What Is Needed For Wind Energy?

Wind energy is the process of using wind to generate mechanical power or electricity. People have harnessed the wind since ancient times to propel sailboats and turn gristmills and windmills. In the late 19th century, windmills were used to generate electricity, and in the 20th century, interest in using wind energy surged after the oil crises of the 1970s spurred investment in renewable energies. Today, wind energy is one of the fastest-growing renewable energy sources. Wind turbines use large blades to capture the wind’s kinetic energy and generate electricity. Global wind power capacity reached over 650 gigawatts in 2019, meeting over 5% of global electricity demand. With the focus on reducing carbon emissions and transitioning to clean energy sources, wind power is projected to continue rapid growth and play a major role in the world’s energy mix in the coming decades.

Table of Contents

Wind Energy Basics

Wind turbines use blades to collect the wind’s kinetic energy. When wind blows over the blades, the air pressure on one side of the blade decreases. The difference in air pressure across the two sides of the blade creates both lift and drag, causing the rotor to spin. The spinning rotor turns a shaft inside the nacelle, which goes into a gearbox. The gearbox increases the rotational speed to the level required by the generator (Energy.gov, 2022).

The generator uses magnetic fields to convert the rotational energy into electrical energy. The power output goes to a transformer, which converts the electricity from the turbine to the right voltage for the power grid (National Grid, 2023).

There are two main types of wind turbines based on the orientation of the rotor axis – horizontal axis and vertical axis. Horizontal axis wind turbines (HAWT) have a main rotor shaft and electrical generator at the top of a tower. The turbine blades face into the wind. Vertical axis wind turbines (VAWT) have the rotor shaft arranged vertically. The Savonius and Darrieus turbines are examples of VAWT designs.

The key components of a horizontal axis wind turbine are the tower, rotor blades, nacelle, and wind sensors/controllers. The tower supports the structure and raises the turbine to greater wind speeds at higher altitudes. The rotor consists of two or more blades attached to a hub. The nacelle houses the mechanical transmission and electrical generator components. Wind sensors control blade pitch to maximize power output and minimize structural loads on the turbine (Energy.gov, 2022).

Wind Resource Assessment

The quality of the wind resource is one of the most important factors in determining the potential viability and profitability of a wind energy project. Wind resource assessment involves analyzing wind speed, direction, and timing to estimate the long-term annual and seasonal energy production at a site.

According to the Wind Resource Assessment Methodology by OneEnergy, key factors that determine the quality of the wind resource include regional weather patterns, local topography, vegetation, buildings, and surface roughness [1]. Areas with consistent, strong winds such as hilltops, open plains, shorelines, and mountain passes provide the best wind resources.

Wind resource maps play a critical role in identifying promising sites for wind energy development. These maps illustrate the estimated wind speeds across different regions and are developed using data from weather models, satellite observations, surface weather stations, and actual wind project data. The Wind Energy Resource Atlas of the United States published by the National Renewable Energy Laboratory (NREL) provides detailed wind resource maps and data for utility-scale wind development [2].

Wind Turbine Siting

When siting wind turbines, there are several important factors to consider in order to maximize energy production and minimize environmental impacts. The primary considerations are wind resources, spacing between turbines, land accessibility, permitting and regulations, and transmission infrastructure.

Wind turbines need to be sited in areas with adequate wind resources. Site selection involves analyzing historical wind data, conducting wind studies, and computer modeling to identify sites with the strongest, most consistent winds. Areas with annual average wind speeds of at least 6.5 m/s at turbine hub height are generally considered economically viable.

Proper spacing between turbines is crucial to minimize wake effects and optimize energy output. Wakes occur when upwind turbines slow down the wind before it reaches downwind turbines. Studies indicate spacing of 3-10 rotor diameters between turbines in the prevailing wind direction minimizes wake losses. For example, for a turbine with 80m diameter blades, spacing of 240-800m would be optimal (Hiester, 1981).

Other factors like local land use laws, terrain, environmental impacts, and access to transmission infrastructure are also evaluated when siting wind projects. Advanced siting techniques and micrositing can help maximize wind resources on site.

Wind Turbine Size and Types

Wind turbines come in a variety of sizes and designs depending on their usage and location. The most common sizes for modern wind turbines are 2-3 megawatts (MW) for onshore wind turbines and 3-12 MW for offshore wind turbines.

Onshore wind turbines typically range from 1.5 to 3 MW. The average turbine size has increased over time as technology has improved. Most new onshore turbines installed today are in the 2-3 MW range with rotor diameters around 100-120 meters.

Offshore wind turbines are larger, ranging from 3 MW up to 12 MW for the most advanced models. Offshore turbines can be bigger since logistical constraints are lower at sea. The Haliade-X 12 MW turbine by GE Renewable Energy has a capacity of 12 MW and stands 260 meters tall.

Bigger wind turbine sizes yield advantages in terms of energy capture and cost efficiency. However, extremely tall towers can face transportation constraints on land. Offshore wind farms allow utilization of larger turbines since they don’t face the same transportation restrictions.

The most common wind turbine designs are horizontal axis turbines, with three blades rotating around a horizontal shaft. Vertical axis turbines exist but are less frequently used. Offshore turbines use similar horizontal axis technology but are reinforced to withstand harsh ocean environments.

