of electricity per year. Given that the total U.S. wind electricity generation from the five top states in 2023 was about 250 billion kWh, we can calculate that the wind electricity from these five states alone could power approximately 23.6 million homes in the U.S. for an entire year, which represent 18% of all US homes.

The Global Growth is Palpable

It is not just the U.S that is seeing the light when it comes to wind.

The GWEC’s 2024 report indicates that both onshore and offshore wind have been experiencing significant growth globally, creating a 50% year-on-year increase from 2022 to 2023. Onshore wind installations surpassed the 100 gigawatts (GW) milestone for the first time, with 105.8 GW of new capacity added, while offshore wind had its second-highest year, with 10.8 GW of new installations.

By the end of 2023, the global cumulative wind power capacity reached 1,021 GW, a 13% increase from the previous year. Onshore wind accounted for the majority of this capacity, with 945 GW installed, representing a 12% year-on-year growth. Offshore wind capacity also grew, reaching a total of 75.2 GW globally.
Technological advancements have played a significant role in the growth of both onshore and offshore wind. Modern wind turbines are becoming increasingly larger and more efficient, with higher hub heights and longer rotor diameters. These improvements have led to increased energy output and lower costs.

In 2021, the average rotor diameter for offshore wind turbines reached 160 meters, a 43% increase from 2010. Onshore wind turbines have also seen significant growth, with the average rotor diameter increasing by 91% in China and 72% in Brazil between 2010 and 2021.

The world’s largest wind turbine, the Goldwind GWH252-16MW, has set a new record for the most power produced by a single turbine in a day. Located offshore from Fujian Province, China, this gigantic turbine has a 252-meter (826.8 feet) diameter. In windy conditions, this one turbine alone can generate more than 380 megawatt hours (MWh) in a day, which is enough to power 170,000 homes.

Electricity Generated by Wind Energy is Getting Cheaper

The increasing adoption of wind energy is driven by a combination of factors, including falling costs, supportive government policies, and the urgent need to combat climate change. Many countries have set ambitious renewable energy targets, with wind power expected to play a crucial role in meeting these goals. According to the International Renewable Energy Agency (IRENA), wind energy could supply 35% of global electricity demand by 2050.

Wind Energy’s Issues

While wind energy boasts a smaller carbon footprint compared to fossil fuels, it is not without its own set of environmental challenges.

For one thing, we don’t see wind turbines in regular households as often as we see solar panels, for a good reason. Commercial wind turbines cost about 2.6-4 million dollars to build and more than 40,000 dollars to operate and manage, while they require 25-40 acres of land to be built and stand, which would be nearly impossible for most residential households to operate.

Residential wind turbines do exist, but according to industry estimates, the cost of installing a small wind turbine can range from 15,000 dollars for a 5-kilowatt system to upwards of 175,000 dollars for larger 15-kilowatt systems, significantly more than the average 27,300 dollars cost for a 10-kilowatt solar panel installation.

Factors such as the need for open space, strict permitting and zoning requirements, limited wind resource availability, and ongoing maintenance costs contribute to the difficulties of implementing wind power on a residential scale. As a result, solar power remains the more accessible and affordable clean energy option for the majority of households.
Another one of the primary concerns surrounding wind turbines is noise pollution. The spinning blades generate both aerodynamic and mechanical noise, which can be a nuisance to nearby communities. Low-frequency noise, in particular, has been linked to sleep disturbances and other potential health effects.

To address these concerns, wind turbine manufacturers and operators are continually working to reduce noise through improved turbine designs, quieter gearboxes, and blade modifications.

Additionally, regulations and guidelines often require that wind farms be sited at a sufficient distance from residential areas to minimize noise impacts and ensure that noise levels stay within acceptable limits.

WIND TURBINES vs BIRDS

Another major concern is wind energy’s impact on wildlife, especially birds. Birds can and do collide with turbine blades, often killing them and there is concern about the potential disruption as well to bird migratory pathways.

