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122-453: PPC was founded by the Greek government in 1950. Its main purpose was to plan and apply a national energy policy which, through the exploitation of the domestic products and resources, would distribute cheap electric power to all Greek citizens. PPC started the integration of all the small local grids to the national interconnected grid. Furthermore, the corporation resolved the purchase of all

244-548: A basal metabolic rate of 80 watts. For example, if our bodies run (on average) at 80 watts, then a light bulb running at 100 watts is running at 1.25 human equivalents (100 ÷ 80) i.e. 1.25 H-e. For a difficult task of only a few seconds' duration, a person can put out thousands of watts, many times the 746 watts in one official horsepower. For tasks lasting a few minutes, a fit human can generate perhaps 1,000 watts. For an activity that must be sustained for an hour, output drops to around 300; for an activity kept up all day, 150 watts

366-462: A battery (from chemical energy to electric energy ), a dam (from gravitational potential energy to kinetic energy of moving water (and the blades of a turbine ) and ultimately to electric energy through an electric generator ), and a heat engine (from heat to work). Examples of energy transformation include generating electric energy from heat energy via a steam turbine, or lifting an object against gravity using electrical energy driving

488-413: A photovoltaic system , or PV system, produces direct current (DC) power which fluctuates with the sunlight's intensity. For practical use this usually requires conversion to alternating current (AC), through the use of inverters . Multiple solar cells are connected inside panels. Panels are wired together to form arrays, then tied to an inverter, which produces power at the desired voltage, and for AC,

610-440: A 470ha wind farm in the communes of Dorobanțu and Topolog generates more than 200GWh per year. PPC Renewables, a subsidiary of Public Power Corporation as of March 2024 operates a fleet of renewable power plants with a capacity of more than 700 MW, with a portfolio of 1 GW of projects under construction, and plans to expand its renewable energy and energy storage portfolio to a total capacity of 5 GW by 2029. The company under

732-435: A Lagrangian; for example, dissipative systems with continuous symmetries need not have a corresponding conservation law. In the context of chemistry , energy is an attribute of a substance as a consequence of its atomic, molecular, or aggregate structure. Since a chemical transformation is accompanied by a change in one or more of these kinds of structure, it is usually accompanied by a decrease, and sometimes an increase, of

854-474: A biological cell or organelle of a biological organism. Energy used in respiration is stored in substances such as carbohydrates (including sugars), lipids , and proteins stored by cells . In human terms, the human equivalent (H-e) (Human energy conversion) indicates, for a given amount of energy expenditure, the relative quantity of energy needed for human metabolism , using as a standard an average human energy expenditure of 12,500 kJ per day and

976-515: A bound system is discrete (a set of permitted states, each characterized by an energy level ) which results in the concept of quanta . In the solution of the Schrödinger equation for any oscillator (vibrator) and for electromagnetic waves in a vacuum, the resulting energy states are related to the frequency by Planck's relation : E = h ν {\displaystyle E=h\nu } (where h {\displaystyle h}

1098-596: A contract for the construction of a conveyor-belt system for waste produced at its generating plant in Megalopolis without following correct advertising procedures under EU public procurement law . The need for the system had arisen following an environmental impact assessment , after which the Greek Ministry of the Environment, Urban Planning and Public Works had imposed a deadline of December 2000 for

1220-417: A core concept. Work , a function of energy, is force times distance. This says that the work ( W {\displaystyle W} ) is equal to the line integral of the force F along a path C ; for details see the mechanical work article. Work and thus energy is frame dependent . For example, consider a ball being hit by a bat. In the center-of-mass reference frame, the bat does no work on

1342-492: A crane motor. Lifting against gravity performs mechanical work on the object and stores gravitational potential energy in the object. If the object falls to the ground, gravity does mechanical work on the object which transforms the potential energy in the gravitational field to the kinetic energy released as heat on impact with the ground. The Sun transforms nuclear potential energy to other forms of energy; its total mass does not decrease due to that itself (since it still contains

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1464-556: A few exceptions, like those generated by volcanic events for example. An example of a solar-mediated weather event is a hurricane, which occurs when large unstable areas of warm ocean, heated over months, suddenly give up some of their thermal energy to power a few days of violent air movement. In a slower process, radioactive decay of atoms in the core of the Earth releases heat. This thermal energy drives plate tectonics and may lift mountains, via orogenesis . This slow lifting represents

1586-474: A given temperature  T . This exponential dependence of a reaction rate on temperature is known as the Arrhenius equation . The activation energy necessary for a chemical reaction can be provided in the form of thermal energy. In biology , energy is an attribute of all biological systems, from the biosphere to the smallest living organism. Within an organism it is responsible for growth and development of

1708-496: A growing number of countries and regions all over the world. The largest manufacturers of solar equipment were based in China. Although concentrated solar power capacity grew more than tenfold, it remained a tiny proportion of the total, because the cost of utility-scale solar PV fell by 85% between 2010 and 2020, while CSP costs only fell 68% in the same timeframe. Despite the rising cost of materials, such as polysilicon , during

1830-587: A high specific heat capacity, and can deliver heat at temperatures compatible with conventional power systems. This method of energy storage is used, for example, by the Solar Two power station, allowing it to store 1.44  TJ in its 68 m storage tank, enough to provide full output for close to 39 hours, with an efficiency of about 99%. In stand alone PV systems , batteries are traditionally used to store excess electricity. With grid-connected photovoltaic power systems , excess electricity can be sent to

1952-477: A kind of gravitational potential energy storage of the thermal energy, which may later be transformed into active kinetic energy during landslides, after a triggering event. Earthquakes also release stored elastic potential energy in rocks, a store that has been produced ultimately from the same radioactive heat sources. Thus, according to present understanding, familiar events such as landslides and earthquakes release energy that has been stored as potential energy in

