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Thursday, August 25, 2022

Physiology

From Wikipedia, the free encyclopedia

Oil painting depicting Claude Bernard, the father of modern physiology, with his pupils

Physiology (/ˌfɪziˈɒləi/; from Ancient Greek φύσις (phúsis) 'nature, origin', and -λογία (-logía) 'study of') is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemical and physical functions in a living system. According to the classes of organisms, the field can be divided into medical physiology, animal physiology, plant physiology, cell physiology, and comparative physiology.

Central to physiological functioning are biophysical and biochemical processes, homeostatic control mechanisms, and communication between cells. Physiological state is the condition of normal function, while pathological state refers to abnormal conditions, including human diseases.

The Nobel Prize in Physiology or Medicine is awarded by the Royal Swedish Academy of Sciences for exceptional scientific achievements in physiology related to the field of medicine.

Foundations

Cells

Although there are differences between animal, plant, and microbial cells, the basic physiological functions of cells can be divided into the processes of cell division, cell signaling, cell growth, and cell metabolism.

Plants

Plant physiology is a subdiscipline of botany concerned with the functioning of plants. Closely related fields include plant morphology, plant ecology, phytochemistry, cell biology, genetics, biophysics, and molecular biology. Fundamental processes of plant physiology include photosynthesis, respiration, plant nutrition, tropisms, nastic movements, photoperiodism, photomorphogenesis, circadian rhythms, seed germination, dormancy, and stomata function and transpiration. Absorption of water by roots, production of food in the leaves, and growth of shoots towards light are examples of plant physiology.

Animals

Humans

Human physiology seeks to understand the mechanisms that work to keep the human body alive and functioning, through scientific enquiry into the nature of mechanical, physical, and biochemical functions of humans, their organs, and the cells of which they are composed. The principal level of focus of physiology is at the level of organs and systems within systems. The endocrine and nervous systems play major roles in the reception and transmission of signals that integrate function in animals. Homeostasis is a major aspect with regard to such interactions within plants as well as animals. The biological basis of the study of physiology, integration refers to the overlap of many functions of the systems of the human body, as well as its accompanied form. It is achieved through communication that occurs in a variety of ways, both electrical and chemical.

Changes in physiology can impact the mental functions of individuals. Examples of this would be the effects of certain medications or toxic levels of substances. Change in behavior as a result of these substances is often used to assess the health of individuals.

Much of the foundation of knowledge in human physiology was provided by animal experimentation. Due to the frequent connection between form and function, physiology and anatomy are intrinsically linked and are studied in tandem as part of a medical curriculum.

Comparative physiology

Involving evolutionary physiology and environmental physiology, comparative physiology considers the diversity of functional characteristics across organisms.

History

The classical era

The study of human physiology as a medical field originates in classical Greece, at the time of Hippocrates (late 5th century BC). Outside of Western tradition, early forms of physiology or anatomy can be reconstructed as having been present at around the same time in China, India and elsewhere. Hippocrates incorporated the theory of humorism, which consisted of four basic substances: earth, water, air and fire. Each substance is known for having a corresponding humor: black bile, phlegm, blood, and yellow bile, respectively. Hippocrates also noted some emotional connections to the four humors, on which Galen would later expand. The critical thinking of Aristotle and his emphasis on the relationship between structure and function marked the beginning of physiology in Ancient Greece. Like Hippocrates, Aristotle took to the humoral theory of disease, which also consisted of four primary qualities in life: hot, cold, wet and dry. Galen (c. 130–200 AD) was the first to use experiments to probe the functions of the body. Unlike Hippocrates, Galen argued that humoral imbalances can be located in specific organs, including the entire body. His modification of this theory better equipped doctors to make more precise diagnoses. Galen also played off of Hippocrates' idea that emotions were also tied to the humors, and added the notion of temperaments: sanguine corresponds with blood; phlegmatic is tied to phlegm; yellow bile is connected to choleric; and black bile corresponds with melancholy. Galen also saw the human body consisting of three connected systems: the brain and nerves, which are responsible for thoughts and sensations; the heart and arteries, which give life; and the liver and veins, which can be attributed to nutrition and growth. Galen was also the founder of experimental physiology. And for the next 1,400 years, Galenic physiology was a powerful and influential tool in medicine.

Early modern period

Jean Fernel (1497–1558), a French physician, introduced the term "physiology". Galen, Ibn al-Nafis, Michael Servetus, Realdo Colombo, Amato Lusitano and William Harvey, are credited as making important discoveries in the circulation of the blood.[20] Santorio Santorio in 1610s was the first to use a device to measure the pulse rate (the pulsilogium), and a thermoscope to measure temperature.

In 1791 Luigi Galvani described the role of electricity in nerves of dissected frogs. In 1811, César Julien Jean Legallois studied respiration in animal dissection and lesions and found the center of respiration in the medulla oblongata. In the same year, Charles Bell finished work on what would later become known as the Bell-Magendie law, which compared functional differences between dorsal and ventral roots of the spinal cord. In 1824, François Magendie described the sensory roots and produced the first evidence of the cerebellum's role in equilibration to complete the Bell-Magendie law.

In the 1820s, the French physiologist Henri Milne-Edwards introduced the notion of physiological division of labor, which allowed to "compare and study living things as if they were machines created by the industry of man." Inspired in the work of Adam Smith, Milne-Edwards wrote that the "body of all living beings, whether animal or plant, resembles a factory ... where the organs, comparable to workers, work incessantly to produce the phenomena that constitute the life of the individual." In more differentiated organisms, the functional labor could be apportioned between different instruments or systems (called by him as appareils).

