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Saturday, October 21, 2023

Fuel cell vehicle

From Wikipedia, the free encyclopedia
 
Foton BJ6123FCEVCH-1 fuel cell bus in operation

A fuel cell vehicle (FCV) or fuel cell electric vehicle (FCEV) is an electric vehicle that uses a fuel cell, sometimes in combination with a small battery or supercapacitor, to power its onboard electric motor. Fuel cells in vehicles generate electricity generally using oxygen from the air and compressed hydrogen. Most fuel cell vehicles are classified as zero-emissions vehicles that emit only water and heat. As compared with internal combustion vehicles, hydrogen vehicles centralize pollutants at the site of the hydrogen production, where hydrogen is typically derived from reformed natural gas. Transporting and storing hydrogen may also create pollutants. Fuel cells have been used in various kinds of vehicles including forklifts, especially in indoor applications where their clean emissions are important to air quality, and in space applications. Fuel cells are being developed and tested in trucks, buses, boats, ships, motorcycles and bicycles, among other kinds of vehicles.

The first road vehicle powered by a fuel cell was the Chevrolet Electrovan, introduced by General Motors in 1966. The Toyota FCHV and Honda FCX, which began leasing on December 2, 2002, became the world's first government-certified commercial fuel cell vehicles, and the Honda FCX Clarity, which began leasing in 2008, was the world's first fuel cell vehicle designed for mass production rather than adapting an existing model. In 2013, Hyundai Motors began production of the Hyundai ix35 FCEV, claimed to be the world's first mass-produced fuel cell electric vehicle, which was subsequently introduced to the market as a lease-only vehicle. In 2014, Toyota began selling the Toyota Mirai, the world's first dedicated fuel cell vehicle.

As of December 2020, 31,225 passenger FCEVs powered with hydrogen had been sold worldwide. As of 2021, there were only two models of fuel cell cars publicly available in select markets: the Toyota Mirai (2014-present) and the Hyundai Nexo (2018–present). The Honda Clarity was produced from 2016 to 2021, when it was discontinued. As of 2020, there was limited hydrogen infrastructure, with fewer than fifty hydrogen fueling stations for automobiles publicly available in the U.S. Critics doubt whether hydrogen will be efficient or cost-effective for automobiles, as compared with other zero-emission technologies, and in 2019, The Motley Fool opined: "What's tough to dispute is that the hydrogen fuel cell dream is all but dead for the passenger vehicle market."

Description and purpose of fuel cells in vehicles

All fuel cells are made up of three parts: an electrolyte, an anode and a cathode. In principle, a hydrogen fuel cell functions like a battery, producing electricity, which can run an electric motor. Instead of requiring recharging, however, the fuel cell can be refilled with hydrogen. Different types of fuel cells include polymer electrolyte membrane (PEM) Fuel Cells, direct methanol fuel cells, phosphoric acid fuel cells, molten carbonate fuel cells, solid oxide fuel cells, reformed methanol fuel cell and Regenerative Fuel Cells.

History

1966 GM Electrovan

The concept of the fuel cell was first demonstrated by Humphry Davy in 1801, but the invention of the first working fuel cell is credited to William Grove, a chemist, lawyer, and physicist. Grove's experiments with what he called a "gas voltaic battery" proved in 1842 that an electric current could be produced by an electrochemical reaction between hydrogen and oxygen over a platinum catalyst. English engineer Francis Thomas Bacon expanded on Grove's work, creating and demonstrating various alkaline fuel cells from 1939 to 1959.

The first modern fuel cell vehicle was a modified Allis-Chalmers farm tractor, fitted with a 15 kilowatt fuel cell, around 1959. The Cold War Space Race drove further development of fuel cell technology. Project Gemini tested fuel cells to provide electrical power during crewed space missions. Fuel cell development continued with the Apollo Program. The electrical power systems in the Apollo capsules and lunar modules used alkali fuel cells. In 1966, General Motors developed the first fuel cell road vehicle, the Chevrolet Electrovan. It had a PEM fuel cell, a range of 120 miles and a top speed of 70 mph. There were only two seats, as the fuel cell stack and large tanks of hydrogen and oxygen took up the rear portion of the van. Only one was built, as the project was deemed cost-prohibitive.

General Electric and others continued working on PEM fuel cells in the 1970s. Fuel cell stacks were still limited principally to space applications in the 1980s, including the Space Shuttle. However, the closure of the Apollo Program sent many industry experts to private companies. By the 1990s, automobile manufacturers were interested in fuel cell applications, and demonstration vehicles were readied. In 2001, the first 700 Bar (10000 PSI) hydrogen tanks were demonstrated, reducing the size of the fuel tanks that could be used in vehicles and extending the range.

Applications

There are fuel cell vehicles for all modes of transport. The most prevalent fuel cell vehicles are cars, buses, forklifts and material handling vehicles.

Automobiles

The Honda FCX, along with the Toyota FCHV, is the world's first government-certified commercial hydrogen fuel cell vehicle.
2008 Honda FCX Clarity

Honda established the world's first fuel cell vehicle dealer network in 2008, and at the time was the only company able to lease hydrogen fuel cell vehicles to private customers. The Honda FCX Clarity was introduced in 2008 for leasing by customers in Japan and Southern California and discontinued by 2015. From 2008 to 2014, Honda leased a total of 45 FCX units in the US. Over 20 other FCEV prototypes and demonstration cars were released in that time period, including the GM HydroGen4, and Mercedes-Benz F-Cell.

The Hyundai ix35 FCEV Fuel Cell vehicle was available for lease from 2014 to 2018, when 54 units were leased. In 2018, Hyundai introduced the Nexo.

Sales of the Toyota Mirai to customers began in Japan in December 2014. Most of the initial customers were expected to be governments and corporations, not individuals. Pricing started at ¥6,700,000 (~US$57,400) before taxes and a government incentive of ¥2,000,000 (~US$19,600). Former European Parliament President Pat Cox estimated that Toyota initially would lose about $100,000 on each Mirai sold. As of December 2017, global sales totaled 5,300 Mirais. The top selling markets were the U.S. with 2,900 units, Japan with 2,100 and Europe with 200.

