Hydropower (also known as hydropower)
Hydroenergy is probably the oldest and most commonly used source of renewable energy. The power in flowing or falling water has been processed and used economically for centuries. Prior to the invention of electric machines and the dissemination of power engineering, hydropower was widely used to drive mills, sawmills, forges and fulling plants. This was done through water wheels, the simplest of which – the so-called The landing wheel was described in the third century BC. The principle of the water wheel is as simple as its construction. It is made of a wooden or metal wheel equipped with blades, cups or partitions forming a driving surface. A circle constructed in such a way, when placed in the river stream, converts water energy into mechanical energy. There are three types of water wheels due to the way the water stream is delivered. In addition to the above-mentioned landing gear, there are also mid-fishing and over-riding wheels. Currently, hydropower is most often converted into electricity using hydroelectric power plants and the engines installed in them called turbines. Water turbines are made of metal rotors equipped, like water wheels, with blades. The impeller constructed in this way rotates by converting the energy of water into mechanical energy. This, in turn, due to the generator coupled with turbines is used to produce electricity. The most commonly used types of turbines include: Kaplan, Francis and Pelton turbines. Hydroelectric power plants use both the energy of flowing inland waters (flow-through power plants) and the energy of their decrease resulting from damming. This category includes: power plants on tanks with periodic flow regulation, power plants in the compact cascade, as well as pump power plants and power plants with a pump member. In addition to these, there are also power plants using sea wave energy (so-called maremotor power plants), power plants that process the energy of moving masses of sea currents, and facilities using energy of high tides and low tides (tidal power plants). Water energy is the most efficient source of renewable energy. The efficiency of its transformation may exceed 80%. Its characteristic parameters include: bleed, that is, the difference in the height from which water falls on the turbine blades and the speed of its flow. These parameters depend on a number of factors, including geographical, hydrological and applied technologies.
Wind energy is the nergy hidden in the movement of air, which is caused by the difference in density of heated air masses and their upward movement. The vacuum created then causes the suction of its cold masses. The air flow is from a higher pressure area to a lower pressure area. It can therefore be said that wind energy is solar energy because the sun heats the air. It is estimated that about 1 to 2% of solar energy reaching Earth is converted to wind kinetic energy. Wind speed and strength depends on the pressure difference between the two points. The greater the difference, the faster the wind speed will be. The movement of air usually occurs in a direction parallel to the Earth’s surface, but with proper terrain it may have a different course, e.g. up-down. From the point of view of the possibility of using wind for energy purposes, it is characterized by three quantities: speed, direction and repeatability. Wind speed increases with height, while the lowest is near the ground, which results from the effects of friction. The wind direction determines the direction from which the wind arrives. In turn, repeatability is the sum of hours during which the wind blows during a year at a certain speed. Wind energy is transformed into electricity using wind turbines, it is also used as mechanical energy in windmills and wind pumps. Wind turbines are equipped with rotors with blades. The wind flowing on them sets the rotor in motion. The rotating rotor then transfers mechanical energy to the generator. A generator, also called a generator, converts it into electricity. Depending on the rotor axis setting, wind turbines are divided into: vertical and horizontal axis of rotation turbines. The efficiency of wind energy use by wind farms is about 30% (coal power plants achieve similar efficiency). Wind energy is widely available, but it is characterized by high variability, both in time and space. The shape of the land and land development have a significant impact on the strength of wind energy.
The energy of the sun, more precisely the energy of solar radiation, is the richest source of energy available to humanity, and at the same time a prerequisite for man to live and function at all. Solar energy can be used for heating and electricity production. In the first case, this is done using systems that mechanically transfer heat using working fluids: oil, water or air. Of all solar radiation processing methods, it is currently the most effective way of using solar energy, both in energy and economic terms. The efficiency of solar energy conversion into usable heat, which can be used to heat rooms (central heating) or production of domestic hot water (hot utility water) reaches as much as 80%. Solar collectors are used for this purpose. There are two types of these devices due to their construction: flat and vacuum collectors. Flat collectors consist of an absorber usually made of copper or aluminum sheet, less often steel, to which copper pipes are attached. It is through them that the working fluid flows. The whole is covered with a highly selective layer, characterized by a high solar radiation absorption coefficient and a low infrared radiation emission coefficient. The absorber is additionally protected against heat loss by placing it in a sealed chamber isolated from the bottom with a polyurethane plate or mineral wool. All these elements are enclosed in a metal frame that is covered with glass. The second type of collectors are vacuum collectors. The absorber is inside them connected to each other by glass tubes, inside which there is a vacuum. Collectors of this type are slightly more efficient, especially in spring and autumn-winter periods, which results from the ability to absorb diffused solar energy. An important feature of solar energy is the ability to generate electromotive force in solids, e.g. silicon wafers. This phenomenon is called the photovoltaic effect and was used in the second case of using solar energy – electricity production. Photovoltaic panels are involved in this process. Photovoltaic (PV) cells are their basic element. A typical PV cell is a semiconductor wafer made of crystalline or polycrystalline silicon. Under the influence of absorption of solar radiation, voltage is generated at the terminals of the cells. After connecting the load, the electric current flows. The efficiency of this type of installation is relatively small and amounts to a maximum of 30%. However, this is a very promising technology, therefore photovoltaics is currently one of the fastest growing branches of the energy industry. A characteristic feature of solar energy, like wind energy, is its large variability. The amount of solar radiation reaching the Earth’s surface fluctuates depending on the time of day, year, orientation towards the Sun and climate zone. However, this is a very promising technology, therefore photovoltaics is currently one of the fastest growing branches of the energy industry. A characteristic feature of solar energy, like wind energy, is its large variability. The amount of solar radiation reaching the Earth’s surface fluctuates depending on the time of day, year, orientation towards the Sun and the climate zone. However, this is a very promising technology, therefore photovoltaics is currently one of the fastest growing branches of the energy industry. A characteristic feature of solar energy, like wind energy, is its large variability. The amount of solar radiation reaching the Earth’s surface fluctuates depending on the time of day, year, orientation towards the Sun and the climate zone.