In 1858, Joseph Lister studied the cause of blood coagulation and inflammation that resulted after previous injuries and surgical wounds. He later discovered and implemented antiseptics in the operating room, and as a result, decreased death rate from surgery by a substantial amount.

The Physiological Society was founded in London in 1876 as a dining club. The American Physiological Society (APS) is a nonprofit organization that was founded in 1887. The Society is, "devoted to fostering education, scientific research, and dissemination of information in the physiological sciences."

In 1891, Ivan Pavlov performed research on "conditional responses" that involved dogs' saliva production in response to a bell and visual stimuli.

In the 19th century, physiological knowledge began to accumulate at a rapid rate, in particular with the 1838 appearance of the Cell theory of Matthias Schleiden and Theodor Schwann. It radically stated that organisms are made up of units called cells. Claude Bernard's (1813–1878) further discoveries ultimately led to his concept of milieu interieur (internal environment), which would later be taken up and championed as "homeostasis" by American physiologist Walter B. Cannon in 1929. By homeostasis, Cannon meant "the maintenance of steady states in the body and the physiological processes through which they are regulated." In other words, the body's ability to regulate its internal environment. William Beaumont was the first American to utilize the practical application of physiology.

Nineteenth-century physiologists such as Michael Foster, Max Verworn, and Alfred Binet, based on Haeckel's ideas, elaborated what came to be called "general physiology", a unified science of life based on the cell actions, later renamed in the 20th century as cell biology.

Late modern period

In the 20th century, biologists became interested in how organisms other than human beings function, eventually spawning the fields of comparative physiology and ecophysiology. Major figures in these fields include Knut Schmidt-Nielsen and George Bartholomew. Most recently, evolutionary physiology has become a distinct subdiscipline.

In 1920, August Krogh won the Nobel Prize for discovering how, in capillaries, blood flow is regulated.

In 1954, Andrew Huxley and Hugh Huxley, alongside their research team, discovered the sliding filaments in skeletal muscle, known today as the sliding filament theory.

Recently, there have been intense debates about the vitality of physiology as a discipline (Is it dead or alive?). If physiology is perhaps less visible nowadays than during the golden age of the 19th century, it is in large part because the field has given birth to some of the most active domains of today's biological sciences, such as neuroscience, endocrinology, and immunology. Furthermore, physiology is still often seen as an integrative discipline, which can put together into a coherent framework data coming from various different domains.

Notable physiologists

Women in physiology

Initially, women were largely excluded from official involvement in any physiological society. The American Physiological Society, for example, was founded in 1887 and included only men in its ranks. In 1902, the American Physiological Society elected Ida Hyde as the first female member of the society. Hyde, a representative of the American Association of University Women and a global advocate for gender equality in education, attempted to promote gender equality in every aspect of science and medicine.

Soon thereafter, in 1913, J.S. Haldane proposed that women be allowed to formally join The Physiological Society, which had been founded in 1876. On 3 July 1915, six women were officially admitted: Florence Buchanan, Winifred Cullis, Ruth C. Skelton, Sarah C. M. Sowton, Constance Leetham Terry, and Enid M. Tribe. The centenary of the election of women was celebrated in 2015 with the publication of the book "Women Physiologists: Centenary Celebrations And Beyond For The Physiological Society." (ISBN 978-0-9933410-0-7)

Prominent women physiologists include:

Subdisciplines

There are many ways to categorize the subdisciplines of physiology:

Physiological societies

Transnational physiological societies include:

National physiological societies include:

Energy transition

From Wikipedia, the free encyclopedia
 
Coal, oil, and natural gas remain the primary global energy sources even as renewables have begun rapidly increasing.

The energy transition is the ongoing process of replacing fossil fuels with low carbon energy sources. More generally, an energy transition is a significant structural change in an energy system regarding supply and consumption.

The industrial revolution was driven by an energy transition from wood and other biomass to coal, followed by oil and most recently natural gas. Historically, there is a correlation between an increasing demand for energy and availability of different energy sources.

The current transition to sustainable energy differs as it is largely driven by a recognition that global greenhouse-gas emissions must be brought to zero. Since fossil fuels are the largest single source of carbon emissions, the quantity that can be produced is limited by the Paris Agreement of 2015 to keep global warming below 1.5 °C. Over 70% of our global greenhouse gas emissions result from the energy sector, for transport, heating, and industrial use.

Wind power and solar photovoltaic systems (PV) have the greatest potential to mitigate climate change. Since the late 2010s, the renewable energy transition is also driven by the rapidly increasing competitiveness of both. Another motivation for the transition is to limit other environmental impact of the energy industry.

The renewable energy transition includes a shift from internal combustion engine powered vehicles to more public transport, reduced air travel and electric vehicles. Electrification also regards the buildings sector, with heat pumps as the most efficient technology by far. For electrical grid scale flexibility, energy storage and super grids are vital to allow for variable, weather-dependent technologies.

Definition

An energy transition designates a significant change for an energy system related to resources, system structure, scale, economics, end use behaviour and energy policy. A prime example is the change from a pre-industrial system relying on traditional biomass, wind, water and muscle power to an industrial system characterized by pervasive mechanization, steam power and the use of coal.

After the 1973 oil crisis, the term was coined by politicians and media. It was popularised by US President Jimmy Carter in his 1977 Address on the Nation on Energy, calling to "look back into history to understand our energy problem. Twice in the last several hundred years, there has been a transition in the way people use energy ... Because we are now running out of gas and oil, we must prepare quickly for a third change--to strict conservation and to the renewed use of coal and to permanent renewable energy sources like solar power." The term was later globalised after the 1979 second oil shock, during the 1981 United Nations in Nairobi on new and renewable sources of energy.

