Power-to-gas

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Power-to-gas

Power-to-gas (often abbreviated P2G) is a technology that uses electric power to produce a gaseous fuel.

Most P2G systems use electrolysis to produce hydrogen. The hydrogen can be used directly, or further steps (known as two-stage P2G systems) may convert the hydrogen into syngas, methane, or LPG. Single-stage P2G systems to produce methane also exist, such as reversible solid oxide cell (rSOC) technology.

Produced gas, just like natural gas or industrially produced hydrogen or methane, is a commodity and may be used as such through existing infrastructure (pipelines and gas storage facilities), including back to power at a loss. However, provided the power comes from renewable energy, it can be touted as a carbon-neutral fuel, renewable, and a way to store variable renewable energy.

Power-to-hydrogen

All current P2G systems start by using electricity to split water into hydrogen and oxygen by means of electrolysis. In a "power-to-hydrogen" system, the resulting hydrogen is injected into the natural gas grid or is used in transport or industry rather than being used to produce another gas type.

ITM Power won a tender in March 2013 for a Thüga Group project, to supply a 360 kW self-pressurising high-pressure electrolysis rapid response proton exchange membrane (PEM) electrolyser Rapid Response Electrolysis Power-to-Gas energy storage plant. The unit produces 125 kg/day of hydrogen gas and incorporates AEG power electronics. It will be situated at a Mainova AG site in the Schielestraße, Frankfurt in the state of Hessen. The operational data will be shared by the whole Thüga group – the largest network of energy companies in Germany with around 100 municipal utility members. The project partners include: badenova AG & Co. kg, Erdgas Mittelsachsen GmbH, Energieversorgung Mittelrhein GmbH, erdgas schwaben GmbH, Gasversorgung Westerwald GmbH, Mainova Aktiengesellschaft, Stadtwerke Ansbach GmbH, Stadtwerke Bad Hersfeld GmbH, Thüga Energienetze GmbH, WEMAG AG, e-rp GmbH, ESWE Versorgungs AG with Thüga Aktiengesellschaft as project coordinator. Scientific partners will participate in the operational phase. It can produce 60 cubic metres of hydrogen per hour and feed 3,000 cubic metres of natural gas enriched with hydrogen into the grid per hour. An expansion of the pilot plant is planned from 2016, facilitating the full conversion of the hydrogen produced into methane to be directly injected into the natural gas grid.

Units like ITM Power's HGas generates hydrogen to be directly injected into the gas network as Power to gas.

In December 2013, ITM Power, Mainova, and NRM Netzdienste Rhein-Main GmbH began injecting hydrogen into the German gas distribution network using ITM Power HGas, which is a rapid response proton exchange membrane electrolyser plant. The power consumption of the electrolyser is 315 kilowatts. It produces about 60 cubic meters per hour of hydrogen and thus in one hour can feed 3,000 cubic meters of hydrogen-enriched natural gas into the network.

On August 28, 2013, E.ON Hanse, Solvicore, and Swissgas inaugurated a commercial power-to-gas unit in Falkenhagen, Germany. The unit, which has a capacity of two megawatts, can produce 360 cubic meters of hydrogen per hour. The plant uses wind power and Hydrogenics electrolysis equipment to transform water into hydrogen, which is then injected into the existing regional natural gas transmission system. Swissgas, which represents over 100 local natural gas utilities, is a partner in the project with a 20 percent capital stake and an agreement to purchase a portion of the gas produced. A second 800 kW power-to-gas project has been started in Hamburg/Reitbrook district and is expected to open in 2015.

In August 2013, a 140 MW wind park in Grapzow, Mecklenburg-Vorpommern owned by E.ON received an electrolyser. The hydrogen produced can be used in an internal combustion engine or can be injected into the local gas grid. The hydrogen compression and storage system stores up to 27 MWh of energy and increases the overall efficiency of the wind park by tapping into wind energy that otherwise would be wasted. The electrolyser produces 210 Nm³/h of hydrogen and is operated by RH2-WKA.

The INGRID project started in 2013 in Apulia, Italy. It is a four-year project with 39 MWh storage and a 1.2 MW electrolyser for smart grid monitoring and control. The hydrogen is used for grid balancing, transport, industry, and injection into the gas network.

The surplus energy from the 12 MW Prenzlau Windpark in Brandenburg, Germany will be injected into the gas grid from 2014 on.

The 6 MW Energiepark Mainz from Stadtwerke Mainz, RheinMain University of Applied Sciences, Linde and Siemens in Mainz (Germany) will open in 2015.

Power to gas and other energy storage schemes to store and utilize renewable energy are part of Germany's Energiewende (energy transition program).

In France, the MINERVE demonstrator of AFUL Chantrerie (Federation of Local Utilities Association) aims to promote the development of energy solutions for the future with elected representatives, companies and more generally civil society. It aims to experiment with various reactors and catalysts. The synthetic methane produced by the MINERVE demonstrator (0.6 Nm³ / h of CH₄) is recovered as CNG fuel, which is used in the boilers of the AFUL Chantrerie boiler plant. The installation was designed and built by the French SME Top Industrie, with the support of Leaf. In November 2017 it achieved the predicted performance, 93.3% of CH₄. This project was supported by the ADEME and the ERDF-Pays de la Loire Region, as well as by several other partners: Conseil départemental de Loire -Atlantic, Engie-Cofely, GRDF, GRTGaz, Nantes-Metropolis, Sydela and Sydev.