2074-572: A large area of sunlight to a hot spot, often to drive a steam turbine . Photovoltaics (PV) were initially solely used as a source of electricity for small and medium-sized applications, from the calculator powered by a single solar cell to remote homes powered by an off-grid rooftop PV system. Commercial concentrated solar power plants were first developed in the 1980s. Since then, as the cost of solar panels has fallen, grid-connected solar PV systems ' capacity and production has doubled about every three years . Three-quarters of new generation capacity

2196-691: A limited effect on the users, but their effect on self-consumption of solar power may be limited. The original political purpose of incentive policies for PV was to facilitate an initial small-scale deployment to begin to grow the industry, even where the cost of PV was significantly above grid parity, to allow the industry to achieve the economies of scale necessary to reach grid parity. Since reaching grid parity, some policies are implemented to promote national energy independence, high tech job creation and reduction of CO 2 emissions. Financial incentives for photovoltaics differ across countries, including Australia , China , Germany , India , Japan , and

2318-490: A local user or users. Utility-scale solar is sometimes used to describe this type of project. This approach differs from concentrated solar power , the other major large-scale solar generation technology, which uses heat to drive a variety of conventional generator systems. Both approaches have their own advantages and disadvantages, but to date, for a variety of reasons, photovoltaic technology has seen much wider use. As of 2019 , about 97% of utility-scale solar power capacity

2440-504: A measure more directly comparable to other forms of power generation. Most solar parks are developed at a scale of at least 1 MW p . As of 2018, the world's largest operating photovoltaic power stations surpassed 1 gigawatt . At the end of 2019, about 9,000 solar farms were larger than 4 MW AC (utility scale), with a combined capacity of over 220 GW AC . Commercial concentrating solar power (CSP) plants, also called "solar thermal power stations", were first developed in

2562-579: A rate ranging from wholesale to retail rate or above, as can be excess annual credits. A community solar project is a solar power installation that accepts capital from and provides output credit and tax benefits to multiple customers, including individuals, businesses, nonprofits, and other investors. Participants typically invest in or subscribe to a certain kW capacity or kWh generation of remote electrical production. In some countries tariffs (import taxes) are imposed on imported solar panels. The overwhelming majority of electricity produced worldwide

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2684-425: A system. This property is responsible for the inertia and strength of gravitational interaction of the system ("mass manifestations"), and is also responsible for the potential ability of the system to perform work or heating ("energy manifestations"), subject to the limitations of other physical laws. In classical physics , energy is a scalar quantity, the canonical conjugate to time. In special relativity energy

2806-463: A tenth of their electricity from solar, with China making up more than half of solar growth. Almost half the solar power installed in 2022 was mounted on rooftops . Much more low-carbon power is needed for electrification and to limit climate change . The International Energy Agency said in 2022 that more effort was needed for grid integration and the mitigation of policy, regulation and financing challenges. Nevertheless solar may greatly cut

2928-440: A thin coating of boron. The “Bell Solar Battery” was described as 6% efficient, with a square yard of the panels generating 50 watts. The first satellite with solar panels was launched in 1957 . By the 1970s, solar panels were still too expensive for much other than satellites . In 1974 it was estimated that only six private homes in all of North America were entirely heated or cooled by functional solar power systems. However,

3050-426: A tiny fraction of the original chemical energy is used for work : It would appear that living organisms are remarkably inefficient (in the physical sense) in their use of the energy they receive (chemical or radiant energy); most machines manage higher efficiencies. In growing organisms the energy that is converted to heat serves a vital purpose, as it allows the organism tissue to be highly ordered with regard to

3172-492: Is transferred to a body or to a physical system , recognizable in the performance of work and in the form of heat and light . Energy is a conserved quantity —the law of conservation of energy states that energy can be converted in form, but not created or destroyed; matter and energy may also be converted to one another. The unit of measurement for energy in the International System of Units (SI)

3294-467: Is (or is predicted to become) the cheapest source of energy in all of Central America, Africa, the Middle East, India, South-east Asia, Australia, and several other regions. Different measurements of solar irradiance (direct normal irradiance, global horizontal irradiance) are mapped below: In cases of self-consumption of solar energy, the payback time is calculated based on how much electricity

3416-481: Is a derived unit that is equal to the energy expended, or work done, in applying a force of one newton through a distance of one metre. However energy can also be expressed in many other units not part of the SI, such as ergs , calories , British thermal units , kilowatt-hours and kilocalories , which require a conversion factor when expressed in SI units. The SI unit of power , defined as energy per unit of time,

3538-497: Is a type of solar cell that includes a perovskite-structured compound, most commonly a hybrid organic–inorganic lead or tin halide-based material as the light-harvesting active layer. Perovskite materials, such as methylammonium lead halides and all-inorganic cesium lead halide, are cheap to produce and simple to manufacture. Concentrated solar power (CSP), also called "concentrated solar thermal", uses lenses or mirrors and tracking systems to concentrate sunlight, then uses

3660-460: Is about the maximum. The human equivalent assists understanding of energy flows in physical and biological systems by expressing energy units in human terms: it provides a "feel" for the use of a given amount of energy. Sunlight's radiant energy is also captured by plants as chemical potential energy in photosynthesis , when carbon dioxide and water (two low-energy compounds) are converted into carbohydrates, lipids, proteins and oxygen. Release of

3782-434: Is also a scalar (although not a Lorentz scalar but a time component of the energy–momentum 4-vector ). In other words, energy is invariant with respect to rotations of space , but not invariant with respect to rotations of spacetime (= boosts ). Energy may be transformed between different forms at various efficiencies . Items that transform between these forms are called transducers . Examples of transducers include