From the 1990s, debates on energy transition have increasingly taken climate change mitigation into account. Since the adoption of the COP21 Paris Agreement in 2015, all 196 participating parties have agreed to reach carbon neutrality by mid-century. Parties to the agreement committed "to limit global warming to "well below 2 °C, preferably 1.5 °C compared to pre-industrial levels". This requires a rapid energy transition with a downshift of fossil fuel production to stay within the carbon emissions budget.

In this context, the term 'energy transition' encompasses a reorientation of energy policy. This could imply a shift from centralized to distributed generation. It also includes attempts to replace overproduction and avoidable energy consumption with energy-saving measures and increased efficiency. In a broader sense the energy transition could also entail a democratization of energy.

History of energy transitions and energy additions

An example of a long-term historic energy transition: share of primary energy by source in Portugal

Historic approaches to past energy transitions are shaped by two main discourses. One argues that humankind experienced several energy transitions in its past, while the other suggests the term "energy additions" as better reflecting the changes in global energy supply in the last three centuries.

The chronologically first discourse was most broadly described by Vaclav Smil. It underlines the change in the energy mix of countries and the global economy. By looking at data in percentages of the primary energy source used in a given context, it paints a picture of the world's energy systems as having changed significantly over time, going from biomass to coal, to oil, and now a mix of mostly coal, oil and natural gas. Until the 1950s, the economic mechanism behind energy systems was local rather than global.

The second discourse was most broadly described by Jean-Baptiste Fressoz. It emphasises that the term "energy transition" was first used by politicians, not historians, to describe a goal to achieve in the future – not as a concept to analyse past trends. When looking at the sheer amount of energy being used by humankind, the picture is one of an ever-increasing energy consumption that is met by an ever-increasing consumption of all the main energy sources available to humankind. For instance, the increased use of coal in the 19th century indeed did not replace wood consumption, but came on top of increased wood consumption. Another example is the deployment of passenger cars in the 20th century. This evolution triggered an increase in both oil consumption (to drive the car) and coal consumption (to make the steel needed for the car). In other words, according to this approach, humankind never performed a single energy transition in its history but performed several energy additions.

Contemporary energy transitions differ in terms of motivation and objectives, drivers and governance. As development progressed, different national systems became more and more integrated becoming the large, international systems seen today. Historical changes of energy systems have been extensively studied. While historical energy changes were generally protracted affairs, unfolding over many decades, this does not necessarily hold true for the present energy transition, which is unfolding under very different policy and technological conditions.

For current energy systems, many lessons can be learned from history. The need for large amounts of firewood in early industrial processes in combination with prohibitive costs for overland transportation led to a scarcity of accessible (e.g. affordable) wood and it has been found that eighteenth century glass-works "operated like a forest clearing enterprise". When Britain had to resort to coal after largely having run out of wood, the resulting fuel crisis triggered a chain of events that two centuries later culminated in the Industrial Revolution. Similarly, increased use of peat and coal were vital elements paving the way for the Dutch Golden Age, roughly spanning the entire 17th century. Another example where resource depletion triggered technological innovation and a shift to new energy sources in 19th Century whaling and how whale oil eventually became replaced by kerosene and other petroleum-derived products. With the success of a rapid energy transition it is also conceivable that there will be government buyouts or bailouts of coal mining regions.

Factors driving the low carbon energy transition

The Climate Change Performance Index is based on GHG emissions, renewable energy, energy use and climate policy.
 
With increasing implementation of renewable energy sources, costs have declined, most notably for energy generated by solar panels. Levelized cost of energy (LCOE) is a measure of the average net present cost of electricity generation for a generating plant over its lifetime.

A rapid energy transition to very-low or zero-carbon sources is required to mitigate the existential effects of climate change. The rise in weather and climate extremes has already led to irreversible impacts as natural and human systems are pushed beyond their ability to adapt. Coal, oil and gas combustion account for 89% of CO2 emissions while they still provide 78% of primary energy consumption. By 2050, burning coal must be reduced by 95%, oil by 60% and gas by 45% compared to 2019 in order to achieve a 50% chance to meet the Paris Agreement target of limiting global heating to 1.5 °C. This refers to pathways with no or limited overshoot.

In spite of the knowledge about the risks of climate change since the 1980s and the vanishing carbon budget for a 1.5 °C path, the global deployment of renewable energy could not catch up with the increasing energy demand for many years. Coal, oil and gas were cheaper. Only in countries with special tariffs and subsidies, wind and solar power gained a considerable share, limited to the power sector.

From 2010-2019, competitiveness of wind and solar power has massively increased. Unit costs of solar energy dropped sharply by 85%, wind energy by 55%, and lithium-ion batteries by 85%, making wind and solar power the cheapest form for new installations in many regions. Levelized costs for combined photovoltaics with storage for a few hours are already lower than for gas peaking power plants. In 2021, the new electricity generating capacity of renewables exceeded 80% of all installed power.

Another important driver is energy security and independence, with increasing importance in Europe from the background of the 2022 Russian invasion of Ukraine.

The deployment of renewable energy can also include co-benefits of climate change mitigation: positive socio-economic effects on employment, industrial development, health and energy access. Depending on the country and the deployment scenario, replacing coal power plants can more than double the number of jobs per average MW capacity. In non-electrified rural areas, the deployment of solar mini-grids can significantly improve electricity access. Employment opportunities by the green transition are associated with the use of renewable energy sources or building activity for infrastructure improvements and renovations. Additionally, the replacement of coal-based energy with renewables can lower the number of premature deaths caused by air pollution and reduce health costs.

