Renewable Energy

Renewable energy . Energy that is obtained from virtually inexhaustible natural sources, either because of the immense amount of energy they contain, or because they are capable of regenerating themselves by natural means.Renewable energies under Energy Sources, include wind, geothermal, hydroelectric, tidal, solar, wave, biomass and biofuels.

Summary

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• 1 Evolution
• 2 Classification
• 3 power sources
  • 1 Non-renewable
    • 1.1 Fossil energy
    • 1.2 Nuclear power
  • 2 Renewable or green
    • 2.1 Hydraulic power
    • 2.2 Solar thermal energy
    • 2.3 Biomass
    • 2.4 Solar energy
    • 2.5 Wind energy
    • 2.6 Geothermal energy
    • 2.7 Tidal energy
  • 4 Environmental impact
  • 5 Advantages and disadvantages
    • 1 Green energies
    • 2 Fuzzy nature
    • 3 Irregularity
    • 4 Polluting renewable sources
    • 5 Geographic diversity
    • 6 Administration of electrical networks
    • 7 Integration in the landscape
  • 6 Present
  • 7 Bibliographies
  • 8 sources

Evolution

Renewable energies have constituted an important part of the energy used by humans since ancient times, especially solar, wind and hydraulic. Sailing, wind or water mills and the constructive arrangements of buildings to take advantage of the sun are good examples of this.

With the invention of the steam engine by James Watt, these forms of use are being abandoned, as they are considered unstable over time and capricious, and thermal and electric motors are increasingly used, at a time when the still relatively low consumption , did not foresee a depletion of the sources, nor other environmental problems that later arose.

Towards the 1970s, renewable energies were considered an alternative to traditional energies, both for their guaranteed present and future availability (unlike fossil fuels that require thousands of years for their formation) and for their lower environmental impact on the environment. case of clean energies, and for this reason they were called alternative energies. Currently many of these energies are a reality, not an alternative, so the name alternatives should no longer be used.

Classification

Renewable energy sources can be divided into two categories: non-polluting or clean and polluting. Among the first:

• The arrival of masses of fresh water to masses of salt water: blue energy.
• The wind : wind energy .
• The heat of the Earth : geothermal energy.
• Freshwater rivers and streams: hydraulic or hydroelectric power.
• The seas and oceans: tidal energy.
• The Sun: solar energy .
• The waves: wave energy.

The pollutants are obtained from organic matter or biomass , and can be used directly as fuel (wood or other solid vegetable matter), either converted into bioethanol or biogas through organic fermentation processes or into biodiesel, through transesterification and conversion reactions. urban waste.

The energies from polluting renewable sources have the same problem as the energy produced by fossil fuels: during combustion they emit carbon dioxide , a greenhouse gas, and are often even more polluting since the combustion is not as clean, emitting soot and other Solid particles. They fall within renewable energies because as long as the plants that produce them can be cultivated, they will not run out. They are also considered cleaner than their fossil counterparts, because theoretically carbon dioxideemitted in combustion has been previously absorbed by transforming into organic matter through photosynthesis. In reality, the quantity previously absorbed is not equivalent to that emitted in combustion, because in the sowing, harvesting, treatment and transformation processes, energy is also consumed, with its corresponding emissions.

In addition, much of the CO2 emissions can be trapped to feed microalgae/certain bacteria and yeast cultures (potential source of fertilizers and feed, salt (in the case of brackish or saltwater microalgae) and biodiesel/ethanol respectively, and medium for the elimination of hydrocarbons and dioxins in the case of bacteria and yeasts (petroleum proteins) and the particulate problem is solved with gasification and complete combustion (combustion at very high temperatures, in an atmosphere very rich in O2 ) in combination with emission decontaminating means such as filters and particle precipitators (such as the Cottrel precipitator), or activated carbon surfaces.

Energy can also be obtained from solid urban waste and sludge from water treatment and purification plants . Energy that is also polluting, but would also be to a great extent if it were not used, since the rotting processes of organic matter are carried out with the emission of natural gas and carbon dioxide .

Energy sources

Energy sources can be divided into two large subgroups: permanent (renewable) and temporary (non-renewable).