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3904-575: Is called the Lagrangian , after Joseph-Louis Lagrange . This formalism is as fundamental as the Hamiltonian, and both can be used to derive the equations of motion or be derived from them. It was invented in the context of classical mechanics , but is generally useful in modern physics. The Lagrangian is defined as the kinetic energy minus the potential energy. Usually, the Lagrange formalism

4026-473: Is defined in terms of the energy operator (Hamiltonian) as a time derivative of the wave function . The Schrödinger equation equates the energy operator to the full energy of a particle or a system. Its results can be considered as a definition of measurement of energy in quantum mechanics. The Schrödinger equation describes the space- and time-dependence of a slowly changing (non-relativistic) wave function of quantum systems. The solution of this equation for

4148-418: Is directly proportional to the mass of the body: E 0 = m 0 c 2 , {\displaystyle E_{0}=m_{0}c^{2},} where For example, consider electron – positron annihilation, in which the rest energy of these two individual particles (equivalent to their rest mass) is converted to the radiant energy of the photons produced in the process. In this system

4270-516: Is either from gravitational collapse of matter (usually molecular hydrogen) into various classes of astronomical objects (stars, black holes, etc.), or from nuclear fusion (of lighter elements, primarily hydrogen). The nuclear fusion of hydrogen in the Sun also releases another store of potential energy which was created at the time of the Big Bang . At that time, according to theory, space expanded and

4392-510: Is extremely large relative to ordinary human scales, the conversion of an everyday amount of rest mass (for example, 1 kg) from rest energy to other forms of energy (such as kinetic energy, thermal energy, or the radiant energy carried by light and other radiation) can liberate tremendous amounts of energy (~ 9 × 10 16 {\displaystyle 9\times 10^{16}} joules = 21 megatons of TNT), as can be seen in nuclear reactors and nuclear weapons. Conversely,

4514-455: Is forecast to be solar, surpassing coal as the largest source of installed power capacity. Utility scale is forecast to become the largest source of electricity in all regions except sub-Saharan Africa by 2050. According to a 2021 study, global electricity generation potential of rooftop solar panels is estimated at 27 PWh per year at costs ranging from $ 40 (Asia) to $ 240 per MWh (US, Europe). Its practical realization will however depend on

4636-571: Is key for high self-consumption. The match can be improved with batteries or controllable electricity consumption. However, batteries are expensive, and profitability may require the provision of other services from them besides self-consumption increase, for example avoiding power outages . Hot water storage tanks with electric heating with heat pumps or resistance heaters can provide low-cost storage for self-consumption of solar power. Shiftable loads, such as dishwashers, tumble dryers and washing machines, can provide controllable consumption with only

4758-623: Is mathematically more convenient than the Hamiltonian for non-conservative systems (such as systems with friction). Noether's theorem (1918) states that any differentiable symmetry of the action of a physical system has a corresponding conservation law. Noether's theorem has become a fundamental tool of modern theoretical physics and the calculus of variations. A generalisation of the seminal formulations on constants of motion in Lagrangian and Hamiltonian mechanics (1788 and 1833, respectively), it does not apply to systems that cannot be modeled with

4880-402: Is no friction or other losses, the conversion of energy between these processes would be perfect, and the pendulum would continue swinging forever. Energy is also transferred from potential energy ( E p {\displaystyle E_{p}} ) to kinetic energy ( E k {\displaystyle E_{k}} ) and then back to potential energy constantly. This

5002-421: Is not purchased from the grid. However, in many cases, the patterns of generation and consumption do not coincide, and some or all of the energy is fed back into the grid. The electricity is sold, and at other times when energy is taken from the grid, electricity is bought. The relative costs and prices obtained affect the economics. In many markets, the price paid for sold PV electricity is significantly lower than

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5124-419: Is owned by PPC, HEDNO S.A. operates independently according to L.4001/2011 and in compliance with 2009/72/EC EU Directive relative to the electricity market organization. On 16 November 2021, the company completed a share capital increase that the Greek government as a shareholder chose not participate in. As a result, the Greek government's shareholding decreased from 51.12% to 34.12%, which is currently held by

5246-695: Is potentially an important issue, particularly in off-grid applications and for future 100% renewable energy scenarios. Solar is intermittent due to the day/night cycles and variable weather conditions. However solar power can be forecast somewhat by time of day, location, and seasons. The challenge of integrating solar power in any given electric utility varies significantly. In places with hot summers and mild winters, solar tends to be well matched to daytime cooling demands. Concentrated solar power plants may use thermal storage to store solar energy, such as in high-temperature molten salts. These salts are an effective storage medium because they are low-cost, have

5368-415: Is referred to as conservation of energy. In this isolated system , energy cannot be created or destroyed; therefore, the initial energy and the final energy will be equal to each other. This can be demonstrated by the following: The equation can then be simplified further since E p = m g h {\displaystyle E_{p}=mgh} (mass times acceleration due to gravity times

5490-489: Is solar, with both millions of rooftop installations and gigawatt-scale photovoltaic power stations continuing to be built. In 2023, solar power generated 5.5% (1,631 TWh) of global electricity and over 1% of primary energy , adding twice as much new electricity as coal. Along with onshore wind power , utility-scale solar is the source with the cheapest levelised cost of electricity for new installations in most countries. As of 2023, 33 countries generated more than

5612-696: Is the Planck constant and ν {\displaystyle \nu } the frequency). In the case of an electromagnetic wave these energy states are called quanta of light or photons . When calculating kinetic energy ( work to accelerate a massive body from zero speed to some finite speed) relativistically – using Lorentz transformations instead of Newtonian mechanics – Einstein discovered an unexpected by-product of these calculations to be an energy term which does not vanish at zero speed. He called it rest energy : energy which every massive body must possess even when being at rest. The amount of energy

