Dawn of solar technology

The early development of solar technologies, beginning in the 1860s, was motivated by the expectation that coal would soon become scarce. However, the development of solar energy stalled at the turn of the century due to the increasing availability and economies of scale of non-renewable sources such as coal and oil.[18] In 1974, it was estimated that only six private homes in all of North America were powered by solar systems.[19] However, the 1973 oil crisis and the 1979 crisis caused a major shift in energy policy around the world and brought it back into focus. of attention on emerging solar technologies.[20]​[21]​ The first development strategies were developed, focused on incentive programs such as the Federal Photovoltaic Utilization Program in the United States and the Sunshine Program in Japan. Other efforts included the creation of research organizations in the United States (NREL), Japan (NEDO), and Germany (Fraunhofer–ISE).[22] Between 1970 and 1983, installations of photovoltaic systems grew rapidly, but the drop in oil prices in the 1980s moderated the growth of solar energy between 1984 and 1996.

From 1998 to today

In the mid-1990s, the development of residential and commercial rooftop PV, as well as grid-connected plants, began to accelerate due to growing concerns over oil and natural gas supply, the Kyoto Protocol, and concerns about climate change, as well as improved cost competitiveness of PV versus other energy sources.[23] At the turn of the century, the adoption of subsidy mechanisms and policies of support for renewable energies, which gave them priority access to the grid, exponentially increased the development of photovoltaic energy, first in Europe and then in the rest of the world. Concentrated solar thermal power (CSP), however, although it has also progressed in recent decades, still represents a small fraction of the global contribution of solar energy to energy supply.

Classification by technologies and their corresponding more general use:.

Passive solar technology is the set of techniques aimed at harnessing solar energy directly, without transforming it into another type of energy, for immediate use or storage without the need for mechanical systems or external energy input, although they can be complemented by them, for example for regulation.

Passive solar technology includes systems with direct and indirect gain for space heating, thermosyphon-based water heating systems, the use of thermal mass and phase change materials to smooth out air temperature fluctuations, solar cookers, solar chimneys to improve natural ventilation#Types_of_Ventilation##Natural_Ventilation "Ventilation (architecture)") and the earth's shelter itself.

Bioclimatic architecture is the application of this principle to building design. The energy is not used through industrialized collectors, but rather the construction elements themselves that absorb the energy during the day and redistribute it at night.

Contenido

La energía solar térmica (o energía termosolar) consiste en el aprovechamiento de la energía del Sol para producir calor que puede aprovecharse para cocinar alimentos o para la producción de agua caliente destinada al consumo de agua doméstico, ya sea agua caliente sanitaria, calefacción, o para producción de energía mecánica y, a partir de ella, de energía eléctrica. Adicionalmente puede emplearse para alimentar una máquina de refrigeración por absorción, que emplea calor en lugar de electricidad para producir frío con el que se puede acondicionar el aire de los locales.

Los colectores de energía solar térmica están clasificados como colectores de baja, media y alta temperatura:.

Low temperature solar thermal energy

A low temperature solar thermal installation is made up of solar collectors, a primary and secondary circuit, heat exchanger, accumulator, expansion vessel and pipes. If the system works using a thermosiphon, it will be the difference in density due to a change in temperature that will move the fluid. If the system is forced, then it will also be necessary to provide the system with a circulation pump and a control system.

Solar collectors are the elements that capture solar radiation and convert it into thermal energy, heat. Flat plate solar collectors, vacuum tube collectors, and unprotected, uninsulated solar collectors are known as solar collectors. Flat (or flat plate) collection systems with a glass cover are the most common in the production of domestic hot water ACS. The glass allows the Sun's rays to pass through, these heat metal tubes that transmit heat to the liquid inside. The tubes are dark in color, since dark surfaces heat up more.

The glass that covers the collector not only protects the installation but also allows heat to be conserved, producing a greenhouse effect that improves the performance of the collector.

They are made up of a closed aluminum casing resistant to marine environments, an aluminum frame, a silicone-free perimeter gasket, thermal insulation (normally rock wool), a cover of highly transparent solar glass, and finally by welded tubes that conduct the heat-carrying fluid to the inside and outside of the collector.

Solar collectors are made up of the following elements:.

