Anúncio

**air** · 10 August 2006, 11:58

Pelo que tenho conhecimento estão a fazer uma unidade de produção de biodiesel no porto de Aveiro. Para começar a funcionar no ano que vem.

**Sphynx** · 10 August 2006, 13:06

Eu tambem ja ouvi isso, mas só o biodiesel não é solução, o biodiesel pode ser aplicado nos automoveis a gasoleo mas ficam a faltar alternativas para grande maioria dos carros, falta uma alternativa para substituir a gasolina, o ethanol, bastava que se plantasse beterraba ou cana de acucar no alentejo e se fizesse 2 ou 3 fabricas de ethanol para essa alternativa ir a frente, se isso acontecesse eu era logo o primeiro a por o meu carro

**Luimio** · 14 August 2006, 23:57

Vejam este Fórum:
www.novaenergia.net/forum

Tem lá muito conteúdo e informação acerca dos biocombustiveis!

Atentamente:
Luís Oliveira

**air** · 15 August 2006, 10:28

O futuro é o hidrogénio.. é só mesmo preciso controlar a sua produção e armazenagem.

**neoxic** · 15 August 2006, 10:45

O futuro é acabar com o transporte privado...

**mundano** · 15 August 2006, 11:33

citação:Originalmente colocada por air

O futuro é o hidrogénio.. é só mesmo preciso controlar a sua produção e armazenagem.

Sabes a quantidade de energia que se desperdiça para produzir hidrogeneo e para produzir energia a partir do hidrogeneo?

Um carro a hidrogeneo na pratica gasta 4 ou 5 vezes mais combustiveis fosseis do que um carro a gasolina.. Só que em vez de ser no proprio carro é numa central termica qualquer..

Isso do hidrogeneo, a não ser que no futuro exista forma de produzir energia eletrica em quantidades astronomicas sem poluir é uma grande treta..

**air** · 15 August 2006, 12:01

E não achas que isso é possível de acontecer no futuro? O grande problema é mesmo a instabilidade do hidrogénio. Seria como andar com uma bomba no carro..

**mundano** · 15 August 2006, 16:16

O Hidrogeneo é apenas uma maneira de trasnportar energia.. Porque não existe na terra hidrogeneo para podermos "quaimar" À vontade..

Para produzir hidrogeneo é preciso pegar em agua e separa-lo do oxigeneo. Isso gasta energia, depois é preciso armazena-lo, isso gasta energia e no fim é preciso voltar a transforma-lo em agua de forma a criar energia, e ai, mais uma vez perdeu-se energia...

No final, se formos a comparar, gastou-se uma enorme quantidade de energia, da qual apenas uma pequena parte é aproveitada..

Por isso volto a repetir, nos proximos 50 anos, o hidrogeneo não passa de uma grande treta. E que é completamente inexequivel em larga escala.. É porreiro para mostrar um prototipo, não é porreiro um pais inteiro com carros a hidrogeneo.

Até porque pensa comigo, para fazer hidrogeneo é preciso electricidade. Actualmente a produção electrica é groso modo de 3 fontes, nuclear, energias renovaveis e de queima de combustiveis fosseis.. No que toca à energia renovavel a sua produção vem a crescer, mas a um ritmo muito lento, provavelmente a este ritmo nunca chegará sequer para alimentar o mercado domestio e industrial que existe actualmente. Pelo que o consumo extra que seria necessario para produzir o hidrogeneo, com a aversão que há ao nuclear, teria que vir na sua maior parte da queima de combustiveis fosseis. E com todos os desperdicios que há no processo do hidrogeneo o mais provavel era que se queimasse 10 litros de petroleo, para por um carro a fazer um percurso a hidrogoeo que com um motor diesel faria com 2 ou 3 litros de petroleo gasto..

**ManuelJasmim** · 15 August 2006, 17:03

citação:Originalmente colocada por neoxic

O futuro é acabar com o transporte privado...

Tens a tua bola de cristal avariada.

**GTSM5** · 15 August 2006, 17:06

Meu carro funciona tanto a álcool quanto a gasolina, e a PSA rodou mais de 300k km com uma Picasso 1.6HDI com biodiesel....sem problemas!

**air** · 15 August 2006, 17:08

citação:Originalmente colocada por mundano

O Hidrogeneo é apenas uma maneira de trasnportar energia.. Porque não existe na terra hidrogeneo para podermos "quaimar" À vontade..

Para produzir hidrogeneo é preciso pegar em agua e separa-lo do oxigeneo. Isso gasta energia, depois é preciso armazena-lo, isso gasta energia e no fim é preciso voltar a transforma-lo em agua de forma a criar energia, e ai, mais uma vez perdeu-se energia...

No final, se formos a comparar, gastou-se uma enorme quantidade de energia, da qual apenas uma pequena parte é aproveitada..

Por isso volto a repetir, nos proximos 50 anos, o hidrogeneo não passa de uma grande treta. E que é completamente inexequivel em larga escala.. É porreiro para mostrar um prototipo, não é porreiro um pais inteiro com carros a hidrogeneo.

Até porque pensa comigo, para fazer hidrogeneo é preciso electricidade. Actualmente a produção electrica é groso modo de 3 fontes, nuclear, energias renovaveis e de queima de combustiveis fosseis.. No que toca à energia renovavel a sua produção vem a crescer, mas a um ritmo muito lento, provavelmente a este ritmo nunca chegará sequer para alimentar o mercado domestio e industrial que existe actualmente. Pelo que o consumo extra que seria necessario para produzir o hidrogeneo, com a aversão que há ao nuclear, teria que vir na sua maior parte da queima de combustiveis fosseis. E com todos os desperdicios que há no processo do hidrogeneo o mais provavel era que se queimasse 10 litros de petroleo, para por um carro a fazer um percurso a hidrogoeo que com um motor diesel faria com 2 ou 3 litros de petroleo gasto..

Tens razão.. No curto é médio prazo é impensável.. Mas tudo tende a evoluir.. Basta ver nos ultimo 15 anos a evolução que houve no mundo automóvel. Claro que é uma alteração bastante grande.. Separar o hidrogénio da água é dificil e perigoso também.. Mas futuramente na minha opinião será o utilizado.. É preciso desenvolver claro..

**ManuelJasmim** · 15 August 2006, 17:24

citação:Originalmente colocada por mundano

O Hidrogeneo é apenas uma maneira de trasnportar energia.. Porque não existe na terra hidrogeneo para podermos "quaimar" À vontade..

Para produzir hidrogeneo é preciso pegar em agua e separa-lo do oxigeneo. Isso gasta energia, depois é preciso armazena-lo, isso gasta energia e no fim é preciso voltar a transforma-lo em agua de forma a criar energia, e ai, mais uma vez perdeu-se energia...

No final, se formos a comparar, gastou-se uma enorme quantidade de energia, da qual apenas uma pequena parte é aproveitada..

Por isso volto a repetir, nos proximos 50 anos, o hidrogeneo não passa de uma grande treta. E que é completamente inexequivel em larga escala.. É porreiro para mostrar um prototipo, não é porreiro um pais inteiro com carros a hidrogeneo.

Até porque pensa comigo, para fazer hidrogeneo é preciso electricidade. Actualmente a produção electrica é groso modo de 3 fontes, nuclear, energias renovaveis e de queima de combustiveis fosseis.. No que toca à energia renovavel a sua produção vem a crescer, mas a um ritmo muito lento, provavelmente a este ritmo nunca chegará sequer para alimentar o mercado domestio e industrial que existe actualmente. Pelo que o consumo extra que seria necessario para produzir o hidrogeneo, com a aversão que há ao nuclear, teria que vir na sua maior parte da queima de combustiveis fosseis. E com todos os desperdicios que há no processo do hidrogeneo o mais provavel era que se queimasse 10 litros de petroleo, para por um carro a fazer um percurso a hidrogoeo que com um motor diesel faria com 2 ou 3 litros de petroleo gasto..