5734-624: Is the joule (J). Forms of energy include the kinetic energy of a moving object, the potential energy stored by an object (for instance due to its position in a field ), the elastic energy stored in a solid object, chemical energy associated with chemical reactions , the radiant energy carried by electromagnetic radiation , the internal energy contained within a thermodynamic system , and rest energy associated with an object's rest mass . All living organisms constantly take in and release energy. The Earth's climate and ecosystems processes are driven primarily by radiant energy from

5856-496: Is the watt , which is a joule per second. Thus, one joule is one watt-second, and 3600 joules equal one watt-hour. The CGS energy unit is the erg and the imperial and US customary unit is the foot pound . Other energy units such as the electronvolt , food calorie or thermodynamic kcal (based on the temperature change of water in a heating process), and BTU are used in specific areas of science and commerce. In 1843, French physicist James Prescott Joule , namesake of

5978-445: Is the main input to Earth's energy budget which accounts for its temperature and climate stability. Sunlight may be stored as gravitational potential energy after it strikes the Earth, as (for example when) water evaporates from oceans and is deposited upon mountains (where, after being released at a hydroelectric dam, it can be used to drive turbines or generators to produce electricity). Sunlight also drives most weather phenomena, save

6100-768: Is then used for power generation or energy storage. Thermal storage efficiently allows overnight electricity generation, thus complementing PV. CSP generates a very small share of solar power and in 2022 the IEA said that CSP should be better paid for its storage. As of 2021 the levelized cost of electricity from CSP is over twice that of PV. However, their very high temperatures may prove useful to help decarbonize industries (perhaps via hydrogen) which need to be hotter than electricity can provide. A hybrid system combines solar with energy storage and/or one or more other forms of generation. Hydro, wind and batteries are commonly combined with solar. The combined generation may enable

6222-424: Is transformed to what other kind) is often determined by entropy (equal energy spread among all available degrees of freedom ) considerations. In practice all energy transformations are permitted on a small scale, but certain larger transformations are not permitted because it is statistically unlikely that energy or matter will randomly move into more concentrated forms or smaller spaces. Energy transformations in

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6344-433: Is trapped in a system with zero momentum, where it can be weighed. It is also equivalent to mass, and this mass is always associated with it. Mass is also equivalent to a certain amount of energy, and likewise always appears associated with it, as described in mass–energy equivalence . The formula E  =  mc ², derived by Albert Einstein (1905) quantifies the relationship between relativistic mass and energy within

6466-435: Is used immediately because traditional generators can adapt to demand and storage is usually more expensive. Both solar power and wind power are sources of variable renewable power , meaning that all available output must be used locally, carried on transmission lines to be used elsewhere, or stored (e.g., in a battery). Since solar energy is not available at night, storing it so as to have continuous electricity availability

6588-459: Is worth 100 million euros and the potential joint investment is estimated at more than 1 billion euros. The 34 major thermal and hydroelectric power plants and the 3 wind farms of the interconnected power grid of the mainland, as well as the 60 autonomous power plants located on Crete , Rhodes and other Greek islands (33 thermal , 2 hydroelectric , 18 wind energy and 5 photovoltaic parks) form PPC's industrial assets and constitute

6710-881: The 1973 oil embargo and 1979 energy crisis caused a reorganization of energy policies around the world and brought renewed attention to developing solar technologies. Deployment strategies focused on incentive programs such as the Federal Photovoltaic Utilization Program in the US and the Sunshine Program in Japan. Other efforts included the formation of research facilities in the United States (SERI, now NREL ), Japan ( NEDO ), and Germany ( Fraunhofer ISE ). Between 1970 and 1983 installations of photovoltaic systems grew rapidly. In

6832-463: The 2021–2022 global energy crisis , utility scale solar was still the least expensive energy source in many countries due to the rising costs of other energy sources, such as natural gas. In 2022, global solar generation capacity exceeded 1 TW for the first time. However, fossil-fuel subsidies have slowed the growth of solar generation capacity. About half of installed capacity is utility scale. Most new renewable capacity between 2022 and 2027

6954-573: The Florina prefecture and around Megalopolis . The operations in Romania acquired on the 25th of October, 2023 from Enel include energy distribution to 3.1 million customers, three energy distribution networks in South Muntenia (including Bucharest ), Banat , and Dobrogea , renewable energy with around 600 MW of capacity, and natural gas sales. In 2005, PPC was found to have awarded

7076-610: The Tsipras Government decided to suspend the privatisation of PPC as one of its first anti-austerity measures. The company was eventually privatised in November 2021, when the Greek government decreased its shareholding to 34.12%. Its remaining shareholding was subsequently transferred to the Greek sovereign wealth fund, the Hellenic Corporation of Assets and Participations (HCAP). In 1982, PPC developed

7198-467: The United States and even across states within the US. In net metering the price of the electricity produced is the same as the price supplied to the consumer, and the consumer is billed on the difference between production and consumption. Net metering can usually be done with no changes to standard electricity meters , which accurately measure power in both directions and automatically report

7320-436: The composite motion of the object's components – while potential energy reflects the potential of an object to have motion, generally being based upon the object's position within a field or what is stored within the field itself. While these two categories are sufficient to describe all forms of energy, it is often convenient to refer to particular combinations of potential and kinetic energy as its own form. For example,

7442-486: The electrical grid . Net metering and feed-in tariff programs give these systems a credit for the electricity they produce. This credit offsets electricity provided from the grid when the system cannot meet demand, effectively trading with the grid instead of storing excess electricity. When wind and solar are a small fraction of the grid power, other generation techniques can adjust their output appropriately, but as these forms of variable power grow, additional balance on