Non-renewable

Fossil fuels are non-renewable resources, whose reserves are limited and deplete with use. At some point they will end, and it will take millions of years to have them again. The main ones are fossil fuels ( oil , natural gas and coal ) and, to a certain extent, nuclear energy .

fossil energy

Fossil fuels can be used in solid ( coal ), liquid ( petroleum ), or gaseous ( natural gas ) form. They are accumulations of living beings that lived millions of years ago and that have fossilized forming carbon or hydrocarbons. In the case of coal, these are forests in swampy areas, and in the case of oil and natural gas, large masses of marine plankton accumulated at the bottom of the sea. In both cases, the organic matter partially decomposed due to lack of oxygen and the action of temperature, pressure and certain bacteria, so that molecules with high-energy bonds were stored.

The most widely used energy in the world is fossil energy. Considering all that is at stake, accurately measuring the planet ‘s fossil fuel reserves is paramount . A distinction is made between “identified reserves” even if they are not exploited, and “probable reserves”, which could be discovered with future technologies. According to calculations, the planet can supply energy for another 40 years (if only oil is used) and more than 200 (if coal continues to be used). There are alternatives currently under study: nuclear fusion energy —non-renewable, but with immense fuel reserves—, renewable energies or hydrogen batteries .

Nuclear energy

The atomic nucleus of heavy elements such as uranium can be disintegrated (nuclear fission) and release radiant and kinetic energy. Thermonuclear power plants harness this energy to produce electricity using steam turbines. It is obtained by “breaking” (fissioning) radioactive mineral atoms in chain reactions that occur inside a nuclear reactor.

A consequence of the production activity of this type of energy is nuclear waste, which can take thousands of years to disappear, because it takes that long to lose radioactivity. However, there is another possibility of nuclear energy that, so far, is only in the research phase: nuclear fusion energy, which consists of uniting (melting) two hydrogen atoms to obtain one helium atom , with abundant energy production. The fuel in this case is hydrogen, abundant on earth, and the residue is helium, neither radioactive nor polluting. If a process were achieved to obtain this energy, it would also be non-polluting energy.

Renewable or green

Green energy is a term that describes energy generated from environmentally friendly primary energy sources . Green energies are renewable energies that do not pollute, that is, whose method of production or use does not emit by-products that may have a negative impact on the environment. Currently, they are becoming more important due to the worsening of the greenhouse effect and the consequent global warming , accompanied by a greater awareness at the international level regarding said problem. Likewise, national economies that do not have or have exhausted their traditional energy sources (such as oil or natural gas )) and need to acquire those resources from other economies, they seek to avoid such energy dependency, as well as the negative in their trade balance that this acquisition represents.

Hydraulic energy

The potential energy accumulated in the waterfalls can be transformed into electrical energy . Hydroelectric power plants take advantage of the energy of rivers to put into operation turbines that move an electric generator. One of the most quantitatively important resources in the structure of renewable energies is that from hydroelectric installations; a clean and indigenous energy source but for which it is necessary to build the necessary infrastructures that allow taking advantage of the available potential with zero fuel cost. The problem with this type of energy is that it depends on weather conditions.

Thermal solar energy

It is about collecting the sun’s energy through solar panels and converting it into heat which can be used to satisfy numerous needs. For example, hot water can be obtained for domestic or industrial consumption, or to heat homes, hotels, schools or factories. Also, cooling can be achieved during hot weather. In agriculture, other types of applications can be achieved, such as solar greenhouses that favor improvements in quality and quantity of crops, agricultural dryers that consume much less energy if combined with a solar system, and purification or desalination plants for water without consuming no type of fuel. With this type of energy, more than 25% of conventional energy consumption in newly built homes could be reduced, with the consequent reduction in the burning of fossil fuels and environmental deterioration.

biomass

The formation of biomass from solar energy is carried out by the process called plant photosynthesis, which in turn triggers the biological chain. Through photosynthesis , plants that contain chlorophyll transform carbon dioxide and water from mineral products without energy value, into organic materials with high energy content and in turn serve as food for other living beings. Biomass through these processes stores solar energy in the form of carbon in the short term. The energy stored in the photosynthetic process can later be transformed into thermal energy, electricity or fuels of vegetable origin, again releasing the stored carbon dioxide.

Solar energy

Solar energy is a source of life and the origin of most other forms of energy on Earth . Each year solar radiation provides the Earth with energy equivalent to several thousand times the amount of energy consumed by humanity. Properly collecting solar radiation , it can be transformed into other forms of energy such as thermal energy or electrical energy using solar panels. Through solar collectors, solar energy can be transformed into thermal energy, and using photovoltaic panels, light energy can be transformed into electrical energy.. Both processes have nothing to do with each other in terms of their technology. Likewise, in solar thermal power plants, the thermal energy of the solar collectors is used to generate electricity.

