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Are good or bad? Everything will depend on ....

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Tesla’s Electric Cars Aren’t as Green as You Might Think

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Despite their green cred, Tesla cars create pollution and carbon emissions in ways that are easily overlooked by consumers and investors.

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But why? Can you give expand your though or give examples?

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But why? Can you give expand your though or give examples?

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They are cool and fast and sometimes are red. But their main disadvantage is that they are scary

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They are cool and fast and sometimes are red. But their main disadvantage is that they are scary

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Battery electric vehicles, or BEVs, use electricity stored in a battery pack to power an electric motor and turn the wheels. When depleted, the batteries are recharged using grid electricity, either from a wall socket or a dedicated charging unit. Since they don't run on gasoline or diesel and are powered entirely by electricity, battery electric cars and trucks are considered "all-electric" vehicles.

When driven, BEVs don't produce tailpipe pollution-they don't even have a tailpipe. However, the electricity they use may produce heat-trapping gases and other pollution at the source of its generation or in the extraction of fossil fuels. The amount of pollution produced depends on how the electricity is made. In the United States, battery electric cars charged off the dirtiest coal-dominated grid still produce less pollution than their gasoline-powered counterparts. BEVs powered by renewable energy sources like wind or solar are virtually emission-free.

Not using gasoline or diesel also means that battery electric cars are significantly cheaper to fuel than conventional vehicles. Exact comparisons depend on the vehicle model and fuel prices, but driving a BEV can save drivers over $1,000 annually in gasoline money.

Battery electric vehicle features

Like other electric and hybrid-electric vehicles, BEVs minimize wasted energy by turning the car off when stopped (" idle-off") and by charging the battery when braking (" regenerative braking "). Electric motors are also inherently more energy-efficient than gasoline or diesel engines.

Battery electric cars have the added benefit of home recharging. A 240-volt outlet, similar to those used for clothes dryers, can charge a vehicle overnight. Fully-charged, most battery electric cars have a driving range of between 70 to 100 miles, well within the day-to-day range requirements of most Americans, though some BEVs can go up to 265 miles on a single charge. An increasing number of public and workplace charging stations provide added charging capacity.

More subjectively, many drivers appreciate the driving experience provided by all-electric cars. Electric motors generate near-instant torque, or turning-force, while the torque of internal combustion engines increases in tandem with the engine's revolutions (RPM). This means that BEVs have extremely fast acceleration and a "light" or "zippy" feel compared to conventional cars and trucks.

Differences between battery electric cars and other EVs

Plug-in hybrid electric vehicles have both an electric motor and a conventional gasoline or diesel engine. Compared to a battery electric vehicle, this extends the total driving range but lowers the all-electric range. Conventional hybrids, which can't be plugged in, aren't considered electric vehicles. Learn more about how plug-in vehicles work >

Fuel cell electric vehicles convert hydrogen gas into electricity to power an electric motor and battery. Fuel cell vehicles are a relatively new technology in passenger vehicles, but have a substantial carbon-cutting role to play alongside other all-electric vehicles. Learn more about how fuel cells and fuel cell vehicles work >

Learn more about electric vehicle technology here, including its potential as a nationwide oil-saving solution.

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Battery electric vehicles, or BEVs, use electricity stored in a battery pack to power an electric motor and turn the wheels. When depleted, the batteries are recharged using grid electricity, either from a wall socket or a dedicated charging unit.

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Stuff They Don't Want You To Know - HowStuffWorks

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Why aren't there more electric cars? | CLASSIC

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If electric cars have been around since the 19th century, then why haven't they become more widespread? Skeptics say the technology isn't viable yet, but conspiracy theorists think there's more to the story. SUBSCRIBE | http://bit.ly/stdwytk-sub WEBSITE | http://bit.ly/stdwytk-home AUDIO PODCAST | http://bit.ly/stdwytk-audio-itunes TWITTER | http://bit.ly/stdwytk-twitter FACEBOOK | http://bit.ly/stdwytk-fb EMAIL | Conspiracy@HowStuffWorks.com STORE | http://stufftheydontwantyoutoknow.spreadshirt.com Here are the facts.

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A Basic Overview of Fuel Cell Technology

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General technical information about fuel cells.

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The want to learn. grow. change. mature. live. excel. step out. do more.