Medium temperature solar thermal energy

Medium temperature installations can use several designs, the most common designs are: pressurized glycol, back drain, batch systems, and newer low pressure freeze tolerant systems using water containing polymer tubing with photovoltaic pumping. European and international standards are being revised to include innovations in design and operation of medium temperature collectors. Operational innovations include the operation of "permanently wet collectors." This technique reduces or even eliminates the occurrence of high temperature non-flow stresses known as stagnation, which reduce the expected life of these collectors.

High temperature solar thermal energy

Temperatures below 95 °C are sufficient for space heating, in which case non-concentrating type flat collectors are generally used. Due to the relatively high heat losses through the glass, flat collectors fail to reach much above 200°C even when the transfer fluid is stagnant. Such temperatures are too low to be used for efficient conversion into electricity.

The efficiency of heat engines increases with the temperature of the heat source. To achieve this in thermal power plants, solar radiation is concentrated through mirrors or lenses to achieve high temperatures using a technology called concentrated solar power (CSP). The practical effect of the greater efficiencies is the reduction in the size of the plant's collectors and the use of land per unit of energy generated, reducing the environmental impact of a power plant as well as its cost.

As the temperature increases, different forms of conversion become practical. Up to 600°C, steam turbines, the standard technology, have an efficiency of up to 41%. Above 600°C, gas turbines can be more efficient. Higher temperatures are problematic and different materials and techniques are needed. One proposal for very high temperatures is to use liquid fluoride salts operating at temperatures between 700 °C to 800 °C, using multi-stage turbine systems to achieve thermal efficiencies of 50% or more.[27] Higher operating temperatures allow the plant to use high-temperature dry heat exchangers for its thermal exhaust, reducing the plant's water use, this being critical for plants located in deserts to be practical. High temperatures also make heat storage more efficient, since more watt-hours are stored per unit of fluid.

Since a concentrating solar power (CSP) plant first generates heat, it can store that heat before converting it into electricity. With current technology, heat storage is much cheaper than electricity storage. In this way, a CSP plant can produce electricity during the day and night. If the location of the CSP plant has predictable solar radiation, then the plant becomes a reliable power generation facility.

Heat accumulation and exchange

Heat storage allows solar thermal plants to produce electricity during daylight hours without sunlight or at night. This allows the use of solar energy for base load generation as well as peak power generation, with the potential to replace fossil fuel-burning plants. Additionally, the use of accumulators reduces the cost of electricity generated with this type of solar power plants.

Heat is transferred to a thermal storage medium in an insulated tank during daylight hours and is recovered for electricity generation at night. Thermal storage media include pressurized steam, concrete, a variety of phase change materials, and molten salts such as calcium, sodium, and potassium nitrate.[28]​[29]​.

La energía solar fotovoltaica consiste en la obtención de electricidad[30]​ directamente a partir de la radiación solar mediante un dispositivo semiconductor denominado célula fotovoltaica, o bien mediante una deposición de metales sobre un sustrato denominada célula solar de película fina.[31]​.

Photovoltaic solar panels

A photovoltaic panel consists of an association of cells, encapsulated in two layers of EVA (ethylene-vinyl-acetate), between a front sheet of glass and a back layer of a thermoplastic polymer (usually tedlar).[32] This assembly is framed in an aluminum structure with the aim of increasing the mechanical resistance of the assembly and facilitating the anchoring of the module to the support structures.[32]​.

The most commonly used cells in photovoltaic panels are silicon, and can be divided into three subcategories:

The standardized parameter to classify the power of a photovoltaic panel is called peak power, and corresponds to the maximum power that the module can deliver under standardized conditions, which are:

Typical efficiencies of a polycrystalline silicon photovoltaic cell range between 14%-20%. For monocrystalline silicon cells, the values ​​range between 15%-21%.[36]​[37]​ The highest are achieved with low-temperature thermal solar collectors (which can reach 70% efficiency in the transfer of solar to thermal energy).

Photovoltaic solar panels do not produce heat that can be reused - although there are lines of research on hybrid panels that allow the generation of electrical and thermal energy simultaneously. However, they are very appropriate for rural electrification projects in areas that do not have an electrical grid, simple rooftop installations and photovoltaic self-consumption.