A full scale 1GW electrolyzer operated by EWE and Tree Energy Solutions is planned at the gas terminal in Wilhelmshaven, Germany. The first 500 MW is expected to begin operation in 2028. Wilhelmshaven can accommodate a second plant, bringing total potential capacity to 2GW.

Grid injection without compression

The core of the system is a proton exchange membrane (PEM) electrolyser. The electrolyser converts electrical energy into chemical energy, which in turn facilitates the storage of electricity. A gas mixing plant ensures that the proportion of hydrogen in the natural gas stream does not exceed two per cent by volume, the technically permissible maximum value when a natural gas filling station is situated in the local distribution network. The electrolyser supplies the hydrogen-methane mixture at the same pressure as the gas distribution network, namely 3.5 bar. 

Power-to-methane

Methanation of CO₂ by electrolytically obtained hydrogen

A power-to-methane system combines hydrogen from a power-to-hydrogen system with carbon dioxide to produce methane (see natural gas) using a methanation reaction such as the Sabatier reaction or biological methanation resulting in an extra energy conversion loss of 8%, the methane may then be fed into the natural gas grid if the purity requirement is reached.

ZSW (Center for Solar Energy and Hydrogen Research) and SolarFuel GmbH (now ETOGAS GmbH) realized a demonstration project with 250 kW electrical input power in Stuttgart, Germany. The plant was put into operation on October 30, 2012.

The first industry-scale Power-to-Methane plant was realized by ETOGAS for Audi AG in Werlte, Germany. The plant with 6 MW electrical input power is using CO₂ from a waste-biogas plant and intermittent renewable power to produce synthetic natural gas (SNG) which is directly fed into the local gas grid (which is operated by EWE). The plant is part of the Audi e-fuels program. The produced synthetic natural gas, named Audi e-gas, enables CO₂-neutral mobility with standard CNG vehicles. Currently it is available to customers of Audi's first CNG car, the Audi A3 g-tron.

HELMETH Power-to-Gas Prototype

In April 2014 the European Union's co-financed and from the KIT coordinated HELMETH (Integrated High-Temperature ELectrolysis and METHanation for Effective Power to Gas Conversion) research project started. The objective of the project is the proof of concept of a highly efficient Power-to-Gas technology by thermally integrating high temperature electrolysis (SOEC technology) with CO₂-methanation. Through the thermal integration of exothermal methanation and steam generation for the high temperature steam electrolysis conversion efficiency > 85% (higher heating value of produced methane per used electrical energy) are theoretically possible. The process consists of a pressurized high-temperature steam electrolysis and a pressurized CO₂-methanation module. The project was completed in 2017 and achieved an efficiency of 76% for the prototype with an indicated growth potential of 80% for industrial scale plants. The operating conditions of the CO₂-methanation are a gas pressure of 10 - 30 bar, a SNG production of 1 - 5.4 m³/h (NTP) and a reactant conversion that produces SNG with H₂ < 2 vol.-% resp. CH₄ > 97 vol.-%. Thus, the generated substitute natural gas can be injected in the entire German natural gas network without limitations. As a cooling medium for the exothermic reaction boiling water is used at up to 300 °C, which corresponds to a water vapour pressure of about 87 bar. The SOEC works with a pressure of up to 15 bar, steam conversions of up to 90% and generates one standard cubic meter of hydrogen from 3.37 kWh of electricity as feed for the methanation.

The technological maturity of Power to Gas is evaluated in the European 27 partner project STORE&GO, which has started in March 2016 with a runtime of four years. Three different technological concepts are demonstrated in three different European countries (Falkenhagen/Germany, Solothurn/Switzerland, Troia/Italy). The technologies involved include biological and chemical methanation, direct capture of CO₂ from atmosphere, liquefaction of the synthesized methane to bio-LNG, and direct injection into the gas grid. The overall goal of the project is to assess those technologies and various usage paths under technical, economic, and legal  aspects to identify business cases on the short and on the long term. The project is co-funded by the European Union's Horizon 2020 research and innovation programme (18 million euro) and the Swiss government (6 million euro), with another 4 million euro coming from participating industrial partners. The coordinator of the overall project is the research center of the DVGW located at the KIT.

Microbial methanation

The biological methanation combines both processes, the electrolysis of water to form hydrogen and the subsequent CO₂ reduction to methane using this hydrogen. During this process, methane forming microorganisms (methanogenic archaea or methanogens) release enzymes that reduce the overpotential of a non-catalytic electrode (the cathode) so that it can produce hydrogen. This microbial power-to-gas reaction occurs at ambient conditions, i.e. room temperature and pH 7, at efficiencies that routinely reach 80-100%. However, methane is formed more slowly than in the Sabatier reaction due to the lower temperatures. A direct conversion of CO₂ to methane has also been postulated, circumventing the need for hydrogen production. Microorganisms involved in the microbial power-to-gas reaction are typically members of the order Methanobacteriales. Genera that were shown to catalyze this reaction are Methanobacterium, Methanobrevibacter, and Methanothermobacter (thermophile).

LPG production

Methane can be used to produce LPG by synthesising SNG with partial reverse hydrogenation at high pressure and low temperature. LPG in turn can be converted into alkylate which is a premium gasoline blending stock because it has exceptional antiknock properties and gives clean burning.