Three separate studies published in 2013 and 2014 estimated that between 140,000 and 679,000 birds die annually in the United States due to collisions with wind turbines, a range that has likely increased over the past decade as more wind farms have been constructed.

Measures such as avian radar systems, which detect birds near wind farms and temporarily shut down turbines, have been implemented in some areas to mitigate these risks. In offshore wind farms, the impact on marine life also raises concerns, with noise from pile-driving during construction affecting sensitive species like fish and marine mammals.
However, the overall impact of wind turbines on bird populations is generally considered to be lower compared to other human activities, such as habitat destruction or collisions with buildings and vehicles. In fact more birds are killed by domesticated cats than wind turbines.

Many wind farms also implement measures to minimize bird collisions, such as placing turbines in less critical habitats, using bird-friendly turbine designs, and conducting pre-construction environmental assessments to avoid key migratory routes.

One technique is to paint one turbine blade black as this is believed to enhance the visibility of the blades. The black color creates a strong visual contrast against the sky and surrounding environment, making the blades more detectable to birds, especially during low-light conditions such as dawn and dusk when bird activity is heightened.
This increased visibility helps birds recognize and avoid the spinning blades, which might otherwise blend into the background and go unnoticed. While this approach is one of several methods employed to mitigate bird fatalities, it is a simple yet relatively effective modification that contributes to reducing the risk of collisions and improving overall safety for avian wildlife around wind farms.

The Plastic Problem

There is another issue with wind turbines that does have to be dealt with head on as well – wind turbines use a lot of plastics, primarily in the construction of their blades. Plastics are not just polluting our planet and impacting wildlife but also negatively hurting human health.

The blades are often made from composite materials that include plastics, specifically epoxy or polyester resins, combined with fiberglass or carbon fiber. These composite materials are used because they are lightweight yet strong, which is crucial for the blades to be both efficient and durable.

Plastics play a key role in wind turbine blades because they help create a smooth, aerodynamic surface that captures wind efficiently. They also contribute to the blade’s ability to withstand harsh environmental conditions, such as high winds and UV radiation.

However, the use of plastics does raise environmental concerns, particularly regarding the disposal and recycling of blades at the end of their life cycle. Efforts are ongoing to improve recycling methods and develop more sustainable materials for future wind turbine blades.
To make wind turbines more sustainable and less reliant on plastics, several innovative materials and approaches are being explored.

Researchers are developing blades from bio-based composites, using natural fibers like flax or hemp combined with plant-derived resins to reduce environmental impact.

Recycled plastics are also being incorporated to lessen the demand for new materials. Additionally, efforts are focused on creating recyclable thermoplastic composites that can be melted and reformed, and experimenting with wood-based materials, which have a lower environmental footprint.

New blade designs that use less material or feature flexible components aim to further minimize impact, while hybrid materials combining metals and ceramics offer potential for enhanced performance and recyclability. These advancements seek to address the environmental challenges of traditional blade materials, improving the overall sustainability of wind energy.
As the global transition to renewable energy accelerates, wind power stands out as a pivotal force in shaping a cleaner, more sustainable future.

Despite challenges such as noise, wildlife impact, and the use of plastics, the advancements in turbine technology, energy storage, and material innovation offer promising solutions.

The impressive growth in wind energy capacity worldwide, coupled with falling costs and increasing efficiency, underscores its crucial role in meeting ambitious climate goals. With continued investment and research, the wind energy sector is poised to overcome its current hurdles and drive the transition to a low-carbon economy. As we embrace the wind’s potential, we move closer to a future where renewable energy not only powers our homes but also preserves the planet for generations to come.
Tags: explainer, sustainability
This article is free to republish on your web site, in your newsletter, magazine, newspaper, publications or blog. The imagery is cleared for use too. Please just keep the author’s name on the piece and that they are from EARTHDAY.ORG. Let us know if you re-publish so that we can try to acknowledge, tag or re post you! You can let us know via an email to [email protected] or [email protected].
Back to News and Stories