Wind Project Development

Developing a wind energy project involves many steps, starting with identifying suitable sites with good wind resources. Project developers must then secure land rights, conduct environmental studies, obtain permits, find buyers for the electricity, and arrange financing before construction can begin.

Typical steps in developing a wind project include:

Conducting wind resource assessment using onsite wind measurements and meteorological modeling to identify sites with sufficient wind speeds.

Securing land rights and wind easements through land leases or purchases. Wind rights often cover not just the turbine sites but buffer areas around them. (from https://www.transect.com/blog/steps-to-secure-a-wind-farm-development-site)
Performing environmental studies like avian and bat surveys, visual impact assessments, noise modeling, and archaeological surveys. These help minimize ecological impacts.
Obtaining permits and approvals from local, state and federal agencies.

Finding power purchasers and securing power purchase agreements (PPAs) to sell the electricity.
Arranging financing through debt and equity financing. Wind projects require large upfront capital costs.
Selecting wind turbine models and vendors.

Designing the wind farm layout to minimize wake effects and optimize energy production.
Constructing access roads, transmission connections, turbines, and other infrastructure.

Offshore wind farms face additional challenges like higher costs and complex permitting for construction in water bodies. However, they benefit from higher wind speeds and more space for large projects. Overall, developing a successful wind energy project requires extensive expertise across many disciplines.

Wind Energy Costs

The cost of wind energy has declined dramatically in recent decades. According to the U.S. Department of Energy’s Land-Based Wind Market Report, the unsubsidized average levelized cost of wind energy has fallen to around $32/MWh in 2022.

There are two primary components that make up the cost of wind energy:

Capital costs – These include the upfront costs of purchasing the wind turbines and constructing the wind project. Wind turbines account for about 75% of capital costs.

Operation and maintenance (O&M) costs – These are the ongoing costs to operate and maintain the wind turbines over their lifetime. O&M costs typically range from $10-$25/MWh.

Some of the key factors that influence wind energy costs include:

Wind resource quality – Projects sited in windier locations with higher capacity factors will have lower costs.

Turbine size – Larger, more efficient turbines reduce capital costs per unit of energy generated.
Project size – Larger wind farms benefit from economies of scale that reduce capital costs.
Technology improvements – Advances in turbine design and materials continue to drive down costs.

Financing costs – Interest rates and access to capital impact project economics.

With continued technology advances and economies of scale, experts expect the cost of wind energy to decrease further in the coming years.

Wind Integration

Integrating wind energy onto the electrical grid can present challenges due to the variable and intermittent nature of wind. Wind power output can fluctuate minute to minute and hour to hour as wind speeds change. This creates difficulties in matching supply with demand, which is essential for maintaining grid reliability and stability (https://link.springer.com/chapter/10.1007/698_2020_610).

There are several solutions for enabling greater grid integration of wind energy. One is forecasting wind production more accurately to better schedule other generation sources. Advanced wind forecasting systems use weather modeling data, historical production patterns, and even satellite imagery to predict wind farm output a day or more in advance (https://onlinelibrary.wiley.com/doi/book/10.1002/9781118703274).

Expanding and strengthening grid infrastructure is another key strategy. Building more transmission lines allows wind power from remote areas to be delivered to population centers. Smart grid technology provides operators greater visibility and control over the grid to respond to fluctuations in wind. Energy storage systems, like batteries and pumped hydro, can store excess wind energy and discharge when wind dies down (https://www.adb.org/sites/default/files/publication/183785/sdwp-043.pdf).

Implementing large regional balancing areas makes it easier to integrate variable wind across a wider footprint. Market reforms that enable fast-ramping natural gas plants to complement wind are also helpful. Overall, a diversified mix of generation sources, flexible operating procedures, and advanced grid technologies can facilitate high contributions of wind power (https://onlinelibrary.wiley.com/doi/book/10.1002/9781118703274).

Wind Energy Policy

Government incentives have played an important role in the growth of wind energy in the United States. The federal government provides incentives including the Production Tax Credit (PTC), which gives wind farm owners a tax credit per kilowatt-hour of electricity generated [1]. The Investment Tax Credit (ITC) is also available which provides a percentage based credit for capital investment in renewable energy projects. These incentives make wind energy more cost competitive with conventional sources of electricity generation.

State renewable portfolio standards (RPS) have also driven growth in wind energy. As of 2021, 30 states had RPS policies which require utilities to supply a certain percentage of their electricity from renewable sources [2]. These standards create demand for wind energy and provide long-term policy stability for investors.

Future of Wind Energy

The future prospects for wind energy are very positive, with great potential for offshore wind and continued technology improvements and cost reductions. According to the IEA, wind power could supply up to 25% of global electricity by 2050 under their Net Zero scenario. Much of this growth is expected to come from offshore wind, which currently only accounts for 0.3% of global wind capacity but offers substantial potential with higher wind speeds and availability. The IEA estimates that with falling costs, offshore wind capacity could increase 15-fold to over 2,000 GW by 2050.

Advancements in wind turbine technology and design will also enable access to better wind resources, improved capacity factors and lower costs. Larger turbines, innovative foundations for deeper waters, and modular manufacturing are some of the innovations that can further reduce costs. According to the Global Wind Energy Council, wind power could supply 18-41% of global electricity demand by 2050. Many countries have announced ambitious offshore wind targets for 2050, including the UK (50 GW), the EU (60-180 GW) and the US (110 GW). With the right policies, investments and grid infrastructure, wind power is poised for massive growth this century.