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7564-487: The gravitational collapse of supernovae to "store" energy in the creation of heavy isotopes (such as uranium and thorium ), and nuclear decay , a process in which energy is released that was originally stored in these heavy elements, before they were incorporated into the Solar System and the Earth. This energy is triggered and released in nuclear fission bombs or in civil nuclear power generation. Similarly, in

7686-416: The matter and antimatter (electrons and positrons) are destroyed and changed to non-matter (the photons). However, the total mass and total energy do not change during this interaction. The photons each have no rest mass but nonetheless have radiant energy which exhibits the same inertia as did the two original particles. This is a reversible process – the inverse process is called pair creation – in which

7808-399: The silicon solar cell in 1954. These early solar cells cost US$ 286/watt and reached efficiencies of 4.5–6%. In 1957, Mohamed M. Atalla developed the process of silicon surface passivation by thermal oxidation at Bell Labs . The surface passivation process has since been critical to solar cell efficiency . As of 2022 over 90% of the market is crystalline silicon . The array of

7930-567: The 1860s was driven by an expectation that coal would soon become scarce, such as experiments by Augustin Mouchot . Charles Fritts installed the world's first rooftop photovoltaic solar array, using 1%-efficient selenium cells, on a New York City roof in 1884. However, development of solar technologies stagnated in the early 20th century in the face of the increasing availability, economy, and utility of coal and petroleum . Bell Telephone Laboratories’ 1950s research used silicon wafers with

8052-684: The 1980s. The 377 MW Ivanpah Solar Power Facility , located in California's Mojave Desert, is the world's largest solar thermal power plant project. Other large CSP plants include the Solnova Solar Power Station (150 MW), the Andasol solar power station (150 MW), and Extresol Solar Power Station (150 MW), all in Spain. The principal advantage of CSP is the ability to efficiently add thermal storage, allowing

8174-588: The EU/IMF/ECB requirements for the financial support of the economy. PPC acquired 600 MW of renewable energy in Romania from Enel Green Power . Public Power Corp. acquired a wind farm in Romania from Lukoil Group in 2023, in addition to the agreed takeover of the Enel portfolio. Lukoil's asset-a special purpose vehicle called Land Power owns an 84MW system located in the province of Dobruja (Dobrogea), while

8296-571: The Earth's gravitational field or elastic strain (mechanical potential energy) in rocks. Prior to this, they represent release of energy that has been stored in heavy atoms since the collapse of long-destroyed supernova stars (which created these atoms). In cosmology and astronomy the phenomena of stars , nova , supernova , quasars and gamma-ray bursts are the universe's highest-output energy transformations of matter. All stellar phenomena (including solar activity) are driven by various kinds of energy transformations. Energy in such transformations

8418-752: The London Stock Exchange they are traded in the form of global depository receipts (GDRs). The Company’s shareholding structure as of 10 March 2023 was as follows: In 2001, PPC carried out a share flotation on the Athens Stock Exchange and consequently was no longer wholly owned by the government, although it was still controlled by it with a 51.1% stake until 2021. In June 2011, the Greek government announced it would sell 17% of its share of PPC to meet conditions of EU / ECB / IMF loan package. The workers of PPC responded by limited power cuts to selected towns across Greece. However,

8540-476: The US, residential solar cost from 2 to 4 dollars/watt (but solar shingles cost much more) and utility solar costs were around $ 1/watt. The productivity of solar power in a region depends on solar irradiance , which varies through the day and year and is influenced by latitude and climate . PV system output power also depends on ambient temperature, wind speed, solar spectrum, the local soiling conditions, and other factors. Onshore wind power tends to be

8662-543: The United States, President Jimmy Carter set a target of producing 20% of U.S. energy from solar by the year 2000, but his successor, Ronald Reagan , removed the funding for research into renewables. Falling oil prices in the early 1980s moderated the growth of photovoltaics from 1984 to 1996. In the mid-1990s development of both, residential and commercial rooftop solar as well as utility-scale photovoltaic power stations began to accelerate again due to supply issues with oil and natural gas, global warming concerns, and

8784-559: The arid tropics and subtropics. Deserts lying in low latitudes usually have few clouds and can receive sunshine for more than ten hours a day. These hot deserts form the Global Sun Belt circling the world. This belt consists of extensive swathes of land in Northern Africa , Southern Africa , Southwest Asia , Middle East , and Australia , as well as the much smaller deserts of North and South America . Thus solar

8906-429: The availability and cost of scalable electricity storage solutions. A photovoltaic power station , also known as a solar park, solar farm, or solar power plant, is a large-scale grid-connected photovoltaic power system (PV system) designed for the supply of merchant power . They are different from most building-mounted and other decentralized solar power because they supply power at the utility level, rather than to

9028-510: The ball. But, in the reference frame of the person swinging the bat, considerable work is done on the ball. The total energy of a system is sometimes called the Hamiltonian , after William Rowan Hamilton . The classical equations of motion can be written in terms of the Hamiltonian, even for highly complex or abstract systems. These classical equations have direct analogs in nonrelativistic quantum mechanics. Another energy-related concept

9150-447: The case of a chemical explosion , chemical potential energy is transformed to kinetic and thermal energy in a very short time. Yet another example is that of a pendulum . At its highest points the kinetic energy is zero and the gravitational potential energy is at its maximum. At its lowest point the kinetic energy is at its maximum and is equal to the decrease in potential energy . If one (unrealistically) assumes that there