In 2015, Toyota announced that it would offer all 5,680 patents related to hydrogen fuel cell vehicles and hydrogen fuel cell charging station technology, which it has been researching for over 20 years, to its competitors free of charge in order to stimulate the market for hydrogen-powered vehicles.

The Honda Clarity Fuel Cell was produced from 2016 to 2021. The 2017 Clarity had the highest combined and city fuel economy ratings among all hydrogen fuel cell cars rated by the EPA that year, with a combined city/highway rating of 67 miles per gallon gasoline equivalent (MPGe), and 68 MPGe in city driving. In 2019, Katsushi Inoue, the president of Honda Europe, stated, "Our focus is on hybrid and electric vehicles now. Maybe hydrogen fuel cell cars will come, but that's a technology for the next era."

By 2017, Daimler phased out its FCEV development, citing declining battery costs and increasing range of EVs, and most of the automobile companies developing hydrogen cars had switched their focus to battery electric vehicles. By 2020, only three car makers were still manufacturing, or had active manufacturing programs for hydrogen cars.

Fuel economy

The following table compares EPA's fuel economy expressed in miles per gallon gasoline equivalent (MPGe) for the two models of hydrogen fuel cell vehicles rated by the EPA as of September 2021, and available in California.

Comparison of fuel economy expressed in MPGe for hydrogen fuel cell vehicles

available for sale or lease in California and rated by the U.S. Environmental Protection Agency as of September 2021

Vehicle Model year Combined

fuel economy

City

fuel economy

Highway

fuel economy

Range Annual

fuel cost

Hyundai Nexo 2019–2021 61 mpg-e 65 mpg-e 58 mpg-e 380 mi (610 km)
Toyota Mirai 2016–2020 66 mpg-e 66 mpg-e 66 mpg-e 312 mi (502 km)
Toyota Mirai 2021 74 mpg-e 76 mpg-e 71 mpg-e 402 mi (647 km)
Notes: One kg of hydrogen has roughly the same energy content as one U.S. gallon of gasoline.

Fuel cells powered by an ethanol reformer

In June 2016, Nissan announced plans to develop fuel cell vehicles powered by ethanol rather than hydrogen. Nissan claims this technical approach would be cheaper, and that it would be easier to deploy the fueling infrastructure than a hydrogen infrastructure. The vehicle would include a tank holding a blend of water and ethanol, which is fed into an onboard reformer that splits it into hydrogen and carbon dioxide. The hydrogen is then fed into a solid oxide fuel cell. According to Nissan, the liquid fuel could be an ethanol-water blend at a 55:45 ratio.

Buses

Yutong F12 in Zhengzhou, China in 2022

As of 2020, 5,648 hydrogen fuel cell buses were in use around the world, with 93.7% of them in China.[54]

From the late 1980s, concern regarding diesel emissions from buses led to experimentation with fuel cells to power them. After initial experiments with phosphoric acid fuel cells, hydrogen-powered fuel-cell buses were tested in cities in the late 1990s. In the 2000s, buses entered trial service in cities around the world; the European Union supported the research project Clean Urban Transport for Europe.

By the 2010s, commercial introduction of hydrogen fuel cell buses was underway around the world. However, many transit operators were purchasing battery electric buses instead, as these were cheaper to operate and purchase. However, battery electric buses lacked range compared to diesel buses, take time to charge (often overnight, compared with hydrogen fuel cell buses, which can be refilled quickly) and have reduced energy storage in cold weather. Some companies have proposed using the fuel cell as a range extender, combining it with a larger battery or a supercapacitor.

Hydrogen fuel cell buses have historically been significantly more expensive to purchase and operate than diesel, hybrid or electric buses. In recent years, costs have been reduced to levels comparable with diesel buses.

A variety of bus manufacturers are currently producing hydrogen fuel cell buses. Bus manufacturers usually work with a provider of hydrogen fuel cells to power the bus, such as Ballard Power Systems or Toyota.

Forklifts

A fuel cell forklift (also called a fuel cell lift truck or a fuel cell forklift) is a fuel cell-powered industrial forklift truck used to lift and transport materials. Most fuel cells used in forklifts are powered by PEM fuel cells.

In 2013, there were over 4,000 fuel cell forklifts used in material handling in the US from which only 500 received funding from DOE (2012). Fuel cell fleets are operated by a large number of companies, including Sysco Foods, FedEx Freight, GENCO (at Wegmans, Coca-Cola, Kimberly Clark, and Whole Foods), and H-E-B Grocers. Europe demonstrated 30 fuel cell forklifts with Hylift and extended it with HyLIFT-EUROPE to 200 units, with other projects in France and Austria. Pike Research stated in 2011 that fuel-cell-powered forklifts will be the largest driver of hydrogen fuel demand by 2020.

PEM fuel-cell-powered forklifts provide significant benefits over petroleum powered forklifts as they produce no local emissions. Fuel-cell forklifts can work for a full 8-hour shift on a single tank of hydrogen, can be refueled in 3 minutes and have a lifetime of 8–10 years. Fuel cell-powered forklifts are often used in refrigerated warehouses as their performance is not degraded by lower temperatures. In design the FC units are often made as drop-in replacements.

Yamaha FC-me motorcycle

Motorcycles and bicycles

In 2005, the British firm Intelligent Energy produced the first working hydrogen run motorcycle called the ENV (Emission Neutral Vehicle). It holds enough fuel to run for four hours, and to travel 160 km (100 mi) in an urban area, at a top speed of 80 km/h (50 mph). There are other examples of bikes and bicycles with a hydrogen fuel cell engine. The Suzuki Burgman received "whole vehicle type" approval in the EU. The PHB was a hydrogen bicycle with an electric motor. It debuted in Shanghai in 2008, but it was discontinued due to lack of hydrogen fuel services. Its predecessor was a hydrogen bicycle called Palcan, based in Vancouver, Canada.

