Wind power

What is wind power?

Wind power, or wind energy, is the use of the kinetic energy of air currents to generate electrical energy. This kinetic energy of the air masses is created by the uneven heating of the Earth's surface by the sun. Because the sun heats different regions of the Earth to different degrees, temperature differences arise in the atmosphere. These temperature differences lead to pressure differences in the air, which in turn create balancing air currents – what we call wind. Wind energy is a renewable energy source because it is inexhaustible and environmentally friendly. Unlike fossil fuels, the use of wind energy does not release harmful emissions such as CO₂ and thus contributes to combating climate change. Wind turbines are used to harness this energy, converting the wind into electrical energy.

Basics of energy generation through wind power

A wind turbine harnesses the kinetic energy of the wind by converting it into rotational energy through the rotor blades. The rotational energy is transferred to a generator via a gearbox or direct drive, where it is converted into electrical energy, similar to a dynamo. The efficiency of converting wind energy into electrical energy is determined, among other things, by the turbine's technical components and site-specific factors. These technical components include the length and aerodynamic profile of the rotor blades, the turbine's tower height, the efficiency of the gearbox and generator design, the yaw system used, and the control system. Site factors include local wind speeds and the respective site conditions in terms of major obstacles in the surrounding area, as well as topographical features.

History and development of wind power

Wind turbines have a long and diverse history, dating back to ancient times. The first known windmills are thought to have been used in 9th-century Persia. These early turbines had a vertical axis and were used primarily for grinding grain and pumping water. By the 12th century, windmills had spread throughout Europe, especially in the Netherlands, England, and France. These European turbines had a horizontal axis and were significantly more efficient than their predecessors in the Middle East. In the Netherlands, the technology was perfected, and numerous windmills were built, which were used for purposes including draining polders, grinding grain, and sawing timber. During the Industrial Revolution in the 18th and 19th centuries, windmills were replaced by steam engines in many parts of the world. Modern wind turbines were not developed until the 20th century. Since the 1970s, the technology has advanced rapidly, particularly through the use of composite materials and advanced aerodynamic blade designs. Today, wind power plays a central role in energy production worldwide, especially in countries such as Germany, Denmark, and the USA.

Types of wind turbines

Today's wind turbines differ in terms of power classes, designs, and the basic aerodynamic principle used. A distinction is made between small, medium, and large wind turbines, each with different power outputs. They range from small residential systems to large megawatt systems installed on land or at sea (onshore and offshore wind turbines). Large wind turbines have the advantage of higher energy production, but are also associated with higher installation and maintenance costs and require a grid infrastructure for energy distribution. In contrast, small wind turbines are more flexible and easier to install and generate energy close to the consumer. In terms of design, a distinction is made between horizontal and vertical wind turbines based on the arrangement of the rotor axis. Vertical turbines include Savonius and Darrieus rotors. Compared to turbines with a horizontal rotor axis, they have a lower power coefficient, meaning the power yield from the incoming wind is lower than with horizontal turbines. To convert the kinetic energy of the wind into mechanical energy, wind turbines operate according to two basic aerodynamic principles: drag and lift. Drag rotors include, for example, the Savonius rotor. This rotor presents a surface area against the wind and converts the wind pressure into mechanical power. The disadvantage of this principle is that half of the rotor surface moves against the wind, which limits the speed and power. Lift rotors use the lift forces acting on the rotor blades to determine speed. These forces arise when the wind impacting a rotor blade is guided above and below the blade. Due to the aerodynamic profile of the rotor blade, a negative pressure is created on the upper side of the rotor blade (suction side) and an excess pressure is created below the rotor blade (pressure side). The pressure difference creates a lift force that drives the rotor blade and causes the rotor to rotate. Wind turbines with a horizontal rotor axis and three rotor blades facing upwind, which act as lift rotors, are by far the most common design. They are far superior to vertical turbines in terms of efficiency.

Technical aspects of wind power

Modern small wind turbines utilize a variety of advanced technologies to maximize the efficiency and reliability of energy generation. The profile of the rotor blades is aerodynamically optimized to capture maximum energy from the wind. These rotor blades are often made of lightweight yet robust materials such as glass-fiber-reinforced plastic (GRP) to ensure high strength and low weight. To ensure optimal alignment of the rotor attached to the nacelle with the wind direction, active yaw systems are already being used in some small wind turbines. Sensors on the nacelle measure the wind direction and speed and use motors to adjust the nacelle in response to changes. Furthermore, the Internet of Things (IoT) and advanced sensors enable remote monitoring and maintenance of the turbines, which increases availability and reduces maintenance costs. Depending on whether a wind turbine is to be installed in a garden or as a rooftop system, specific technical requirements arise, for example, with regard to structural stability and noise emissions.

Economic aspects of wind power

The costs for the construction and operation of a small wind turbine consist of several components. First, there are the acquisition costs for the turbine itself, which depend on its output and technical equipment. Installation costs include the construction of the foundation, assembly of the turbine, cabling, and connection to the power grid. These costs vary depending on the location and local conditions. Furthermore, additional costs may arise depending on whether the wind turbine is to be installed in the garden or as a rooftop system. The total cost of a small wind turbine can therefore range between €3,000 and €10,000 per kilowatt (kW) of rated power. Operation and maintenance costs include regular inspections, lubrication, any necessary repairs, and the replacement of wearing parts. These costs are often calculated as a percentage of the initial investment per year and are typically between 1% and 3%.

