Posted in | Electric Vehicles | Battery

Stanford Study Reveals Battery Electric Cars Reduce Emissions Better Than Fuel Cell Vehicles

Researcher Matthew Pellow charges his all-electric Nissan Leaf at Stanford. Pellow has found that battery electric vehicles are a more cost-efficient choice for reducing carbon dioxide emissions than cars powered by hydrogen. (Image credit: Mark Shwartz)

Electric vehicles running on batteries would be a better investment than hydrogen fuel cells in a number of communities.

This finding is based on a study published in the November issue of the journal Energy by researchers at Stanford University and the Technical University of Munich (TUM). They did a comparative study on cars that function on batteries versus hydrogen fuel cells in a hypothetical future where the price of electric vehicles is more economical.

We looked at how large-scale adoption of electric vehicles would affect total energy use in a community, for buildings as well as transportation. We found that investing in all-electric battery vehicles is a more economical choice for reducing carbon dioxide emissions, primarily due to their lower cost and significantly higher energy efficiency.

Markus Felgenhauer, Doctoral Candidate, TUM

“Studies such as these are needed to identify the lowest cost and most efficient pathways to deep decarbonization of the global energy system,” added study co-author Sally Benson, a professor of energy resources engineering at Stanford and director of GCEP.

Batteries vs. Fuel Cells

There are two types of electric vehicles: plug-in cars containing rechargeable batteries, and fuel cell vehicles capable of converting hydrogen gas into clean electricity.

Compared to gasoline-powered cars, fuel cell and battery vehicles release zero carbon when driven. However, an expensive new infrastructure will be required to deliver hydrogen fuel or charging batteries if these vehicles have to be deployed at scale.

Policymakers are faced with this key question - which transportation technology reduces total emissions at the lowest price - fuel cells or batteries?

Another question is will hydrogen technology also be able to provide clean energy for lighting and heating buildings, as a some studies indicate?

The new study is the first to provide answers to both questions.

The research team focused on California, a key player in electric vehicle transportation. Across the state, battery electric cars are gaining popularity. However, only some manufacturers have started offering fuel cell vehicles. With the intention to promote wider adoption, the state has come forward and awarded over $92 million for a chain of 50 hydrogen-refueling stations by 2017.

Currently, both the energy sources are not totally emissions free. A few people plug into the power grid to charge their battery electric cars. The electricity supplied by the power grid is produced mostly from carbon-emitting fossil fuels.

Similarly, a large quantity of hydrogen fuel is procured from natural gas via an industrial method that releases carbon dioxide as a byproduct.

An alternative device known as electrolyzer is designed to use solar-generated electricity to split water into clean hydrogen and oxygen, but the method is very energy intensive and costly.

Future Scenarios

During the study, the researchers developed future scenarios for the Town of Los Altos Hills, an affluent community with approximately 8,000 residents. The community was located in Santa Clara County, a few miles from the Stanford campus.

Los Altos Hills is distinguished by an unusually high solar-generation capacity in the county with the highest share of electric vehicles in the state.

Markus Felgenhauer, Doctoral Candidate, TUM

The scenarios were based on the assumption that battery and fuel cell vehicles would be in wide usage in 10 to 20 years, and that electrolyzers and solar power would also be cost competitive with the electric grid.

A particular scenario that focused on the year 2035, estimated that electric vehicles would make up 38% of the town’s vehicle fleet. It also estimated that fuel cell vehicles would be powered by locally produced hydrogen created with the low-priced electricity - either obtained from the grid or solar generated.

A computational model, developed by study co-author Thomas Hamacher, a professor of electrical and computer engineering at TUM, was fed with the data gathered about Los Altos Hills.

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. 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.

Matthew Pellow, Electric Power Research Institute

The team also took into consideration the carbon dioxide emissions produced in each case while comparing each scenario’s costs to its climate benefits. The researchers also looked into the potential advantages of using the hydrogen infrastructure to stock clean energy for use on demand.

During daylight hours, the electrolyzers can generate hydrogen from excess solar power that would otherwise be wasted. That hydrogen can be stored and converted into renewable electricity, or used as a clean substitute to natural gas to light and heat buildings.

Results

The results were perfect.

In terms of overall costs, we found that battery electric vehicles are better than fuel cell vehicles for reducing emissions. The analysis showed that to be cost competitive, fuel cell vehicles would have to be priced much lower than battery vehicles. 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.

Markus Felgenhauer, Doctoral Candidate, TUM

According to the authors, the results are also applicable for several bedroom communities with plenty of sunlight across California.

Going forward, they hope to investigate larger networks of communities and analyze other factors that could impact consumers’ choices when deciding whether to buy a fuel cell or battery car.

“Our goal is to provide objective, data-driven analysis to help inform policymakers in California and elsewhere about which technology pathway is likely to be more cost-effective in combating climate change,” Pellow said.

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