Current technologies

Gold Ray Dam on the Rogue River (Oregon)
 
Wind farm in Idaho, United States.
 
Photovoltaic array in Colorado.
 
Salt tanks at Solana CSP in Arizona provide 1 GWh thermal energy storage.

Renewable energy

Global renewable energy capacity additions in 2020 included a 90% rise in global wind capacity (green) and a 23% expansion of new photovoltaic installations (yellow).
 
Companies, governments and households committed $501.3 billion to decarbonization in 2020, including solar, wind, electric vehicles, charging infrastructure, storage, heating systems, CCS and hydrogen.

The energy sources that are considered the most important in the low carbon energy transition are wind power and solar power. Both offer the potential to reduce net emissions by 4 Gt CO2 equivalents per year each, half of it with lower net lifetime costs than the reference.

By 2022, hydroelectricity is the largest source of renewable electricity in the world, providing 16% of the world's total electricity in 2019. However, because of its heavy dependence on geography and the generally high environmental and social impact of hydroelectric power plants, the growth potential of this technology is limited. Wind and solar power are considered more scalable, but still require vast quantities of land and materials. They have higher potential for growth. These sources have grown nearly exponentially in recent decades thanks to rapidly decreasing costs. In 2019, wind power supplied 5.3% worldwide electricity while solar power supplied 2.6%.

While production from most types of hydropower plants can be actively controlled, production from wind and solar power depends on the weather. Electrical grids must be extended and adjusted to avoid wastage. Hydropower is therefore considered a dispatchable source, while solar and wind are variable renewable energy sources. These sources require dispatchable backup generation or energy storage to provide continuous and reliable electricity. For this reason, storage technologies also play a key role in the renewable energy transition. As of 2020, the largest scale storage technology is pumped storage hydroelectricity, accounting for the great majority of energy storage capacity installed worldwide. Other important forms of energy storage are electric batteries and power to gas.

Other renewable energy sources include bioenergy, geothermal energy and tidal energy.

Regarding energy use and efficiency the electrification of road transport is one key technology.

Nuclear power

Timeline of commissioned and decommissioned nuclear capacity since the 1950s.

In the 1970s and 1980s, nuclear power gained a large share in some countries. In France and Slovakia more than half of the electrical power is still nuclear. It is regarded as a low carbon energy source but comes with risks and increasing costs. Since the late 1990s, deployment has slowed down. Decommissioning increases as many reactors are close to the end of their lifetime. Germany has announced to stop its last three nuclear power plants by the end of 2022. On teh other hand, the China General Nuclear Power Group has articulated the goal of 200 GW by 2035, produced by 150 additional reactors.

Economic aspects

A shift in energy sources has the potential to redefine relations and dependencies between countries, stakeholders and companies. Countries or land owners with resources - fossil or renewable - face massive losses or gains depending on the development of any energy transition. In 2021, energy costs reached 13% of the global gross domestic product. Global rivalries have contributed to the driving forces of the economics behind the low carbon energy transition. Technological innovations developed within a country have the potential to become an economic force.

Social aspects

Influences

The energy transition discussion is heavily influenced by contributions from the oil industry. The oil industry controls the larger part of the world's energy supply and needs as petroleum continues to be the most accessible and available resource present today. With a history of continued success and sustained demand, the oil industry has become a stable aspect of society, the economy and the energy sector. To transition to renewable energy technologies, the government and economy must address the oil industry and its control of the energy sector.

A booth for the Citizens' Climate Lobby, at a rally for science in Minnesota, 2018.

One way that oil companies are able to continue their work despite growing environmental, social and economic concerns is through lobbying efforts within local and national government systems. Lobbying is defined as to conduct activities aimed at influencing public officials and especially members of a legislative body on legislation

Historically, the fossil fuel lobby has been highly successful in limiting regulations on the oil industry and enabling business-as-usual techniques. From 1988 to 2005, Exxon Mobil, one of the largest oil companies in the world, spent nearly $16 million in anti-climate change lobbying and providing misleading information about climate change to the general public. The oil industry acquires significant support through the existing banking and investment structure. By investing in the fossil fuel industry, it is provided with financial support to continue its business ventures. The concept that the industry should no longer be financially supported has led to the social movement known as divestment. Divestment is defined as the removal of investment capital from stocks, bonds or funds in oil, coal and gas companies for both moral and financial reasons

Banks, investing firms, governments, universities, institutions and businesses are all being challenged with this new moral argument against their existing investments in the fossil fuel industry and many such as Rockefeller Brothers Fund, the University of California, New York City and more have begun making the shift to more sustainable, eco-friendly investments.

Impacts

The low carbon energy transition has many benefits and challenges that are associated with it. One of the positive social impacts that is predicted is the use of local energy sources to provide stability and economic stimulation to local communities. Not only does this benefit local utilities through portfolio diversification, but it also creates opportunities for energy trade between communities, states and regions. Additionally, energy security has been a struggle worldwide that has led to many issues in the OPEC countries and beyond. Energy security is evaluated by analyzing the accessibility, availability, sustainability, regulatory and technological opportunity of our energy portfolio. Renewable Energy presents an opportunity to increase our energy security by becoming energy independent and have localized grids that decrease energy risks geopolitically. In this sense, the benefits and positive outcomes of the renewable energy transition are profound.