Learning is always happening but it takes a certain amount of purpose to grasp the lessons, hold on and truly grow.

I've decided that learning is always, always a good thing.
I want to learn so many things. "There is no end to education. It is not that you read a book, pass an examination, and finish with education. The whole of life, from the moment you are born to the moment you die, is a process of learning." -Jiddu Krishnamurti
For me, the past years have been full of a huge list of things I've learned.

Travel, moving, culture, language... the lessons are many and the challenges great.

Yet, there is acknowledgement in my heart that I have more things to learn.
Much more.
New things that God is doing... new things that just might require pulling up the boot straps and actually stepping out into the waters of something new.
Part of learning is getting up, getting out and moving forward. Stretching, slowly building momentum to something greater... and that is what I sense God doing in my heart.
Some of these things are spiritual. Some are practical. Some are things I've been wanting to do. Some are things I've been asked to do... just an all around personal learning to-do list.

Want to Learn

1} Learn how to be me again - that might sound just crazy to you, but to me (and a lot of other missionary expats) this is very real. We check ourselves at the airport and don't know how to find ourselves within an entirely new context. This author said it like this, "Expats too often check significant parts of their lives at the airport. They assume that they can't do things because it is not instantly obvious how they can." We all know it IS possible to do and be those things... we just don't know how. So my number one on this list is to learn how. Do you ever feel like you need to learn how to be you again after a life change, transition, struggle or growth step?

2} Learn to keep growing in my relationship with God - New seasons take new depths with Jesus. I'm learning that God's Word is truly alive and active for my circumstance, my stage of life. He is deep and wide and full of things to learn. The Holy Spirit longs to teach us and grow us and take us further. I want that. I want to learn to DO that. Even if time with God is messy and life is busy, I need to keep growing in God.

3} Learn to communicate - Communicating in a new culture, a culture that has its own sub-cultures, it very tricky. Facial expressions, hand motions, words in many languages all blend into a whole new way of communicating with people. There is so much to learn about communication in other countries and cultures. Communication opens so many incredible doors to learning about ourselves and those around us.

4} Learn how share our story more clearly - Navigating social media and story sharing for a missionary family is terribly difficult. This goes with learning to communicate. Things change so quickly with technology that it is hard to keep up. Learning to stay on top of it is a daily challenge. Learning to share our story fully, honestly, meaningfully and creatively. Psalm 107:2 says, "Let the redeemed of the Lord tell their story ..." We all need to learn how to do that effectively, purposefully and for His glory.

5} Learn new skills - Overseas life requires some serious pioneer woman skills. Slowly but surely, I'm learning new things and getting into a little bit of baking bread, making tortillas { which I've learned and you can too!} and so on. Jeremy is a huge help in this because he enjoys being in the kitchen {much to the amazement of our Senegalese friends!} and I'm so thankful for his love of all things cooking! And learning to share the kitchen, work together and end the day with jobs well done.

Another new skill I want to know more about is essential oils and how to help our family's health with the right oils. This has been something I've been learning by doing. I have a few key oils that literally have gotten me through this first term overseas and helped my health greatly.

6} Learn to be home - This is starting to feel like home. Which is another huge long-term missionary milestone. Learning to be "home" wherever we find ourselves, where our family is together, where love is. And knowing it is a temporary home with a future home in heaven waiting for us. Home is a rough topic for expats and learning to understand the many facets of this is challenging but good. It means being able to live in the present and look ahead and do both of them well.

7} Learn to live fully - As part of mending, I'm realizing that I've been in survival mode for a long, long time. Just survive the application process. Just survive itinerating. Just survive all the goodbyes. Just survive language school. Just survive our first year overseas. Just survive rainy season... just survive. From one day to the next. Survive. Now, it is time to live. Not just survive. Because of our newness, there will still be great moments, long days of survival to come. But I need to make pockets of living. Where a day or two or three feels less like survival mode and more like normal life.

8} Learn to process well - The same author states, "Processing and complaining can start with the exact same statement. For example "This is really hard." That is a fair and true statement but what you do with it sets you on one of two trajectories that ultimately lead to very different places. Processing the hard stuff is absolutely critical for staying well." And after all we've been through, I want to stay well. Which means learning to process well. Process the new places, new cultures, new foods, new experiences, new feelings, new trials, new everything... and process it well.
"Learning is not attained by chance. It must be sought for with ardor and attended to with diligence." Abigail Adams
9} Learn to read - What? me? learn to read? I am an avid reader. But an avid FICTION reader. I rarely read anything other than fiction, except my Bible... I rarely dig in too far to other genres. maybe once or twice a year... But this year, I'm already falling deeply in love with reading other things like the sermons of CS Lewis and the raw beauty of Elisabeth Elliot and the true stories of Lilias Trotter ... learning to read and soak in new things.