Geothermal energy (also known as geothermal energy or geothermal energy)
Geothermal energy is the thermal energy inside the Earth, accumulated in rocks, waters and vapors. The Earth’s interior contains heat energy of around 140 million EJ to a depth of about 5 km. It is almost fifty times more energy than that which reaches the earth’s surface during the year from the Sun. Initially, the Earth’s internal heat came from the gravitational contraction occurring during planet formation. Currently, the most heat (45-90%) comes from the decay of radioactive isotopes of potassium, uranium, and thorium. Geothermal energy belongs to renewable energy sources because its source – the hot interior of the globe – is practically inexhaustible. Geothermal energy is discussed primarily when the heat carrier is water or steam. In order to extract geothermal waters to the surface, wells are drilled to the depth of their retention. Then a second well should be drilled at a distance from the tapping hole. Before the geothermal water will be pumped back into the bed after receiving the heat. There are two ways to use geothermal water: direct, in which water is supplied through a pipe system, and indirect – by giving heat to cool water in a closed circuit. Geothermal energy is used as the primary heat source in central heating systems, as well as for the production of electricity. In the latter case, it is paid only if the water in the source is particularly hot. The global production of electricity generated by geothermal energy is based on sources with a temperature exceeding 100 ° C. It is then possible to use a steam turbine directly. Currently, binary systems technology enabling the use of heat sources with a minimum temperature of 90 ° C is becoming more and more popular. However, water with a lower temperature is not suitable for generating electricity for technical reasons. This would require the use of huge heat exchangers to obtain even a small amount of electricity. Geothermal waters are usually heavily salted, which is the reason for the difficult working conditions of heat exchangers and other fittings of geothermal installations. However, water with a lower temperature is not suitable for generating electricity for technical reasons. This would require the use of huge heat exchangers to obtain even a small amount of electricity. Geothermal waters are usually heavily salted, which is the reason for the difficult working conditions of heat exchangers and other fittings of geothermal installations. However, water with a lower temperature is not suitable for generating electricity for technical reasons. This would require the use of huge heat exchangers to obtain even a small amount of electricity. Geothermal waters are usually heavily salted, which is the reason for the difficult working conditions of heat exchangers and other fittings of geothermal installations.
Biomass is all organic matter present on Earth, i.e. all kinds of plant and animal substances that are biodegradable. Traditionally, biomass means waste and residues from households and industry. However, the so-called energy crops, which are characterized by high annual growth, high calorific value, considerable resistance to diseases and pests, as well as relatively low soil requirements. An extremely important factor is also the possibility of mechanization of agrotechnical works at the stage of plantation establishment and crop harvesting. The biomass consists of carbohydrates, starch and lignin. Carbohydrates together with starch are food for animals and people, they are also raw materials for the production of ethanol, which can be used for energy. The rest of the biomass components do not have nutritional properties. Lignin, cellulose and hemicellulose are a very good energy resource. The most efficient way to obtain energy from biomass is to burn it. This can be done by direct combustion, as a biogas or biofuel. The heat obtained in this process is then used to generate electricity. The by-product of its production is carbon dioxide (CO2). However, it is not harmful to carbon dioxide and has no greenhouse effect. This is due to the fact that it remains in a closed circuit due to the process of photosynthesis. Compared to hard coal, biomass has a higher oxygen and hydrogen content, and a lower carbon content. For example, the calorific value of yellow straw is 14.3 MJ / kg, firewood 13 MJ / kg, and coal 29.3 MJ / kg. It follows that one ton of hard coal in energy terms balances with two tons of wood or straw. Biomass is currently one of the cheapest sources of renewable energy, and its production can take place automatically, or be supported by appropriate treatments such as fertilization or the fight against pests. The biomass belonging to renewable energy is evidenced by the fact that it is available cyclically at regular intervals.