Airplanes

The Boeing Fuel Cell Demonstrator powered by a hydrogen fuel cell

Boeing researchers and industry partners throughout Europe conducted experimental flight tests in February 2008 of a crewed airplane powered only by a fuel cell and lightweight batteries. The Fuel Cell Demonstrator Airplane, as it was called, used a Proton-Exchange Membrane (PEM) fuel cell/lithium-ion battery hybrid system to power an electric motor, which was coupled to a conventional propeller. In 2003, the world's first propeller driven airplane to be powered entirely by a fuel cell was flown. The fuel cell was a unique FlatStack stack design which allowed the fuel cell to be integrated with the aerodynamic surfaces of the plane.

There have been several fuel cell powered unmanned aerial vehicles (UAV). A Horizon fuel cell UAV set the record distance flown by a small UAV in 2007. The military is especially interested in this application because of the low noise, low thermal signature and ability to attain high altitude. In 2009, the Naval Research Laboratory's (NRL's) Ion Tiger utilized a hydrogen-powered fuel cell and flew for 23 hours and 17 minutes. Boeing is completing tests on the Phantom Eye, a high-altitude, long endurance (HALE) to be used to conduct research and surveillance flying at 20,000 m (65,000 ft) for up to four days at a time. Fuel cells are also being used to provide auxiliary power for aircraft, replacing fossil fuel generators that were previously used to start the engines and power on board electrical needs. Fuel cells can help airplanes reduce CO2 and other pollutant emissions and noise.

Boats

The Hydra fuel cell boat

The world's first Fuel Cell Boat HYDRA used an AFC system with 6.5 kW net output. For each liter of fuel consumed, the average outboard motor produces 140 times less the hydrocarbons produced by the average modern car. Fuel cell engines have higher energy efficiencies than combustion engines, and therefore offer better range and significantly reduced emissions. Amsterdam introduced its first fuel cell powered boat in 2011 that ferries people around the city's canals.

Submarines

The first submersible application of fuel cells is the German Type 212 submarine. Each Type 212 contains nine PEM fuel cells, spread throughout the ship, providing between 30 kW and 50 kW each of electrical power. This allows the Type 212 to remain submerged longer and makes them more difficult to detect. Fuel cell powered submarines are also easier to design, manufacture, and maintain than nuclear-powered submarines.

Trains

Debut of the Alstom Coradia iLint at InnoTrans 2016

In March 2015, China South Rail Corporation (CSR) demonstrated the world's first hydrogen fuel cell-powered tramcar at an assembly facility in Qingdao. 83 miles of tracks for the new vehicle were built in seven Chinese cities. China had plans to spend 200 billion yuan ($32 billion) over the next five years to increase tram tracks to more than 1,200 miles.

In 2016, Alstom debuted the Coradia iLint, a regional train powered by hydrogen fuel cells. It was designed to reach 140 kilometres per hour (87 mph) and travel 600–800 kilometres (370–500 mi) on a full tank of hydrogen. The train entered service in Germany in 2018 and is expected to be tested in the Netherlands beginning in 2019.

Swiss manufacturer Stadler Rail signed a contract in California to supply a hydrogen fuel cell train in the US, the FLIRT H2 train, in 2024 as part of the Arrow rail project.

Trucks

Hyundai Xcient Fuel Cell in Winterthur, Switzerland

For transport applications such as long-haul trucks, fuel cells are a potential solution for zero emission transport. A 2022 study in Energies magazine cites relatively fast refueling times compared with electric truck charging times and the current limitations of the energy density of batteries, but they note that "operating constraints" include the "high amount of CO2 emissions [caused by] hydrogen production", the lack of storage and refueling infrastructure, H2 leakage and safety challenges, efficiency "losses in compression, storage and dispensing".

In 2020, Hyundai started to manufacture hydrogen powered 34-ton cargo trucks under the model name XCIENT, making an initial shipment of 10 of the vehicles to Switzerland. They are able to travel 400 kilometres (250 mi) on a full tank and take 8 to 20 minutes to fill up.

In 2022, Total Transportation Services (TTSI), Toyota Logistics Services (TLS), UPS, and Southern Counties Express (SCE) are operating a 12-month "Shore-to-Store (S2S) project" running hydrogen fuel cell trucks on trips from Los Angeles area ports. The Kenworth T680 hydrogen prototype used in Los Angeles and Long Beach was unveiled in 2018 and has also been tested in the Seattle area.

Hydrogen infrastructure

Eberle and Rittmar von Helmolt stated in 2010 that challenges remain before fuel cell cars can become competitive with other technologies and cite the lack of an extensive hydrogen infrastructure in the U.S.: As of July 2020, there were 43 publicly accessible hydrogen refueling stations in the US, 41 of which were located in California. In 2013, Governor Jerry Brown signed AB 8, a bill to fund $20 million a year for 10 years to build up to 100 stations. In 2014, the California Energy Commission funded $46.6 million to build 28 stations.

Japan got its first commercial hydrogen fueling station in 2014. By March 2016, Japan had 80 hydrogen fueling stations, and the Japanese government aims to double this number to 160 by 2020. In May 2017, there were 91 hydrogen fueling stations in Japan. Germany had 18 public hydrogen fueling stations in July 2015. The German government hoped to increase this number to 50 by end of 2016, but only 30 were open in June 2017.

Codes and standards

Under United Nations global technical regulations for wheeled vehicles, specifically regarding hydrogen usage, there are international standards which define aspects of engineering and overall integrity, performance, safety, part lifecycle, and various other categories. One notable area of these regulations is regarding the compressed hydrogen storage systems that typically reach the end of qualified service life at 15 or fewer years in use.