There are also risks and negative impacts on society because of the renewable energy transition that need to be mitigated. The coal mining industry plays a large part in the existing energy portfolio and is one of the biggest targets for climate change activists due to the intense pollution and habitat disruption that it creates. The transition to renewable is expected to have decrease the need and viability of coal mining in the future. This is a positive for climate change action, but can have severe impacts on the communities that rely on this business. Coal mining communities are considered vulnerable to the renewable energy transition. Not only do these communities face energy poverty already, but they also face economic collapse when the coal mining businesses move elsewhere or disappear altogether. These communities need to quickly transition to alternative forms of work to support their families, but lack the resources and support to invest in themselves. This broken system perpetuates the poverty and vulnerability that decreases the adaptive capacity of coal mining communities. Potential mitigation could include expanding the program base for vulnerable communities to assist with new training programs, opportunities for economic development and subsidies to assist with the transition. Ultimately, the social impacts of the renewable energy transition will be extensive, but with mitigation strategies, governments can ensure that it becomes a positive opportunity for all citizens.

Mineral extraction

The renewable energy transition has begun to stimulate debate considering it requires a significant increase in extraction of some kinds of minerals and therefore will lead to an increase of the mining processes themselves and of the associated environmental and societal impacts. A potential solution that has arisen for this energy transition dilemma is to explore collection of minerals from new sources like polymetallic nodules lying on the seabed, but this could damage biodiversity. Ongoing research is exploring this as a way to facilitate the energy transition in a more sustainable manner.

Reasons for a fast energy transition

6 advantages of an energy transition (for example in Europe) - Energy Atlas 2018

Solving the global warming problem is regarded as the most important challenge facing humankind in the 21st century, and under the Paris climate agreement emissions must cease by 2040 or 2050. Barring a breakthrough in carbon sequestration technologies, this requires an energy transition away from fossil fuels such as oil, natural gas, lignite, and coal. This energy transition is also known as the decarbonization of the energy system or "energy turnaround". Available technologies are nuclear power (fission), wind, hydropower, solar power, geothermal, and marine energy.

A timely implementation of the energy transition requires multiple approaches in parallel. Energy conservation and improvements in energy efficiency thus play a major role. Smart electric meters can schedule energy consumption for times when electricity is abundant, reducing consumption at times when the more variable renewable energy sources are scarce (night time and lack of wind).

Technology has been identified as an important but difficult-to-predict driver of change within energy systems. Published forecasts have systematically tended to overestimate the potential of new energy and conversion technologies and underestimated the inertia in energy systems and energy infrastructure (e.g. power plants, once built, characteristically operate for many decades). The history of large technical systems is very useful for enriching debates about energy infrastructures by detailing many of their long-term implications. The speed at which a transition in the energy sector needs to take place will be historically rapid. Moreover, the underlying technological, political, and economic structures will need to change radically — a process one author calls regime shift.

Risks and barriers

Despite the widespread understanding that a transition to low carbon energy is necessary, there are a number of risks and barriers to making it more appealing than conventional energy. Low carbon energy rarely comes up as a solution beyond combating climate change, but has wider implications for food security and employment. This further supports the recognized dearth of research for clean energy innovations, which may lead to quicker transitions. Overall, the transition to renewable energy requires a shift among governments, business, and the public. Altering public bias may mitigate the risk of subsequent administrations de-transitioning - through perhaps public awareness campaigns or carbon levies.

Amongst the key issues to consider in relation to the pace of the global transition to renewables is how well individual electric companies are able to adapt to the changing reality of the power sector. For example, to date, the uptake of renewables by electric utilities has remained slow, hindered by their continued investment in fossil fuel generation capacity.

Labour

A large portion of the global workforce works directly or indirectly for the fossil fuel economy. Moreover, many other industries are currently dependent on unsustainable energy sources (such as the steel industry or cement and concrete industry). Transitioning these workforces during the rapid period of economic change requires considerable forethought and planning. The international labor movement has advocated for a just transition that addresses these concerns.

Predictions

Possible energy transition timeline. The energy transition on this timeline is too slow to correspond with the Paris Agreement.

After a transitional period, renewable energy production is expected to make up most of the world's energy production. In 2018, the risk management firm, DNV GL, forecasts that the world's primary energy mix will be split equally between fossil and non-fossil sources by 2050. A 2011 projection by the International Energy Agency expects solar PV to supply more than half of the world's electricity by 2060, dramatically reducing the emissions of greenhouse gases.

The GeGaLo index of geopolitical gains and losses assesses how the geopolitical position of 156 countries may change if the world fully transitions to renewable energy resources. Former fossil fuels exporters are expected to lose power, while the positions of former fossil fuel importers and countries rich in renewable energy resources is expected to strengthen.

Status in specific countries

Global energy consumption by source.
 
Global energy consumption by source (in %).

The U.S. Energy Information Administration (EIA) estimates that, in 2013, total global primary energy supply (TPES) was 157.5 petawatt hours or 1.575×1017 Wh (157.5 thousand TWh; 5.67×1020 J; 13.54 billion toe) or about 18 TW-year. From 2000–2012 coal was the source of energy with the total largest growth. The use of oil and natural gas also had considerable growth, followed by hydropower and renewable energy. Renewable energy grew at a rate faster than any other time in history during this period. The demand for nuclear energy decreased, in part due to fear mongering and inaccurate media portrayal of some nuclear disasters (Three Mile Island in 1979, Chernobyl in 1986, and Fukushima in 2011). More recently, consumption of coal has declined relative to low carbon energy. Coal dropped from about 29% of the global total primary energy consumption in 2015 to 27% in 2017, and non-hydro renewables were up to about 4% from 2%.