Não sei se hei-de rir[}

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A barbaridade que gostei mais foi:
" Hidrogeneo é apenas uma maneira de trasnportar energia.. "

Então porra , o gasóleo a gasolina são o quê?

Eu respondo-te: é Hidrogénio com impurezas! E não passam de formas de transportar energia!

e mais, o problema não é falta de energia, mas sim transporta-la e converte-la na forma que mais nos convém.

O futuro é E renovaveis, é nuclear, não há alternativa

e é hidrogénio, puro ou combinado, isso vai depender da solução tecnica que se implantar dentro de 15 anos ou talvez menos...

**mundano** · 15 August 2006, 17:45

Manuel Jasmim, se não queres entender é problema teu, escusas é de vir com comentarios idiotas que nada acrescentam... Acho que dá para entender muito bem que a diferença é que petroleo tens na natureza, só precisas de queima-lo e pronto..

Hidrogeneo não... Tens que ter uma fonte de energia para o produzir e só depois ele tem utilidade..

**ManuelJasmim** · 17 August 2006, 17:45

citação:Originalmente colocada por mundano

Manuel Jasmim, se não queres entender é problema teu, escusas é de vir com comentarios idiotas que nada acrescentam... Acho que dá para entender muito bem que a diferença é que petroleo tens na natureza, só precisas de queima-lo e pronto..

Hidrogeneo não... Tens que ter uma fonte de energia para o produzir e só depois ele tem utilidade..

Relativamente aos comentários idiotas...apliquemos o :

"E diz o roto ao nú: Porque não te vestes tu?"

O petroleo é como tu dizes, é queima-lo e pronto nunca mais há nada, excepto os residuos da sua combustão...

Reitero o que disse, não há falta de energia. Apenas existe uma grande dificuldade em aproveitar a energia que temos, em tarnsformar as diferentes formas de energia.

O hidrógenio é uma excelente forma de acumular energia que de outra forma seria inutilizavel. Se conheceres outra melhor, partilha com o resto do pessoal, a humanidade vai agradecer o teu contributo.

As células de combustivel são o futuro. Células de combustivel alimentadas a H. O problema do transporte será resolvido (já está resolvido mas de forma ainda muito dispendiosa) em breve.

**pcnunes7** · 17 August 2006, 17:52

citação:Originalmente colocada por air

Pelo que tenho conhecimento estão a fazer uma unidade de produção de biodiesel no porto de Aveiro. Para começar a funcionar no ano que vem.

onde é que está essa informação?

existe alguma projecção relativamente a custos do biodiesel?

**mundano** · 17 August 2006, 18:02

citação:Originalmente colocada por Manuel Jasmim

Relativamente aos comentários idiotas...apliquemos o :

"E diz o roto ao nú: Porque não te vestes tu?"

O petroleo é como tu dizes, é queima-lo e pronto nunca mais há nada, excepto os residuos da sua combustão...

Reitero o que disse, não há falta de energia. Apenas existe uma grande dificuldade em aproveitar a energia que temos, em tarnsformar as diferentes formas de energia.

O hidrógenio é uma excelente forma de acumular energia que de outra forma seria inutilizavel. Se conheceres outra melhor, partilha com o resto do pessoal, a humanidade vai agradecer o teu contributo.

As células de combustivel são o futuro. Células de combustivel alimentadas a H. O problema do transporte será resolvido (já está resolvido mas de forma ainda muito dispendiosa) em breve.

É idiota porque vens como o dono da verdade e não disseste nada... Se queres contrapor o que eu disse, força é para isso que aqui estamos.. Se só vens dizer que é asneiras e que te dá vontade de rir, para mim não passa de um comentario imbecil..

Alem de que neste post acabaste de reafirmar o que eu disse e que antes chamaste de barbaridade.. Vá lá um gajo tentar entender-te...

Mas já que resolveste discutir o assunto eu respondo-te..

Que o hidrogeneo será provavelmente a melhor forma de "acumular" energia no futuro, já eu sei.. MAs muita gente pensa que é a grande solução, que basta abrir uns poços para extrair o hidrogeneo mete-se nos carros e tá a andar.. E farta um bocado todo esse "hype" em torno do hidrogeneo que só induz as pessoas em erro..

O hidrogeneo não é a solução para nada, é apenas uma "pilha"... Teremos que arranjar forma de produzir electricidade para a carregar.. E neste momento não existe nenhuma solução viavel para produzir toda essa electricidade que é necessaria.

A solução final para o problema da produção energia de forma barata, não poluente e em quantidades capazes de substituir a energia dos combustiveis fosseis , não é o hidrogeneo, nunca será, nem é essa a finalidade das celulas de combustivel alimentadas a hidrogeneo.. Por isso não iludam as pessoas..

E por isso é que nos proximos anos o hidrogeneo é uma treta.. Enquanto não produzirmos electricidade abundante não podemos pensar em substituir a frota que há por carros a hidrogeneo.

**ManuelJasmim** · 17 August 2006, 20:13

citação:Originalmente colocada por mundano

citação:Originalmente colocada por Manuel Jasmim

Relativamente aos comentários idiotas...apliquemos o :

"E diz o roto ao nú: Porque não te vestes tu?"

O petroleo é como tu dizes, é queima-lo e pronto nunca mais há nada, excepto os residuos da sua combustão...

Reitero o que disse, não há falta de energia. Apenas existe uma grande dificuldade em aproveitar a energia que temos, em tarnsformar as diferentes formas de energia.

O hidrógenio é uma excelente forma de acumular energia que de outra forma seria inutilizavel. Se conheceres outra melhor, partilha com o resto do pessoal, a humanidade vai agradecer o teu contributo.

As células de combustivel são o futuro. Células de combustivel alimentadas a H. O problema do transporte será resolvido (já está resolvido mas de forma ainda muito dispendiosa) em breve.

É idiota porque vens como o dono da verdade e não disseste nada... Se queres contrapor o que eu disse, força é para isso que aqui estamos.. Se só vens dizer que é asneiras e que te dá vontade de rir, para mim não passa de um comentario imbecil..

Alem de que neste post acabaste de reafirmar o que eu disse e que antes chamaste de barbaridade.. Vá lá um gajo tentar entender-te...

Mas já que resolveste discutir o assunto eu respondo-te..

Que o hidrogeneo será provavelmente a melhor forma de "acumular" energia no futuro, já eu sei.. MAs muita gente pensa que é a grande solução, que basta abrir uns poços para extrair o hidrogeneo mete-se nos carros e tá a andar.. E farta um bocado todo esse "hype" em torno do hidrogeneo que só induz as pessoas em erro..

O hidrogeneo não é a solução para nada, é apenas uma "pilha"... Teremos que arranjar forma de produzir electricidade para a carregar.. E neste momento não existe nenhuma solução viavel para produzir toda essa electricidade que é necessaria.

A solução final para o problema da produção energia de forma barata, não poluente e em quantidades capazes de substituir a energia dos combustiveis fosseis , não é o hidrogeneo, nunca será, nem é essa a finalidade das celulas de combustivel alimentadas a hidrogeneo.. Por isso não iludam as pessoas..

