Which is the main source of energy
The term Energy source describes in general a way of generating useful energy for an application. Energy sources according to general and political usage are used to generate useful energy (electricity, heating, drive energy) for human use. Energy sources are z. B. nuclear and fossil fuels, as well as regenerative energy such as solar energy, wind energy, water energy or geothermal energy.
The term Energy source is strictly physically incorrect, since - globally speaking - there are no energy sources or sinks (law of conservation of energy). Energy can only be converted.
In the field of politics, the term Energy source as a synonym for Energy source used. However, energy storage media (e.g. hydrogen, batteries, etc.) are not energy sources, but secondary energy carriers.
Fossil energy sources
Main article: Fossil energy
The fossil fuels that can be used as a source of energy are substances made from biomass that - sealed off from the atmosphere by layers of sediment - could not rot and thus received their chemical energy. Fossil fuels are coal, natural gas, crude oil and methane hydrate. All fossil fuels have in common that they are only available to a limited extent and their use with CO2Emissions (see greenhouse effect, climate change, climate protection).
Fossil energy sources used
Brown and hard coal
Hard coal and lignite were formed in the Carboniferous and Tertiary from dead plants that sagged in the mud and were slowly compressed. The process in which dead organic material is first converted into peat, then into lignite and then into hard coal is known as coalification and is characterized by an increase in the relative proportion of carbon.
Hard coal is the lower-lying, older type of coal and is mainly mined underground in tunnels and shafts, while the lignite lying further above can be mined in open-cast mining after the surface layers (overburden) have been cleared. The deeper the coal lies, the less oxygen and the more carbon it contains. This increases the calorific value of the coal.
Hard coal and lignite are burned in steam power plants. The resulting thermal energy is used to convert water into water vapor and thus to generate mechanical energy via a steam turbine and electrical energy from it via a generator. Furthermore, hard coal is used in steel production and to a lesser extent, like lignite, for the operation of living space heating systems (coal stoves).
Coal is a domestic energy source, so it secures jobs and reduces dependence on imports; In addition, electricity from coal-fired power plants can be called up as required, so no “shadow power plants” are required to compensate for fluctuations. However, this only applies to a very limited extent to lignite power plants, as these are operated at the base load, i.e. with constant output. This is countered by the fact that domestic coal is very expensive compared to imported coal and must be heavily subsidized in order to remain competitive.
Coal is only available to a limited extent as a fossil fuel, and as a raw material for the chemical industry it is actually too good to burn. In addition, when compared to other fossil fuels (crude oil, natural gas), the combustion of coal has a comparatively high level of CO2-Emissions, since coal is essentially - as the name suggests - made up of carbon. The combustion of coal is also associated with relatively high pollutant emissions (sulfur compounds, nitrogen compounds, dust), due to the impurities it contains, which can only be reduced with a high level of technical effort. Above all, however, the mining of coal - especially the opencast mining of lignite - causes enormous environmental damage. After the incineration, there are also ash and filter dust left for disposal, as well as gypsum from the flue gas desulphurisation.
About 70 million years ago, crude oil was formed from dead aquatic animals and plants through sedimentation of microorganisms in connection with suspended mineral matter. It mainly consists of hydrocarbons. Typical impurities are sulfur compounds, hydrogen sulfide and nitrogen compounds. Crude oil is used to generate electricity in steam power plants, as a raw material for fuels (gasoline, diesel), for heating and as a raw material in the chemical industry.
Electricity from oil-fired power plants can be called up as required, so no “shadow power plants” are required to compensate for fluctuations. To a lesser extent than coal, oil from the North Sea is a domestic energy source, so it secures jobs. However, the occurrences in the North Sea are very limited.
As a fossil fuel, crude oil is only available to a limited extent, and as an essential and versatile raw material for the chemical industry (raw material for lubricants, plastics and many other things) it is far more valuable than coal. In addition, the combustion of crude oil is also in comparison with other fossil fuels with comparatively high CO2Emissions, although the combustion produces less CO2 than that of coal. The combustion of crude oil is also associated with relatively high pollutant emissions (sulfur compounds, nitrogen compounds), due to the impurities it contains, which can only be reduced with a high level of technical effort. Last but not least, crude oil is an environmental pollutant (oil spill), the extraction of crude oil leads to enormous environmental pollution - both during normal extraction (leaks) and in the event of tanker accidents (see e.g. Exxon Valdez, Amoco Cadiz, etc.). After the incineration, filter dust remains for disposal as well as gypsum from the flue gas desulphurisation. In addition, there is a problem with petroleum in that Peak oil named maximum funding. Is the PeakWhen the maximum is reached, the delivery rate begins to decrease. If the consumption of crude oil remains the same or even - as is actually the case - increases, this leads to an immense price increase and also to supply bottlenecks.