US programs

In 2003, US President George Bush proposed the Hydrogen Fuel Initiative (HFI). The HFI aimed to further develop hydrogen fuel cells and infrastructure technologies to accelerate the commercial introduction of fuel cell vehicles. By 2008, the U.S. had contributed 1 billion dollars to this project. In 2009, Steven Chu, then the US Secretary of Energy, asserted that hydrogen vehicles "will not be practical over the next 10 to 20 years". In 2012, however, Chu stated that he saw fuel cell cars as more economically feasible as natural gas prices had fallen and hydrogen reforming technologies had improved. In June 2013, the California Energy Commission granted $18.7M for hydrogen fueling stations. In 2013, Governor Brown signed AB 8, a bill to fund $20 million a year for 10 years for up to 100 stations. In 2013, the US DOE announced up to $4 million planned for "continued development of advanced hydrogen storage systems". On May 13, 2013, the Energy Department launched H2USA, which is focused on advancing hydrogen infrastructure in the US.

Cost

By 2010, advancements in fuel cell technology had reduced the size, weight and cost of fuel cell electric vehicles. In 2010, the U.S. Department of Energy (DOE) estimated that the cost of automobile fuel cells had fallen 80% since 2002 and that such fuel cells could potentially be manufactured for $51/kW, assuming high-volume manufacturing cost savings. Fuel cell electric vehicles have been produced with "a driving range of more than 250 miles between refueling". They can be refueled in less than 5 minutes. Deployed fuel cell buses have a 40% higher fuel economy than diesel buses. EERE's Fuel Cell Technologies Program claims that, as of 2011, fuel cells achieved a 42 to 53% fuel cell electric vehicle efficiency at full power, and a durability of over 75,000 miles with less than 10% voltage degradation, double that achieved in 2006. In 2012, Lux Research, Inc. issued a report that concluded that "Capital cost ... will limit adoption to a mere 5.9 GW" by 2030, providing "a nearly insurmountable barrier to adoption, except in niche applications". Lux's analysis concluded that by 2030, PEM stationary fuel cell applications will reach $1 billion, while the vehicle market, including fuel cell forklifts, will reach a total of $2 billion.

As of September 2023, hydrogen cost $36 per kilogram at public charging stations in California, 14 times as much per mile for a Mirai as compared with a Tesla Model 3.

Environmental impact

The environmental impact of fuel cell vehicles depends on the primary energy with which the hydrogen was produced. Fuel cell vehicles are only environmentally benign when the hydrogen was produced with renewable energy. If this is the case fuel cell cars may be cleaner and more efficient than fossil fuel cars. However, they are not as efficient as battery electric vehicles which consume much less energy. Usually a fuel cell car consumes 2.4 times more energy than a battery electric car, because electrolysis and storage of hydrogen is much less efficient than using electricity to directly load a battery. In addition, a 2023 study by the Centre for International Climate and Environmental Research (CICERO) estimated that leaked hydrogen has a global warming effect 11.6 times stronger than CO₂.

As of 2009, motor vehicles used most of the petroleum consumed in the U.S. and produced over 60% of the carbon monoxide emissions and about 20% of greenhouse gas emissions in the United States, however production of hydrogen for hydrocracking used in gasoline production, chief amongst its industrial uses, was responsible for approximately 10% of fleet wide greenhouse gas emissions. A vehicle fueled with pure hydrogen emits few pollutants at the tailpipe, producing mainly water and heat, although the production of the hydrogen would create pollutants unless the hydrogen used in the fuel cell were produced using only renewable energy.

In a 2005 well-to-wheels analysis, the DOE estimated that fuel cell electric vehicles using hydrogen produced from natural gas would result in emissions of approximately 55% of the CO2 per mile of internal combustion engine vehicles and have approximately 25% less emissions than hybrid vehicles. In 2006, Ulf Bossel stated that the large amount of energy required to isolate hydrogen from natural compounds (water, natural gas, biomass), package the light gas by compression or liquefaction, transfer the energy carrier to the user, plus the energy lost when it is converted to useful electricity with fuel cells, leaves around 25% for practical use." Richard Gilbert, co-author of Transport Revolutions: Moving People and Freight without Oil (2010), comments similarly, that producing hydrogen gas ends up using some of the energy it creates. Then, energy is taken up by converting the hydrogen back into electricity within fuel cells. "'This means that only a quarter of the initially available energy reaches the electric motor' ... Such losses in conversion don't stack up well against, for instance, recharging an electric vehicle (EV) like the Nissan Leaf or Chevy Volt from a wall socket". A 2010 well-to-wheels analysis of hydrogen fuel cell vehicles report from Argonne National Laboratory states that renewable H2 pathways offer much larger green house gas benefits. This result has recently been confirmed. In 2010, a US DOE well-to-wheels publication assumed that the efficiency of the single step of compressing hydrogen to 6,250 psi (43.1 MPa) at the refueling station is 94%. A 2016 study in the November issue of the journal Energy by scientists at Stanford University and the Technical University of Munich concluded that, even assuming local hydrogen production, "investing in all-electric battery vehicles is a more economical choice for reducing carbon dioxide emissions, primarily due to their lower cost and significantly higher energy efficiency."

Criticism of fuel cell cars

In 2008, professor Jeremy P. Meyers, in the Electrochemical Society journal Interface wrote that fuel cells "are not as efficient as batteries, due primarily to the inefficiency of the oxygen reduction reaction. ... [T]hey make the most sense for operation disconnected from the grid, or when fuel can be provided continuously. For applications that require frequent and relatively rapid start-ups ... where zero emissions are a requirement, as in enclosed spaces such as warehouses." Also in 2008, Wired News reported that "experts say it will be 40 years or more before hydrogen has any meaningful impact on gasoline consumption or global warming, and we can't afford to wait that long. In the meantime, fuel cells are diverting resources from more immediate solutions." In 2008, Robert Zubrin, the author of Energy Victory, said: "Hydrogen is 'just about the worst possible vehicle fuel'". If hydrogen could be produced using renewable energy, "it would surely be easier simply to use this energy to charge the batteries of all-electric or plug-in hybrid vehicles." The Los Angeles Times wrote in 2009, "Any way you look at it, hydrogen is a lousy way to move cars." The Washington Post asked in November 2009, "[W]hy would you want to store energy in the form of hydrogen and then use that hydrogen to produce electricity for a motor, when electrical energy is already waiting to be sucked out of sockets all over America and stored in auto batteries...?"