10} Learn to do things in new ways - I'm continuing to learn to do things differently. to think differently. Learn how to shop here. Learn how to eat here. Learn how to have friendships here. Learn. learn. learn. learn. all things I know... but now I need to know them differently. Learn to do them in new ways. Culturally correct ways.

11} Learn to speak less - I want to learn to speak less. I need to listen. Just listen. and learn while listening. Listen rather than voice an opinion or add a thought. Just listen. Or just be silent and watch.

12} Learn to pray - Of course, I pray now. But I want that spiritual discipline to grow. I want to speak less to others and speak more to God. I want to go to Him first for all things. I want to deepen an already growing relationship. I want to hear His voice. I want to know Him more. and for that, I must learn to pray. more. longer. deeper. quieter. still.

Lessons I want to learn.

Ways I want my heart to grow and change.

Things that I hope to build.

Character, strength, trust, life.
What are things you want to learn?

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Want to Learn - What do you want to learn in this season?

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The want to learn. grow. change. mature. live. excel. step out. do more. Learning is always happening but it takes a certain amount of purpose to grasp the lessons, hold on and truly grow. I've decided that learning is always, always a good thing. I want to learn so many things.

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A quick little behind-the-scenes update (and we have been talking about this on Facebook over the last day or so...feel free to hop into the conversation over there as well).

Working on a new series for the show where I'll be bringing on folks to teach us something cool and specific so we can be all be awesome at everything.

Why? Because, I bet like me, you are a curious cat (aren't we all) and have some kind of skill or topic you want to learn more about (and perhaps learn things you didn't even know you wanted to learn about). And then we can dominate the world with our knowledge (muhahahaha).
For example, here have been some suggestions so far of things RISE nation wants to learn (topics and specifics):
-How to read faster
-Fitness tips/how to lose weight/how to get in better shape
-Tips on dominating poker and blackjack
-Tips on traveling (world travel a big topic)
-Learning about the latest gadgets and tech goodies
-How to say simple phrases in Mandarin Chinese
-Dating and relationship advice (perhaps how to plan a really romantic date or who knows what, dating mistakes, etc.)
-How to select a wine at a restaurant without looking like an idiot
-Simple recipes and cooking tips
-How to be great in any social situation

What do you want to learn? Leave your thoughts/suggestions/ideas below (it can be a specific topic and also if you have a suggestion for a person who is the MASTER of that topic let me know as well especially someone that can talk from experience and not fluffy bunny theory). I will track 'em down.

Together we can become smarter...at everything. And dominate life (and cocktail parties or whatever). Sound good?

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A quick little behind-the-scenes update (and we have been talking about this on Facebook over the last day or so...feel free to hop into the conversation over there as well). Working on a new series for the show where I'll be bringing on folks to teach us something cool and specific so we can be all be awesome at everything.

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Do not worry ...
We are just beginning...
Exactly. And I understand nothing... Makes me sad and concerned. Maybe I should drop the course. Or seek counsil.
Everything will be just fine

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I dont understand anything. Are you in U on Saturday around 10 pm?

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I dont understand anything. Are you in U on Saturday around 10 pm?

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Behind the application...

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What are fuel cells?| Explore | physics.org

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But some have suggested that hydrogen can instead by produced at home by using sunlight to split water with the help of a catalyst, titanium dioxide - the white in white paint. With more centralised production, a large infrastructure of hydrogen refueling stations would be required if vehicles powered by fuel cells are to become used more widely than just by demonstration taxis.

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Researchers at MIT have developed a practical and physically-based way of treating the surface of materials called perovskite oxides, to make them more durable and improve their performance. These materials are promising candidates to serve as electrodes in energy-conversion devices such as fuel cells and electrolyzers. This surface treatment could solve one of the major challenges that has hindered widespread deployment of fuel cell technology that, when operated reversibly, can present a promising alternative to batteries for renewable-energy storage.