E por isso é que nos proximos anos o hidrogeneo é uma treta.. Enquanto não produzirmos electricidade abundante não podemos pensar em substituir a frota que há por carros a hidrogeneo.

Para mim, continuo a achar que o H2 é a solução e é com esta barbaridade que tu não concordas, estás no teu direito...

Já agora, importavas-te de explicar qual é a finalidade das células de combustivel?

Quanto a imbecilidade, julgo que também dás o teu contributo quando nesta discussão juntas o "pessoal dos poços de H2"...não havia necessidade, ambos sabemos que não somos propriamente analfabetos, certo?

**mundano** · 17 August 2006, 20:55

Já vi que para ti tudo o que for diferente daquilo que a tua mentalidadezinha entende como certo é "uma barbaridade"..

Se achas que é a solução explica-me como vais produzir hidrogeneo nas quantidades necessarias para abastecer o parque automovel mundial. Se me explicares isso eu dou-te razão.

**ManuelJasmim** · 17 August 2006, 21:19

citação:Originalmente colocada por mundano

Já vi que para ti tudo o que for diferente daquilo que a tua mentalidadezinha entende como certo é "uma barbaridade"..

Se achas que é a solução explica-me como vais produzir hidrogeneo nas quantidades necessarias para abastecer o parque automovel mundial. Se me explicares isso eu dou-te razão.

Nuclear, claro!

Continuas sem explicar para que servem as células de combustivel, aguardo com bastante expectativa...

mentalidadezinha? deixa estar, tu és um verdadeiro "open mind", e isso vê-se pela forma como encaixas as criticas e a diversidade de opiniões.;)

**air** · 17 August 2006, 22:29

citação:Originalmente colocada por pcnunes7

citação:Originalmente colocada por air

Pelo que tenho conhecimento estão a fazer uma unidade de produção de biodiesel no porto de Aveiro. Para começar a funcionar no ano que vem.

onde é que está essa informação?

existe alguma projecção relativamente a custos do biodiesel?

http://www.martifer.com/news/display...20%20%20&k=214

É a unica coisa que sei!

**pcnunes7** · 17 August 2006, 22:34

citação:Originalmente colocada por air

citação:Originalmente colocada por pcnunes7

citação:Originalmente colocada por air

Pelo que tenho conhecimento estão a fazer uma unidade de produção de biodiesel no porto de Aveiro. Para começar a funcionar no ano que vem.

onde é que está essa informação?

existe alguma projecção relativamente a custos do biodiesel?

http://www.martifer.com/news/display...20%20%20&k=214

É a unica coisa que sei!

;)

**air** · 17 August 2006, 23:00

Vamos ver como será.. ;)

**CarlosL** · 17 August 2006, 23:07

O grande problema é o acesso continuado a combustíveis fósseis baratos.

Um dia que o barril de petróleo chegue aos 200 USD, ou mais, (e este é um número atirado para o ar...) teremos que nos desenrascar.

E pensar de outro modo no nosso estilo de vida.

Entendo que o futuro irá ser elétrico e que para tal, iremos começar pelo nuclear. Acredito que o futuro nos transportes irá ser a célula de combustível e o único processo que conheço que se me afigura rentável é o tal de Hidrogénio. Para o condutor, é simples. A combinação entre o Oxigénio e Hidrogénio produz energia elétrica.

Claro que produzir Hidrogénio é caro, armazená-lo também, bem como providenciar o seu transporte de modo seguro e prático nos nossos transportes.

Mas para mim, esse será o futuro.

Até lá, há muita coisa a fazer. Especialmente preparar o futuro.

**pcnunes7** · 17 August 2006, 23:08

citação:Originalmente colocada por air

Vamos ver como será.. ;)

é pena que no link que me deste, nada esteja quanto a prespectivas de custos de venda.
Todavia, espero que, como não é necessário petróleo, esse bem carissimo, possa ser substancialmente mais barato, e eu como sou um gajo optimista, quem sabe ao preço do GPL:D

e em relação à prepaação dos carros para o biodiesel, como é que é?

**air** · 17 August 2006, 23:25

É pena sim.. Apenas soube também por ter tido interesse na empresa e vi a noticia. De resto será complicado ir para o preço do GPL.. LOL

Penso que não é necessário alterações nos carros até uma certa percentagems de oleos..

**pcnunes7** · 17 August 2006, 23:26

citação:Originalmente colocada por air

É pena sim.. Apenas soube também por ter tido interesse na empresa e vi a noticia. De resto será complicado ir para o preço do GPL.. LOL

Penso que não é necessário alterações nos carros até uma certa percentagems de oleos..

;)

**mundano** · 17 August 2006, 23:27

Depende como são feitas as criticas, se são feitas num tom imbecil encaixo mal.. Se responderes ao que eu digo com contra-argumentos tenho todo o gosto em rebater os teus argumentos, ou se achar que tens razão calo-me..

Quanto as celulas de combustivel, se sabes o que são para que perguntas? Não me apetece gastar latin sem finalidade nenhuma..

Quanto ao "Nuclear, claro!".. Bem, antes de mais, isso é uma resposta tipica de quem não faz ideia do que está a falar..

Logo para começar, neste momento toda a electricidade produzida por exemplo nos EUA, não dava para produzir hidrogeneo para substituir 50% da gasolina gasta pela frota de veiculos ligeiros..

Imaginas quantas centrais nucleares seria preciso para isso? Achas que algum pais aceitaria a construção de centrais nucleares como cogumelos pra correr atrás de uma tecnologia que até agora ainda não deu provas nenhumas?

Depois, sabes os custos e as dificuldades de transportar hidrogeneo? Sabes que o hidrogeneo armazenado em contentores de aço evapora a um racio de 1,5% ao dia, ou 4% se for liquefeito? Sabes que o hidrogeneo corroi o aço e produz fugas que podem ser potencialmente perigosas dado e elevadissimo potencial de ignição do hidrogeneo? Sabes que o hidrogeneo tem uam chama quase invisivel e há pessoas que chegaram a ir de encontro a uma labareda simplesmente porque não a viram? A produção centralizada com distribuição a nivel de um pais, sem algumas revoluções tecnologicas nunca será viavel nem nunca atingirá niveis de segurança que o permitam tornar como algo para o uso publico..

Pelas melhores expectativas, se vier a haver carros a hidrogeneo a unica maneira viavel de o produzir em massa nas proximas decadas será com pequenas estações de reconversão nos postos de abastecimento que transformam gas natural em hidrogeneo.. Só que isso será uma estupides, porque esse gas natural seria muito melhor usado a substituir centrais termicas de queima de carvão.. Alem de que, estima-se que a electricidade necessaria para produzir um KG de hidrogeneo implicaria a mesma poluição que queimar um galão de gasolina..

Enfim... Na melhor das hipoteses o hidrogeneo será uma tecnologia para a 2ª metade do seculo.. E para que isso aconteça é preciso alguns milagres tecnologicos que resolvam alguns dos complicadissimos entraves que o hidrogeneo representa em termos de segurança, eficiencia e custo.. A tecnologia actual, pelo que dizem os especialistas por muito que evolua nunca tornará o hidrogeneo viavel para o grande publico. E as revoluções tecnologicas, ou novas tecnologias poderão aparecer, ou não..

E agora, se quiseres aprender um bocado para não andares ai iludido com tretas, recomendo-te que leias este excelente artigo escrito por este senhor:

The author, Joseph J. Romm, was born on June 27, 1960 in Middletown, New York. Dr. Romm is executive director and founder of the Center for Energy and Climate Solutions, a consulting firm based in Washington DC that helps businesses and states adopt high-leverage strategies for saving energy and cutting pollution. He served as Acting Assistant Secretary at the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy during 1997 and Principal Deputy Assistant Secretary from 1995 though 1998. He holds B.S. and Ph.D. degrees in physics from M.I.T. and has published a number of other books on energy efficiency (including "Cool Companies") and other technology and environment topics.