Power to food

The synthetic methane generated from electricity can also be used for generating protein rich feed for cattle, poultry and fish economically by cultivating Methylococcus capsulatus bacteria culture with tiny land and water footprint. The carbon dioxide gas produced as by-product from these plants can be recycled in the generation of synthetic methane (SNG). Similarly, oxygen gas produced as by product from the electrolysis of water and the methanation process can be consumed in the cultivation of bacteria culture. With these integrated plants, the abundant renewable solar and wind power potential can be converted into high value food products without any water pollution or greenhouse gas (GHG) emissions.

Biogas-upgrading to biomethane

In the third method the carbon dioxide in the output of a wood gas generator or a biogas plant after the biogas upgrader is mixed with the produced hydrogen from the electrolyzer to produce methane. The free heat coming from the electrolyzer is used to cut heating costs in the biogas plant. The impurities carbon dioxide, water, hydrogen sulfide, and particulates must be removed from the biogas if the gas is used for pipeline storage to prevent damage.

2014-Avedøre wastewater Services in Avedøre, Kopenhagen (Denmark) is adding a 1 MW electrolyzer plant to upgrade the anaerobic digestion biogas from sewage sludge. The produced hydrogen is used with the carbon dioxide from the biogas in a Sabatier reaction to produce methane. Electrochaea is testing another project outside P2G BioCat with biocatalytic methanation. The company uses an adapted strain of the thermophilic methanogen Methanothermobacter thermautotrophicus and has demonstrated its technology at laboratory-scale in an industrial environment. A pre-commercial demonstration project with a 10,000-liter reactor vessel was executed between January and November 2013 in Foulum, Denmark.

In 2016 Torrgas, Siemens, Stedin, Gasunie, A.Hak, Hanzehogeschool/EnTranCe and Energy Valley intend to open a 12 MW Power to Gas facility in Delfzijl (The Netherlands) where biogas from Torrgas (biocoal) will be upgraded with hydrogen from electrolysis and delivered to nearby industrial consumers.

Power-to-syngas

Power-to-syngas process

 

Water

CO2

Electrolysis of Water

Oxygen

Hydrogen

Conversion Reactor

Water

Hydrogen

CO

Syngas is a mixture of hydrogen and carbon monoxide. It has been used since Victorian times, when it was produced from coal and known as "towngas". A power-to-syngas system uses hydrogen from a power-to-hydrogen system to produce syngas.

• 1st step: Electrolysis of Water (SOEC) −water is split into hydrogen and oxygen.
• 2nd step: Conversion Reactor (RWGSR) −hydrogen and carbon dioxide are inputs to the Conversion Reactor that outputs hydrogen, carbon monoxide, and water. 3H₂ + CO₂ → (2H₂ + CO)^syngas + H₂O
• Syngas is used to produce synfuels.

Power-to-syngas feedstock is the same as feedstock derived from other sources.

Initiatives

Other initiatives to create syngas from carbon dioxide and water may use different water splitting methods.

• CSP
  • 2004 Sunshine-to-Petrol —Sandia National Laboratories.
  • 2013 NewCO2Fuels —New CO2 Fuels Ltd (IL) and Weizmann Institute of Science.
  • 2014 Solar-Jet Fuels —Consortium partners ETH, SHELL, DLR, Bauhaus Luftfahrt, ARTTIC.
• HTE / Alkaline water electrolysis
  • 2004 Syntrolysis Fuels —Idaho National Laboratory and Ceramatec, Inc. (US).
  • 2008 WindFuels —Doty Energy (US).
  • 2012 Air Fuel Synthesis —Air Fuel Synthesis Ltd (UK). Air Fuel Synthesis Ltd have become insolvent.
  • 2013 Green Feed —BGU and Israel Strategic Alternative Energy Foundation (I-SAEF).
  • 2014 E-diesel —Sunfire, a clean technology company and Audi.

The US Naval Research Laboratory (NRL) is designing a power-to-liquids system using the Fischer-Tropsch Process to create fuel on board a ship at sea, with the base products carbon dioxide (CO₂) and water (H₂O) being derived from sea water via "An Electrochemical Module Configuration For The Continuous Acidification Of Alkaline Water Sources And Recovery Of CO₂ With Continuous Hydrogen Gas Production".

Energy storage and transport

Power-to-gas systems may be deployed as adjuncts to wind parks or solar power plants. The excess power or off-peak power generated by wind generators or solar arrays may then be used hours, days, or months later to produce electrical power for the electrical grid. In the case of Germany, before switching to natural gas, the gas networks were operated using towngas, which for 50–60 % consisted of hydrogen. The storage capacity of the German natural gas network is more than 200,000 GWh which is enough for several months of energy requirement. By comparison, the capacity of all German pumped-storage hydroelectricity plants amounts to only about 40 GWh. Natural gas storage is a mature industry that has been in existence since Victorian times. The storage/retrieval power rate requirement in Germany is estimated at 16 GW in 2023, 80 GW in 2033 and 130 GW in 2050. The storage costs per kilowatt hour are estimated at €0.10 for hydrogen and €0.15 for methane.