Natural gas was created together with crude oil; it is the part of the conversion process that is gaseous under normal temperature conditions. Natural gas mainly consists of methane (CH4). Typical impurities are sulfur compounds, hydrogen sulfide and nitrogen compounds. Natural gas is used to generate electricity with gas turbines, for heating and, for some time now, also as a car fuel (CNG). Natural gas is also the starting material for synthesis gas, which is used in the chemical industry (production of acetylene, methanol, hydrogen and ammonia).
Compared to coal and crude oil, natural gas contains considerably fewer impurities (e.g. sulfur compounds), so it releases fewer pollutants when it is burned and is therefore a comparatively environmentally friendly fossil fuel. From a chemical point of view, natural gas also contains a higher proportion of hydrogen than coal or crude oil and therefore emits less greenhouse gas CO with the same energy yield2 free. However, unburned methane, the main component of natural gas, is itself a very effective greenhouse gas (see GWP). Natural gas from leaks also promotes the greenhouse effect. Today, natural gas is mainly used to generate electricity in gas turbine or combined cycle power plants (gas and steam power plants). These power plants achieve a very high degree of efficiency of 55-60% and, unlike coal or nuclear power plants, can deliver electricity at very short notice if required. B. be used by wind turbines.
As a fossil fuel, natural gas is only available to a limited extent; moreover, a large part of natural gas has to be imported, which makes it dependent on imports.
So far unused fossil energy sources
The previously unused fossil energy sources are not (or not economically) obtainable so far, and can only become economical at significantly higher energy prices.
Methane hydrate (Methane clathrate, Methane ice) consists of methane stored in frozen water, with the water molecules completely enclosing the methane. One speaks therefore of an embedment connection (clathrate). Methane hydrate was first discovered in the Black Sea in 1971. Methane hydrate forms on the bottom of oceans or deep lakes, where the pressure is high and the temperature low enough. At lower pressure, methane hydrate is unstable and decomposes to water and free methane, which could theoretically be used in a similar way to natural gas with a similar composition. The largest deposits of methane hydrate were found on the slopes of the continental shelves.
With an estimated twelve trillion tons of methane hydrate, more than twice as much carbon is bound there as in all oil, natural gas and coal reserves in the world. However, due to the instability, the dismantling of the methane hydrate fields is difficult and is currently still speculation.
The combustion of methane hydrate emits roughly the same amount of CO2-Emissions free like those of natural gas, so that this also contributes to global warming, but to a lesser extent than coal or crude oil. Furthermore, methane itself is a powerful greenhouse gas that is far more effective than CO2 (see GWP). During the dismantling process, high demands would have to be made on the avoidance of leakages and other methane releases.
The exploitation of methane hydrate deposits on continental shelves continues to require extensive investigations into slope stability. With their size of several hundred kilometers, landslides on continantal shelves can lead to tsunamis.
Renewable energy sources
Main article: Renewable energy
Renewable energy sources bear their name because, in contrast to the limited availability of fossil fuels, they are constantly supplied directly (sunlight) or indirectly (wind, hydropower, waves, biomass) from the sun or from other, non-fossil sources (geothermal energy: radioactive decay in the Earth's interior, tidal power plants: movement of the moon and earth). You therefore almost never run out. Apart from wind energy, regenerative energy sources are currently not yet completely competitive with established energy sources and, like nuclear energy before, are therefore dependent on subsidies in order to make their use attractive and to accelerate further development. However, there is still a clear imbalance in favor of nuclear energy with regard to the support services provided by the general public.
Renewable energy sources used
Main article: wind power
Air layers of different warmth lead to a displacement of air, which is referred to as wind. Wind turbines today use the kinetic energy of the wind to convert it into mechanical energy with the help of propellers and finally into electrical energy in a generator. Wind energy has been used in windmills to grind grain since the 10th century.