Grosso modo ele foi o principal conselheiro para as energias eficiente e redução da poluição da administração Clinton.. E é autor de varios livros sobre o assunto, sendo que o ultimo se chama: The Hype about Hydrogen, Fact and Fiction in the Race to Save the Climate.

Cá vai o artigo, é longo, mas para quem quiser aprender e deixar de dizer asneiras é util e interessante:

citação:JOSEPH J. ROMM

The Hype about Hydrogen

We can't use hydrogen's long-term potential as an excuse to avoid taking action now on reducing greenhouse gas emissions.

Hydrogen and fuel cell cars are being hyped today as few technologies have ever been. In his January 2003 State of the Union address, President Bush announced a $1.2 billion research initiative, "so that the first car driven by a child born today could be powered by hydrogen, and pollution-free." The April 2003 issue of Wired magazine proclaimed, "How Hydrogen Can Save America." In August 2003, General Motors said that the promise of hydrogen cars justified delaying fuel-efficiency regulations.

Yet for all the hype, a number of recent studies raise serious doubts about the prospects for hydrogen cars. In February 2004, a study by the National Academies' National Academy of Engineering and National Research Council concluded, "In the best-case scenario, the transition to a hydrogen economy would take many decades, and any reductions in oil imports and carbon dioxide (CO2) emissions are likely to be minor during the next 25 years." Realistically, a major effort to introduce hydrogen cars before 2030 would actually undermine efforts to reduce emissions of heat-trapping greenhouse gases such as CO2.

As someone who helped oversee the Department of Energy's (DOE's) program for clean energy, including hydrogen, for much of the 1990s--during which time hydrogen funding was increased by a factor of 10--I believe that continued research into hydrogen remains important because of its potential to provide a pollution-free substitute for oil in the second half of this century. But if we fail to limit greenhouse gas emissions over the next decade, and especially if we fail to do so because we have bought into the hype about hydrogen's near-term prospects, we will be making an unforgivable national blunder that may lock in global warming for the United States of 1 degree Fahrenheit per decade by midcentury.

Hydrogen is not a readily accessible energy source like coal or wind. It is bound up tightly in molecules such as water and natural gas, so it is expensive and energy-intensive to extract and purify. A hydrogen economy--a time in which the economy's primary energy carrier would be hydrogen made from sources of energy that have no net emissions of greenhouse gases--rests on two pillars: a pollution-free source for the hydrogen itself and a fuel cell for efficiently converting it into useful energy without generating pollution.

Fuel cells are small, modular electrochemical devices, similar to batteries, but which can be continuously fueled. For most purposes, you can think of a fuel cell as a "black box" that takes in hydrogen and oxygen and puts out only water plus electricity and heat. The most promising fuel cell for transportation uses is the proton exchange membrane (PEM), first developed in the early 1960s by General Electric for the Gemini space program. The price goal for transportation fuel cells is to come close to that of an internal combustion engine, roughly $30 per kilowatt. Current PEM costs are about 100 times greater. It has taken wind and solar power each about 20 years of major government and private-sector investments in R&D to see a 10-fold decline in prices, and they still each comprise well under 1 percent of U.S. electricity generation. A major technology breakthrough is needed in transportation fuel cells before they will be practical.

Running a fuel cell car on pure hydrogen, the option now being pursued by most automakers and fuel cell companies, means the car must be able to safely, compactly, and cost-effectively store hydrogen onboard. This is a major technical challenge. At room temperature and pressure, hydrogen takes up some 3,000 times more space than gasoline containing an equivalent amount of energy. The DOE's 2003 Fuel Cell Report to Congress notes that, "Hydrogen storage systems need to enable a vehicle to travel 300 to 400 miles and fit in an envelope that does not compromise either passenger space or storage space. Current energy storage technologies are insufficient to gain market acceptance because they do not meet these criteria."

The most mature storage options are liquefied hydrogen and compressed hydrogen gas. Liquid hydrogen is widely used today for storing and transporting hydrogen. Indeed, for storage and fueling, liquids enjoy considerable advantages over gases: They have high energy density, are easier to transport, and are typically easier to handle. Hydrogen, however, is not typical. It becomes a liquid only at 423 degrees Fahrenheit, just a few degrees above absolute zero. It can be stored only in a superinsulated cryogenic tank.

Liquid hydrogen is exceedingly unlikely to be a major part of a hydrogen economy because of the cost and logistical problems in handling it and because liquefaction is so energy-intensive. Some 40 percent of the energy of the hydrogen is required to liquefy it for storage. Liquefying one kilogram (kg) of hydrogen using electricity from the U.S. grid would by itself release some 18 to 21 pounds of CO2 into the atmosphere, roughly equal to the CO2 emitted by burning one gallon of gasoline.

Nearly all prototype hydrogen vehicles today use compressed hydrogen storage. Hydrogen is compressed up to pressures of 5,000 pounds per square inch (psi) or even 10,000 psi in a multistage process that requires energy input equal to 10 to 15 percent of the hydrogen's usable energy content. For comparison, atmospheric pressure is about 15 psi. Working at such high pressures creates overall system complexity and requires materials and components that are sophisticated and costly. And even a 10,000-psi tank would take up seven to eight times the volume of an equivalent-energy gasoline tank or perhaps four times the volume for a comparable range (because the fuel cell vehicle will be more fuel efficient than current cars).

The National Academies' study concluded that both liquid and compressed storage have "little promise of long-term practicality for light-duty vehicles" and recommended that DOE halt research in both areas. Practical hydrogen storage requires a major technology breakthrough, most likely in solid-state hydrogen storage.

Hydrogen has some safety advantages over liquid fuels such as gasoline. When a gasoline tank leaks or bursts, the gasoline can pool, creating a risk that any spark would start a fire, or it can splatter, posing a great risk of spreading an existing fire. Hydrogen, however, will escape quickly into the atmosphere as a very diffuse gas. Also, hydrogen gas is nontoxic.

Yet hydrogen has its own major safety issues. It is highly flammable, with an ignition energy that is 20 times smaller than that of natural gas or gasoline. It can be ignited by cell phones or by electrical storms located miles away. Hence, leaks pose a significant fire hazard, particularly because they are hard to detect. Hydrogen is odorless, and the addition of common odorants such as sulfur is impractical, in part because they poison fuel cells. Hydrogen burns nearly invisibly, and people have unwittingly stepped into hydrogen flames. Hydrogen can cause many metals, including the carbon steel widely used in gas pipelines, to become brittle. In addition, any high-pressure storage tank presents a risk of rupture. For these reasons, hydrogen is subject to strict and cumbersome codes and standards, especially when used in an enclosed space where a leak might create a growing gas bubble.

Some 22 percent or more of hydrogen accidents are caused by undetected hydrogen leaks. These leaks occur "despite the special training, standard operating procedures, protective clothing, electronic flame gas detectors provided to the limited number of hydrogen workers," points out Russell Moy, former group leader for energy storage programs at Ford, in the November 2003 Energy Law Journal. Moy concludes that "with this track record, it is difficult to imagine how hydrogen risks can be managed acceptably by the general public when wide-scale deployment of the safety precautions would be costly and public compliance impossible to ensure." Thus, major innovations in safety will be required before a hydrogen economy is practical.