The existing natural gas transport infrastructure conveys massive amounts of gas for long distances profitably using pipelines. It is now profitable to ship natural gas between continents using LNG carriers. The transport of energy through a gas network is done with much less loss (<0.1%) than in an electrical transmission network (8%). This infrastructure can transport methane produced by P2G without modification. It is possible to use it for up to 20% hydrogen. The use of the existing natural gas pipelines for hydrogen was studied by the EU NaturalHy project and the United States Department of Energy (DOE). Blending technology is also used in HCNG.

Efficiency

In 2013, the round-trip efficiency of power-to-gas-storage was well below 50%, with the hydrogen path being able to reach a maximum efficiency of ~ 43% and methane of ~ 39% by using combined cycle power plants. If cogeneration plants are used that produce both electricity and heat, efficiency can be above 60%, but is still less than pumped hydro or battery storage. However, there is potential to increase the efficiency of power-to-gas storage. In 2015 a study published in Energy and Environmental Science found that by using reversible solid oxide cells and recycling waste heat in the storage process, electricity-to-electricity round-trip efficiencies exceeding 70% can be reached at low cost. In addition, a 2018 study using pressurized reversible solid oxide cells and a similar methodology found that round-trip efficiencies (power-to-power) of up to 80% might be feasible.

Overall energy conversion efficiency by pathway and fuel
using electrolysis of water, plus methanation to produce methane

Fuel	Efficiency	Conditions
Pathway: Electricity→Gas
Hydrogen	54–72 %	200 bar compression
Methane (SNG)	49–64 %
Hydrogen	57–73 %	80 bar compression (Natural gas pipeline)
Methane (SNG)	50–64 %
Hydrogen	64–77 %	without compression
Methane (SNG)	51–65 %
Pathway: Electricity→Gas→Electricity
Hydrogen	34–44 %	80 bar compression up to 60% back to electricity
Methane (SNG)	30–38 %
Pathway: Electricity→Gas→Electricity & heat (cogeneration)
Hydrogen	48–62 %	80 bar compression and electricity/heat for 40/45 %
Methane (SNG)	43–54 %

Electrolysis technology

• Relative advantages and disadvantages of electrolysis technologies.

Alkaline Electrolysis

Advantage	Disadvantage
Commercial technology (high technology readiness level)	Limited cost reduction and efficiency improvement potential
Low investment electrolyser	High maintenance intensity
Large stack size	Modest reactivity, ramp rates and flexibility (minimal load 20%)
Extremely low hydrogen impurity (0.001%)	Stacks < 250 kW require unusual AC/DC converters
	Corrosive electrolyte deteriorates when not operating nominally

Proton Exchange Membrane Electrolysis (PEME)

Advantage	Disadvantage
Reliable technology (no kinetics) and simple, compact design	High investment costs (noble metals, membrane)
Very fast response time	Limited lifetime of membranes
Cost reduction potential (modular design)	Requires high water purity

Solid Oxide Electrolysis Cell (SOEC)

Advantage	Disadvantage
Highest electrolysis efficiency	Very low technology readiness level (proof of concept)
Low capital costs	Poor lifetime because of high temperature and affected material stability
Possibilities for integration with chemical methanation (heat recycling)	Limited flexibility; constant load required

Virtue ethics

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Virtue_ethics

Virtue ethics (also aretaic ethics, from Greek ἀρετή [aretḗ]) is a philosophical approach that treats virtue and character as the primary subjects of ethics, in contrast to other ethical systems that put consequences of voluntary acts, principles or rules of conduct, or obedience to divine authority in the primary role.

Virtue ethics is usually contrasted with two other major approaches in ethics, consequentialism and deontology, which make the goodness of outcomes of an action (consequentialism) and the concept of moral duty (deontology) central. While virtue ethics does not necessarily deny the importance to ethics of goodness of states of affairs or of moral duties, it emphasizes virtue, and sometimes other concepts, like eudaimonia, to an extent that other ethics theories do not.

Key concepts

Virtue and vice

Main articles: Virtue and Moral character

In virtue ethics, a virtue is a characteristic disposition to think, feel, and act well in some domain of life. In contrast, a vice is a characteristic disposition to think, feel, and act poorly in some domain of life. Virtues are not everyday habits; they are character traits, in the sense that they are central to someone’s personality and what they are like as a person.

In early versions and some modern versions of virtue ethics, a virtue is defined as a character trait that promotes or exhibits human "flourishing and well being" in the person who exhibits it. Some modern versions of virtue ethics do not define virtues in terms of well being or flourishing, and some go so far as to define virtues as traits that tend to promote some other good that is defined independently of the virtues, thereby subsuming virtue ethics under (or somehow merging it with) consequentialist ethics.

To Aristotle, a virtue was not a skill that made you better able to achieve eudaimonia but was itself an expression of eudaimonia — eudaimonia in activity.

In contrast with consequentialist and deontological ethical systems, in which one may be called upon to do the right thing even though it is not in one's own interests (one is to do it instead for the greater good, or out of duty), in virtue ethics, one does the right thing because it is in one's own interests. Part of training in practical virtue ethics is to come to see the coincidence of one's enlightened self-interest and the practice of the virtues, so that one is virtuous willingly, gladly, and enthusiastically because one knows that being virtuous is the best thing one can do with oneself.

Virtue and emotion

In ancient Greek and modern eudaimonic virtue ethics, virtues and vices are complex dispositions that involve both affective and intellectual components. That is, they are dispositions that involve both being able to reason well about the right thing to do (see below on phronesis), and also to engage emotions and feelings correctly.