The generation of electricity through wind energy is - apart from the construction of the power plants - CO2-free and - apart from the emissions caused by power plant construction and removal - does not release any further pollutants. The energetic amortization period is extremely short, ranging from a few months to a year. The use of wind energy does not pose any significant safety risks. A wind turbine is very reliable, the technical availability is between 95 percent and 99 percent, the energetic around 90 percent. All installed wind turbines together cannot fail at the same time, nor is it likely that they will deliver no or maximum electricity at the same time. In addition, wind energy is independent of fuels and their price development; the electricity costs arise almost exclusively from the costs of financing the necessary investments. This factor means that with conventional energy prices rising further, the generation of electricity from wind energy becomes more competitive. As a purely domestic energy source, it reduces the dependence on the global price increases of other energy sources.
Wind turbines are directly dependent on the prevailing wind conditions, so generation fluctuates. When there is no wind or a storm, they do not generate any electricity. Since electricity can currently only be stored with pumped storage power plants that are subject to conversion losses, conventional power plants that obtain their electricity from sources that are not subject to fluctuations have to compensate for these fluctuations. However, due to the fact that the wind supply can now be forecast quite well, this proportion sinks to below 10% of the wind energy capacity and can be generated by existing power plants within their regular activity. The reduction in efficiency is just a few percentage points, as is the case with regular activity due to changing requirements.
Wind turbines are ecologically controversial because there is a risk of bird strikes, but the absolute risk of this is a factor of 10,000 lower than in road traffic. Wind turbines can emit harmful infrasound during operation and, due to their conspicuous design, lead to (albeit subjective) optical pollution on land.
Wind turbines pose a risk of ice throwing near roads and settlements in winter. In the visibility of roads, wind turbines endanger road safety because the driver's attention is unconsciously diverted.
Unless external effects are taken into account, wind power is currently still more expensive than conventionally generated power, but wind power cannot look back on decades of massive support for other energy sources (e.g. hard coal). In regions with a poorly developed power grid, such as For example, the power supply on islands or in developing countries, wind turbines are already competitive with conventional energy sources.
Hydroelectric power plants use the energy from gravity or kinetic energy from constantly flowing water in order to generate mechanical energy from it by means of water turbines and from this in turn electrical energy. Since the natural water cycle is powered by the sun, hydropower is indirectly a form of solar energy. Hydropower is mainly used to generate electricity, the direct use of mechanical work (water mills) is rather negligible.
The generation of hydropower is - apart from the construction of power plants - CO2-free and does not release any other pollutants. Furthermore, electricity from hydropower plants can be called up as required, so no “shadow power plants” are required to compensate for fluctuations.
The reservoirs usually required for hydropower plants are dependent on suitable terrain structures that are only available to a limited extent. Hydropower is therefore severely limited in terms of the amount that can be extracted; the possibilities in Germany are largely exhausted. In addition, the construction of reservoirs requires a lot of space. If forests are flooded during the creation of reservoirs, the subsequent rotting of the organic material produces a large amount of methane, which acts as a greenhouse gas. In addition, oxygen is consumed in the process, so that in this phase (which can take many years) the reservoir is rather hostile to life for water dwellers.
Tidal power plants use the kinetic energy of the ocean currents associated with the tides to generate electrical energy. For this purpose, dams with turbines are being built in suitably shaped river mouths or on similar coastlines with a strong tidal range. One of the most famous tidal power plants is located in the Rance estuary near Saint-Malo, France.
The generation of electricity in tidal power plants is - apart from the construction and removal of the power plants - CO2-free and - apart from the emissions caused by the power plant construction - does not release any further pollutants.
Tidal power plants are only profitable in places that have a suitable coastline with a strong tidal range; such places are very limited. In addition, tidal power plants can, under certain circumstances, significantly interfere with what are sometimes very sensitive ecosystems.
Wave power plants use the energy of the waves generated by the wind on the surface of the sea. The development is currently still in its infancy. Nevertheless, since 2000 there has been the world's first wave power plant with a pneumatic chamber that feeds electricity into a commercial power grid.
Wave power plants with buoyancy bodies have also been in commercial use since mid-2006. They use the wave movement in serpentine form to hydraulically transfer the movement to generators between several links.