The new findings are being reported today in the journal Nature Materials, in a paper by MIT Associate Professor Bilge Yildiz of the departments of Nuclear Science and Engineering and Materials Science and Engineering, former MIT postdoc Nikolai Tsvetkov, graduate students Qiyang Lu and Lixin Sun, and Ethan Crumlin of the Lawrence Berkeley National Laboratory.

Perovskites have become a bustling area of research in recent years, with potential applications in areas ranging from fuel cell electrodes, to nonvolatile memory chips for computers, to solar thermochemical fuel production through the splitting of water and carbon dioxide. They are a broad class of oxide materials, and many teams are exploring variations of perovskite composition in search of the most promising candidates for different uses. But the relative instability of the material's surface over time has been one of the major limitations to use of perovskites.

The surfaces of these materials, when exposed to water or gases such as oxygen or carbon dioxide at elevated temperatures, as they often are in actual applications, "suffer from degradation because of chemical segregation and phase separation," Yildiz explains. She says "we, as well as others in the field, have discovered in the past several years that the surfaces of these perovskites get covered up by a strontium-oxide related layer, and this layer is insulating against oxygen reduction and oxygen evolution reactions, which are critical for the performance of fuel cells, electrolyzers, and thermochemical fuel production. This layer on the electrode surface is detrimental to the efficiency and durability of the device, causing the surface reactions to slow down by more than an order of magnitude."

In earlier work, Yildiz and her team uncovered the reasons behind such detrimental surface segregation of strontium. "We have found it to be governed by enrichment of oxygen vacancies at the surface," she says. Oxygen vacancies are atomic defects in the lattice where oxygen atoms are missing. "Then the solution was to kill some of those oxygen vacancies." This idea is contrary to the conventional understanding that oxygen vacancies assist reactions with oxygen molecules at the perovskite oxide surface and improve the rate of oxygen reduction reaction in fuel cells.

So, simply adding a small fraction of more oxidizable elements at the perovskite surface "annihilates some of the oxygen vacancies, makes the surface more oxidized, and prevents the formation of insulating phases that block oxygen exchange reactions at the surface of the material," Yildiz says. In this way, the surface retains the intrinsically good electronic, ionic, and catalytic properties of the perovskite oxide and enables fast oxygen exchange reactions.

The team's analysis shows that there is a sweet spot in the addition of more oxidizable elements to the surface, both in terms of the composition and the concentration. In these initial experiments, they tried several different elements to provide the protective effect. The improvement increases up to a certain concentration, and then adding more of the surface additives starts to make things worse again. So for any given material, there will be an optimum amount that should be added, they found. Using hafnium, the new treatment has been shown to reduce the rate of degradation, and increase by 30 times the rate of oxygen exchange reactions at the surface.

The result was quite unexpected, Yildiz says. "Nobody would have planned to use hafnium to improve anything in this field," she says, as that element or its oxide shows almost no reactivity by itself. But as a surface treatment for the perovskite, it caused the greatest improvement of all the elements tested, "because it provides a good balance between the stability of the surface and the availability of oxygen vacancies," she explains.

Importantly, Yildiz adds: "We believe the value of the work is not only in having found a potential improvement to fuel cell electrode durability, but also in fundamentally proving the mechanism behind this improvement. For that, our in situ X-ray spectroscopy experiments enabled by the Advanced Light Source have been critical."

The surface treatment process is simple and requires only a tiny amount of the additive elements deposited from a solution of the metal chloride. "What we put on the surface is a very small amount, so it's not changing the bulk material," Yildiz says. In fact, the surface treatment amounts no more than a single atomic layer over the bulk material.

The findings could be quite significant in making perovskite oxide electrocatalysts for some applications, she says, including solid oxide fuel cells. "The bulk electronic and ionic properties of perovskite oxides are really good, as they have been optimized over several decades for use in fuel cells," she explains, but "the bottleneck now was to improve the oxygen reduction reaction kinetics at the surface," and many teams have been stymied because the behavior of the material at its surface turned out to be "not nearly as good as hoped," or as models predicted. Now, the researchers say they have a handle on why the problem occurs, and how to deal with it.

"The observations could be used to produce more robust fuel cells with lower degradation rates, which at the moment is a major target for solid oxide fuel cell developers," says John Kilner, a professor of energy materials at Imperial College, London, who was not involved in this work.

