Brintdrevne køretøjer:En realistisk vej til ren energi?

Hver morgen ved et transitanlæg i Canton, Ohio, kører mere end et dusin busser op til en tankstation, før de flyver ud til deres ruter i denne by syd for Cleveland.

Busserne - lavet af El Dorado National og ejet af Stark Area Regional Transit Authority - ligner alle andre. Men tilsammen afspejler de forkant med en teknologi, der kunne spille en nøglerolle i at producere renere transport mellem byer. I stedet for diesel, der bøvser forurening, kører en fjerdedel af styrelsens busser på brint. De udsender intet andet end harmløs vanddamp.

Brint, det mest udbredte grundstof i universet, betragtes i stigende grad sammen med elektriske køretøjer som en måde at bremse den miljøødelæggende påvirkning af planetens 1,2 milliarder køretøjer, hvoraf de fleste brænder benzin og diesel. Producenter af store lastbiler og erhvervskøretøjer begynder at omfavne brintbrændselscelleteknologier som en vej frem. Det samme er producenter af fly, tog og passagerkøretøjer.

Transport er den største enkeltstående amerikanske bidragyder til klimaændringer, og derfor ses brintkraft i det lange løb som en potentielt vigtig måde at hjælpe med at reducere kulstofemissioner.

For at være sikker er brint stadig langt fra en magisk løsning. For nu er den brint, der produceres globalt hvert år, hovedsageligt til raffinaderier og gødningsfremstilling, ved hjælp af naturgas eller kul. Den proces forurener luften og opvarmer planeten i stedet for at redde den. Faktisk fandt en ny undersøgelse foretaget af forskere fra Cornell og Stanford universiteter, at det meste af brintproduktionen udleder kuldioxid, hvilket betyder, at brintdrevet transport endnu ikke kan betragtes som ren energi.

Alligevel siger tilhængere af brint-drevet transport, at brintproduktion i det lange løb er bestemt til at blive mere miljømæssigt sikker. De forestiller sig et stigende forbrug af elektricitet fra vind- og solenergi, som kan adskille brint og ilt i vand. Da sådanne vedvarende energiformer vinder bredere anvendelse, bør brintproduktion blive en renere og billigere proces.

Inden for tre år planlægger General Motors, Navistar og vognmandsfirmaet J.B. Hunt at bygge tankstationer og køre brintlastbiler på adskillige amerikanske motorveje. Toyota, Kenworth og Los Angeles havn er begyndt at teste brintlastbiler til at transportere varer fra skibe til lagre.

Volvo Trucks, Daimler Trucks AG og andre producenter har også annonceret partnerskaber. Virksomhederne håber at kommercialisere deres forskning ved at tilbyde nul-emissionslastbiler, der sparer penge og opfylder strengere forureningsregler.

I Tyskland begyndte et brintdrevet tog at køre i 2018, og flere er på vej. Fransk-baserede Airbus, verdens største producent af passagerfly, overvejer også brint.

"Dette er omtrent det tætteste, jeg har set os komme så langt på det virkelige vendepunkt," sagde Shawn Litster, professor i maskinteknik ved Carnegie Mellon University, som har studeret brintbrændselsceller i næsten to årtier.

Brint har længe været et råmateriale til produktion af gødning, stål, petroleum, beton og kemikalier. Det har også kørt køretøjer i årevis:Omkring 35.000 gaffeltrucks i USA, omkring 4% af landets samlede, er drevet af brint. Its eventual use on roadways, to haul heavy loads of cargo, could begin to replace diesel-burning polluters.

No one knows when, or even whether, hydrogen will be adopted for widespread use. Craig Scott, Toyota's head of advanced technology in North America, says the company is perhaps two years from having a hydrogen truck ready for sale. Building more fueling stations will be crucial to widespread adoption.

Kirt Conrad, CEO of Canton's transit authority since 2009, says other transit systems have shown so much interest in the technology that SARTA takes its buses around the country for demonstrations. Canton's system, which bought its first three hydrogen buses in 2016, has since added 11. It's also built a fueling station. Two California transit systems, in Oakland and Riverside County, have hydrogen buses in their fleets.