For example, a generous person can reason well about when and how to help people, and such a person also helps people with pleasure and without conflict. In this, virtuous people are contrasted not only with vicious people (who reason poorly about what to do and are emotionally attached to the wrong things) and with the incontinent (who are tempted by their feelings into doing the wrong thing even though they know what is right), but also with the merely continent (whose emotions tempt them toward doing the wrong thing but whose strength of will lets them do what they know is right).

According to Rosalind Hursthouse, in Aristotelian virtue ethics, the emotions have moral significance because "virtues (and vices) are all dispositions not only to act, but to feel emotions, as reactions as well as impulses to action... [and] In the person with the virtues, these emotions will be felt on the right occasions, toward the right people or objects, for the right reasons, where 'right' means 'correct'..."

Phronesis and eudaimonia

Phronesis (φρόνησις; prudence, practical virtue, or practical wisdom) is an acquired trait that enables its possessor to identify the best thing to do in any given situation. Unlike theoretical wisdom, practical reason results in action or decision. As John McDowell puts it, practical wisdom involves a "perceptual sensitivity" to what a situation requires.

Eudaimonia (εὐδαιμονία) is a state variously translated from Greek as 'well-being', 'happiness', 'blessedness', and in the context of virtue ethics, 'human flourishing'. Eudaimonia in this sense is not a subjective, but an objective, state. It characterizes the well-lived life.

According to Aristotle, the most prominent exponent of eudaimonia in the Western philosophical tradition, eudaimonia defines the goal of human life. It consists of exercising the characteristic human quality—reason—as the soul's most proper and nourishing activity. In his Nicomachean Ethics, Aristotle, like Plato before him, argued that the pursuit of eudaimonia is an "activity of the soul in accordance with perfect virtue", which further could only properly be exercised in the characteristic human community—the polis or city-state.

Although eudaimonia was first popularized by Aristotle, it now belongs to the tradition of virtue theories generally. For the virtue theorist, eudaimonia describes that state achieved by the person who lives the proper human life, an outcome that can be reached by practicing the virtues. A virtue is a habit or quality that allows the bearer to succeed at his, her, or its purpose. The virtue of a knife, for example, is sharpness; among the virtues of a racehorse is speed. Thus, to identify the virtues for human beings, one must have an account of what is the human purpose.

Not all modern virtue ethics theories are eudaimonic; some place another end in place of eudaimonia, while others are non-teleological: that is, they do not account for virtues in terms of the results that the practice of the virtues produce or tend to produce.

History of virtue

Like much of the Western tradition, virtue theory originated in ancient Greek philosophy.

Virtue ethics began with Socrates, and was subsequently developed further by Plato, Aristotle, and the Stoics. Virtue ethics concentrates on the character of the individual, rather than the acts (or consequences thereof) of the individual. There is debate among adherents of virtue ethics concerning what specific virtues are praiseworthy. However, most theorists agree that ethics is demonstrated by the practice of virtues.

Plato and Aristotle's treatments of virtues are not the same. Plato believes virtue is effectively an end to be sought, for which a friend might be a useful means. Aristotle states that the virtues function more as means to safeguard human relations, particularly authentic friendship, without which one's quest for happiness is frustrated.

Discussion of what were known as the four cardinal virtues—wisdom, justice, fortitude, and temperance—can be found in Plato's Republic. The virtues also figure prominently in Aristotle's ethical theory found in Nicomachean Ethics.

Virtue theory was inserted into the study of history by moralistic historians such as Livy, Plutarch, and Tacitus. The Greek idea of the virtues was passed on in Roman philosophy through Cicero and later incorporated into Christian moral theology by Ambrose of Milan. During the scholastic period, the most comprehensive consideration of the virtues from a theological perspective was provided by Thomas Aquinas in his Summa Theologiae and his Commentaries on the Nicomachean Ethics.

After the Reformation, Aristotle's Nicomachean Ethics continued to be the main authority for the discipline of ethics at Protestant universities until the late seventeenth century, with over fifty Protestant commentaries published on the Nicomachean Ethics before 1682.

Though the tradition receded into the background of European philosophical thought in the past few centuries, the term "virtue" remained current during this period, and in fact appears prominently in the tradition of classical republicanism or classical liberalism. This tradition was prominent in the intellectual life of 16th-century Italy, as well as 17th- and 18th-century Britain and America; indeed the term "virtue" appears frequently in the work of Tomás Fernández de Medrano, Niccolò Machiavelli, David Hume, the republicans of the English Civil War period, the 18th-century English Whigs, and the prominent figures among the Scottish Enlightenment and the American Founding Fathers.