Development of photovoltaic solar energy in the world

Due to the growing demand for renewable energy, the manufacturing of solar cells and photovoltaic installations has advanced considerably in recent years.[38]​

[39]​ Photovoltaic solar energy was traditionally used since its popularization in the late 1970s to power countless autonomous devices, to supply shelters or houses isolated from the electrical grid, but above all, increasingly in recent years,[40]​ to produce electricity on a large scale through distribution networks, either by injection into the grid or for domestic self-consumption.

Germany is, along with Japan, China and the United States, one of the countries where photovoltaics is experiencing the most rapid growth. By the end of 2015, nearly 230 GW of photovoltaic power had been installed worldwide,[41]​ making photovoltaics the third most important source of renewable energy in terms of installed capacity globally, after hydroelectric and wind energy, and already represents a significant fraction of the electricity mix in the European Union, covering on average 3.5% of electricity demand and reaching 7% in peak periods. production.[41]​.

The considerable installed power in Germany (38 GW in 2014) has set several records in recent years. In June 2014, it produced up to 50.6% of all the country's electricity demand during a single day, reaching an instantaneous power above 24 GW,[42][43][44]​ which is equivalent to the generating power of almost 25 nuclear power plants working at full capacity.[45]​.

Photovoltaic self-consumption and grid parity

Photovoltaic self-consumption consists of the small-scale individual production of electricity for one's own consumption, through solar panels. This can be complemented with the net balance. This production scheme, which allows electricity consumption to be offset by what is generated by a photovoltaic installation at times of lower consumption, has already been successfully implemented in many countries. It was proposed in Spain by the photovoltaic association ASIF to promote renewable electricity without the need for additional financial support.[48]​ The net balance was in the project phase by the IDAE.[49]​ and has been included in the Renewable Energy Plan 2011-2020[50]​ and Royal Decree 1699/2011, of November 18, which regulates the connection to the grid of electrical energy production facilities of small power.[51]​.

To encourage the development of technology with a view to achieving grid parity - equalizing the price of obtaining energy to that of other currently more economical sources - there are production bonuses, which guarantee a fixed purchase price by the electrical network. This is the case of Germany, Italy or Spain. This incentive scheme has already borne fruit, bringing the costs of photovoltaic energy below the sales price of traditional electricity in a growing number of regions.

The energy of the future

According to Greenpeace reports, photovoltaics will be able to supply electricity to two-thirds of the world's population in 2030.[52]​ And according to a study published in 2007 by the World Energy Council, by the year 2100, 70% of the energy consumed will be of solar origin.[53]​.

On the other hand, some countries, such as Tokelau, an archipelago located in the Pacific Ocean, do not have an electricity mix, since they obtain all the electricity they need from the sun.[54]​ The country is made up of about 125 islets that cover an area of 10 km² and has about 1,500 inhabitants.[55]​ The geographical location of the archipelago makes the use of fossil fuels comparatively much more expensive and difficult to implement. maintain than a photovoltaic system.

The Tokelau facility is an example that other countries in Oceania have already taken note of. In fact, the neighboring Cook Islands and the Tuvalu archipelago also intend to be completely supplied with renewable energy by 2020.[54]​.

Net balance and costs

Photovoltaic self-consumption consists of the small-scale individual production of electricity for one's own consumption, through renewable electricity equipment (photovoltaic solar panels, wind turbines), some of which are self-installable. It can be complemented with the net balance in autonomous installations or facilitate energy independence (disconnected installations).[56]​[57]​.

The net balance allows the excess produced by a self-consumption system to be poured into the electrical grid in order to be able to use that excess at another time. In this way, the electric company that provides the electricity when the demand is higher than the production of the self-consumption system, will deduct the excesses discharged into the network consumption from the bill.

In recent years, due to the growing rise of small renewable energy installations, self-consumption with net balance has begun to be regulated in various countries around the world, being a reality in countries such as Germany, Italy, Denmark, Japan, Australia, the United States, Canada and Mexico, among others, due in part to the constant drop in the cost of photovoltaic modules. To help achieve this goal, many countries are also launching grants, subsidies[58]​ or tax aid to help citizens and companies finance these types of facilities.