Two components are distinguished in solar radiation : direct radiation and diffuse radiation. Direct radiation is that which arrives directly from the solar focus, without intermediate reflections or refractions. The diffuse one is the one emitted by the diurnal celestial vault thanks to the multiple phenomena of solar reflection and refraction in the atmosphere , in the clouds, and the rest of atmospheric and terrestrial elements. Direct radiation can be reflected and concentrated for use, while diffuse light coming from all directions cannot be concentrated. However, both direct radiation and diffuse radiation are usable.

Active and passive receivers can be differentiated in that the former use mechanisms to orient the receiver system towards the Sun -called followers- and better capture direct radiation.

An important advantage of solar energy is that it allows the generation of energy in the same place of consumption through architectural integration in buildings. Thus, we can give rise to distributed generation systems in which losses related to transport -which currently account for approximately 40% of the total- and energy dependency are almost completely eliminated.

The different photovoltaic technologies are adapted to get the most out of the energy we receive from the sun. In this way, for example, concentrating photovoltaic solar systems (CPV) use direct radiation with active receivers to maximize energy production and thus achieve a lower cost per kWh produced. This technology is very efficient for places with high solar radiation, but currently it cannot compete in price in locations with low solar radiation such as Central Europe, where technologies such as the thin-film solar cell (also called Thin Film) are also managing to reduce the price of traditional photovoltaic technology to levels never seen before.

Wind power

Wind energy is the energy obtained from the force of the wind, that is, by using the kinetic energy generated by air currents . It is obtained by means of wind turbines that convert the kinetic energy of the wind into electrical energy by means of blades or propellers that rotate a central shaft connected, through a series of gears (the transmission) to an electric generator.

The term wind comes from the Latin Aeolicus (ancient Greek Αἴολος / Aiolos), belonging to or related to Éolo or Eolo, god of the winds in Greek mythology and, therefore, belonging to or related to the wind . Wind energy has been harnessed since ancient times to move ships powered by sails or to run mill machinery by moving their blades. It is a type of green energy.

Wind energy is related to the movement of air masses that move from areas of high atmospheric pressure to adjacent areas of low pressure, with proportional speeds (pressure gradient). So it can be said that wind energy is a non-direct form of solar energy . The different temperatures and pressures in the atmosphere , caused by the absorption of solar radiation , are what set the wind in motion.

It is a clean energy and also the least expensive to produce, which explains the strong enthusiasm for its applications. Of all of them, the most widespread, and the one with the greatest growth, is that of wind farms for electricity production.

A wind farm is the integrated installation of a set of electrically interconnected wind turbines. Wind turbines are the key elements of the installation of wind farms that, basically, are an evolution of traditional windmills . As such, they are rotating machines that usually have three blades, about 20-25 meters long, attached to a shaft. The collection element or rotor that is attached to this shaft captures the energy of the wind. The movement of the blades or vanes, driven by the wind, activates an electric generator that converts the mechanical energy of rotation into electrical energy .

These wind turbines are usually about 40-50 meters high depending on the topography of the place, but they can be even higher. This is one of the great problems that affects populations from an aesthetic point of view.

Wind turbines can work alone or in wind farms, on land forming wind farms, on the sea coast or they can even be installed on the waters at a certain distance from the coast in what is called an offshore wind farm, which is generating large conflicts on all those coasts where wind farms are to be built.

The great environmental benefit provided by the use of the wind for the generation of electrical energy is given, firstly, by the levels of gaseous emissions avoided, compared to those produced in thermal power plants. In short, it contributes to the climatic stability of the planet . An important development of wind-based electrical energy may therefore be one of the most effective measures to avoid the greenhouse effect , since, on a global level, the electricity sector is considered to be responsible for 29% of CO2 emissions. of the planet.

As clean energy, it contributes to minimizing global warming . Focusing on the social and economic advantages that concern us in a much more direct way, they are greater than the benefits that conventional energies bring. The development of this type of energy can strengthen the general competitiveness of the industry and have positive and tangible effects on regional development, economic and social cohesion and employment.