Contemporary "aretaic turn"

Although some Enlightenment philosophers (e.g. Hume) continued to emphasise the virtues, with the ascendancy of utilitarianism and deontological ethics, virtue theory moved to the margins of Western philosophy. The contemporary revival of virtue theory is frequently traced to the philosopher Elizabeth Anscombe's 1958 essay "Modern Moral Philosophy". Following this:

• In the 1976 paper "The Schizophrenia of Modern Ethical Theories", Michael Stocker summarises the main aretaic criticisms of deontological and consequentialist ethics.
• Philosopher, psychologist, and encyclopedist Mortimer Adler appealed to Aristotelian ethics, and the virtue theory of happiness or eudaimonia throughout his published work.
• Philippa Foot, published a collection of essays in 1978 entitled Virtues and Vices.
• Alasdair MacIntyre made an effort to reconstruct a virtue-based theory in dialogue with the problems of modern and postmodern thought; his works include After Virtue and Three Rival Versions of Moral Enquiry.
• Paul Ricoeur accorded an important place to Aristotelian teleological ethics in his hermeneutical phenomenology of the subject, most notably in his book Oneself as Another.
• Theologian Stanley Hauerwas found the language of virtue helpful in his own project.
• Richard Taylor argues for the restoration of classical virtues as the basis for morality in Virtue Ethics An Introduction (1991) 
• Roger Crisp and Michael Slote edited a collection of important essays titled Virtue Ethics.
• Martha Nussbaum and Amartya Sen employed virtue theory in theorising the capability approach to international development.
• Julia Annas wrote The Morality of Happiness (1993).
• Lawrence C. Becker identified current virtue theory with Greek Stoicism in A New Stoicism. (1998).
• Rosalind Hursthouse published On Virtue Ethics (1999).
• Psychologist Martin Seligman drew on classical virtue ethics in conceptualizing positive psychology.
• Psychologist Daniel Goleman opens his book on Emotional Intelligence with a challenge from Aristotle's Nicomachean Ethics.
• Michael Sandel discusses Aristotelian ethics to support his ethical theory of justice in his book Justice: What's the Right Thing to Do?

The aretaic turn in moral philosophy is paralleled by analogous developments in other philosophical disciplines. One of these is epistemology, where a distinctive virtue epistemology was developed by Linda Zagzebski and others. In political theory, there has been discussion of "virtue politics", and in legal theory, there is a small but growing body of literature on virtue jurisprudence. The aretaic turn also exists in American constitutional theory, where proponents argue for an emphasis on virtue and vice of constitutional adjudicators.

Aretaic approaches to morality, epistemology, and jurisprudence have been the subject of intense debates. One criticism focuses on the problem of guidance; one opponent, Robert Louden in his article "Some Vices of Virtue Ethics", questions whether the idea of a virtuous moral actor, believer, or judge can provide the guidance necessary for action, belief formation, or the resolution of legal disputes.

Lists of virtues

There are several lists of virtues. Socrates argued that virtue is knowledge, which suggests that there is really only one virtue. The Stoics identified four cardinal virtues: wisdom, justice, courage, and temperance. Wisdom is subdivided into good sense, good calculation, quick-wittedness, discretion, and resourcefulness. Justice is subdivided into piety, honesty, equity, and fair dealing. Courage is subdivided into endurance, confidence, high-mindedness, cheerfulness, and industriousness. Temperance or moderation is subdivided into good discipline, seemliness, modesty, and self-control.

John McDowell argues that virtue is a "perceptual capacity" to identify how one ought to act, and that all particular virtues are merely "specialized sensitivities" to a range of reasons for acting.

Aristotle's list

Aristotle identifies approximately 18 virtues that demonstrate a person is performing their human function well. He distinguished virtues pertaining to emotion and desire from those relating to the mind. The first he calls moral virtues, and the second intellectual virtues (though both are "moral" in the modern sense of the word).

Moral virtues

Aristotle suggested that each moral virtue was a mean (see golden mean) between two corresponding vices, one of excess and one of deficiency. Each intellectual virtue is a mental skill or habit by which the mind arrives at truth, affirming what is or denying what is not. In the Nicomachean Ethics he discusses about 11 moral virtues:

SPHERE OF ACTION OR FEELING	EXCESS	MEAN: MORAL VIRTUE	DEFICIENCY
Fear and confidence	Rashness	Courage in the face of fear	Cowardice
Pleasure and pain	Licentiousness / self-indulgence	Temperance in the face of pleasure and pain	Insensibility
Getting and spending (minor)	Prodigality	Liberality with wealth and possessions	Illiberality / meanness
Getting and spending (major)	Vulgarity / tastelessness	Magnificence with great wealth and possessions	Pettiness / stinginess
Honor and dishonor (major)	Vanity	Magnanimity with great honors	Pusillanimity
Honor and dishonor (minor)	Ambition/empty vanity	Proper ambition with normal honors	Unambitiousness / undue humility
Anger	Irascibility	Patience/good temper	Lack of spirit/unirascibility
Self-expression	Boastfulness	Truthfulness with self-expression	Understatement / mock modesty
Conversation	Buffoonery	Wittiness in conversation	Boorishness
Social conduct	Obsequiousness	Friendliness in social conduct	Cantankerousness
Indignation	Envy	Justice and righteous indignation in the face of injury	Malicious enjoyment / spitefulness

Intellectual virtues

1. Nous (intelligence), which apprehends fundamental truths (such as definitions, self-evident principles)
2. Episteme (science), which is skill with inferential reasoning (such as proofs, syllogisms, demonstrations)
3. Sophia (theoretical wisdom), which combines fundamental truths with valid, necessary inferences to reason well about unchanging truths.

Aristotle also mentions several other traits:

• Gnome (good sense) – passing judgment, "sympathetic understanding"
• Synesis (understanding) – comprehending what others say, does not issue commands
• Phronesis (practical wisdom) – knowledge of what to do, knowledge of changing truths, issues commands
• Techne (art, craftsmanship)

Aristotle's list is not the only list, however. As Alasdair MacIntyre observed in After Virtue, thinkers as diverse as Homer, the authors of the New Testament, Thomas Aquinas, and Benjamin Franklin have all proposed lists. Walter Kaufmann proposed as the four cardinal virtues: ambition/humility ("humbition"), love, courage, and honesty.