Australia

Australia has one of the fastest deployment rates of renewable energy worldwide. The country has deployed 5.2 GW of solar and wind power in 2018 alone and at this rate, is on track to reach 50% renewable electricity in 2024 and 100% in 2032. However, Australia may be one of the leading major economies in terms of renewable deployments, but it is one of the least prepared at a network level to make this transition, being ranked 28th out of the list of 32 advanced economies on the World Economic Forum's 2019 Energy Transition Index. Nuclear energy is banned in Australia.

China

China is the largest emitter of greenhouse gases, and plays a key role in the low carbon energy transition and climate change mitigation. China has a goal to be carbon neutral by 2060.

European Union

The European Green Deal is a set of policy initiatives by the European Commission with the overarching aim of making Europe climate neutral in 2050. An impact assessed plan will also be presented to increase the EU's greenhouse gas emission reductions target for 2030 to at least 50% and towards 55% compared with 1990 levels. The plan is to review each existing law on its climate merits, and also introduce new legislation on the circular economy, building renovation, biodiversity, farming and innovation. The president of the European Commission, Ursula von der Leyen, stated that the European Green Deal would be Europe's "man on the Moon moment", as the plan would make Europe the first climate-neutral continent.

A survey found that digitally advanced companies put more money into energy-saving strategies. In the European Union, 59% of companies that have made investments in both basic and advanced technologies have also invested in energy efficiency measures, compared to only 50% of US firms in the same category. Overall, there is a significant disparity between businesses' digital profiles and investments in energy efficiency.

Austria

Austria electricity supply by source
 

Austria embarked on its energy transition (Energiewende) some decades ago. Due to geographical conditions, electricity production in Austria relies heavily on renewable energies, specifically hydropower. 78.4% of domestic electricity production in 2013 came from low carbon energy, 9.2% from natural gas and 7.2% from petroleum. On the basis of the Federal Constitutional Law for a Nuclear-Free Austria, no nuclear power stations are in operation in Austria.

Domestic energy production makes up only 36% of Austria's total energy consumption, which among other things encompasses transport, electricity production, and heating. In 2013, oil accounts for about 36.2% of total energy consumption, renewable energies 29.8%, gas 20.6%, and coal 9.7%. In the past 20 years, the structure of gross domestic energy consumption has shifted from coal and oil to new renewables. The EU target for Austria require a renewables share of 34% by 2020 (gross final energy consumption).

Energy transition in Austria can be also seen on the local level, in some villages, towns and regions. For example, the town of Güssing in the state of Burgenland is a pioneer in independent and sustainable energy production. Since 2005, Güssing has already produced significantly more heating (58 gigawatt hours) and electricity (14 GWh) from renewable resources than the city itself needs.

Denmark

Denmark electricity generation by source

Denmark, as a country reliant on imported oil, was impacted particularly hard by the 1973 oil crisis. This roused public discussions on building nuclear power stations to diversify energy supply. A strong anti-nuclear movement developed, which fiercely criticized nuclear power plans taken up by the government, and this ultimately led to a 1985 resolution not to build any nuclear power stations in Denmark. The country instead opted for renewable energy, focusing primarily on wind power. Wind turbines for power generation already had a long history in Denmark, as far back as the late 1800s. As early as 1974 a panel of experts declared "that it should be possible to satisfy 10% of Danish electricity demand with wind power, without causing special technical problems for the public grid." Denmark undertook the development of large wind power stations — though at first with little success (like with the Growian project in Germany).

Small facilities prevailed instead, often sold to private owners such as farms. Government policies promoted their construction; at the same time, positive geographical factors favored their spread, such as good wind power density and Denmark's decentralized patterns of settlement. A lack of administrative obstacles also played a role. Small and robust systems came on line, at first in the power range of only 50-60 kilowatts — using 1940s technology and sometimes hand-crafted by very small businesses. In the late seventies and the eighties a brisk export trade to the United States developed, where wind energy also experienced an early boom. In 1986 Denmark already had about 1200 wind power turbines, though they still accounted for just barely 1% of Denmark's electricity. This share increased significantly over time. In 2011, renewable energies covered 41% of electricity consumption, and wind power facilities alone accounted for 28%. The government aims to increase wind energy's share of power generation to 50% by 2020, while at the same time reducing carbon dioxide emissions by 40%. On 22 March 2012, the Danish Ministry of Climate, Energy and Building published a four-page paper titled "DK Energy Agreement," outlining long-term principles for Danish energy policy.

The installation of oil and gas heating is banned in newly constructed buildings from the start of 2013; beginning in 2016 this will also apply to existing buildings. At the same time an assistance program for heater replacement was launched. Denmark's goal is to reduce the use of fossil fuels 33% by 2020. The country is scheduled to attain complete independence from petroleum and natural gas by 2050.

France

Electricity production in France.

Since 2012, political discussions have been developing in France about the energy transition and how the French economy might profit from it.

In September 2012, Minister of the Environment Delphine Batho coined the term "ecological patriotism." The government began a work plan to consider starting the energy transition in France. This plan should address the following questions by June 2013:

  • How can France move towards energy efficiency and energy conservation? Reflections on altered lifestyles, changes in production, consumption, and transport.
  • How to achieve the energy mix targeted for 2025? France's climate protection targets call for reducing greenhouse gas emissions 40% by 2030, and 60% by 2040.
  • Which renewable energies should France rely on? How should the use of wind and solar energy be promoted?
  • What costs and funding models will likely be required for alternative energy consulting and investment support? And how about for research, renovation, and expansion of district heating, biomass, and geothermal energy? One solution could be a continuation of the CSPE, a tax that is charged on electricity bills.