The generation of electricity by wave power plants is - apart from the construction and removal of the power plants - CO2-, free of pollutants and emissions.
Since there is not yet sufficient experience with wave power plants, we know about the ecological effects, e.g. B. on marine life, so far little.
An ocean current power plant uses the kinetic energy from the natural ocean current to provide electricity
There are currently some marine current power plants in the trial stage:
- Leprechaun (Strait of Messina)
- Hammerfest (Norway)
The Seaflow was planned by the University of Kassel and built with the support of a British Ministry off the coast of Cornwall in the Strait of Bristol in south-west England. It is currently being tested.
Direct use of solar energy
Main article: Solar energy
For direct use of the energy from the sun's radiation, it can either be converted directly (photovoltaics) or indirectly (solar thermal) into electricity or used directly as solar heat.
The use of solar energy is - apart from the construction of the systems - CO2-free and does not release any other pollutants. There are no fuel costs, but a solar power plant does require a certain amount of maintenance.
The supply of solar energy is linked to daylight and therefore fluctuates (day / night, weather, season), so the generation of solar power is associated with the use of controllable reserve energy ("shadow power plants"). In Central Europe, both the supply of solar energy and the weather situation are absolutely inadequate. Solar thermal power plants and in climatically more favorable regions (southern Europe, Africa, etc.) are currently failing due to a lack of possibilities for effective transport (power lines would have too many losses); hydrogen technology, which is still in its infancy, could offer a solution here in the future.
In photovoltaics, sunlight is converted directly into electrical direct current using solar cells.
The use of solar energy is - apart from the construction of the systems and their subsequent removal - CO2-free and - apart from the emissions caused by power plant construction and removal - has no further emissions of exhaust gases, radiation, dust, noise or waste heat. In addition, the use of solar energy does not involve any specific safety risks. The energetic amortization period is relatively short, it is a few years. Together with a very long service life of several decades, this results in a multiple of the production energy as useful energy. The solar energy supply roughly follows the current electricity demand, during the day and especially at midday the solar energy reaches its maximum supply, it is therefore very well suited for peak and medium load coverage and therefore a valuable component in the energy mix. In addition, photovoltaics is independent of fuels and their price development; the electricity costs arise exclusively from investment and (low) maintenance costs. This factor enables the cost of electricity from photovoltaics to fall continuously as conventional energy prices continue to rise. Solar energy is a purely domestic energy source and thus prevents dependence on global price increases for other energy sources. A photovoltaic system is very reliable and practically maintenance-free. All installed systems together cannot fail at the same time. They do not provide any electricity in the dark, but then the electricity demand is also lower. In Germany, photovoltaics is implemented as a decentralized technology, the energy is generated where it is actually used, and there are no line losses. In contrast to conventional energy sources, the physical possibilities of efficiency and the optimization of production costs have not yet been exhausted; through intensified research, photovoltaics should become increasingly more efficient and cheaper in the future.
With solar thermal energy (use of solar heat), the heat generated by absorption when sunlight hits a surface is collected in solar collectors via a carrier medium (e.g. water) and used for heating or domestic hot water. It is not economically feasible to use it to generate electricity in Central Europe.
The supply of solar energy is linked to daylight and therefore fluctuates (day / night, weather, season); However, fluctuations in the time of day and weather can now be largely compensated for when using solar heat by means of heat storage technologies (e.g. latent heat storage). The seasonal fluctuations are more serious, since solar heat is least available for heating purposes exactly when it is needed. Long-term storage of heat from summer to winter is technically possible despite the thermal losses, but is currently unsuccessful, and fuel prices are not high enough for this.
Solar thermal power plants and solar thermal power plants
| In solar thermal power plants, the sunlight is concentrated on a collector via a large number of mirrors, which means that the temperatures required for a power plant with a steam cycle are reached. |
With a suitable construction (an inverted funnel), updraft power plants generate a strong thermal updraft, which can be used with turbines.
Biomass is one of the renewable raw materials, i. H. it is not available indefinitely (like wind energy, for example), but (in contrast to fossil fuels) it can be created again naturally within a short time after harvesting. Biomass is created by converting energy from solar radiation with the help of plants through the process of photosynthesis into organic matter. Biomass thus represents stored solar energy. The difference between biomass and other types of use of solar energy is its independence from the times of solar radiation. Biomass can be used in many different ways, e.g. B. by
- the direct combustion of wood and other biomass (the oldest use of biomass for energy production),
- Conversion by microorganisms into biogas that can be used for power plants, as fuel or for heating,
- Conversion through chemical processes, e.g. B. in biodiesel or alcohols.