"In many catalytic materials, stability and performance do not come hand-in-hand - the most active catalysts are also the least stable ones," says William Chueh, an assistant professor of materials science and engineering at Stanford University, who also was not connected with the research. "In this work, Yildiz and co-workers identified a new way to substantially improve the stability of cobalt-based electrocatalysts simply by adding a small amount of dopants on the surface."

Chueh adds, "The most promising application of this work is to substantially improve the stability of solid-oxide fuel cells. This is the key issue that controls the cost, and limits the widespread adoption of this technology. The work is excellent in both fundamental insights and technological implications."

The work received support from the National Science Foundation, Division of Materials Research, Ceramics Program with a CAREER Award, and from the NASA Jet Propulsion Laboratory, and made use of the Advanced Light Source facility at the Lawrence Berkeley National Laboratory, supported by the Department of Energy.

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Researchers find a way to extend life and improve performance of fuel cell electrodes

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Researchers at MIT have developed a practical and physically-based way of treating the surface of materials called perovskite oxides, to make them more durable and improve their performance. These materials are promising candidates to serve as electrodes in energy-conversion devices such as fuel cells and electrolyzers.

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from research organizations

Washington State University researchers have determined a key step in improving solid oxide fuel cells (SOFCs), a promising clean energy technology that has struggled to gain wide acceptance in the marketplace.

The researchers determined a way to improve one of the primary failure points for the fuel cell, overcoming key issues that have hindered its acceptance. Their work is featured on the cover of the latest issue of Journal of Physical Chemistry C.

Fuel cells offer a clean and highly efficient way to convert the chemical energy in fuels directly into electrical energy. They are similar to batteries in that they have an anode, cathode and electrolyte and create electricity, but they use fuel to create a continuous flow of electricity.

Fuel cells can be about four times more efficient than a combustion engine because they are based on electrochemical reactions, but researchers continue to struggle with making them cheaply and efficiently enough to compete with traditional power generation sources.

An SOFC is made of solid materials, and the electricity is created by oxygen ions traveling through the fuel cell. Unlike other types of fuel cells, SOFCs don't require the use of expensive metals, like platinum, and can work with a large variety of fuels, such as gasoline or diesel fuel.

When gasoline is used for fuel, however, a carbon-based material tends to build up in the fuel cell and stop the conversion reaction. Other chemicals, in particular sulfur, can also poison and stop the reactions.

In their study, the WSU researchers improved understanding of the process that stops the reactions. Problems most often occur at a place on the anode's surface, called the triple-phase boundary, where the anode connects with the electrolyte and fuel.

The researchers determined that the presence of an electric field at this boundary can prevent failures and improve the system's performance. To properly capture the complexity of this interface, they used the Center for Nanoscale Materials supercomputer at the Argonne National Laboratory to perform computations.

The researchers studied similar issues in solid oxide electrolysis cells (SOECs), which are like fuel cells that run in reverse to convert carbon dioxide and water to transportation fuel precursors.

The work provides guidance that industry can eventually use to reduce material buildup and poisoning and improve performance of SOFCs and SOECs, said Jean-Sabin McEwen, assistant professor in the Gene and Linda Voiland School of Chemical Engineering and Bioengineering, who led the project.

The research is in keeping with WSU's Grand Challenges, a suite of research initiatives aimed at large societal issues. It is particularly relevant to the challenge of sustainable resources and its theme of energy.

Journal Reference:

Fanglin Che, Su Ha, Jean-Sabin McEwen. Elucidating the Role of the Electric Field at the Ni/YSZ Electrode: A DFT Study. The Journal of Physical Chemistry C, 2016; 120 (27): 14608 DOI: 10.1021/acs.jpcc.6b01292

Cite This Page:

Below are relevant articles that may interest you. ScienceDaily shares links and proceeds with scholarly publications in the TrendMD network.

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fuel cells; energy and resources; alternative fuels; fossil fuels; energy and the environment; renewable energy; environmental science; sustainability

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Key improvement for fuel cells: Work improves understanding of process that stops reactions

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Researchers have determined a key step in improving solid oxide fuel cells, a promising clean energy technology that has struggled to gain wide acceptance in the marketplace. The researchers determined a way to improve one of the primary failure points for the fuel cell, overcoming key issues that have hindered its acceptance.