In 2013, the price of solar modules had fallen by 80% in 5 years, putting solar energy for the first time in a competitive position with the price of electricity paid by the consumer in a good number of sunny countries. The average cost of electricity generation from solar photovoltaic energy is already competitive with that of conventional energy sources in a growing list of countries,[59]​ particularly when considering the time of generation of such energy, as electricity is usually more expensive during the day.[60]​ There has been stiff competition in the production chain, and further falls in the cost of photovoltaic energy are expected in the coming years, posing a growing threat to the dominance of solar-based generation sources. fossil energies.[61]​ As time goes by, renewable generation technologies are generally cheaper,[62][63]​ while fossil energies become more expensive:.

In 2011, the cost of photovoltaics had fallen well below that of nuclear energy, and is expected to continue falling:[65]​.

The trend is for prices to decrease further over time once photovoltaic components have entered a clear and direct industrial phase.[67]​.

The Earth receives 174 petawatts of incoming solar radiation (insolation) from the uppermost layer of the atmosphere.[6] Approximately 30% returns to space, while clouds, oceans, and land masses absorb the remainder. The electromagnetic spectrum of sunlight on the Earth's surface is mainly occupied by visible light and the infrared ranges with a small part of ultraviolet radiation.[7]​.

The power of the radiation varies depending on the time of day, the atmospheric conditions that attenuate it, and the latitude. Under acceptable radiation conditions, the power is approximately equivalent to 1000 W/m² at the Earth's surface. This power is called irradiance. Note that in global terms practically all the radiation received is reemitted into space (otherwise abrupt warming would occur). However, there is a notable difference between the radiation received and that emitted.

Radiation is usable in its direct and diffuse components, or in the sum of both. Direct radiation is that which arrives directly from the solar source, without intermediate reflections or refractions. The diurnal sky emits diffuse radiation due to the multiple phenomena of solar reflection and refraction in the atmosphere, in clouds and the rest of the atmospheric and terrestrial elements. Direct radiation can be reflected and concentrated for use, while diffuse light coming from all directions cannot be concentrated.

The normal direct irradiance (or perpendicular to the sun's rays) outside the atmosphere is called the solar constant and has an average value of 1366 W/m² (which corresponds to a maximum value at perihelion of 1395 W/m² and a minimum value at aphelion of 1308 W/m²).

The radiation absorbed by the oceans, clouds, air and land masses increases their temperature. Heated air is that which contains evaporated water that rises from the oceans, and also in part from the continents, causing atmospheric circulation or convection. When the air rises to the upper layers, where the temperature is low, its temperature decreases until the water vapor condenses, forming clouds. The latent heat of water condensation amplifies convection, producing phenomena such as wind, storms and anticyclones.[8]​ The solar energy absorbed by the oceans and land masses keeps the surface at 14 °C.[9]​ For the photosynthesis of green plants, solar energy is converted into chemical energy, which produces food, wood and biomass, from which fossil fuels are also derived.[10]​.

It is estimated that the total energy absorbed by the atmosphere, oceans and continents may be 3,850,000 exajoules "Joule (unit)") per year.[11]​ In 2002, this energy in one hour was equivalent to the world's global energy consumption for one year.[16][17] Photosynthesis captures approximately 3,000 EJ per year in biomass, which represents only 0.08% of the energy received by the Earth.[13]​ The amount of solar energy received annually is so vast that it is equivalent to approximately double all the energy ever produced by other non-renewable energy sources such as oil, coal, uranium and natural gas.

Dawn of solar technology

The early development of solar technologies, beginning in the 1860s, was motivated by the expectation that coal would soon become scarce. However, the development of solar energy stalled at the turn of the century due to the increasing availability and economies of scale of non-renewable sources such as coal and oil.[18] In 1974, it was estimated that only six private homes in all of North America were powered by solar systems.[19] However, the 1973 oil crisis and the 1979 crisis caused a major shift in energy policy around the world and brought it back into focus. of attention on emerging solar technologies.[20]​[21]​ The first development strategies were developed, focused on incentive programs such as the Federal Photovoltaic Utilization Program in the United States and the Sunshine Program in Japan. Other efforts included the creation of research organizations in the United States (NREL), Japan (NEDO), and Germany (Fraunhofer–ISE).[22] Between 1970 and 1983, installations of photovoltaic systems grew rapidly, but the drop in oil prices in the 1980s moderated the growth of solar energy between 1984 and 1996.