State subsidies and incentive programs

Government subsidies can improve the economic viability of small wind turbines. In Germany, there are various government subsidies and incentive programs for small wind turbines. The Renewable Energy Sources Act (EEG) provides feed-in tariffs for the electricity generated that is fed into the public grid. However, these tariffs have declined significantly in recent years. In addition, some federal states offer special funding programs that include investment grants or low-interest loans for small wind turbine projects. Municipal funding programs also exist, depending on the regional focus, for renewable energies. The economic viability of small wind turbines compared to other renewable energies such as photovoltaics depends heavily on the location. In general, small wind turbines have higher specific investment costs per kW of installed capacity than large wind turbines or photovoltaic systems. The latter have become significantly more cost-effective in recent years and are often more economical than small wind turbines, especially in areas with high solar irradiation. Small wind turbines can represent an economically attractive solution, especially in windy regions, off-grid areas, or as a supplement to photovoltaic systems. The economic viability is influenced by the feed-in tariff, the self-consumption of the generated electricity, and possible government subsidies. A careful site analysis and consideration of specific wind conditions are crucial for the economic viability of small wind turbines.

Practical examples and environmental and social aspects of wind power

Small wind turbines in the garden or as rooftop systems generate electricity without burning fossil fuels and thus contribute to reducing CO₂ emissions. This is a crucial contribution to climate protection and combating global climate change. Compared to photovoltaics, small wind turbines require only a very small footprint for the same output and can often be installed on existing agricultural or industrial land without additional sealing. This reduces impacts on natural habitats and protects biodiversity. Although wind energy offers many ecological benefits, there are also challenges that must be considered. For example, the potential impact on bird and bat populations is being discussed. Even though many studies conclude that the construction of wind turbines does not have a major impact on bird populations, for example, these aspects should be considered. Modern technologies such as bat protection circuits that switch off the small wind turbine during bat activity times and careful site selection can reduce such problems.

Private use of wind turbines

More and more private individuals are interested in using wind turbines in their backyards for various reasons. The use of small wind turbines offers a way to become independent of rising electricity prices and energy suppliers. Furthermore, the use of renewable energies makes an active contribution to climate protection and reduces one's personal carbon footprint. Finally, many regions offer financial incentives and funding programs that reduce investment costs and increase the profitability of small wind turbines. However, there are several challenges to consider when using wind turbines in private backyards. The choice of location is crucial: The turbines can only be operated efficiently and economically in areas with sufficient and consistent wind speeds. Furthermore, building regulations and permitting requirements must be observed, which can vary depending on the region.

Planning and installation of private wind turbines

Planning a small private wind turbine, especially one for a backyard wind turbine, begins with a thorough site analysis. This involves measuring and evaluating wind speeds over a period of time to ensure the site has sufficient wind resources. It is also advisable to familiarize yourself with local building codes and legal requirements that apply to the installation of a small wind turbine. Another important step is calculating the household's energy needs to determine the correct size and power output of the wind turbine. Next, potential financing and incentive options should be explored to reduce the investment costs.

Technical aspects of private wind power use

Private small wind turbines, whether rooftop systems or freestanding wind turbines, for example, in the garden, must meet a number of technical requirements to operate safely and efficiently. First, they must be robustly constructed to withstand various weather conditions such as storms, rain, and snow. The systems must be made of high-quality materials to ensure longevity and reliability. They should also have built-in safety mechanisms, such as automatic shutdown systems, to prevent damage in the event of excessive wind. Modern, high-quality small wind turbines demonstrate their quality through certifications according to national and international norms and standards. Examples include type certifications according to IEC 61400-2, grid compatibility certifications according to VDE-AR-N 4105 (2018) or VDE 0124-100 (2022), or sound measurements according to IEC 400-11. The output of private small wind turbines is usually between 1 kW and 10 kW, depending on the household's energy needs and wind conditions. A 5 kW system can typically supply an average household. A needs analysis and site assessment are necessary to determine the optimal size and power. Regular maintenance is required to ensure the longevity and efficiency of the system. Operating costs include maintenance, repairs, and any required spare parts.

Economic viability of private wind power use

The economic viability of private small-scale wind turbines is comprised of the investment costs, ongoing operating costs, and savings from lower energy costs. Many countries offer numerous financial support and incentives for private individuals who want to invest in wind energy, including grants and tax breaks. Private users can optimize their own consumption and generate additional income through feed-in tariffs.

Examples of successful private wind power projects

There are many successful private wind power projects around the world that can serve as role models. These projects demonstrate how innovative approaches and technologies can lead to the efficient use of wind turbines, even in one's own backyard. Others can learn from these projects by adopting proven methods and adapting them to their specific conditions.

Why does the private use of wind power make sense?

Private use of wind power in one's own backyard offers long-term benefits, including lower energy costs and promoting renewable energy. It contributes to the energy transition by reducing dependence on fossil fuels and minimizing environmental impact. Future developments in private wind power promise further improvements in efficiency and cost-effectiveness, making it an attractive option for individuals seeking a sustainable energy supply. Innovative concepts demonstrate that private wind power is a promising option for a sustainable energy supply, offering both economic and ecological benefits.

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