The Environmental Conference on Sustainable Development on 14 and 15 September 2012 treated the issue of the environmental and energy transition as its main theme.

On 8 July 2013, the national debate leaders submits some proposals to the government. Among them, there were environmental taxation, and smart grid development.

In 2015, the National Assembly has adopted legislation for the transition to low emission vehicles.

France is second only to Denmark as having the world's lowest carbon emissions in relation to gross domestic product.

Germany

Gross generation of electricity by source in Germany 1990–2020

Germany has played an outsized role in the transition away from fossil fuels and nuclear power to renewables. The energy transition in Germany is known as die Energiewende (literally, "the energy turn") indicating a turn away from old fuels and technologies to new one. The key policy document outlining the Energiewende was published by the German government in September 2010, some six months before the Fukushima nuclear accident; legislative support was passed in September 2010.

The policy has been embraced by the German federal government and has resulted in a huge expansion of renewables, particularly wind power. Germany's share of renewables has increased from around 5% in 1999 to 17% in 2010, reaching close to the OECD average of 18% usage of renewables. Producers have been guaranteed a fixed feed-in tariff for 20 years, guaranteeing a fixed income. Energy co-operatives have been created, and efforts were made to decentralize control and profits. The large energy companies have a disproportionately small share of the renewables market. Nuclear power stations were closed, and the existing nine stations will close earlier than necessary, in 2022.

The reduction of reliance on nuclear stations has had the consequence of increased reliance on fossil fuels. One factor that has inhibited efficient employment of new renewable energy has been the lack of an accompanying investment in power infrastructure to bring the power to market. It is believed 8300 km of power lines must be built or upgraded.

Different Länder have varying attitudes to the construction of new power lines. Industry has had their rates frozen and so the increased costs of the Energiewende have been passed on to consumers, who have had rising electricity bills. Germans in 2013 had some of the highest electricity costs in Europe. Nonetheless, for the first time in more than ten years, electricity prices for household customers fell at the beginning of 2015.

South Korea

The South Korean Ministry of Trade, Industry, and Energy (MOTIE) has claimed that an energy transition is necessary in order to comply with the public's demands for their lives, their safety, and the environment. In addition, the ministry has stated that the direction of the future energy policy is "to transition (from conventional energy sources) to safe and clean energy sources." Unlike in the past, the keynote of the policy is to put emphasis on safety and the environment rather than on stability of supply and demand and economic feasibility and is to shift its reliance on nuclear power and coal to clean energy sources like renewables.

In 1981, the primary energy was sourced predominantly by oil and coal with oil accounting for 58.1% and coal 33.3%. As the shares of nuclear power and liquefied natural gas have increased over the years, the share of oil has decreased gradually. The primary energy broke down as follows in 1990: 54% oil, 26% coal, 14% nuclear power, 3% liquefied natural gas, and 3% renewables. Later on, with efforts to reduce greenhouse gas emissions in the country through international cooperation and to improve environmental and safety performances, it broke down as follows in 2017: 40% oil, 29% coal, 16% liquefied natural gas, 10% nuclear power, and 5% renewables. Under the 8th Basic Plan for Long-term Electricity Supply and Demand, presented at the end of 2017, the shares of nuclear and coal are getting decreased while the share of renewables is expanding.

In June 2019, the Korean government confirmed the Third Energy Master Plan, also called a constitutional law of the energy sector and renewed every five years. Its goal is to achieve sustainable growth and enhance the quality of life through energy transition. There are five major tasks to achieve this goal. First, with regards to consumption, the goal is to improve energy consumption efficiency by 38% compared to the level of 2017 and to reduce energy consumption by 18.6% below the BAU level by 2040. Second, with respect to generation, the task is to bring a transition towards a safe and clean energy mix by raising the share of renewable energy in power generation (30~35% by 2040) and by implementing a gradual phase-out of nuclear power and a drastic reduction of coal. Third, regarding the systems, the task is to raise the share of distributed generation nearby where demand is created with renewables and fuel cells and to enhance the roles and responsibility of local governments and residents. Fourth, with regards to the industry, the task is to foster businesses related to renewables, hydrogen, and energy efficiency as a future energy industry, to help the conventional energy industry develop higher value-added businesses, and to support the nuclear power industry to maintain its main ecosystem. The fifth task is to improve the energy market system of electricity, gas, and heat in order to promote energy transition and is to develop an energy big data platform in order to create new businesses.

Switzerland

Due to the high share of hydroelectricity (59.6%) and nuclear power (31.7%) in electricity production, Switzerland's per capita energy-related CO2 emissions are 28% lower than the European Union average and roughly equal to those of France. On 21 May 2017, Swiss voters accepted the new Energy Act establishing the 'energy strategy 2050'. The aims of the energy strategy 2050 are: to reduce energy consumption; to increase energy efficiency ; and to promote renewable energies (such as water, solar, wind and geothermal power as well as biomass fuels). The Energy Act of 2006 forbids the construction of new nuclear power plants in Switzerland.

United Kingdom

Primary energy mix in the United Kingdom over time, differentiated by energy source (in % of the total energy consumption)

By law production of greenhouse gas emissions by the United Kingdom will be reduced to net zero by 2050. To help in reaching this statutory goal national energy policy is mainly focusing on the country's off-shore wind power and delivering new and advanced nuclear power. The increase in national renewable power - particularly from biomass - together with the 20% of electricity generated by nuclear power in the United Kingdom meant that by 2019 low carbon British electricity had overtaken that generated by fossil fuels.