From 1998 to today

In the mid-1990s, the development of residential and commercial rooftop PV, as well as grid-connected plants, began to accelerate due to growing concerns over oil and natural gas supply, the Kyoto Protocol, and concerns about climate change, as well as improved cost competitiveness of PV versus other energy sources.[23] At the turn of the century, the adoption of subsidy mechanisms and policies of support for renewable energies, which gave them priority access to the grid, exponentially increased the development of photovoltaic energy, first in Europe and then in the rest of the world. Concentrated solar thermal power (CSP), however, although it has also progressed in recent decades, still represents a small fraction of the global contribution of solar energy to energy supply.

Classification by technologies and their corresponding more general use:.

Passive solar technology is the set of techniques aimed at harnessing solar energy directly, without transforming it into another type of energy, for immediate use or storage without the need for mechanical systems or external energy input, although they can be complemented by them, for example for regulation.

Passive solar technology includes systems with direct and indirect gain for space heating, thermosyphon-based water heating systems, the use of thermal mass and phase change materials to smooth out air temperature fluctuations, solar cookers, solar chimneys to improve natural ventilation#Types_of_Ventilation##Natural_Ventilation "Ventilation (architecture)") and the earth's shelter itself.

Bioclimatic architecture is the application of this principle to building design. The energy is not used through industrialized collectors, but rather the construction elements themselves that absorb the energy during the day and redistribute it at night.

Contenido

La energía solar térmica (o energía termosolar) consiste en el aprovechamiento de la energía del Sol para producir calor que puede aprovecharse para cocinar alimentos o para la producción de agua caliente destinada al consumo de agua doméstico, ya sea agua caliente sanitaria, calefacción, o para producción de energía mecánica y, a partir de ella, de energía eléctrica. Adicionalmente puede emplearse para alimentar una máquina de refrigeración por absorción, que emplea calor en lugar de electricidad para producir frío con el que se puede acondicionar el aire de los locales.

Los colectores de energía solar térmica están clasificados como colectores de baja, media y alta temperatura:.

Low temperature solar thermal energy

A low temperature solar thermal installation is made up of solar collectors, a primary and secondary circuit, heat exchanger, accumulator, expansion vessel and pipes. If the system works using a thermosiphon, it will be the difference in density due to a change in temperature that will move the fluid. If the system is forced, then it will also be necessary to provide the system with a circulation pump and a control system.

Solar collectors are the elements that capture solar radiation and convert it into thermal energy, heat. Flat plate solar collectors, vacuum tube collectors, and unprotected, uninsulated solar collectors are known as solar collectors. Flat (or flat plate) collection systems with a glass cover are the most common in the production of domestic hot water ACS. The glass allows the Sun's rays to pass through, these heat metal tubes that transmit heat to the liquid inside. The tubes are dark in color, since dark surfaces heat up more.

The glass that covers the collector not only protects the installation but also allows heat to be conserved, producing a greenhouse effect that improves the performance of the collector.

They are made up of a closed aluminum casing resistant to marine environments, an aluminum frame, a silicone-free perimeter gasket, thermal insulation (normally rock wool), a cover of highly transparent solar glass, and finally by welded tubes that conduct the heat-carrying fluid to the inside and outside of the collector.

Solar collectors are made up of the following elements:.

Medium temperature solar thermal energy

Medium temperature installations can use several designs, the most common designs are: pressurized glycol, back drain, batch systems, and newer low pressure freeze tolerant systems using water containing polymer tubing with photovoltaic pumping. European and international standards are being revised to include innovations in design and operation of medium temperature collectors. Operational innovations include the operation of "permanently wet collectors." This technique reduces or even eliminates the occurrence of high temperature non-flow stresses known as stagnation, which reduce the expected life of these collectors.

High temperature solar thermal energy

Temperatures below 95 °C are sufficient for space heating, in which case non-concentrating type flat collectors are generally used. Due to the relatively high heat losses through the glass, flat collectors fail to reach much above 200°C even when the transfer fluid is stagnant. Such temperatures are too low to be used for efficient conversion into electricity.