9272-965: The case of animals. The daily 1500–2000  Calories (6–8 MJ) recommended for a human adult are taken as food molecules, mostly carbohydrates and fats, of which glucose (C 6 H 12 O 6 ) and stearin (C 57 H 110 O 6 ) are convenient examples. The food molecules are oxidized to carbon dioxide and water in the mitochondria C 6 H 12 O 6 + 6 O 2 ⟶ 6 CO 2 + 6 H 2 O {\displaystyle {\ce {C6H12O6 + 6O2 -> 6CO2 + 6H2O}}} C 57 H 110 O 6 + ( 81 1 2 ) O 2 ⟶ 57 CO 2 + 55 H 2 O {\displaystyle {\ce {C57H110O6 + (81 1/2) O2 -> 57CO2 + 55H2O}}} and some of

9394-605: The cheapest source of electricity in Northern Eurasia, Canada, some parts of the United States, and Patagonia in Argentina whereas in other parts of the world mostly solar power (or less often a combination of wind, solar and other low carbon energy) is thought to be best. Modelling by Exeter University suggests that by 2030, solar will be least expensive in all countries except for some in north-eastern Europe. The locations with highest annual solar irradiance lie in

9516-532: The complete conversion of matter (such as atoms) to non-matter (such as photons) is forbidden by conservation laws . Solar PV Solar power , also known as solar electricity , is the conversion of energy from sunlight into electricity , either directly using photovoltaics (PV) or indirectly using concentrated solar power . Solar panels use the photovoltaic effect to convert light into an electric current . Concentrated solar power systems use lenses or mirrors and solar tracking systems to focus

9638-451: The complex organisms can occupy ecological niches that are not available to their simpler brethren. The conversion of a portion of the chemical energy to heat at each step in a metabolic pathway is the physical reason behind the pyramid of biomass observed in ecology . As an example, to take just the first step in the food chain : of the estimated 124.7 Pg/a of carbon that is fixed by photosynthesis , 64.3 Pg/a (52%) are used for

9760-553: The concept of special relativity. In different theoretical frameworks, similar formulas were derived by J.J. Thomson (1881), Henri Poincaré (1900), Friedrich Hasenöhrl (1904) and others (see Mass–energy equivalence#History for further information). Part of the rest energy (equivalent to rest mass) of matter may be converted to other forms of energy (still exhibiting mass), but neither energy nor mass can be destroyed; rather, both remain constant during any process. However, since c 2 {\displaystyle c^{2}}

9882-399: The conservation of energy is a consequence of the fact that the laws of physics do not change over time. Thus, since 1918, theorists have understood that the law of conservation of energy is the direct mathematical consequence of the translational symmetry of the quantity conjugate to energy, namely time. In the International System of Units (SI), the unit of energy is the joule . It

10004-415: The cost of energy. Geography affects solar energy potential because different locations receive different amounts of solar radiation. In particular, with some variations, areas that are closer to the equator generally receive higher amounts of solar radiation. However, solar panels that can follow the position of the Sun can significantly increase the solar energy potential in areas that are farther from

10126-560: The cost of solar power, which is a problem for countries where contracts may not be honoured, such as some African countries. Some countries are considering price caps , whereas others prefer contracts for difference . In many countries, solar power is the lowest cost source of electricity. In Saudi Arabia, a power purchase agreement (PPA) was signed in April 2021 for a new solar power plant in Al-Faisaliah. The project has recorded

10248-402: The country sovereign wealth fund, the Hellenic Corporation of Assets and Participations (HCAP). This change in shareholding means PPC has been privatised and is no longer controlled by the Greek government. On 3 March 2022, CVC Capital Partners acquired 10% of the company's shareholding. The Company’s shares are traded in the «Large Cap» category of the Athens Stock Exchange (ATHEX), while in

10370-581: The desired frequency/phase. Many residential PV systems are connected to the grid when available, especially in developed countries with large markets. In these grid-connected PV systems , use of energy storage is optional. In certain applications such as satellites, lighthouses, or in developing countries, batteries or additional power generators are often added as back-ups. Such stand-alone power systems permit operations at night and at other times of limited sunlight. In "vertical agrivoltaics " system, solar cells are oriented vertically on farmland, to allow

10492-421: The difference, and because it allows homeowners and businesses to generate electricity at a different time from consumption, effectively using the grid as a giant storage battery. With net metering, deficits are billed each month while surpluses are rolled over to the following month. Best practices call for perpetual roll over of kWh credits. Excess credits upon termination of service are either lost or paid for at

10614-586: The dispatching of electricity over up to a 24-hour period. Since peak electricity demand typically occurs at about 5 pm, many CSP power plants use 3 to 5 hours of thermal storage. The typical cost factors for solar power include the costs of the modules, the frame to hold them, wiring, inverters, labour cost, any land that might be required, the grid connection, maintenance and the solar insolation that location will receive. Photovoltaic systems use no fuel, and modules typically last 25 to 40 years. Thus upfront capital and financing costs make up 80% to 90% of

10736-432: The energy basis of all financial activities of the country. The total installed capacity of the 97 PPC's power plants is currently 12,760 MW with a net generation of 53.9 TWh in 2007. PPC has mining areas adjacent to many of its power plants. Some of these power plants produce electricity and power from lignite , while other plants use coal . The largest mining areas are located around Ptolemaida , around Amyntaio in

10858-473: The energy is used to convert ADP into ATP : The rest of the chemical energy of the carbohydrate or fat are converted into heat: the ATP is used as a sort of "energy currency", and some of the chemical energy it contains is used for other metabolism when ATP reacts with OH groups and eventually splits into ADP and phosphate (at each stage of a metabolic pathway , some chemical energy is converted into heat). Only

10980-457: The energy stored during photosynthesis as heat or light may be triggered suddenly by a spark in a forest fire, or it may be made available more slowly for animal or human metabolism when organic molecules are ingested and catabolism is triggered by enzyme action. All living creatures rely on an external source of energy to be able to grow and reproduce – radiant energy from the Sun in the case of green plants and chemical energy (in some form) in

