Wind Electricity Generators
The Wind Generator Types
It is possible to classify the wind turbines based on the grid, as well as the method of rotation of the blades. Considering wind turbines in terms of connection with the grid, there are off-grid systems, partially grid-tied generators with battery, and fully grid-tied generators. Off-grid generators (battery-based systems) operates on the principle of electric power storage, then transported in its batteries. This is a complete wind turbine, which does not depend on external factors, in addition to the weather ones. Supply of electricity from the utility company is completely absent. This property makes off-grid generators a reliable source of electricity in almost any weather. Therefore, this type of generator is one of the most common devices to generate electricity worldwide. Batteries can accumulate electricity whereas when the generator blades rotate. This energy is enough to power the entire house for a while fully. Despite the high cost, more and more households install off-grid generators for electricity supply.
The next type of wind turbine is a grid-tied system with battery backup (hybrid wind turbines). Generators of this type also have a battery that stores electric power produced by the generator. However, hybrid generators also have access to power, which is the main source. Accumulation of energy generated by the generator is an additional source of power, but not the major one. However, this disadvantage is actually used with advantage. Once the batteries are filled thanks to wind generators, the system automatically starts the supply of electricity to the service company, dedicated to the main power supply. Thus, households have the ability to repay a certain percentage of payment for municipal services. Thus, the service company may use such energy during crashes, accidents, storms, et cetera. Such systems are also ideal for remote sites such as military installations.
The last type is called grid-tied wind systems. Such systems do not have batteries, as they connected directly to the mains. Thus, the turbine generator produces energy, which is immediately fed to the main service provider. However, at the same time, the power company is the primary source of energy not only for the wind turbine but also for the household as a whole. The main advantage of this type is that households cannot pay utility bills, as the energy of wind turbine installed often completely offset all energy costs, which were supplied by the company. At the same time, the power company can also use wind energy in the event of an emergency as a source of additional power. Batteries for wind turbines are expensive, and not every household can afford them. Grid-tied systems is cost-effective option. Moreover, many wind turbines have the option to switch the energy supply, so owners of the system could supply power to their house in case of an emergency.
Considering the types of wind turbines in terms of the provisions of the blades, there are generators with vertical and horizontal blades. The most common type of wind generators is wind turbines with the horizontal axis of rotation. These wind turbines are set to be used as the continental winds and sea ones. It should be said that offshore wind is more constant and stronger, therefore, wind turbines with the horizontal axis of rotation are ideally suited for these conditions. Also, wind turbines with the horizontal axis of rotation can use lift or drag force to convert wind energy. Devices using lift force are more preferred because they can develop several times greater power than devices with direct action of resistance.
Wind turbines with a vertical axis of rotation are more expensive than horizontal axis, they have a more complex structure, but they are more suited to the area with frequent wind direction change. In addition, the wind turbines with vertical rotation are more compact. There are two types of wind turbines with a vertical axis of rotation: Rotor Savonius and Darrieus rotor. Wind turbines with a Darrieus rotor do not require a lot of space, do not require guidance systems (not depend on wind direction), and are easy to install. On the downside is the fact that they have a low utilization of wind energy, poor self-starting (the acceleration of the rotor is needed), low mechanical strength, and greater noise during operation. Savonius wind generator also has a low coefficient of wind energy compared to conventional wind turbines, large consumption of materials, but it has the advantage of working with any wind direction.
Environmental Issues and Safety
At first glance, wind energy is completely environmentally clean and does not harm nature and people. However, it is not so. Powerful wind farms with hundreds or thousands of wind turbines bring many problems: they produce incredible noise and can interfere with radio and television broadcasts. In addition, the huge wind towers often hinder bird migration. Of course, compared to the enormous damage to nature, which is applied to thermal power plants, damage from wind turbines is almost imperceptible, but if people want to have clean energy in the future, the problem of the impact of wind turbines on the environment must be addressed now.
Considering the noise problem in more detail, it should be said that the work of windmills and wind power is not regulated by the noise level in any state. Sound waves generated by the rotation of the blades of wind turbines have a frequency of 20 Hz that is below the threshold of the human ear. Studies show that such waves could cause emerging diseases in humans. However, energy companies involved in the installation of wind power denies the possibility of harm to human health. Their representatives claim that this frequency of sound vibrations is natural and occurs in nature. Nevertheless, it is an indisputable fact that that infrasound can cause various forms of nervous tic, cramps, feeling of anxiety, a feeling of pitching. These sound waves often occur when the shock wave from the approaching earthquake or hurricane.
It should be recognized that the significant problem of wind power, which requires solutions, is recycling of wind blades made of composite materials. At the present rate of development of wind power and durability of wind turbines (about 25 years), this problem will be faced by humanity in 2020, when the mass of the blades, requiring utilization around the world, will be close to the mark of 50,000 tons. Moreover, the problem of waste is not only the problem of wind power plants, but also solar plants. Photovoltaics is very dirty in the production and creates problems in recycling. Solar energy demands of production and circulation (recycling) a huge amount of lead and acid (for solar panels and batteries). It is even hard to count harm to the environment. Incidentally, zinc and lithium (extremely harmful elements) are also used in the production of solar generators.
Today, there are two main methods of recycling: mechanical and thermal. The mechanical processing method is quite simple and includes three steps (removal and separation of the parts for transportation, mechanical grinding with resin extraction, and separating fibers from larger fibers and smaller beads). Currently, the thermal processing method of the blades is also popular. Its simplest kind is burning. However, everybody knows that a large amount of ash formed after combustion (about 60% of the burned mass), requiring subsequent disposal. A promising method is a pyrolysis (heating without access of oxygen at 500 C), whereby, the blades fiber can be reused, and the resulting gas is burned to generate electricity. Unfortunately, now the proposed methods have a number of shortcomings, which does not allow saying about solving the problem of processing blades fully.
Offshore wind farms can harm marine life. Industrial and construction wastewater, contaminated storm water and domestic wastewater generated at the sites may be potential sources of contamination of surface water and groundwater. Wastewater caused by rain contain mainly suspended solids and oil. Many of the wind turbines do not provide sewage functions, therefore, wastewater containing the resin, oil, and other harmful substances enter the water. In addition, noise and vibration of turbines can harm marine animals, and repel them away from the original habitat, disrupt biorhythms, and so on.
The construction of any power (the wind or solar in particular) requires the use of many elements. During the construction of generators and green plants, there are air pollution, the pollution of water bodies, soil, as well as waste disposal and rejection of agricultural and forest lands, harm to flora and fauna. The main burden on the air in the process of construction is determined by emissions of pollutants from motor vehicles and construction machines and mechanisms, air pollution during welding and painting works and use of bulk construction materials and others. Carbon monoxide, nitrogen oxide and nitrogen dioxide, sulfur dioxide, benzene, kerosene, soot, dust, iron and manganese oxides, fluorides, and some other materials into the atmosphere during construction. Despite the fact that the nature and sources of impact on the environment during the construction of green power are not much different from those in other capital construction projects, environmental damage is obvious.