The efficiency of heat engines increases with the temperature of the heat source. To achieve this in thermal power plants, solar radiation is concentrated through mirrors or lenses to achieve high temperatures using a technology called concentrated solar power (CSP). The practical effect of the greater efficiencies is the reduction in the size of the plant's collectors and the use of land per unit of energy generated, reducing the environmental impact of a power plant as well as its cost.

As the temperature increases, different forms of conversion become practical. Up to 600°C, steam turbines, the standard technology, have an efficiency of up to 41%. Above 600°C, gas turbines can be more efficient. Higher temperatures are problematic and different materials and techniques are needed. One proposal for very high temperatures is to use liquid fluoride salts operating at temperatures between 700 °C to 800 °C, using multi-stage turbine systems to achieve thermal efficiencies of 50% or more.[27] Higher operating temperatures allow the plant to use high-temperature dry heat exchangers for its thermal exhaust, reducing the plant's water use, this being critical for plants located in deserts to be practical. High temperatures also make heat storage more efficient, since more watt-hours are stored per unit of fluid.

Since a concentrating solar power (CSP) plant first generates heat, it can store that heat before converting it into electricity. With current technology, heat storage is much cheaper than electricity storage. In this way, a CSP plant can produce electricity during the day and night. If the location of the CSP plant has predictable solar radiation, then the plant becomes a reliable power generation facility.

Heat accumulation and exchange

Heat storage allows solar thermal plants to produce electricity during daylight hours without sunlight or at night. This allows the use of solar energy for base load generation as well as peak power generation, with the potential to replace fossil fuel-burning plants. Additionally, the use of accumulators reduces the cost of electricity generated with this type of solar power plants.

Heat is transferred to a thermal storage medium in an insulated tank during daylight hours and is recovered for electricity generation at night. Thermal storage media include pressurized steam, concrete, a variety of phase change materials, and molten salts such as calcium, sodium, and potassium nitrate.[28]​[29]​.

La energía solar fotovoltaica consiste en la obtención de electricidad[30]​ directamente a partir de la radiación solar mediante un dispositivo semiconductor denominado célula fotovoltaica, o bien mediante una deposición de metales sobre un sustrato denominada célula solar de película fina.[31]​.

Photovoltaic solar panels

A photovoltaic panel consists of an association of cells, encapsulated in two layers of EVA (ethylene-vinyl-acetate), between a front sheet of glass and a back layer of a thermoplastic polymer (usually tedlar).[32] This assembly is framed in an aluminum structure with the aim of increasing the mechanical resistance of the assembly and facilitating the anchoring of the module to the support structures.[32]​.

The most commonly used cells in photovoltaic panels are silicon, and can be divided into three subcategories:

The standardized parameter to classify the power of a photovoltaic panel is called peak power, and corresponds to the maximum power that the module can deliver under standardized conditions, which are:

Typical efficiencies of a polycrystalline silicon photovoltaic cell range between 14%-20%. For monocrystalline silicon cells, the values ​​range between 15%-21%.[36]​[37]​ The highest are achieved with low-temperature thermal solar collectors (which can reach 70% efficiency in the transfer of solar to thermal energy).

Photovoltaic solar panels do not produce heat that can be reused - although there are lines of research on hybrid panels that allow the generation of electrical and thermal energy simultaneously. However, they are very appropriate for rural electrification projects in areas that do not have an electrical grid, simple rooftop installations and photovoltaic self-consumption.

Development of photovoltaic solar energy in the world

Due to the growing demand for renewable energy, the manufacturing of solar cells and photovoltaic installations has advanced considerably in recent years.[38]​

[39]​ Photovoltaic solar energy was traditionally used since its popularization in the late 1970s to power countless autonomous devices, to supply shelters or houses isolated from the electrical grid, but above all, increasingly in recent years,[40]​ to produce electricity on a large scale through distribution networks, either by injection into the grid or for domestic self-consumption.

Germany is, along with Japan, China and the United States, one of the countries where photovoltaics is experiencing the most rapid growth. By the end of 2015, nearly 230 GW of photovoltaic power had been installed worldwide,[41]​ making photovoltaics the third most important source of renewable energy in terms of installed capacity globally, after hydroelectric and wind energy, and already represents a significant fraction of the electricity mix in the European Union, covering on average 3.5% of electricity demand and reaching 7% in peak periods. production.[41]​.