An expensive fuel

A key problem with the hydrogen economy is that pollution-free sources of hydrogen are unlikely to be practical and affordable for decades. Indeed, even the pollution-generating means of making hydrogen are currently too expensive and too inefficient to substitute for oil.

Bridging the gap between current hydrogen technologies and the marketplace will require revolutionary conceptual breakthroughs.Natural gas (methane, or CH4) is the source of 95 percent of U.S. hydrogen. The overall energy efficiency of the steam CH4 reforming process (the ratio of the energy in the hydrogen output to the energy in the natural gas fuel input) is about 70 percent. According to a 2002 analysis for the National Renewable Energy Laboratory by Dale Simbeck and Elaine Chang, the cost of producing and delivering hydrogen from natural gas, or producing hydrogen onsite at a local filling station, is $4 to $5 per kg (excluding fuel taxes), comparable to a gasoline price of $4 to $5 a gallon. (A kg of hydrogen contains about the same usable energy as a gallon of gasoline.) This is more than three times the current untaxed price of gasoline. Considerable R&D is being focused on efforts to reduce the cost of producing hydrogen from natural gas, but fueling a significant fraction of U.S. cars with hydrogen made from natural gas makes little sense, either economically or environmentally, as discussed below.

Water can be electrolyzed into hydrogen and oxygen by a process that is extremely energy-intensive. Typical commercial electrolysis units require about 50 kilowatt-hours per kg, an energy efficiency of 70 percent. The cost today of producing and delivering hydrogen from a central electrolysis plant is estimated at $7 to $9 per kg. The cost of onsite production at a local filling station is estimated at $12 per kg. Replacing one-half of U.S. ground transportation fuels in 2025 (mostly gasoline) with hydrogen from electrolysis would require about as much electricity as is sold in the United States today.

From the perspective of global warming, electrolysis makes little sense for the foreseeable future. Burning a gallon of gasoline releases about 20 pounds of CO2. Producing 1 kg of hydrogen by electrolysis would generate, on average, 70 pounds of CO2. Hydrogen could be generated from renewable electricity, but that would be even more expensive and, as discussed below, renewable electricity has better uses for the next few decades.

Other greenhouse gasfree means of producing hydrogen are being pursued. DOE's FutureGen project is aimed at designing, building, and constructing a 270-megawatt prototype coal plant that would cogenerate electricity and hydrogen while removing 90 percent of the CO2. The goal is to validate the viability of the system by 2020. If a permanent storage location, such as an underground reservoir, can be found for the CO2, this would mean that coal could be a virtually carbon-free source of hydrogen. DOE is also pursuing thermochemical hydrogen production systems using nuclear power with the goal of demonstrating commercial-scale production by 2015. Biomass (plant matter) can be gasified and converted into hydrogen in a process similar to coal gasification. The cost of delivered hydrogen from gasification of biomass has been estimated at $5 to $6.30 per kg. It is unlikely that any of these approaches could provide large-scale sources of hydrogen at competitive prices until after 2030.

Stranded investment is one of the greatest risks faced by near-term hydrogen production technologies. For instance, if during the next two decades we built a hydrogen infrastructure around small CH4 reformers in local fueling stations and then decided that U.S. greenhouse gas emissions must be dramatically reduced, we would have to replace that infrastructure almost entirely. John Heywood, director of the Sloan Automotive Lab at the Massachusetts Institute of Technology, argues, "If the hydrogen does not come from renewable sources, then it is simply not worth doing, environmentally or economically." A major technology breakthrough will be needed to deliver low-cost zero-carbon hydrogen.

The chicken-and-egg problem

Another key issue is the chicken-and-egg problem. At the National Hydrogen Association annual conference in March 2003, Bernard Bulkin, British Petroleum's chief scientist, said that, "if hydrogen is going to make it in the mass market as a transport fuel, it has to be available in 30 to 50 percent of the retail network from the day the first mass-manufactured cars hit the showrooms." Yet a 2002 analysis by Argonne National Laboratory found that even with improved technology, "the hydrogen delivery infrastructure to serve 40 percent of the light duty fleet is likely to cost over $500 billion." Major breakthroughs in hydrogen production and delivery will be required to reduce that figure significantly.

Who will spend the hundreds of billions of dollars on a wholly new nationwide infrastructure to provide ready access to hydrogen for consumers with fuel cell vehicles until millions of hydrogen vehicles are on the road? And who will manufacture and market such vehicles until the infrastructure is in place to fuel those vehicles? Will car companies and fuel providers be willing to take this chance before knowing whether the public will embrace these cars? I fervently hope to see an economically, environmentally, and politically plausible scenario for how this classic chasm can be bridged; it does not yet exist.

Centralized production of hydrogen is the ultimate goal. A pure hydrogen economy requires that hydrogen be generated from CO2-free sources, which would almost certainly require centralized hydrogen production closer to giant wind farms or at coal/biomass gasification power plants in which CO2 is extracted for permanent underground storage. That will require some way of delivering massive quantities of hydrogen to tens of thousands of local fueling stations.

Tanker trucks carrying liquefied hydrogen are commonly used to deliver hydrogen today, but make little sense in a hydrogen economy because of liquefaction's high energy cost. Also, few automakers are pursuing onboard storage with liquid hydrogen. So after delivery, the fueling station would still have to use an energy-intensive pressurization system. This might mean that storage and transport alone would require some 50 percent of the energy in the hydrogen delivered, negating any potential energy and environmental benefits from hydrogen.

Pipelines are also used for delivering hydrogen today. Interstate pipelines are estimated to cost $1 million per mile or more. Yet we have very little idea today what hydrogen generation processes will win in the marketplace during the next few decades, or whether hydrogen will be able to successfully compete with future high-efficiency vehicles, perhaps running on other pollution-free fuels. This uncertainty makes it unlikely anyone would commit to spending tens of billions of dollars on hydrogen pipelines before there are very high hydrogen flow rates transported by other means and before the winners and losers at both the production end and the vehicle end of the marketplace have been determined. In short, pipelines are unlikely to be the main hydrogen transport means until the post-2030 period.

Trailers carrying compressed hydrogen canisters are a flexible means of delivery but are relatively expensive because hydrogen has such a low energy density. Even with technology advances, a 40-metric-ton truck might deliver only about 400 kg of hydrogen into onsite high-pressure storage. A 2003 study by ABB researchers found that for a delivery distance of 300 miles, the delivery energy approaches 40 percent of the usable energy in the hydrogen delivered. Without dramatic improvement in high-pressure storage systems, this approach seems impractical for large-scale hydrogen delivery.

Producing hydrogen onsite at local fueling stations is the strategy advocated by those who want to deploy hydrogen vehicles in the next two decades. Onsite electrolysis is impractical for large-scale use because it would be highly expensive and inefficient while generating large amounts of greenhouse gases and other pollutants. The hydrogen would need to be generated from small CH4 reformers. Although onsite CH4 reforming seems viable for limited demonstration and pilot projects, it is impractical and unwise for large-scale application, for a number of reasons.

First, the upfront cost is very high: more than $600 billion just to provide hydrogen fuel for 40 percent of the cars on the road, according to Argonne. A reasonable cost estimate for the initial hydrogen infrastructure, derived from Royal Dutch/Shell figures, is $5,000 per car.

Second, the cost of the delivered hydrogen itself in this option is also higher than for centralized production. Not only are the small reformers and compressors typically more expensive and less efficient than larger units, but they also will likely pay a much higher price for the electricity and gas to run them. A 2002 analysis put the cost at $4.40 per kg (equal to $4.40 per gallon of gasoline).