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Buen día, ¿cuál es la temática que crees es más relevante de tú curso?
Hola! La temática más relevante esta relacionada con las celdas de combustible ... sus aplicaciones, como funcionan, como pueden mejorarse para que sean comercialmente viables

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Contact: Allan Chen

On the one hand, fuel cells are touted as a clean, sustainable energy solution; on the other, they are dismissed as too expensive and too far from market. Behind the contradictory perceptions lies a technology suitable for many applications - and rich in variations. Among the problems that need solving before fuel cells become common in the marketplace are lowering their cost and increasing the durability of their materials - and developing clean, sustainable ways to generate, distribute, and store hydrogen, the fuel cell's fuel.

"Fuel cells are costly to study in the laboratory," says Adam Weber of Berkeley Lab's Environmental Energy Technologies Division (EETD), who uses computer models to simulate what goes on inside fuel cells. "It's very hard to characterize what's going on in a fuel cell locally. Imaging techniques are difficult and expensive to use in a cell's interior, and the resolution of existing techniques is often not high enough."

Computer simulation of the processes in the cell, however, is a cost-effective way to figure out what's going on inside. "It let's you think outside the box," Weber says. "What if we made a new electrode material? What properties should it have? Simulation provides an approximate idea of the distribution of heat, fuel, and water within different parts of the cell, and how these distributions affect the cell's power output."

One of Weber's projects is studying thermal and water management in polymer-electrolyte fuel cells (PEFCs) using computer simulation. Understanding the flow of water in a fuel cell is important, because if water is not managed properly the fuel cell will not produce its maximum power, let alone operate. In the long term, improper water management could also lead to shorter fuel-cell lifetime, which affects the economic viability of the technology. The ultimate goal of the research is to provide guidance to other scientists and fuel cell manufacturers so that they can optimize fuel cell performance at minimum cost.

Where does the water come from?

"The fuel cell is an energy conversion device, not an energy storage device like a battery," Weber explains. The conversion process begins with hydrogen, the fuel input. Hydrogen flows into the fuel cell and encounters a gas diffusion layer, where it spreads out evenly on a plane.

The gas now reacts with electrolyte at the cell's anode layer, resulting in the dissociation of hydrogen into protons and electrons. The electrons are the cell's power output - they flow out of the cell as an electric current and do useful work, such as moving an automobile or providing electricity to a building or space vehicle.

The rest of the hydrogen gas, the positively charged protons, flows through the electrolyte, a negatively charged polymer termed an ionomer, to the cathode layer. The electrolyte is crucial: its role is to conduct protons, not electrons or gas.

At the cathode, in a series of chemical reactions, the protons recombine with electrons and with oxygen, which is flowing into the cell from the atmosphere, to form water - the primary source of the water within the cell.

The material that forms a fuel cell's electrolyte defines the type of fuel cell. Weber's research focuses on polymer-electrolyte fuel cells, considered promising for automotive and small, stationary applications, with operating temperatures usually less than 100°C (212°F). The typical material in use today consists of fluorinated polymers (Teflon, for example) with acid-group side chains.

In solid-oxide fuel cells, the electrolyte is a ceramic that conducts oxygen ions. Solid-oxide fuel cells operate at much higher temperatures, more than 700°C (1,260°F). Solid-oxide fuel cells are considered ideal for stationary applications, such as powering buildings, thanks to their cogeneration capabilities and use of natural gas as a fuel.

Dueling trends

A fuel cell that is generating an electrical current is also generating heat and water. The water in the cell is either liquid or a vapor, depending on the local temperature at the point in the cell where the water is passing through.

The polymer electrolyte needs to be wet in order to conduct efficiently, so some liquid water in the ionomer separating the anode from the cathode is desired. Liquid water also hydrates the membrane much better than water vapor. However, if liquid water fills up the pore pathways in the diffusion layer and blocks access of the reactant gases to the reaction sites, more vapor and less liquid is desirable.

"This is an optimization problem," says Weber. "The problem is to keep sufficient water in the membrane so it can do its job of conducting, without having too much in the cell. The structure of an optimized backing layer depends on factors like the number and size of pores in the layer, their distribution, and total porosity."