Criticisms

Proponents of virtue theory sometimes argue that a central feature of a virtue is its universal applicability. In other words, any character trait defined as a virtue must reasonably be universally regarded as a virtue for all people. According to this view, it is inconsistent to claim, for example, servility as a female virtue, while at the same time not proposing it as a male one.

Other proponents of virtue theory, notably Alasdair MacIntyre, respond to this objection by arguing that any account of the virtues must indeed be generated out of the community in which those virtues are to be practiced: the very word ethics implies ethos. That is to say that the virtues are, and necessarily must be, grounded in a particular time and place. What counts as a virtue in 4th-century BCE Athens would be a ludicrous guide to proper behaviour in 21st-century CE Toronto and vice versa. To take this view does not necessarily commit one to the argument that accounts of the virtues must therefore be static: moral activity—that is, attempts to contemplate and practice the virtues—can provide the cultural resources that allow people to change, albeit slowly, the ethos of their own societies.

MacIntyre appears to take this position in his seminal work on virtue ethics, After Virtue.

Another objection to virtue theory is that virtue ethics does not focus on what sorts of actions are morally permitted and which ones are not, but rather on what sort of qualities someone ought to foster in order to become a good person. In other words, while some virtue theorists may not condemn, for example, murder as an inherently immoral or impermissible sort of action, they may argue that someone who commits a murder is severely lacking in several important virtues, such as compassion and fairness. Still, antagonists of the theory often object that this particular feature of the theory makes virtue ethics useless as a universal norm of acceptable conduct suitable as a base for legislation. Some virtue theorists concede this point, but respond by opposing the very notion of legitimate legislative authority instead, effectively advocating some form of anarchism as the political ideal. Other virtue theorists argue that laws should be made by virtuous legislators, and still another group argue that it is possible to base a judicial system on the moral notion of virtues rather than rules. Aristotle himself saw his Nicomachean Ethics as a prequel for his Politics and felt that the point of politics was to create the fertile soil for a virtuous citizenry to develop in, and that one purpose of virtue was that it helps you to contribute to a healthy polis.

Some virtue theorists might respond to this overall objection with the notion of a "bad act" also being an act characteristic of vice. That is to say that those acts that do not aim at virtue, or that stray from virtue, would constitute our conception of "bad behavior". Although not all virtue ethicists agree to this notion, this is one way the virtue ethicist can re-introduce the concept of the "morally impermissible". One could raise an objection that he is committing an argument from ignorance by postulating that what is not virtuous is unvirtuous. In other words, just because an action or person 'lacks of evidence' for virtue does not, all else constant, imply that said action or person is unvirtuous.

Subsumed in deontology and utilitarianism

Martha Nussbaum suggested that while virtue ethics is often considered to be anti-Enlightenment, "suspicious of theory and respectful of the wisdom embodied in local practices", it is actually neither fundamentally distinct from, nor does it qualify as a rival approach to deontology and utilitarianism. She argues that philosophers from these two Enlightenment traditions often include theories of virtue. She pointed out that Kant's "Doctrine of Virtue" (in The Metaphysics of Morals) "covers most of the same topics as do classical Greek theories", "that he offers a general account of virtue, in terms of the strength of the will in overcoming wayward and selfish inclinations; that he offers detailed analyses of standard virtues such as courage and self-control, and of vices, such as avarice, mendacity, servility, and pride; that, although in general, he portrays inclination as inimical to virtue, he also recognizes that sympathetic inclinations offer crucial support to virtue, and urges their deliberate cultivation."

Nussbaum also points to considerations of virtue by utilitarians such as Henry Sidgwick (The Methods of Ethics), Jeremy Bentham (The Principles of Morals and Legislation), and John Stuart Mill, who writes of moral development as part of an argument for the moral equality of women (The Subjection of Women). She argues that contemporary virtue ethicists such as Alasdair MacIntyre, Bernard Williams, Philippa Foot, and John McDowell have few points of agreement and that the common core of their work does not represent a break from Kant.

Kantian critique

Immanuel Kant's position on virtue ethics is contested. Those who argue that Kantian deontology conflicts with virtue ethics include Alasdair MacIntyre, Philippa Foot, and Bernard Williams. In the Groundwork of the Metaphysics of Morals and the Critique of Practical Reason, Immanuel Kant offers many different criticisms of ethical frameworks and against moral theories before him. Kant rarely mentioned Aristotle by name but did not exclude his moral philosophy of virtue ethics from his critique. Many Kantian arguments against virtue ethics claim that virtue ethics is inconsistent, or sometimes that it is not a real moral theory at all.

In "What Is Virtue Ethics All About?", Gregory Velazco y Trianosky identified the key points of divergence between virtue ethicists and what he called "neo-Kantianism", in the form these nine neo-Kantian moral assertions:

1. The crucial moral question is "what is it right/obligatory to do?"
2. Moral judgments are those that concern the rightness of actions.
3. Such judgments take the form of rules or principles.
4. Such rules or principles are universal, not respecting persons.
5. They are not based on some concept of human good that is independent of moral goodness.
6. They take the form of categorical imperatives that can be justified independently of the desires of the person they apply to.
7. They are motivating; they can compel action in an agent, also independently of that agent's desires.
8. An action, in order to be morally virtuous, must be motivated by this sort of moral judgment (not, for example, merely coincidentally aligned with it).
9. The virtuousness of a character trait, or virtue, derives from the relationship that trait has to moral judgments, rules, and principles.