The biological substances suitable for use are also diverse, so in addition to vegetable oils and fruits for biodiesel, the remaining parts of the plants, such as wood, straw, etc. for z. B. BtL fuel and animal excrement for biogas and biological municipal waste (landfill gas) can be used to obtain heating fuels.
The use of biomass for energy generation is in principle not CO2-free, since CO during combustion2 is released. Since this CO2 but when the biomass was extracted from the atmosphere, the use of biomass - apart from the emissions during production - is CO in the balance sheet2-neutral. Biomass makes sense as a niche energy source as long as it uses waste products from agricultural and forestry processes or biodegradable municipal waste and helps to dispose of it. A large-scale use with specially generated biomass, z. B. for large-scale conversion from diesel to biodiesel, largely fails due to the enormous amount of space required to generate the biomass. In addition, the ecological pollution caused by intensive agricultural use is problematic. Last but not least, the resource biomass is limited by the generation capacity of the earth (energy contribution from the sun, available area) and is already used to a considerable extent by humans. .
When using environmental energy with the help of heat pumps, which are usually electrically driven, the thermal energy available in the environment can be used for heating and domestic water heating. For this purpose, a suitable medium in the environment (air, soil, water, groundwater, tunnel water, pit water) is cooled according to the refrigerator principle and the medium in the heating circuit of a building or the service water is heated with the heat obtained.
Heat pumps are not an energy source in the true sense of the word, as they require the use of considerable amounts of drive energy for thermodynamic reasons. Their benefit is that they deliver more heat than they need in terms of drive energy. It can therefore be viewed as a kind of energy amplifier.
The generation of the drive energy is decisive for considering the environmental impact. If this takes place with low efficiency in steam power plants as in the conventional electricity mix, the overall system can be more inefficient than the direct use of primary energy, e.g. B. in the form of gas.
A higher efficiency in the overall system can often be achieved if the inlet temperature of the heat pump is at a higher level, e.g. B. in combination with the use of geothermal energy.
Geothermal energy is the energy stored beneath the earth's surface in the form of thermal energy (commonly known as heat). Immense amounts (around 1,011 terawatt years) of thermal energy are stored in the earth's interior, some of which have been preserved from the time the earth was formed, but which are mainly created by the decay of natural radioactive isotopes. The temperature in the core of the earth is estimated at 6000 ° C, in the upper mantle still 1300 ° C. 99 percent of the globe is hotter than 1000 ° C, only 0.1 percent is cooler than 100 ° C. The temperature increases on average by 3 ° C per 100 m depth. However, some areas have a higher temperature gradient, for example areas in the USA, Italy, Iceland, Indonesia or New Zealand.
The use of geothermal energy to generate electricity, especially in the heating market (heating and cooling) - apart from the construction of the systems - is CO2-free and - apart from the emissions caused by the power plant construction and subsequent disposal - does not release any further pollutants as long as the hot water conveyed does not contain dissolved gases that are released. In addition, the generation of geothermal energy is hardly associated with other emissions (e.g. infrasound) or impairment of the landscape.
So far unused regenerative energy sources
The following energy source is still under development and not yet in commercial use.
Osmosis power plants are hydropower plants that can generate energy from the different salt content of fresh and salt water. According to the principle of osmosis, an ion-poor liquid (e.g. fresh water from a river) penetrates a membrane in the direction of a more ion-rich liquid (e.g. sea water), whereby an osmotic pressure builds up. With a suitable structure, the flow of liquid can drive a turbine and generate electricity in the process. 
In Scandinavia there are already test facilities at estuaries, but the process is still far from being profitable.
The main advantage (in contrast to wind and sun, for example) is the constant availability of energy as long as both fresh and salt water are available.
Nuclear energy sources
Main article: Nuclear power
Used nuclear energy sources
The nuclear fission of uranium or plutonium produces energy and neutrons, which in turn trigger further fission. This energy released in this chain reaction is used in a controlled manner in a nuclear reactor.