In order to meet the net zero target energy networks must be strengthened. Electricity is only a part of energy in the United Kingdom, so natural gas used for industrial and residential heat and petroleum used for transport in the United Kingdom must also be replaced by either electricity or another form of low-carbon energy, such as sustainable bioenergy crops or green hydrogen.

Although the need for the energy transition is not disputed by any major political party, in 2020 there is debate about how much of the funding to try and escape the COVID-19 recession should be spent on the transition, and how many jobs could be created, for example in improving energy efficiency in British housing. Some believe that due to post-covid government debt that funding for the transition will be insufficient. Brexit may significantly affect the energy transition, but this is unclear as of 2020. The government is urging UK business to sponsor the climate change conference in 2021, possibly including energy companies but only if they have a credible short term plan for the energy transition.

United States

U.S. energy consumption by source.
 
The Shepherds Flat Wind Farm is an 845 megawatt (MW) wind farm in the U.S. state of Oregon.
 
The 550 MW Desert Sunlight Solar Farm in California.
 
The 392 MW Ivanpah Solar Power Facility in California: The facility's three towers.
 
Parabolic trough power station for electricity production, near the town of Kramer Junction in California's San Joaquin Valley

The Obama administration made a large push for green jobs, particularly in his first term. The Trump administration, however, took action to reverse the pro-environmental policies of his predecessor, including withdrawing the United States from the Paris Climate Accords.

In the United States, the share of renewable energy in electricity generation has grown to 21% (2020). Oil use is expected to decline in the US owing to the increasing efficiency of the vehicle fleet and replacement of crude oil by natural gas as a feedstock for the petrochemical sector. One forecast is that the rapid uptake of electric vehicles will reduce oil demand drastically, to the point where it is 80% lower in 2050 compared with today.

In December 2016, Block Island Wind Farm became the first commercial US offshore wind farm. It consists of five 6 MW turbines (together 30 MW) located near-shore (3.8 miles (6.1 km) from Block Island, Rhode Island) in the Atlantic Ocean. At the same time, Norway-based oil major Statoil laid down nearly $42.5 million on a bid to lease a large offshore area off the coast of New York.

100% renewable energy

100% renewable energy is an energy system where all energy use is sourced from renewable energy sources. The endeavor to use 100% renewable energy for electricity, heating/cooling and transport is motivated by global warming, pollution and other environmental issues, as well as economic and energy security concerns. Shifting the total global primary energy supply to renewable sources requires a transition of the energy system, since most of today's energy is derived from non-renewable fossil fuels.

According to the Intergovernmental Panel on Climate Change there are few fundamental technological limits to integrating a portfolio of renewable energy technologies to meet most of total global energy demand. Renewable energy use has grown more quickly than even advocates anticipated. As of 2019, however, it needs to grow six times faster to limit global warming to 2 °C (3.6 °F).

100% renewable energy in a country is typically a more challenging goal than carbon neutrality. The latter is a climate mitigation target, politically decided by many countries, and may also be achieved by balancing the total carbon footprint of the country (not only emissions from energy and fuel) with carbon dioxide removal and carbon projects abroad.

As of 2018 according to REN21 transformation is picking up speed in the power sector, but urgent action is required in heating, cooling and transport. There are many places around the world with grids that are run almost exclusively on renewable energy. At the national level, at least 30 nations already have renewable energy contributing more than 20% of the energy supply.

According to a review of the 181 peer-reviewed papers on 100% renewable energy which were published until 2018, "[t]he great majority of all publications highlights the technical feasibility and economic viability of 100% RE systems." While there are still many publications which focus on electricity only, there is a growing number of papers that cover different energy sectors and sector-coupled, integrated energy systems. This cross-sectoral, holistic approach is seen as an important feature of 100% renewable energy systems and is based on the assumption "that the best solutions can be found only if one focuses on the synergies between the sectors" of the energy system such as electricity, heat, transport or industry.

Stephen W. Pacala and Robert H. Socolow of Princeton University have developed a series of "climate stabilization wedges" that can allow us to maintain our quality of life while avoiding catastrophic climate change, and "renewable energy sources," in aggregate, constitute the largest number of their "wedges."

Mark Z. Jacobson, professor of civil and environmental engineering at Stanford University and director of its Atmosphere and Energy program, says that producing all new energy with wind power, solar power, and hydropower by 2030 is feasible, and that existing energy supply arrangements could be replaced by 2050. Barriers to implementing the renewable energy plan are seen to be "primarily social and political, not technological or economic". Jacobson says that energy costs today with a wind, solar, and water system should be similar to today's energy costs from other optimally cost-effective strategies. The main obstacle against this scenario is the lack of political will. His conclusions have been disputed by other researchers. Jacobson published a response that disputed the piece point by point and claimed that the authors were motivated by allegiance to energy technologies that the 2015 paper excluded.

Similarly, in the United States, the independent National Research Council has noted that "sufficient domestic renewable resources exist to allow renewable electricity to play a significant role in future electricity generation and thus help confront issues related to climate change, energy security, and the escalation of energy costs ... Renewable energy is an attractive option because renewable resources available in the United States, taken collectively, can supply significantly greater amounts of electricity than the total current or projected domestic demand."

The main barriers to the widespread implementation of large-scale renewable energy and low-carbon energy strategies are political rather than technological. According to the 2013 Post Carbon Pathways report, which reviewed many international studies, the key roadblocks are: climate change denial, the fossil fuels lobby, political inaction, unsustainable energy consumption, outdated energy infrastructure, and financial constraints.

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