The Motley Fool stated in 2013 that "there are still cost-prohibitive obstacles [for hydrogen cars] relating to transportation, storage, and, most importantly, production." Volkswagen's Rudolf Krebs said in 2013 that "no matter how excellent you make the cars themselves, the laws of physics hinder their overall efficiency. The most efficient way to convert energy to mobility is electricity." He elaborated: "Hydrogen mobility only makes sense if you use green energy", but ... you need to convert it first into hydrogen "with low efficiencies" where "you lose about 40 percent of the initial energy". You then must compress the hydrogen and store it under high pressure in tanks, which uses more energy. "And then you have to convert the hydrogen back to electricity in a fuel cell with another efficiency loss". Krebs continued: "in the end, from your original 100 percent of electric energy, you end up with 30 to 40 percent."

In 2014, electric automotive and energy futurist Julian Cox wrote that producing hydrogen from methane "is significantly more carbon intensive per unit of energy than coal. Mistaking fossil hydrogen from the hydraulic fracturing of shales for an environmentally sustainable energy pathway threatens to encourage energy policies that will dilute and potentially derail global efforts to head-off climate change due to the risk of diverting investment and focus from vehicle technologies that are economically compatible with renewable energy." In 2014, former Dept. of Energy official Joseph Romm concluded that renewable energy cannot economically be used to make hydrogen for an FCV fleet "either now or in the future." GreenTech Media's analyst reached similar conclusions in 2014. In 2015, Clean Technica listed some of the disadvantages of hydrogen fuel cell vehicles.

A 2017 analysis published in Green Car Reports found that the best hydrogen fuel cell vehicles consume "more than three times more electricity per mile than an electric vehicle ... generate more greenhouse-gas emissions than other powertrain technologies ... [and have] very high fuel costs. ... Considering all the obstacles and requirements for new infrastructure (estimated to cost as much as $400 billion), fuel-cell vehicles seem likely to be a niche technology at best, with little impact on U.S. oil consumption. In 2017, Michael Barnard, writing in Forbes, listed the continuing disadvantages of hydrogen fuel cell cars and concluded that "by about 2008, it was very clear that hydrogen was and would be inferior to battery technology as a storage of energy for vehicles. [B]y 2025 the last hold outs should likely be retiring their fuel cell dreams.” A 2019 video by Real Engineering noted that using hydrogen as a fuel for cars does not help to reduce carbon emissions from transportation. The 95% of hydrogen still produced from fossil fuels releases carbon dioxide, and producing hydrogen from water is an energy-consuming process. Storing hydrogen requires more energy either to cool it down to the liquid state or to put it into tanks under high pressure, and delivering the hydrogen to fueling stations requires more energy and may release more carbon. The hydrogen needed to move a FCV a kilometer costs approximately eight times as much as the electricity needed to move a BEV the same distance. Also in 2019, Katsushi Inoue, the president of Honda Europe, stated, "Our focus is on hybrid and electric vehicles now. Maybe hydrogen fuel cell cars will come, but that's a technology for the next era."

Assessments since 2020 have concluded that hydrogen vehicles are still only 38% efficient, while battery EVs from 80% to 95% efficient. A 2021 assessment by CleanTechnica concluded that while hydrogen cars are far less efficient than electric cars, the vast majority of hydrogen being produced is polluting grey hydrogen, and delivering hydrogen would require building a vast and expensive new infrastructure, the remaining two "advantages of fuel cell vehicles – longer range and fast fueling times – are rapidly being eroded by improving battery and charging technology." A 2022 study in Nature Electronics agreed.

Innovation

Graph showing increase in fuel cell patent applications

Fuel cell patent fillings in the area of hydrogen fuel cells increased in the 1960s, partly due to NASAs space program; another increase in the 80s was driven by research for automobiles. This was followed by a surge in filings from 2000 to 2005 by inventors in Japan, US and South Korea. Since then, China has dominated patent fillings in the field, with a smaller number in Japan, Germany, South Korea and the US. Between 2016 and 2020, annual filings, particularly for transportation applications, increased by a further 23%.

Almost 80% of the patents in the area of fuel cells for transportation were filed by car companies. Academia is collaborating actively with the industry. Although filings related to road vehicles such as cars and trucks dominate, inventions in other areas like shipping, aviation, rail and other special vehicles is increasing. Airbus, a major aircraft manufacturer, has increased its patenting activity in the area since 2019. The number of fuel cell patents for shipping applications is comparable in size to the one for aviation and similarly slow in growth.

A 2022 World Intellectual Property Organization report argues that because heavy-duty vehicles, such as construction vehicles, forklifts, and airport tugs require a higher payload, the high energy density of hydrogen can make fuel cells a more advantageous solution than battery applications.

Color theory

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Color_theory

In the visual arts, color theory is the body of practical guidance for color mixing and the visual effects of a specific color combination. Color terminology based on the color wheel and its geometry separates colors into primary color, secondary color, and tertiary color. The understanding of color theory dates to antiquity. Aristotle (d. 322 BCE) and Claudius Ptolemy (d. 168 CE) already discussed which and how colors can be produced by mixing other colors. The influence of light on color was investigated and revealed further by al-Kindi (d. 873) and Ibn al-Haytham (d.1039). Ibn Sina (d. 1037), Nasir al-Din al-Tusi (d. 1274), and Robert Grosseteste (d. 1253) discovered that contrary to the teachings of Aristotle, there are multiple color paths to get from black to white. More modern approaches to color theory principles can be found in the writings of Leone Battista Alberti (c. 1435) and the notebooks of Leonardo da Vinci (c. 1490). A formalization of "color theory" began in the 18th century, initially within a partisan controversy over Isaac Newton's theory of color (Opticks, 1704) and the nature of primary colors. From there it developed as an independent artistic tradition with only superficial reference to colorimetry and vision science.