There are those who consider that wind power is not an alternative to current energy sources, since it does not constantly generate energy when the wind is not blowing . Intermittency is one of its main drawbacks. The detrimental impact on the quality of the landscape, the effects on birds and noise, are usually the negative effects that are generally cited as environmental drawbacks of wind farms.

With regard to the effects on the avifauna, the impact of the wind turbines is not as important as it might seem at first. Another of the major drawbacks is the screen effect that notably limits the visibility and control possibilities that constitute the raison d’être of their respective locations, as a result of the alignment of the wind turbines. Added to the visual limitations are the foreseeable electromagnetic interferences in the communication systems.

Geothermal energy

Geothermal energy is that energy that can be obtained by human beings by harnessing the heat from inside the Earth . Part of the internal heat of the Earth (5,000 °C) reaches the earth’s crust. In some areas of the planet, near the surface, groundwater can reach boiling temperatures and, therefore, be used to drive electric turbines or for heating. The heat inside the Earth is due to several factors, among which the geothermal gradient and radiogenic heat stand out. Geothermal comes from the Greek geo, “Earth”; and from thermos, “heat”; literally heat from the Earth.

Seawater energy

Marine energy or energy from the seas (also sometimes referred to as ocean energy or ocean energy) refers to the renewable energy produced by ocean waves, tides, salinity, and ocean temperature differences . The movement of water in the world’s oceans creates a vast store of kinetic energy, or energy in motion. This energy can be harnessed to generate electricity to power homes, transportation, and industry. The main types are:

• Wave energy, wave or wave energy.
• Tidal energy or tidal energy.
• Energy of the currents: it consists of the use of the kinetic energy contained in the marine currents. The capture process is based on kinetic energy converters similar to wind turbines, in this case using underwater installations for water currents .
• Tidal heat: it is based on the use of thermal energy from the sea based on the temperature difference between the sea surface and deep water. The use of this type of energy requires that the thermal gradient be at least 20º. The tidal power plants transform thermal energy into electrical energy using the thermodynamic cycle called the “Rankine cycle” to produce electrical energy whose hot source is the water on the sea surface and the cold source is the water from the depths.
• Osmotic energy: it is the energy of salinity gradients.

Environmental impact

All energy sources produce some degree of environmental impact.

Geothermal energy can be very harmful if it brings heavy metals and greenhouse gases to the surface; the wind produces a visual impact on the landscape, low frequency noise, it can be a trap for birds.

The least aggressive hydraulic system is mini-hydraulics, since large dams cause biodiversity loss , generate methane from unremoved plant matter, cause pandemics such as yellow fever, dengue, schistosomiasis, particularly in temperate climates and hot climates, flood areas with cultural heritage or landscape, they generate the movement of entire populations, among others Aswan, Itaipú, Yacyretá and increase the salinity of the fluvial channels.

Solar energy is among the least aggressive due to the possibility of its distributed generation, except for photovoltaic and thermoelectric electricity produced in large grid-connected plants, which generally use a large area of ​​land.

The tidal power has been discontinued due to the extremely high initial costs and the environmental impact they entail. The energy of the waves together with the energy of the marine currents usually have a low environmental impact since they are usually located on rough coasts. Biomass energy produces pollution during combustion due to CO2 emission but which is reabsorbed by the growth of cultivated plants and requires arable land for its development, reducing the amount of arable land available for human consumption and for livestock, with the danger of increasing the cost of food and favoring monocultures.

Advantages and disadvantages

ecological energies

Renewable energy sources are different from fossil fuel or nuclear power plants due to their diversity and abundance. The Sun is considered to supply these energy sources ( solar radiation , wind , rain , etc.) for the next four billion years. The first advantage of a certain number of renewable energy sources is that they do not produce greenhouse gases or other emissions, contrary to what happens with fuels, whether fossil or renewable. Some renewable sources do not emit carbon dioxideexcept those necessary for its construction and operation, and do not present any additional risk, such as nuclear risk.

However, some renewable energy systems generate particular ecological problems. Thus, the first wind turbines were dangerous for birds, as their blades rotated very quickly, while hydroelectric power plants can create obstacles to the migration of certain fish, a serious problem in many rivers in the world (in those of northwestern North America that flow into the Pacific Ocean , the salmon population was drastically reduced).

fuzzy nature

An inherent problem with renewable energy is its diffuse nature, with the exception of geothermal energy, which, however, is only accessible where the earth’s crust is thin, such as hot springs and geysers. Since certain renewable energy sources provide energyof a relatively low intensity, distributed over large areas, new types of “central” are necessary to convert them into usable sources. With four square meters of solar thermal collector, a home can obtain a large part of the energy needed for domestic hot water although, due to the use of simultaneity, apartment buildings can achieve the same performance with less surface area of ​​collectors and, which is more important, with much lower investment per home.