We should not pursue a strategy to reduce greenhouse gas emissions in transportation that would undermine efforts to reduce emissions in electric generation.Third, "the risk of stranded investment is significant, since much of an initial compressed hydrogen station infrastructure could not be converted later if either a noncompression hydrogen storage method or liquid fuels such as a gasoline-ethanol combination proved superior" for fuel cell vehicles. This was the conclusion of a 2001 study for the California Fuel-Cell Partnership, a Sacramento-based public-private partnership to help commercialize fuel cells. Most of a CH4-based investment would also likely be stranded once the ultimate transition to a pure hydrogen economy was made, because that would almost certainly rely on centralized production and not make use of small CH4 reformers. Moreover, it's possible that the entire investment would be stranded in the scenario in which hydrogen cars simply never achieve the combination of popularity, cost, and performance to triumph in the marketplace.

In the California analysis, it takes 10 years for investment in infrastructure to achieve a positive cash flow, and to achieve this result requires a variety of technology advances in components and manufacturing. Also, even a small tax on hydrogen (to make up the revenue lost from gasoline taxes) appears to delay positive cash flow indefinitely. The high-risk and long-payback nature of this investment would seem far too great for most investors, especially given the history of alternative fuel vehicles.

The United States has a great deal of relevant experience in the area of alternative fuel vehicles that is often ignored in discussions about hydrogen. The 1992 Energy Policy Act established the goal of having alternative fuels replace at least 10 percent of petroleum fuels in 2000 and at least 30 percent in 2010. By 1999, some one million alternative fuel vehicles were on the road, only about 0.4 percent of all vehicles. A 2000 General Accounting Office report explained the reasons for the lack of success, concluding that, " Fundamental economic impediments--such as the relatively low price of gasoline, the lack of refueling stations for alternative fuels, and the additional cost to purchase these vehicles--explain much of why both mandated fleets and the general public are disinclined to acquire alternative fuel vehicles and use alternative fuels." It seems likely that all three of these problems will hinder hydrogen cars. Compared to other alternative fuels, such as ethanol and natural gas, the best analysis today suggests that hydrogen will have a much higher price for the fuel, the fueling stations, and the vehicles.

The fourth reason that producing hydrogen on-site from natural gas at local fueling stations is impractical is that natural gas is simply the wrong fuel on which to build a hydrogen-based transportation system. The United States consumes nearly 23 trillion cubic feet (tcf) of natural gas today and is projected to consume more than 30 tcf in 2025. Replacing 40 percent of ground transportation fuels with hydrogen in 2025 would probably require an additional 10 tcf of gas, plus 300 billion kilowatt-hours of electricity, or 10 percent of current power usage. Politically, given the firestorm over recent natural gas supply constraints and price spikes, it seems very unlikely that the U.S. government and industry would commit to natural gas as a substitute for even a modest fraction of U.S. transportation energy.

In addition, much if not most incremental U.S. natural gas consumption for transportation would likely come from imported liquefied natural gas (LNG). LNG is dangerous to handle, and LNG infrastructure is widely viewed as a likely terrorist target. Yet one of the major arguments in favor of alternative fuels has been their ability to address concerns over security and import dependence.

Finally, natural gas has too much economic and environmental value to the electric utility, industrial, and building sectors to justify diverting significant quantities to the transportation sector, thereby increasing the price for all users. In fact, using natural gas to generate significant quantities of hydrogen for transportation would, for the foreseeable future, undermine efforts to combat global warming.

Thus, beyond limited pilot stations, it would be unwise to build thousands of local refueling stations based on steam CH4 reforming or, for that matter, based on any technology not easily adaptable to delivery of greenhouse gas-free hydrogen.

The global warming century

Perhaps the ultimate reason why hydrogen cars are a post-2030 technology is the growing threat of global warming. Our energy choices are now inextricably tied to the fate of our global climate. The burning of fossil fuels--oil, gas and coal--emits CO2 into the atmosphere, where it builds up, blankets the earth, and traps heat, accelerating global warming. We now have greater concentrations of CO2 in the atmosphere than at any time in the past 420,000 years and probably at any time in the past 3 million years.

Carbon-emitting products and facilities have a long lifetime. Cars last 13 to 15 years or more; coal plants can last 50 years. Also, CO2 lingers in the atmosphere, trapping heat for more than a century. These two facts together create an urgency to avoid constructing another massive and long-lived generation of energy infrastructure that will cause us to miss the window of opportunity for carbon-free energy until the next century.

Between 2000 and 2030, the International Energy Agency projects that coal generation will double. The projected new plants would commit the planet to total CO2 emissions of some 500 billion metric tons over their lifetime, which is roughly half the total emissions from all fossil fuel consumed worldwide during the past 250 years. Building these coal plants would dramatically increase the chances of catastrophic climate change. What we need to build is carbon-free power. A March 2003 analysis in Science by Ken Caldeira and colleagues concluded that if our climate's sensitivity to greenhouse gas emissions is in the midrange of current estimates, "stabilization at 4°C warming would require installation of 410 megawatts of carbon emissions-free energy capacity each day" for 50 years. Yet current projections for the next 30 years are for building just 80 megawatts per day. Because planetary warming accelerates over time and because temperatures over the continental United States are projected to rise faster than the average temperature of the planet, a warming of 4° C means that by mid-century, the U.S. temperature could well be rising as much per decade as it rose during the entire past century: one degree Fahrenheit.

Unfortunately, the path set by the current energy policy of the United States and countries in the developing world will dramatically increase emissions during the next few decades, which will force sharper and more painful reductions in the future when we finally do act. Global CO2 emissions are projected to rise more than 50 percent by 2030. From 2001 to 2025, the U. S. Energy Information Administration projects a 40 percent increase in U.S. coal consumption for electricity generation. And the U.S. transportation sector is projected to generate nearly half of the 40 percent rise in U.S. CO2 emissions forecast for 2025, which again is long before hydrogen-powered cars could have a positive impact on greenhouse gas emissions.

Two points are clear. First, we cannot wait for hydrogen cars to address global warming. Second, we should not pursue a strategy to reduce greenhouse gas emissions in the transportation sector that would undermine efforts to reduce greenhouse gas emissions in the electric generation sector. Yet that is precisely what a hydrogen car strategy would do for the next few decades. For near-term deployment, hydrogen would almost certainly be produced from fossil fuels. Yet running a fuel cell car on such hydrogen in 2020 would offer no significant life cycle greenhouse gas advantage over the 2004 Prius running on gasoline.

Further, fuel cell vehicles are likely to be much more expensive than other vehicles, and their fuel is likely to be more expensive (and the infrastructure will probably cost hundreds of billions of dollars). Although hybrids and clean diesels may cost more than current vehicles, at least when first introduced, their greater efficiency means that, unlike fuel cell vehicles, they will pay for most if not all of that extra upfront cost over the lifetime of the vehicle. A June 2003 analysis in Science by David Keith and Alex Farrell put the cost of CO2 avoided by fuel cells running on zero-carbon hydrogen at more than $250 per ton even with a very optimistic fuel cell cost. An advanced internal combustion engine could reduce CO2 for far less and possibly for a net savings because of the reduced fuel bill.