Weber's computer simulations show that the shape of the gradient, the temperature profile of the fuel cell, reflects the cell's water distribution and management, with trade-offs for performance. Temperature reaches a maximum at the cathode where the oxygen is reduced to water - an inefficient reaction. Water vapor moves out of the cell in the diffusion layers; meanwhile the temperature decreases from the cathode to the gas channels.

Higher temperatures increase the rate of chemical reactions, the diffusion of reactant gases, and the conductivity of the electrolyte - all to the good, because these factors tend to increase power output. But higher temperatures at the membrane dilute liquid water; water vapor dilutes the reactants in the cell; and the flow of water vapor out of the cell inhibits hydrogen and oxygen from entering.

Weber's simulation results suggest that these latter effects are the dominating factors, reducing the cell's performance if the vapor is not managed. The simulations show water vapor moving out of the cell and condensing, while liquid water moves into the cell - all because of the temperature gradient.

"A lot of water is moving through the cell because of condensation of the vapor to liquid, and evaporation of the liquid to vapor," says Weber. "Water is also changing from liquid to vapor and back at the membrane. But these heat-related effects almost exactly balance each other in the cell."

Simple measurements of the inputs and outputs of the cell would not explain what is going on inside it. "In fact," says Weber, "only a degree or so temperature gradient at 80°C can move as much water as the cell generates - and results in more absolute heat effects than that generated by the electrochemical reactions."

A design for better water and thermal management

Weber points out that there are several engineering solutions to the water and thermal management problem. "You can tailor a microporous layer to do a better job of keeping liquid water in contact with the membrane. Wicks or porous plates can help remove excess liquid water. Distributed liquid-water injections can help maximize the liquid water at the membrane and reduce the temperature, so that less water vapor forms. You can induce temperature gradients to move water where you want it."

Because of Weber's work, enough is now known about the temperature and moisture conditions inside polymer-electrolyte fuel cells to point fuel cell designers in the right direction to solve these problems. But other, large challenges remain.

"The materials problem is the big one," says Weber. "We need a better membrane material for higher temperature conditions in the fuel cell." Operating the cell at higher temperatures, above 100°C, increases efficiency and power output but degrades the cell faster, shortening its lifetime.

Weber and EETD researcher John Kerr are conducting research in this area to model and create membrane materials capable of operating at elevated temperatures. Weber is also working on computer models that relate the impacts of material tolerances and manufacturing defects, a key route for eventual large-scale fuel cell production. Their goal is to help develop the materials that can meet goals established by the Department of Energy's fuel-cell research program.

Among these goals are fuel cells that will last 5,000 hours (equivalent to about 150,000 miles of driving), cost less than $50 per kilowatt - automobile combustion engines currently cost $30 to $35 per kilowatt - and operate at the full range of environmental conditions as cars powered by internal combustion engines, from extreme cold in winter to hot, humid summer conditions. The fuel cells will also have to start up quickly and reach 50 percent of rated power within 30 seconds - combustion engines turn on very quickly, but current fuel cells have a slower start-up curve.

There's still plenty to do!

Additional Information

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Modeling to Build a Better Fuel Cell | Berkeley Lab

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Contact: Allan Chen On the one hand, fuel cells are touted as a clean, sustainable energy solution; on the other, they are dismissed as too expensive and too far from market. Behind the contradictory perceptions lies a technology suitable for many applications - and rich in variations.

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Batteries and Fuel Cells Modeling in COMSOL Multiphysics®

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Introduction & Agenda (0:00) Numerical Simulation with COMSOL Multiphysics (1:16) Modeling Batteries and Fuel Cells (7:05) Batteries with Binary Electrolyte (20:15) Live Demo: Lithium-Ion Battery (23:12) Electrochemical Impedance Spectroscopy (32:55) Live Demo: Electrochemical Impedance Spectroscopy (36:01) Live Demo: Application Builder (40:25) Fuel Cell Modeling (46:19) Live Demo: PEM Fuel Cell (47:52) Q&A Session (50:14) How to Try COMSOL Multiphysics® (57:25) Contact Us (59:51)

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How theory and simulation can drive fuel cell electrocatalysis

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How theory and simulation can drive fuel cell electrocatalysis - ScienceDirect

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Over the last decade, theory and modeling have become essential tools to navigate the parameter space that governs activity and stability of electrocatalyst systems for polymer electrolyte fuel cells. This perspective covers essential phenomena from atomic scale to nanoscale and discusses the impact of the key parameters at play.