Irregularity

The production of permanent electrical energy requires reliable power sources or storage media (hydraulic pump storage systems, batteries, future hydrogen fuel cells, etc.). Thus, due to the high costs of energy storage , a small autonomous system is rarely economical, except in isolated situations, when connection to the power grid implies higher costs.

polluting renewable sources

As far as biomass is concerned, it is true that it actively stores carbon from carbon dioxide , forming its mass with it and it grows while releasing the oxygen again, burning it again combines carbon with oxygen, forming carbon dioxide again. of carbon. Theoretically, the closed cycle would result in a null balance of carbon dioxide emissions, since the emissions resulting from combustion would remain fixed in the new biomass . In practice, polluting energy is used in planting, harvesting and processing, so the balance is negative.

On the other hand, biomass is also not really inexhaustible, even though it is renewable. Its use can only be done in limited cases. There are doubts about the ability of agriculture to provide the amounts of plant mass needed if this source becomes popular, which is being demonstrated by the increase in cereal prices due to their use for the production of biofuels. On the other hand, all biofuels produce more carbon dioxide per unit of energy produced than their fossil equivalents.

Geothermal energy is not only highly restricted geographically, but some of its sources are considered polluting. This is due to the fact that the extraction of groundwater at high temperature generates the dragging of unwanted and toxic salts and minerals to the surface. The main geothermal plant is located in Tuscany, near the city of Pisa and is called Larderello Geothermal Plant. An image of the plant in the central part of a valley and the view of kilometers of pipes one meter in diameter leading to the thermal plant show the landscape impact it generates.

geographic diversity

The geographic diversity of the resources is also significant. Some countries and regions have significantly better resources than others, particularly in the renewable energy sector. Some countries have important resources close to the main housing centers where the demand for electricity is important. The use of such resources on a large scale, however, requires considerable investment in transformation and distribution networks, as well as in production itself.

Administration of electrical networks

If the production of electrical energyfrom renewable sources were generalized, the distribution and transformation systems would no longer be the great distributors of electrical energy, but would work to locally balance the electricity needs of small communities. Those with surplus energy would sell to deficit sectors, that is, the exploitation of the network should go from a “passive management” where some generators are connected and the system is driven to obtain the “descending” electricity towards the consumer, to an “active” management, where some generators are distributed in the network, having to constantly supervise the inputs and outputs to guarantee the local balance of the system. That would require major changes in the way networks are managed.

However, the small-scale use of renewable energy, which can often be produced on-site, reduces the need for electricity distribution systems. Current systems, rarely profitable financially, revealed that an average household with a solar system with energy storage , and panels of sufficient size, only has to rely on external electricity sources for a few hours per week. Therefore, advocates of renewable energy think that electricity distribution systems should be less important and easier to control.

integration into the landscape

An obvious drawback of renewable energy is its visual impact on the local environment. Some people hate the aesthetics of wind generators and mention nature conservation when talking about large solar power installations outside of cities. However, everyone finds charm in the sight of the “old windmills” which, in their time, were a conspicuous display of available technique.

Others try to use these technologies in an effective and aesthetically pleasing way: fixed solar panels can double noise barriers along motorways, roofs are available and could even be replaced entirely by solar collectors, amorphous photovoltaic cells that can be used to tint the windows and produce energy, etc.

Present

They represent 20% of the world’s electricity consumption, with 90% of hydraulic origin. The rest is very marginal: biomass 5.5%, geothermal 1.5%, wind 0.5% and solar 0.5%. About 80% of the energy needs in Western industrial societies are centered around industry, heating, air conditioning of buildings and transportation (cars, trains, planes). However, most of the large-scale applications of renewable energy are concentrated in the production of electricity. In Spain , renewables were responsible for 19.8% of electricity production. In 2007 , the generation of electricity with renewable energies surpassed that of nuclear origin. In the United States , in 2011Renewable energy production surpassed nuclear energy for the first time, generating 11.73% of the country’s total energy . 48% of renewable energy production came from biofuels, and 35% from hydroelectric plants, the other 16% being wind, geothermal and solar.