It would be bad policy for DOE to continue shifting money away from efficiency and renewable energy research toward hydrogen.Probably the biggest analytical mistake made in most hydrogen studies, including the recent National Academies' report, is failing to consider whether the fuels that might be used to make hydrogen, such as natural gas or renewable sources, could be better used simply to make electricity. For example, the life cycle or "well-to-wheels" efficiency of a hydrogen car running on gas-derived hydrogen is likely to be under 30 percent for the next two decades. The efficiency of gas-fired power plants is already 55 percent (and likely to be 60 percent or higher in 2020). Cogeneration of electricity and heat using natural gas is more than 80 percent efficient. And by displacing coal, the natural gas would be displacing a fuel that has much higher carbon emissions per unit of energy than gasoline. For these reasons, natural gas is far more cost-effectively used to reduce CO2 emissions in electric generation than it is in transportation.

The same is true for renewable energy. A megawatt-hour of electricity from a renewable source such as wind power, if used to manufacture hydrogen for use in a future fuel cell vehicle, would save slightly less than 500 pounds of CO2 as compared to the best current hybrids. That is less than the savings from using the same amount of renewable electricity to displace a future natural gas plant (800 pounds) and far less than the savings from displacing coal power (2,200 pounds).

As the June 2003 Science analysis concluded: "Until CO2 emissions from electricity generation are virtually eliminated, it will be far more cost effective to use new CO2-neutral electricity (such as wind) to reduce emissions by substituting for fossil-electric generation than to use the new electricity to make hydrogen." Barring a drastic change in U.S. energy policy, our electric grid will not be close to CO2-free until well past 2030.

Major breakthroughs needed

Hydrogen and fuel cell vehicles should be viewed as post-2030 technologies. In September 2003, a DOE panel on Basic Research Needs for the Hydrogen Economy concluded that the gaps between current hydrogen technologies and what is required by the marketplace "cannot be bridged by incremental advances of the present state of the art" but instead require "revolutionary conceptual breakthroughs." In sum, "the only hope of narrowing the gap significantly is a comprehensive, long-range program of innovative, high risk/high payoff basic research." The National Academies' study came to a similar conclusion.

DOE should focus its hydrogen R&D budget on exploratory breakthrough research. Given that there are few potential zero-carbon replacements for oil, DOE is not spending too much on hydrogen R&D. But given our urgent need for reducing greenhouse gas emissions with clean energy, DOE is spending far too little on energy efficiency and renewable energy. Unless DOE's overall clean energy budget is increased, however, it would be bad policy to continue shifting money away from efficiency and renewable energy toward hydrogen. Any incremental money given to DOE should probably be focused on deploying the cost-effective technologies we have today in order to buy us more time for some of the breakthrough research to succeed.

The National Academies' panel wrote that "it seems likely that, in the next 10 to 30 years, hydrogen produced in distributed rather than centralized facilities will dominate," and so it recommended increased funding for improving small-scale natural gas reformers and water electrolysis systems. Yet any significant shift toward cars running on distributed hydrogen from natural gas or grid electrolysis would undermine efforts to fight global warming. DOE should not devote any R&D to these technologies. In hydrogen production, DOE should be focused solely on finding a low-cost zero-carbon source, which will almost certainly be centralized. That probably means we won't begin the hydrogen transition until after 2030 because of the logistical and cost problems associated with a massive hydrogen delivery infrastructure.

But we shouldn't be rushing to deploy hydrogen cars in the next two decades anyway, because not only are several R&D breakthroughs required but we also need a revolution in clean energy that dramatically accelerates the penetration rates of new CO2-neutral electricity. Hydrogen cars might find limited value as city cars in very polluted cities before 2030, but they are unlikely to achieve mass-market commercialization by then. That is why neither government policy nor business investment should be based on the belief that hydrogen cars will have meaningful commercial success in the near or medium term.

The priority for today is to deploy existing clean energy technologies and to avoid any expansion of the inefficient carbon-emitting infrastructure. If we fail to act now to reduce greenhouse gas emissions--especially if we fail to act because we have bought into the hype about hydrogen's near-term prospects--future generations will condemn us because we did not act when we had the facts to guide us, and they will most likely be living in a world with a much hotter and harsher climate than ours, one that has undergone an irreversible change for the worse.

Recommended reading

American Physical Society, "The Hydrogen Initiative," March 2004 (www.aps.org).

Center for Energy and Climate Solutions (www.coolcompanies.org).

National Academy of Engineering and National Research Council, The Hydrogen Economy: Opportunities, Costs, Barriers, and R&D Needs, February 2004 (www.nap.edu/books/0309091632/html).

National Renewable Energy Laboratory, "Hydrogen Supply: Cost Estimate for Hydrogen Pathways," July 2002 (www.nrel.gov/docs/fy03osti/32525.pdf).

U.S. DOE, "Basic Research Needs for the Hydro-gen Economy," 2003 (www.sc.doe.gov/bes/hydrogen.pdf).

U.S. DOE, Hydrogen, Fuel Cells and Infrastructure Technologies Program (www.eere.energy.gov/hydrogenandfuelcells/).

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Joseph J. Romm (jromm@getf.org) is executive director of the Center for Energy and Climate Solutions in Arlington, Virginia, and a principal with the Capital E Group in Washington, D.C. During the Clinton administration, he served as Acting Assistant Secretary of Energy for Energy Efficiency and Renewable Energy. He is author of The Hype about Hydrogen: Fact and Fiction in the Race to Save the Climate (Island Press, 2004).

Não deia de ser curioso que os principais criticos do hidrogeneo sejam aqueles que sempre lutaram por um melhor ambiente e não os construtores de carros ou as empresas do sector energetico.. Para esses o que se ve é a possibilidade de um novo mercado de carros caros e na moda como acontece com o Prius actualmente, e as energias energeticas vêm mercado para uma nova rede de energia com um combustivel bem mais caro do que a gasolina... Do outro lado há os cepticos, que vêm que a unica maneira de haver carros a hidrogeneo nas proximas decadas será a partir do hidrogeneo negro, produzido a partir da queima de carvão ou da energia nuclear.. E não o hidrogeneo limpo que os primeiros publicitam...

**mundano** · 17 August 2006, 23:39

Mais um artigo interessante.. E cheio de factos interessantes...

citação:Spencer Abraham's Hydrogen Dream

The media was all aglow recently with Spencer Abraham's announcement that the U.S. now has a roadmap for making the transition to a hydrogen economy. Secretary of Energy Abraham announced the plan at the Global Forum on Personal Transportation held in Dearborn, Mich. In his presentation, he touted the line that hydrogen produced from renewable resources can provide unlimited energy with no impact on the environment. Secretary Abraham noted that the transition to hydrogen would be a long-term process, which will require the participation of both industry and government.

As a first step, in January 2002 Secretary Abraham, along with officials from the automotive industry and Congress, unveiled a FreedomCAR partnership to develop hydrogen fuel cell vehicles.

The National Hydrogen Energy Roadmap is available on the internet in pdf form. This roadmap glows with positive energy. In all areas of production, delivery, storage, conversion and applications, the document beams about what we can achieve if we put our minds to it, but inevitably winds up by saying that we have a long way to go in order to make it a reality.

The document does mention the various challenges to each area of fuel cell development, but makes little of the obstacles and instead comes off sounding like a pep talk. Buried in the text, they admit "The transition to a hydrogen economy... could take several decades to achieve."

The document speaks of wind, solar and geothermal production, biomass, nuclear-thermo-chemical water splitting, photoelectrochemical electrolysis, and bioengineering. But they admit that all of these processes will require a great deal more research.

The intention is to bootstrap the move by first developing small "reformers" that will run on natural gas, propane, methanol or diesel. But the authors admit that even this technology requires further refinement for improved reliability, longer catalyst life, and integration with storage systems and fuel cells.