"We've demonstrated that our buses are reliable and cost-efficient, and as a result, we're breaking down barriers that have slowed wider adoption of the technology," Conrad said.

The test at the Port of Los Angeles started in April, when the first of five semis with Toyota hydrogen powertrains began hauling freight to warehouses in Ontario, California, about 60 miles away. The $82.5 million public-private project eventually will have 10 semis.

Hydrogen fuel is included in President Joe Biden's plans to cut emissions in half by 2030. The infrastructure bill the Senate approved passed this week includes $9 billion for research to reduce the cost of making clean hydrogen, and for regional hydrogen manufacturing hubs.

The long-haul trucking industry appears to be the best bet for early adoption of hydrogen. Fuel cells, which convert hydrogen gas into electricity, provide a longer range than battery-electric trucks, fare better in cold weather and can be refueled much faster than electric batteries can be recharged. Proponents say the short refueling time for hydrogen vehicles gives them an edge over electric vehicles for use in taxis or delivery trucks, which are in constant use.

That advantage was important for London-based Green Tomato Cars, which uses 60 hydrogen fuel cell-powered Toyota Mirai cars in its 500-car zero emission fleet to transport corporate customers. Co-founder Jonny Goldstone said his drivers can travel over 300 miles (500 kilometers) on a tank and refuel in three minutes.

Because drivers' earnings depend on fares, Goldstone said, "if they have to spend 40, 50 minutes, an hour, two hours plugging a car in in in the middle of the working day, that for them is just not acceptable."

For now, Green Tomato is among the largest operators of hydrogen vehicles in what is still a tiny market in Europe, with about 2,000 fuel cell cars, garbage trucks and delivery vans on the roads.

About 7,500 hydrogen fuel cell cars are on the road in the U.S., mostly in California. Toyota, Honda and Hyundai produce the cars, which are priced thousands more than gasoline-powered vehicles. California has 45 public fueling stations, with more planned or under construction.

Unlike with buses and heavy trucks, experts say the future of passenger vehicles in the U.S. lies mainly with electric battery power, not hydrogen. Fully electric vehicles can travel farther than most people need to go on a relatively small battery.

And for now, hydrogen production is adding to rather than reducing pollution. The world produces about 75 million tons a year, most of it in a carbon emission-creating processes involving steam reformation of natural gas. China uses higher-polluting coal.

So-called "blue" hydrogen, made from natural gas, requires an additional step. Carbon dioxide emitted in the process is sent below the earth's surface for storage. The Cornell and Stanford study found that manufacturing blue hydrogen emitted 20% more carbon than burning natural gas or coal for heat.

That's why industry researchers are focused on electrolysis, which uses electricity to separate hydrogen and oxygen in water. Hydrogen mixes with oxygen in a vehicle's fuel cell to produce power. The amount of electricity generated by wind and solar is growing worldwide, making electrolysis cleaner and cheaper, said Joe Cargnelli, director of hydrogen technologies for Cummins, which makes electrolyzers and fuel cell power systems.

Currently, it costs more to make a hydrogen truck and produce the fuel than to put a diesel-powered truck on the road. Hydrogen costs about $13 per kilogram in California, and 1 kilogram can deliver slightly more energy than a gallon of diesel fuel. By contrast, diesel fuel is only about $3.25 per gallon in the U.S.

But experts say that disparity will narrow.

"As they scale up the technology for production, the hydrogen should come down," said Carnegie Mellon's Litster.

While a diesel semi can cost around $150,000 depending on how it's equipped, it's unclear how much fuel cell trucks would cost. Nikola, a startup electric and hydrogen fuel cell truck maker, estimated last year that it would receive about $235,000 for each hydrogen semi it sells.

Clean electricity might eventually be used to make and store hydrogen at a rail yard, where it could refuel locomotives and semis, all with zero emissions.

Cummins foresees the widespread use of hydrogen in the U.S. by 2030, sped by stricter diesel emissions regulations and government zero-emissions vehicle requirements. Already, Europe has set ambitious green hydrogen targets designed to accelerate its use.

"That's just going to blow the market open and kind of drive it," Cargnelli said. "Then you'll see other places like North America kind of follow suit."