Trianosky says that modern sympathizers with virtue ethics almost all reject neo-Kantian claim #1, and many of them also reject certain of the other claims.

Utopianism and pluralism

Robert B. Louden criticizes virtue ethics on the basis that it promotes a form of unsustainable utopianism. Trying to arrive at a single set of virtues is immensely difficult in contemporary societies as, according to Louden, they contain "more ethnic, religious, and class groups than did the moral community which Aristotle theorized about" with each of these groups having "not only its own interests but its own set of virtues as well". Louden notes in passing that MacIntyre, a supporter of virtue-based ethics, has grappled with this in After Virtue but that ethics cannot dispense with building rules around acts and rely only on discussing the moral character of persons.

Topics in virtue ethics

Virtue ethics as a category

Further information: Utilitarianism, Utilitarianism (book), and On Liberty

Virtue contrasts with deontological and consequentialist ethics; the three are the most predominant contemporary normative-ethical theories. Deontological ethics, sometimes referred to as duty ethics, emphasizes adherence to ethical principles or duties. How these duties are defined, however, is often a subject of debate. One rule scheme used by deontologists is divine command theory. Deontology also depends upon meta-ethical realism in postulating the existence of moral absolutes, regardless of circumstances. Immanuel Kant is considered a foremost theorist of deontological ethics.

The next predominant school of thought in normative ethics is consequentialism. While deontology emphasizes doing one's duty, consequentialism bases the morality of an action on its outcome. Instead of saying that one has a moral duty to abstain from murder, a consequentialist would say that we should abstain from murder because it has undesirable effects. The main contention is what outcomes should (or can) be identified as objectively desirable.

John Stuart Mill's greatest happiness principle is a commonly-adopted criterion of what is objectively desirable. Mill asserts that the desirability of an action is the net amount of happiness it brings, the number of people it brings happiness to, and the duration of that happiness. He tries to delineate classes of happiness, some preferable to others, but classifying such a concept is difficult.

A virtue ethicist identifies virtues (also known as desirable characteristics) that a good person embodies. Exhibiting these virtues is the aim of ethics, and one's actions are a reflection of one's virtues. To the virtue philosopher, action cannot be used as a demarcation of morality because a virtue encompasses more than a selection of an action; it is a way of being that leads the person exhibiting the virtue to consistently make certain types of choices. There is disagreement in virtue ethics about what are, and what are not, virtues. There are also difficulties in identifying the "virtuous" action to take in all circumstances, and how to define a virtue.

Consequentialist and deontological theories often still employ the term virtue in a restricted sense: as a tendency (or disposition) to adhere to the system's principles or rules. In those theories, virtue is secondary and the principles (or rules) are primary. These differing senses of what constitutes virtue are a potential source of confusion. Dogmatic claims about the purpose of human life, or about what a good life is for human beings, are typically controversial.

Virtue and politics

Virtue theory emphasizes Aristotle's belief in the polis as the acme of political organization, and the role of the virtues in enabling human beings to flourish in that environment. In contrast, classical republicanism emphasizes Tacitus's concern that power and luxury can corrupt individuals and destroy liberty, as Tacitus perceived in the transformation of the Roman Republic into the Roman Empire. Virtue for classical republicans is a shield against this sort of corruption and a means to preserve the good life one has, rather than a means by which to achieve the good life one does not yet have. Another way to put the distinction between the two traditions is that virtue ethics relies on Aristotle's fundamental distinction between the human-being-as-he-is from the human-being-as-he-should-be, while classical republicanism relies on the Tacitean distinction of the risk-of-becoming.

Virtue ethics has a number of contemporary applications:

Social and political philosophy

Within the field of social ethics, Deirdre McCloskey argues that virtue ethics can provide a basis for a balanced approach to understanding capitalism and capitalist societies.

Education

Within the field of philosophy of education, James Page argues that virtue ethics can provide a rationale and foundation for peace education.

Health care and medical ethics

Thomas Alured Faunce argued that whistleblowing in healthcare settings would be more respected within clinical governance pathways if it had a firmer academic foundation in virtue ethics. He called for whistleblowing to be expressly supported in the UNESCO Universal Declaration on Bioethics and Human Rights. Barry Schwartz argues that "practical wisdom" is an antidote to much of the inefficient and inhumane bureaucracy of modern health care systems.

Technology and the virtues

In her book Technology and the Virtues, Shannon Vallor proposed a series of "technomoral" virtues that people need to cultivate in order to flourish in our socio-technological world: Honesty (Respecting Truth), Self-control (Becoming the Author of Our Desires), Humility (Knowing What We Do Not Know), Justice (Upholding Rightness), Courage (Intelligent Fear and Hope), Empathy (Compassionate Concern for Others), Care (Loving Service to Others), Civility (Making Common Cause), Flexibility (Skillful Adaptation to Change), Perspective (Holding on to the Moral Whole), and Magnanimity (Moral Leadership and Nobility of Spirit).