Stanford research says battery electric beats fuel cells for environmental benefits
Battery electric vehicles have an advantage over hydrogen fuel cell vehicles in reducing emissions, according to research out of Stanford University. The study concludes that the infrastructure required for electric vehicles would offer more possibilities for reducing energy use in communities as well, resulting in steeper reductions of emissions levels.
The study was recently published in the journal "Energy." It was completed by scientists from Stanford and the Technical University of Munich, with support from Stanford's Global Climate and Energy Project as well as the BMW Group.
"We looked at how large-scale adoption of electric vehicles would affect total energy use in a community, for buildings as well as transportation," said Markus Felgenhauer, who is the lead author of the study, a former visiting scholar at the Stanford GCEP, and a doctoral candidate at TUM. "We found that investing in all-electric battery vehicles is a more significant economical choice for reducing carbon dioxide emissions, primarily due to their lower cost and significantly higher energy efficiency."
Both battery electric and hydrogen fuel cell vehicles emit zero carbon emissions when they are driven. Electric vehicles run on a charge received by plugging into a power source, while fuel cell vehicles use hydrogen fuel that produces only water vapor and warm air for emissions.
The researchers acknowledged that while the vehicles themselves are emission-free, the processes required to fuel them produce pollution. Electric vehicles are often charged by hooking up to a grid supplied by power stations which burn fossil fuels and release carbon dioxide into the air.
Hydrogen fuel is usually derived from natural gas in an industrial process that gives off carbon dioxide as a byproduct. It is also possible to create this fuel with an electrolyzer, a solar-powered device that splits water into hydrogen and oxygen, but the process is currently expensive and energy intensive.
In addition, electric and fuel cell vehicles are typically more expensive than conventional vehicles powered by gasoline. The study set up scenarios in a hypothetical future where vehicles using alternative fuels are more affordable, and where solar power and electrolyzers are more competitive with other methods of producing electricity.
The study sought to determine if either electric or fuel cell vehicles offered a clear advantage in reducing emissions at a lower cost. It also analyzed whether the new infrastructure needed to recharge electric vehicles or deliver hydrogen fuel could be used to provide clean energy for heating and electrifying buildings.
The researchers established scenarios in Los Altos Hills, a California community of about 8,000 people. The town, located near Stanford University, has a high solar generation capacity as well as the highest share of electric vehicles in the state.
The study set up scenarios for 10 to 20 years in the future. In one scenario, researchers used the assumption that electric vehicles would make up 38 percent of the vehicles in Los Altos Hills. The same scenario assumed that fuel cell vehicles in the town would be powered by hydrogen produced locally with the cheapest available electricity, which could be derived from either solar power or a conventional electric grid.
Once these parameters were established, the data was run through a computational model. This model was developed by Thomas Hamacher, a co-author of the study and a professor of electrical and computer engineering at TUM.
"We provided data on the amount of energy Los Altos Hills needs throughout the day, as well as financial data on the cost of building new energy infrastructures," said Matthew Pellow, a co-author of the study and former GCEP postdoctoral fellow who now works with the Electric Power Research Institute. "We included the cost of making solar panels, electrolyzers, batteries, and everything else. Then we told the model, given our scenario for 2035, 'Tell us the most economical way to meet the total energy demand of the community.'"
Researchers also looked at the potential benefits of the technologies in other areas. They compared how well battery and fuel cell vehicles could reduce emissions, as well as whether a hydrogen fuel infrastructure would be able to store clean energy for use at a later time. For example, electrolyzers could potentially use surplus solar energy to produce extra hydrogen to be stored and converted into electricity or used as an alternative to natural gas for powering and heating structures.
Felgenhauer says the computer model determined that battery electric vehicles were more cost-effective than fuel cell vehicles in reducing emissions.
"The analysis showed that to be cost competitive, fuel cell vehicles would have to be priced much lower than battery vehicles," he said. "However, fuel cell vehicles are likely to be significantly more expensive than battery vehicles for the foreseeable future. Another supposed benefit of hydrogen—storing surplus solar energy—didn't pan out in our analysis either. We found that in 2035, only a small amount of solar hydrogen storage would be used for heating and lighting buildings."
The researchers said these results are relevant not just for Los Altos Hills, but also any California communities with significant levels of sunlight. They say they hope to look at larger networks of communities in future studies to help policymakers determine the best ways to reduce emissions and improve infrastructure for alternative fuels.
"Studies such as these are needed to identify the lowest cost and most efficiency pathways to deep decarbonization of the global energy system," said GCEP director Sally Benson, who is also a co-author of the study and professor of energy resources engineering at Stanford.
Fuel cell advocates have argued that the technology is advantageous over battery electric vehicles in a number of ways. H2Gen Innovations, a hydrogen generator manufacturer in Alexandria, Virginia, says these include powertrains that are lighter, less expensive, and take up less room in the vehicle. Fuel cell vehicles can also be refueled more quickly than it takes to charge a battery electric vehicle, and can travel farther than the range of an electric vehicle.
A 2010 analysis by researchers at Imperial College London also compared the benefits and disadvantages of electric, fuel cell, and plug-in hybrid vehicles in the creation of a sustainable transportation system. That study concluded that the best option for future development would be a combination battery and fuel cell vehicle, which would allow the use of battery power for short trips as well as hydrogen fuel to extend its range.
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