Classifications

Colors can be classified as:

  1. Warm and cold
  2. Receding and advancing
  3. Positive and negative
  4. Subtractive and additive

Color abstractions

Additive color mixing (such as in a computer)
Subtractive color mixing (such as in a printer)

The foundations of pre-20th-century color theory were built around "pure" or ideal colors, characterized by different sensory experiences rather than attributes of the physical world. This has led to several inaccuracies in traditional color theory principles that are not always remedied in modern formulations.

Another issue has been the tendency to describe color effects holistically or categorically, for example as a contrast between "yellow" and "blue" conceived as generic colors, when most color effects are due to contrasts on three relative attributes which define all colors:

  1. Value (light vs. dark, or white vs. black),
  2. Chroma [saturation, purity, strength, intensity] (intense vs. dull), and
  3. Hue (e.g. the name of the color family: red, yellow, green, cyan, blue, magenta).

The visual impact of "yellow" vs. "blue" hues in visual design depends on the relative lightness and saturation of the hues.

These confusions are partly historical and arose in scientific uncertainty about color perception that was not resolved until the late 19th century when artistic notions were already entrenched. They also arise from the attempt to describe the highly contextual and flexible behavior of color perception in terms of abstract color sensations that can be generated equivalently by any visual media.

Many historical "color theorists" have assumed that three "pure" primary colors can mix into all possible colors, and any failure of specific paints or inks to match this ideal performance is due to the impurity or imperfection of the colorants. In reality, only imaginary "primary colors" used in colorimetry can "mix" or quantify all visible (perceptually possible) colors; but to do this, these imaginary primaries are defined as lying outside the range of visible colors; i.e., they cannot be seen. Any three real "primary" colors of light, paint or ink can mix only a limited range of colors, called a gamut, which is always smaller (contains fewer colors) than the full range of colors humans can perceive.

Historical background

Color theory was originally formulated in terms of three "primary" or "primitive" colors—red, yellow and blue (RYB)—because these colors were believed capable of mixing all other colors.

Goethe's color wheel from his 1810 Theory of Colours

The RYB primary colors became the foundation of 18th-century theories of color vision, as the fundamental sensory qualities that are blended in the perception of all physical colors, and conversely, in the physical mixture of pigments or dyes. These theories were enhanced by 18th-century investigations of a variety of purely psychological color effects, in particular the contrast between "complementary" or opposing hues that are produced by color afterimages and in the contrasting shadows in colored light. These ideas and many personal color observations were summarized in two founding documents in color theory: the Theory of Colours (1810) by the German poet Johann Wolfgang von Goethe, and The Law of Simultaneous Color Contrast (1839) by the French industrial chemist Michel Eugène Chevreul. Charles Hayter published A New Practical Treatise on the Three Primitive Colours Assumed as a Perfect System of Rudimentary Information (London 1826), in which he described how all colors could be obtained from just three.

Page from 1826 A New Practical Treatise on the Three Primitive Colours Assumed as a Perfect System of Rudimentary Information by Charles Hayter

Subsequently, German and English scientists established in the late 19th century that color perception is best described in terms of a different set of primary colors—red, green and blue-violet (RGB)—modeled through the additive mixture of three monochromatic lights. Subsequent research anchored these primary colors in the differing responses to light by three types of color receptors or cones in the retina (trichromacy). On this basis the quantitative description of the color mixture or colorimetry developed in the early 20th century, along with a series of increasingly sophisticated models of color space and color perception, such as the opponent process theory.

Across the same period, industrial chemistry radically expanded the color range of lightfast synthetic pigments, allowing for substantially improved saturation in color mixtures of dyes, paints, and inks. It also created the dyes and chemical processes necessary for color photography. As a result, three-color printing became aesthetically and economically feasible in mass printed media, and the artists' color theory was adapted to primary colors most effective in inks or photographic dyes: cyan, magenta, and yellow (CMY). (In printing, dark colors are supplemented by black ink, known as the CMYK system; in both printing and photography, white is provided by the color of the paper.) These CMY primary colors were reconciled with the RGB primaries, and subtractive color mixing with additive color mixing, by defining the CMY primaries as substances that absorbed only one of the retinal primary colors: cyan absorbs only red (−R+G+B), magenta only green (+R−G+B), and yellow only blue-violet (+R+G−B). It is important to add that the CMYK, or process, color printing is meant as an economical way of producing a wide range of colors for printing, but is deficient in reproducing certain colors, notably orange and slightly deficient in reproducing purples. A wider range of colors can be obtained with the addition of other colors to the printing process, such as in Pantone's Hexachrome printing ink system (six colors), among others.

Munsell's 1905 color system represents colors using three color-making attributes, value (lightness), chroma, and hue.

For much of the 19th century artistic color theory either lagged behind scientific understanding or was augmented by science books written for the lay public, in particular Modern Chromatics (1879) by the American physicist Ogden Rood, and early color atlases developed by Albert Munsell (Munsell Book of Color, 1915, see Munsell color system) and Wilhelm Ostwald (Color Atlas, 1919). Major advances were made in the early 20th century by artists teaching or associated with the German Bauhaus, in particular Wassily Kandinsky, Johannes Itten, Faber Birren and Josef Albers, whose writings mix speculation with an empirical or demonstration-based study of color design principles.

Traditional color theory

Complementary colors

Chevreul's 1855 "chromatic diagram" based on the RYB color model, showing complementary colors and other relationships

For the mixing of colored light, Isaac Newton's color wheel is often used to describe complementary colors, which are colors that cancel each other's hue to produce an achromatic (white, gray or black) light mixture. Newton offered as a conjecture that colors exactly opposite one another on the hue circle cancel out each other's hue; this concept was demonstrated more thoroughly in the 19th century. An example of complementary colors would be magenta and green.