11102-456: The equator. Daytime cloud cover can reduce the light available for solar cells. Land availability also has a large effect on the available solar energy. Solar power plants use one of two technologies: A solar cell , or photovoltaic cell, is a device that converts light into electric current using the photovoltaic effect . The first solar cell was constructed by Charles Fritts in the 1880s. The German industrialist Ernst Werner von Siemens

11224-459: The first wind farm in the world, combined with a photo-voltaic station to supply electricity to the isolated power system of the island of Kythnos . The PPC has committed to buying renewable-source energy from independent producers at five times its selling rate until 2034. Legislation before Parliament in 2013-14 included making the PPC responsible for collection of the real estate tax, part of

11346-493: The first time in the work of Aristotle in the 4th century BC. In contrast to the modern definition, energeia was a qualitative philosophical concept, broad enough to include ideas such as happiness and pleasure. In the late 17th century, Gottfried Leibniz proposed the idea of the Latin : vis viva , or living force, which defined as the product of the mass of an object and its velocity squared; he believed that total vis viva

11468-457: The grid is needed. As prices are rapidly declining, PV systems increasingly use rechargeable batteries to store a surplus to be used later at night. Batteries used for grid-storage can stabilize the electrical grid by leveling out peak loads for a few hours. In the future, less expensive batteries could play an important role on the electrical grid, as they can charge during periods when generation exceeds demand and feed their stored energy into

11590-413: The height) and E k = 1 2 m v 2 {\textstyle E_{k}={\frac {1}{2}}mv^{2}} (half mass times velocity squared). Then the total amount of energy can be found by adding E p + E k = E total {\displaystyle E_{p}+E_{k}=E_{\text{total}}} . Energy gives rise to weight when it

11712-555: The improving economic position of PV relative to other energy technologies. In the early 2000s, the adoption of feed-in tariffs —a policy mechanism, that gives renewables priority on the grid and defines a fixed price for the generated electricity—led to a high level of investment security and to a soaring number of PV deployments in Europe. For several years, worldwide growth of solar PV was driven by European deployment , but it then shifted to Asia, especially China and Japan , and to

11834-413: The installation of the system. PPC had therefore decided to negotiate a deal for the construction instead of advertising the opportunity; the court held that these circumstances did not quality as "extreme urgency" for the purposes of the procurement regulations. Energy Energy (from Ancient Greek ἐνέργεια ( enérgeia )  'activity') is the quantitative property that

11956-638: The land to both grow crops and generate renewable energy. Other configurations include floating solar farms , placing solar canopies over parking lots, and installing solar panels on roofs. A thin-film solar cell is a second generation solar cell that is made by depositing one or more thin layers, or thin film (TF) of photovoltaic material on a substrate, such as glass, plastic or metal. Thin-film solar cells are commercially used in several technologies, including cadmium telluride (CdTe), copper indium gallium diselenide (CIGS), and amorphous thin-film silicon (a-Si, TF-Si). A perovskite solar cell (PSC)

12078-482: The marginalia of her French language translation of Newton's Principia Mathematica , which represented the first formulation of a conserved measurable quantity that was distinct from momentum , and which would later be called "energy". In 1807, Thomas Young was possibly the first to use the term "energy" instead of vis viva , in its modern sense. Gustave-Gaspard Coriolis described " kinetic energy " in 1829 in its modern sense, and in 1853, William Rankine coined

12200-424: The mass equivalent of an everyday amount energy is minuscule, which is why a loss of energy (loss of mass) from most systems is difficult to measure on a weighing scale, unless the energy loss is very large. Examples of large transformations between rest energy (of matter) and other forms of energy (e.g., kinetic energy into particles with rest mass) are found in nuclear physics and particle physics . Often, however,

12322-474: The metabolism of green plants, i.e. reconverted into carbon dioxide and heat. In geology , continental drift , mountain ranges , volcanoes , and earthquakes are phenomena that can be explained in terms of energy transformations in the Earth's interior, while meteorological phenomena like wind, rain, hail , snow, lightning, tornadoes and hurricanes are all a result of energy transformations in our atmosphere brought about by solar energy . Sunlight

12444-427: The molecules it is built from. The second law of thermodynamics states that energy (and matter) tends to become more evenly spread out across the universe: to concentrate energy (or matter) in one specific place, it is necessary to spread out a greater amount of energy (as heat) across the remainder of the universe ("the surroundings"). Simpler organisms can achieve higher energy efficiencies than more complex ones, but

12566-527: The price of bought electricity, which incentivizes self-consumption. Moreover, separate self-consumption incentives have been used in e.g., Germany and Italy. Grid interaction regulation has also included limitations of grid feed-in in some regions in Germany with high amounts of installed PV capacity. By increasing self-consumption, the grid feed-in can be limited without curtailment , which wastes electricity. A good match between generation and consumption

12688-423: The project has acquired three Intrakat entities cumulatively owning wind power projects in operation, under construction or prepared for construction with a total capacity of 164 MW. And PPC Renewables is also participating in four other Intrakat entities engaged in wind and solar PV projects with a combined capacity of about 1.6 GW. The deal will possibly include battery energy storage projects as well. The deal

12810-405: The rest mass of particles is created from the radiant energy of two (or more) annihilating photons. In general relativity, the stress–energy tensor serves as the source term for the gravitational field, in rough analogy to the way mass serves as the source term in the non-relativistic Newtonian approximation. Energy and mass are manifestations of one and the same underlying physical property of

12932-422: The resulting heat to generate electricity from conventional steam-driven turbines. A wide range of concentrating technologies exists: among the best known are the parabolic trough , the compact linear Fresnel reflector , the dish Stirling and the solar power tower . Various techniques are used to track the sun and focus light. In all of these systems a working fluid is heated by the concentrated sunlight and