The document also includes a short list of people who are in charge of various areas of development and transition. The list includes: Frank Balog of Ford Motor Company, Gene Nemanich of ChevronTexaco Technology Ventures, Mike Davis of Avista Labs Energy, Art Katsaros of Air Products and Chemicals Incorporated, Alan Niedzwiecki of Quantum Technologies, Joan Ogden of Princeton University Systems, and Jeff Serfass of The National Hydrogen Association. This team will ensure that the new technology remains firmly in the hands of the top corporations.

The document is at least 80 percent public relations. While admitting that in all areas there are serious problems to be overcome before we will be able to make a transition to hydrogen fuel cells, nowhere does this document take a serious look at the obstacles. Instead, this paper paints a pretty picture of our hydrogen future and leaves the details to future research and investment. So let us look at a few of the difficulties of developing a hydrogen fuel cell economy.

First off, because hydrogen is the simplest element, it will leak from any container, no mater how strong and no matter how well insulated. For this reason, hydrogen in storage tanks will always evaporate, at a rate of at least 1.7 percent per day. Hydrogen is very reactive. When hydrogen gas comes into contact with metal surfaces it decomposes into hydrogen atoms, which are so very small that they can penetrate metal. This causes structural changes that make the metal brittle.

Perhaps the largest problem for hydrogen fuel cell transportation is the size of the fuel tanks. In gaseous form, a volume of 238,000 litres of hydrogen gas is necessary to replace the energy capacity of 20 gallons of gasoline.

So far, demonstrations of hydrogen-powered cars have depended upon compressed hydrogen. Because of its low density, compressed hydrogen will not give a car as useful a range as gasoline. Moreover, a compressed hydrogen fuel tank would be at risk of developing pressure leaks either through accidents or through normal wear, and such leaks could result in explosions.

If the hydrogen is liquefied, this will give it a density of 0.07 grams per cubic centimeter. At this density, it will require four times the volume of gasoline for a given amount of energy. Thus, a 15-gallon gas tank would equate to a 60-gallon tank of liquefied hydrogen. Beyond this, there are the difficulties of storing liquid hydrogen. Liquid hydrogen is cold enough to freeze air. In test vehicles, accidents have occurred from pressure build-ups resulting from plugged valves.

Beyond this, there are the energy costs of liquefying the hydrogen and refrigerating it so that it remains in a liquid state. No studies have been done on the energy costs here, but they are sure to further decrease the Energy Return on Energy Invested (EROEI) of hydrogen fuel.

A third option is the use of powdered metals to store the hydrogen in the form of metal hydrides. In this case, the storage volume would be little more than the volume of the metals themselves. Moreover, stored in this form, hydrogen would be far less reactive. However, as you can imagine, the weight of the metals will make the storage tank very heavy.

Now we come to the production of hydrogen. Hydrogen does not freely occur in nature in useful quantities, therefore hydrogen must be split from molecules, either molecules of methane derived from fossil fuels or from water.

Currently, most hydrogen is produced by the treatment of methane with steam, following the formula: CH4 (g) + H2O + e > 3H2(g) + CO(g). The CO(g) in this equation is carbon monoxide gas, which is a byproduct of the reaction.

Not entered into this formula is the energy required to produce the steam, which usually comes from the burning of fossil fuels.

For this reason, we do not escape the production of carbon dioxide and other greenhouse gases. We simply transfer the generation of this pollution to the hydrogen production plants. This procedure of hydrogen production also results in a severe energy loss. First we have the production of the feedstock methanol from natural gas or coal at a 32 percent to 44 percent net energy loss. Then the steam treatment process to procure the hydrogen will result in a further 35 percent energy loss.

It has often been pointed out that we have an inexhaustible supply of water from which to derive hydrogen. However, this reaction, 2H2O + e = 2H2(g) + O2(g), requires a substantial energy investment per unit of water (286kJ per mole). This energy investment is required by elementary principles of chemistry and can never be reduced.

Several processes are being explored to derive hydrogen from water, most notably electrolysis of water and thermal decomposition of water. But the basic chemistry mentioned above requires major energy investments from all of these processes, rendering them unprofitable in terms of EROEI.

Much thought has been given to harnessing sunlight through photovoltaic cells and using the resulting energy to split water in order to derive hydrogen. The energy required to produce 1 billion kWh (kilowatt hours) of hydrogen is 1.3 billion kWh of electricity. Even with recent advances in photovoltaic technology, the solar cell arrays would be enormous, and would have to be placed in areas with adequate sunlight.

Likewise, the amount of water required to generate this hydrogen would be equivalent to 5 percent of the flow of the Mississippi River. As an example of a solar-to-hydrogen set up, were Europe to consider such a transition, their best hope would lie in erecting massive solar collectors in the Saharan desert of nearby Africa. Using present technology, only 5 percent of the energy collected at the Sahara solar plants would be delivered to Europe. Such a solar plant would probably cost 50 times as much as a coal fired plant, and would deliver an equal amount of energy.

The basic problem of hydrogen fuel cells is that the second law of thermodynamics dictates that we will always have to expend more energy deriving the hydrogen than we will receive from the usage of that hydrogen. The common misconception is that hydrogen fuel cells are an alternative energy source when they are not.

In reality, hydrogen fuel cells are a storage battery for energy derived from other sources. In a fuel cell, hydrogen and oxygen are fed to the anode and cathode, respectively, of each cell. Electrons stripped from the hydrogen produce direct current electricity which can be used in a DC electric motor or converted to alternating current.

Because of the second law of thermodynamics, hydrogen fuel cells will always have a bad EROEI. If fossil fuels are used to generate the hydrogen, either through the Methane-Steam method or through Electrolysis of Water, there will be no advantage over using the fossil fuels directly. The use of hydrogen as an intermediate form of energy storage is justified only when there is some reason for not using the primary source directly. For this reason, a hydrogen-based economy must depend on large-scale development of nuclear power or solar electricity.

Therefore, the development of a hydrogen economy will require major investments in fuel cell technology research and nuclear or solar power plant construction. On top of this, there is the cost of converting all of our existing technology and machinery to hydrogen fuel cells. And all of this will have to be accomplished under the economic and energy conditions of post-peak fossil fuel production.

Based on all of this, I submit that Secretary of Energy Spencer Abraham does indeed have ulterior motives for his Hydrogen Energy Roadmap. First, I suggest that this distant goal will help to pacify the public once they begin to suffer from the effects of fossil fuel withdrawal. Secondly, this project will allow the elite to transfer more money from the general public to the pockets of the rich. Third, in the words of Karl Davies, this proposal will deflect a stock market collapse once news of declining oil production becomes generally recognized.

Tied to this, it will brace stock prices of the auto corporations and oil majors to help them survive well into the era of oil depletion. And finally, the idea that we are working on a transition from fossil fuels to a hydrogen-based economy will help to destabilize OPEC, hopefully making it easier to deal with that organization and the Arab oil states.

**mundano** · 17 August 2006, 23:40

citação:I believe that hydrogen has a place in an economy in which the following are true:
1. We use much less total energy than we do know
2. We are much less mobile than we are now.
When we do travel we use walking and bicycling for short trips and buses, trains and sailing ships for longer trips.
Trains and buses are mostly electric.
Cars have a very secondary role.
Airplanes have almost been eliminated.
3. Energy comes from renewable sources.
4. Energy is stored as:
A. Water in dams
B. Biomass
C. Biomass methane
D. Hydrogen for storing energy from windmills and solar
E. Hydrogen for long-distance transportation away from the electric grid

Trying to perpetuate our existing high-energy lifestyle with hydrogen is a pipe dream.

Anúncio

Ethanol, Methanol, Bio Diesel...porque?????

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