The use of nuclear energy is not entirely CO2-free, as CO during extraction and processing of the fuel as well as during its transport and disposal2Emissions occur. The CO2-Emissions, however, are - in relation to the amount of energy converted - an order of magnitude below the emissions of a fossil-fuel-fired power plant. Furthermore, during the construction and removal of the nuclear power plant, the enormous amount of material used means that CO2-Emissions, which - since a nuclear power plant generates enormous amounts of electricity during its operating life - are not very significant in relation to the total amount of energy generated. Furthermore, even during normal operation, a nuclear power plant releases small amounts of radioactive substances with exhaust air (noble gases) and wastewater into the environment; the radiation exposure of the population is far below the fluctuation range of natural radiation exposure and is also much lower than the radiation exposure that, for example, a coal power plant by releasing the natural radioactivity contained in the fuel (14C, 40K, uranium, thorium). Apart from annual maintenance, nuclear power plants are highly available, (more than 90%) are particularly suitable for constant power output and are therefore classic base load power plants; they are competitive with fossil fuels in terms of power generation costs. Nuclear power plants have a long service life, and some in the USA have had their operating licenses extended to a duration of up to 60 years.
The construction of a nuclear power plant requires a very high investment (example: the new nuclear power plant in Olkiluoto (Finland) is estimated at 3.2 billion euros construction costs), a large part of the electricity price from nuclear power results from the construction and capital costs; the demolition also causes costs of around 500 million euros. Since the fuel and disposal costs only make up a small proportion of the costs, nuclear energy is extremely robust in comparison to fossil fuels against fluctuations in the uranium price.
The operation and disposal of a nuclear power plant generates radioactive waste, the amount (mass, volume) of which is small compared to the waste from fossil power plants. However, due to their radiation, these represent a potential hazard and have to be conditioned and disposed of in a complex manner. The disposal of radioactive waste through final storage in deep geological formations has largely been solved technically, but is politically controversial.
In the event of serious accidents and terrorist attacks, nuclear power plants represent a considerable potential hazard. In order to counteract this potential hazard, nuclear power plants are subject to strict monitoring, they are designed in a safety-oriented manner in all aspects of the design and kept state-of-the-art. Due to its inertia and the enormous basic costs, nuclear energy is primarily suitable for covering the base load and to a limited extent for medium loads. That is why fluctuations in electricity demand (medium and peak load) must be taken over by other types of power plant at higher costs. The use of nuclear fission to generate electricity in a nuclear power plant takes place as with all thermal power plants (all fossil as well as solar thermal) with a low efficiency of approx. 35 percent, the rest is unused waste heat, which is dissipated by river water or via cooling towers. The resulting warming of the rivers poses a threat to the life they contain, but is usually (generally in Germany) limited by regulations to a safe level.
|The decay of radioactive substances can be used as an energy source, while the resulting decay heat is used in radioisotope generators to generate electricity on a thermoelectric basis and for heating. The amount of energy that can be obtained is small, but radioisotope generators are very robust, absolutely maintenance-free and durable. Nuclear decay generators were previously used, inter alia. used for pacemakers, nowadays they are mainly used as a power source and heating for space probes in the outer solar system, since there solar cells do not provide sufficient power and no heat. In the strict sense, the earth is also a radioisotope generator, since the geothermal energy used in geothermal energy, according to current doctrine, largely comes from the radioactive decay of long-lived radioisotopes in the earth's interior.|
Nuclear energy sources under development
Nuclear fusion is the fusion of light atomic nuclei to form heavier ones. This creates a new chemical element. The sun and other stars get their energy through nuclear fusion. To ignite the fusion in a power plant, the fuel (hydrogen plasma) must be enclosed in magnetic fields and heated to 100 million degrees. The greatest energy yield is provided by the reaction between the two heavy types of hydrogen - deuterium and tritium. When it fuses to form a helium nucleus, a fast neutron is released that carries 80 percent of the energy gained. This means that 50,000 kilowatt hours of energy can be obtained from one gram of this fuel through nuclear fusion, as much as the heat of combustion from eleven tons of coal. The raw materials required for the fusion process are available in almost unlimited quantities and are distributed all over the world. However, the first fusion power plant on an industrial scale is not expected before 2050.
Category: Nuclear Technology
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