The considerable installed power in Germany (38 GW in 2014) has set several records in recent years. In June 2014, it produced up to 50.6% of all the country's electricity demand during a single day, reaching an instantaneous power above 24 GW,[42][43][44]​ which is equivalent to the generating power of almost 25 nuclear power plants working at full capacity.[45]​.

Photovoltaic self-consumption and grid parity

Photovoltaic self-consumption consists of the small-scale individual production of electricity for one's own consumption, through solar panels. This can be complemented with the net balance. This production scheme, which allows electricity consumption to be offset by what is generated by a photovoltaic installation at times of lower consumption, has already been successfully implemented in many countries. It was proposed in Spain by the photovoltaic association ASIF to promote renewable electricity without the need for additional financial support.[48]​ The net balance was in the project phase by the IDAE.[49]​ and has been included in the Renewable Energy Plan 2011-2020[50]​ and Royal Decree 1699/2011, of November 18, which regulates the connection to the grid of electrical energy production facilities of small power.[51]​.

To encourage the development of technology with a view to achieving grid parity - equalizing the price of obtaining energy to that of other currently more economical sources - there are production bonuses, which guarantee a fixed purchase price by the electrical network. This is the case of Germany, Italy or Spain. This incentive scheme has already borne fruit, bringing the costs of photovoltaic energy below the sales price of traditional electricity in a growing number of regions.

The energy of the future

According to Greenpeace reports, photovoltaics will be able to supply electricity to two-thirds of the world's population in 2030.[52]​ And according to a study published in 2007 by the World Energy Council, by the year 2100, 70% of the energy consumed will be of solar origin.[53]​.

On the other hand, some countries, such as Tokelau, an archipelago located in the Pacific Ocean, do not have an electricity mix, since they obtain all the electricity they need from the sun.[54]​ The country is made up of about 125 islets that cover an area of 10 km² and has about 1,500 inhabitants.[55]​ The geographical location of the archipelago makes the use of fossil fuels comparatively much more expensive and difficult to implement. maintain than a photovoltaic system.

The Tokelau facility is an example that other countries in Oceania have already taken note of. In fact, the neighboring Cook Islands and the Tuvalu archipelago also intend to be completely supplied with renewable energy by 2020.[54]​.

Net balance and costs

Photovoltaic self-consumption consists of the small-scale individual production of electricity for one's own consumption, through renewable electricity equipment (photovoltaic solar panels, wind turbines), some of which are self-installable. It can be complemented with the net balance in autonomous installations or facilitate energy independence (disconnected installations).[56]​[57]​.

The net balance allows the excess produced by a self-consumption system to be poured into the electrical grid in order to be able to use that excess at another time. In this way, the electric company that provides the electricity when the demand is higher than the production of the self-consumption system, will deduct the excesses discharged into the network consumption from the bill.

In recent years, due to the growing rise of small renewable energy installations, self-consumption with net balance has begun to be regulated in various countries around the world, being a reality in countries such as Germany, Italy, Denmark, Japan, Australia, the United States, Canada and Mexico, among others, due in part to the constant drop in the cost of photovoltaic modules. To help achieve this goal, many countries are also launching grants, subsidies[58]​ or tax aid to help citizens and companies finance these types of facilities.

In 2013, the price of solar modules had fallen by 80% in 5 years, putting solar energy for the first time in a competitive position with the price of electricity paid by the consumer in a good number of sunny countries. The average cost of electricity generation from solar photovoltaic energy is already competitive with that of conventional energy sources in a growing list of countries,[59]​ particularly when considering the time of generation of such energy, as electricity is usually more expensive during the day.[60]​ There has been stiff competition in the production chain, and further falls in the cost of photovoltaic energy are expected in the coming years, posing a growing threat to the dominance of solar-based generation sources. fossil energies.[61]​ As time goes by, renewable generation technologies are generally cheaper,[62][63]​ while fossil energies become more expensive:.

In 2011, the cost of photovoltaics had fallen well below that of nuclear energy, and is expected to continue falling:[65]​.

The trend is for prices to decrease further over time once photovoltaic components have entered a clear and direct industrial phase.[67]​.