13054-474: The same total energy even in different forms) but its mass does decrease when the energy escapes out to its surroundings, largely as radiant energy . There are strict limits to how efficiently heat can be converted into work in a cyclic process, e.g. in a heat engine, as described by Carnot's theorem and the second law of thermodynamics . However, some energy transformations can be quite efficient. The direction of transformations in energy (what kind of energy

13176-467: The situation is the reverse. Chemical reactions are usually not possible unless the reactants surmount an energy barrier known as the activation energy . The speed of a chemical reaction (at a given temperature  T ) is related to the activation energy  E by the Boltzmann's population factor e ; that is, the probability of a molecule to have energy greater than or equal to  E at

13298-719: The small private and local electric power production units. Today, PPC Group consists of 5 subsidiary companies in Greece PPC S.A., the Hellenic Electricity Distribution Network Operator (HEDNO or DEDDIE) S.A., PPC RENEWABLES S.A., PPC Fibegrip and Kotsovolos . Also PPC Group consists of 3 subsidiary companies in Romania PPC Romania, Retele Electrice and PPC Renewables Romania. Even if HEDNO S.A. (the Greek DSO)

13420-526: The sum of translational and rotational kinetic and potential energy within a system is referred to as mechanical energy , whereas nuclear energy refers to the combined potentials within an atomic nucleus from either the nuclear force or the weak force , among other examples. The word energy derives from the Ancient Greek : ἐνέργεια , romanized :  energeia , lit.   'activity, operation', which possibly appears for

13542-420: The sun . The energy industry provides the energy required for human civilization to function, which it obtains from energy resources such as fossil fuels , nuclear fuel , and renewable energy . The total energy of a system can be subdivided and classified into potential energy , kinetic energy , or combinations of the two in various ways. Kinetic energy is determined by the movement of an object – or

13664-407: The system to vary power output with demand, or at least smooth the solar power fluctuation. There is much hydro worldwide, and adding solar panels on or around existing hydro reservoirs is particularly useful, because hydro is usually more flexible than wind and cheaper at scale than batteries, and existing power lines can sometimes be used. The early development of solar technologies starting in

13786-429: The term " potential energy ". The law of conservation of energy was also first postulated in the early 19th century, and applies to any isolated system . It was argued for some years whether heat was a physical substance, dubbed the caloric , or merely a physical quantity, such as momentum . In 1845 James Prescott Joule discovered the link between mechanical work and the generation of heat. These developments led to

13908-461: The theory of conservation of energy, formalized largely by William Thomson ( Lord Kelvin ) as the field of thermodynamics . Thermodynamics aided the rapid development of explanations of chemical processes by Rudolf Clausius , Josiah Willard Gibbs , and Walther Nernst . It also led to a mathematical formulation of the concept of entropy by Clausius and to the introduction of laws of radiant energy by Jožef Stefan . According to Noether's theorem ,

14030-420: The total energy of the substances involved. Some energy may be transferred between the surroundings and the reactants in the form of heat or light; thus the products of a reaction have sometimes more but usually less energy than the reactants. A reaction is said to be exothermic or exergonic if the final state is lower on the energy scale than the initial state; in the less common case of endothermic reactions

14152-406: The unit of measure, discovered that the gravitational potential energy lost by a descending weight attached via a string was equal to the internal energy gained by the water through friction with the paddle. In classical mechanics, energy is a conceptually and mathematically useful property, as it is a conserved quantity . Several formulations of mechanics have been developed using energy as

14274-421: The universe cooled too rapidly for hydrogen to completely fuse into heavier elements. This meant that hydrogen represents a store of potential energy that can be released by fusion. Such a fusion process is triggered by heat and pressure generated from gravitational collapse of hydrogen clouds when they produce stars, and some of the fusion energy is then transformed into sunlight. In quantum mechanics , energy

14396-401: The universe over time are characterized by various kinds of potential energy, that has been available since the Big Bang , being "released" (transformed to more active types of energy such as kinetic or radiant energy) when a triggering mechanism is available. Familiar examples of such processes include nucleosynthesis , a process ultimately using the gravitational potential energy released from

14518-471: The world's lowest cost for solar PV electricity production of USD 1.04 cents/ kWh. Expenses of high-power band solar modules has greatly decreased over time. Beginning in 1982, the cost per kW was approximately 27,000 American dollars, and in 2006 the cost dropped to approximately 4,000 American dollars per kW. The PV system in 1992 cost approximately 16,000 American dollars per kW and it dropped to approximately 6,000 American dollars per kW in 2008. In 2021 in

14640-454: Was PV. In some countries, the nameplate capacity of photovoltaic power stations is rated in megawatt-peak (MW p ), which refers to the solar array's theoretical maximum DC power output. In other countries, the manufacturer states the surface and the efficiency. However, Canada, Japan, Spain, and the United States often specify using the converted lower nominal power output in MW AC ,

14762-506: Was among those who recognized the importance of this discovery. In 1931, the German engineer Bruno Lange developed a photo cell using silver selenide in place of copper oxide , although the prototype selenium cells converted less than 1% of incident light into electricity. Following the work of Russell Ohl in the 1940s, researchers Gerald Pearson, Calvin Fuller and Daryl Chapin created

14884-440: Was conserved. To account for slowing due to friction, Leibniz theorized that thermal energy consisted of the motions of the constituent parts of matter, although it would be more than a century until this was generally accepted. The modern analog of this property, kinetic energy , differs from vis viva only by a factor of two. Writing in the early 18th century, Émilie du Châtelet proposed the concept of conservation of energy in

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