A key assumption in Newton's hue circle was that the "fiery" or maximum saturated hues are located on the outer circumference of the circle, while achromatic white is at the center. Then the saturation of the mixture of two spectral hues was predicted by the straight line between them; the mixture of three colors was predicted by the "center of gravity" or centroid of three triangle points, and so on.

Primary, secondary, and tertiary colors of the RYB color model

According to traditional color theory based on subtractive primary colors and the RYB color model, yellow mixed with purple, orange mixed with blue, or red mixed with green produces an equivalent gray and are the painter's complementary colors. These contrasts form the basis of Chevreul's law of color contrast: colors that appear together will be altered as if mixed with the complementary color of the other color. A piece of yellow fabric placed on a blue background will appear tinted orange because orange is the complementary color to blue.

However, when complementary colors are chosen based on the definition by light mixture, they are not the same as the artists' primary colors. This discrepancy becomes important when color theory is applied across media. Digital color management uses a hue circle defined according to additive primary colors (the RGB color model), as the colors in a computer monitor are additive mixtures of light, not subtractive mixtures of paints.

One reason the artist's primary colors work at all is due to the imperfect pigments being used have sloped absorption curves and change color with concentration. A pigment that is pure red at high concentrations can behave more like magenta at low concentrations. This allows it to make purples that would otherwise be impossible. Likewise, a blue that is ultramarine at high concentrations appears cyan at low concentrations, allowing it to be used to mix green. Chromium red pigments can appear orange, and then yellow, as the concentration is reduced. It is even possible to mix very low concentrations of the blue mentioned and the chromium red to get a greenish color. This works much better with oil colors than it does with watercolors and dyes.

The old primaries depend on sloped absorption curves and pigment leakages to work, while newer scientifically derived ones depend solely on controlling the amount of absorption in certain parts of the spectrum.

Another reason the correct primary colors were not used by early artists is they were not available as durable pigments. Modern methods in chemistry were needed to produce them.

Warm vs. cool colors

The distinction between "warm" and "cool" colors has been important since at least the late 18th century. The difference (as traced by etymologies in the Oxford English Dictionary), seems related to the observed contrast in landscape light, between the "warm" colors associated with daylight or sunset, and the "cool" colors associated with a gray or overcast day. Warm colors are often said to be hues from red through yellow, browns, and tans included; cool colors are often said to be the hues from blue-green through blue violet, most grays included. There is a historical disagreement about the colors that anchor the polarity, but 19th-century sources put the peak contrast between red-orange and greenish-blue.

Color theory has described perceptual and psychological effects to this contrast. Warm colors are said to advance or appear more active in a painting, while cool colors tend to recede; used in interior design or fashion, warm colors are said to arouse or stimulate the viewer, while cool colors calm and relax. Most of these effects, to the extent they are real, can be attributed to the higher saturation and lighter value of warm pigments in contrast to cool pigments; brown is a dark, unsaturated warm color that few people think of as visually active or psychologically arousing.

The traditional warm/cool association of a color is reversed relative to the color temperature of a theoretical radiating black body; the hottest stars radiate blue (cool) light, and the coolest radiate red (warm) light.

The hottest radiating bodies (e.g. stars) have a "cool" color, while the less hot bodies radiate with a "warm" color. (image is in Kelvin scale)
Doppler redshift for receding and blueshift for advancing

This contrast is further seen in the psychological associations of colors with the Doppler effect seen in astronomical objects. Traditional psychological associations, where warm colors are associated with advancing objects and cool colors with receding objects, are directly opposite those seen in astrophysics, where stars or galaxies moving towards our viewpoint on Earth are blueshifted (advancing) and stars or galaxies moving away from Earth are redshifted (receding).

Achromatic colors

Any color that lacks strong chromatic content is said to be unsaturated, achromatic, near-neutral, or neutral. Near neutrals include browns, tans, pastels, and darker colors. Near neutrals can be of any hue or lightness. Pure achromatic, or neutral colors include black, white and all grays.

Near neutrals are obtained by mixing pure colors with white, black or grey, or by mixing two complementary colors. In color theory, neutral colors are easily modified by adjacent more saturated colors, and they appear to take on the hue complementary to the saturated color; e.g., next to a bright red couch, a gray wall will appear distinctly greenish, this is a property of human vision.

Black and white have long been known to combine "well" with almost any other colors; black decreases the apparent saturation or brightness of colors paired with it and white shows off all hues to equal effect.

Tints and shades

When mixing colored light (additive color models), the achromatic mixture of spectrally balanced red, green, and blue (RGB) is always white, not gray or black. When mixing colorants, such as the pigments in paint mixtures, a color is produced which is always darker and lower in chroma, or saturation, than the parent colors. This moves the mixed color toward a neutral color—a gray or near-black. Lights are made brighter or dimmer by adjusting their brightness, or energy level; in painting, lightness is adjusted through mixture with white, black, or a color's complement.

It is common among some painters to darken a paint color by adding black paint—producing colors called shades—or lighten a color by adding white—producing colors called tints. However, it is not always the best way for representational painting, as an unfortunate result is for colors to also shift in hue. For instance, darkening a color by adding black can cause colors such as yellows, reds, and oranges, to shift toward the greenish or bluish part of the spectrum. Lightening a color by adding white can cause a shift towards blue when mixed with reds and oranges. Another practice when darkening a color is to use its opposite, or complementary, color (e.g. purplish-red added to yellowish-green) in order to neutralize it without a shift in hue and darken it if the additive color is darker than the parent color. When lightening a color this hue shift can be corrected with the addition of a small amount of an adjacent color to bring the hue of the mixture back in line with the parent color (e.g. adding a small amount of orange to a mixture of red and white will correct the tendency of this mixture to shift slightly towards the blue end of the spectrum).

Split primary palette

In painting and other visual arts, two-dimensional color wheels or three-dimensional color solids are used to represent the essential relationships between colors. The split-primary palette is a color-wheel model that attempts to explain, and to compensate for, the unsatisfactory results often produced when mixing the traditional primary colors, red, yellow, and blue.

Painters have long considered red, yellow, and blue to be primary colors. In practice, however, many of the mixtures produced from these colors lack chromatic intensity. Rather than adopting an updated set of primary colors, proponents of split-primary theory explain this lack of chroma by the purported presence of chemical impurities, small amounts of other colors, in the paints, or biases away from the ideal primary toward one or the other of the adjacent colors. Every red paint, for example, is said to be tainted with, or biased toward, either blue or yellow, every blue paint toward either red or green, and every yellow toward either green or orange. These biases are said to result in mixtures that contain sets of complementary colors, darkening the resulting color. In order to obtain vivid mixed colors, according to split-primary theory, it is necessary to employ two primary colors whose biases both fall in the direction, on the color wheel, of the color to be mixed, combining, for example, green-biased blue and green-biased yellow to make bright green. Based on this reasoning, proponents of split-primary theory conclude that two versions of each primary color are needed in order to mix a wide gamut of high-chroma colors.

In fact, the perceived bias of colors is not due to chemical impurities. Rather, the appearance of any given colorant is inherent to its chemical and physical properties, the purity of such a substance being unrelated to whether it conforms to our arbitrary conception of an ideal hue. Moreover, the identity of gamut-optimizing primary colors is determined by the physiology underlying human color vision. Although no set of three primary paints can be mixed to obtain the complete color gamut perceived by humans, red, yellow, and blue are a poor choice if high-chroma mixtures are desired. This is because painting is a subtractive color process, for which red and blue are secondary, not primary, colors.

Although flawed in principle, the split-primary system can be successful in practice, because the recommended blue-biased red and green-biased blue positions are often filled by near approximations of magenta and cyan, respectively, while orange-biased red and violet-biased blue serve as secondary colors, which tend to further widen the mixable gamut.

This system is in effect a simplified version of Newton's geometrical rule that colors closer together on the hue circle will produce more vibrant mixtures. A mixture, however, produced from two primary colors will be much more highly saturated than one produced from two secondary colors, even though both pairs are the same distance apart on the hue circle, revealing the limitations of the circular model in the prediction of color mixing results.

Color harmony

Georg Christoph Lichtenberg. Göttingen, 1775, plate III.
Ignaz Schiffermüller, Versuch eines Farbensystems (Vienna, 1772), plate I.

It has been suggested that "Colors seen together to produce a pleasing affective response are said to be in harmony". However, color harmony is a complex notion because human responses to color are both affective and cognitive, involving emotional response and judgment. Hence, our responses to color and the notion of color harmony is open to the influence of a range of different factors. These factors include individual differences (such as age, gender, personal preference, affective state, etc.) as well as cultural, sub-cultural, and socially-based differences which gives rise to conditioning and learned responses about color. In addition, context always has an influence on responses about color and the notion of color harmony, and this concept is also influenced by temporal factors (such as changing trends) and perceptual factors (such as simultaneous contrast) which may impinge on human response to color. The following conceptual model illustrates this 21st-century approach to color harmony:

wherein color harmony is a function (f) of the interaction between color/s (Col 1, 2, 3, …, n) and the factors that influence positive aesthetic response to color: individual differences (ID) such as age, gender, personality and affective state; cultural experiences (CE), the prevailing context (CX) which includes setting and ambient lighting; intervening perceptual effects (P) and the effects of time (T) in terms of prevailing social trends.

In addition, given that humans can perceive over 2.8 million different colors, it has been suggested that the number of possible color combinations is virtually infinite thereby implying that predictive color harmony formulae are fundamentally unsound. Despite this, many color theorists have devised formulae, principles or guidelines for color combination with the aim being to predict or specify positive aesthetic response or "color harmony".

Color wheel models have often been used as a basis for color combination principles or guidelines and for defining relationships between colors. Some theorists and artists believe juxtapositions of complementary color will produce strong contrast, a sense of visual tension as well as "color harmony"; while others believe juxtapositions of analogous colors will elicit a positive aesthetic response. Color combination guidelines (or formulas) suggest that colors next to each other on the color wheel model (analogous colors) tend to produce a single-hued or monochromatic color experience and some theorists also refer to these as "simple harmonies".

In addition, split complementary color schemes usually depict a modified complementary pair, with instead of the "true" second color being chosen, a range of analogous hues around it are chosen, i.e. the split complements of red are blue-green and yellow-green. A triadic color scheme adopts any three colors approximately equidistant around a color wheel model. Feisner and Mahnke are among a number of authors who provide color combination guidelines in greater detail.

Color combination formulae and principles may provide some guidance but have limited practical application. This is due to the influence of contextual, perceptual, and temporal factors which will influence how color/s are perceived in any given situation, setting, or context. Such formulae and principles may be useful in fashion, interior and graphic design, but much depends on the tastes, lifestyle, and cultural norms of the viewer or consumer.

As early as the ancient Greek philosophers, many theorists have devised color associations and linked particular connotative meanings to specific colors. However, connotative color associations and color symbolism tends to be culture-bound and may also vary across different contexts and circumstances. For example, red has many different connotative and symbolic meanings from exciting, arousing, sensual, romantic, and feminine; to a symbol of good luck; and also acts as a signal of danger. Such color associations tend to be learned and do not necessarily hold irrespective of individual and cultural differences or contextual, temporal or perceptual factors. It is important to note that while color symbolism and color associations exist, their existence does not provide evidential support for color psychology or claims that color has therapeutic properties.

Monochromatic

The monochromatic formula chooses only one color (or hue). Variations of the color are created by changing the value and saturation of the color. Since only one hue is used, the color and its variations are guaranteed to work.

Current status

Color theory has not developed an explicit explanation of how specific media affect color appearance: colors have always been defined in the abstract, and whether the colors were inks or paints, oils or watercolors, transparencies or reflecting prints, computer displays or movie theaters, was not considered especially relevant. Josef Albers investigated the effects of relative contrast and color saturation on the illusion of transparency, but this is an exception to the rule.

Entropy (statistical thermodynamics)

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