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Electricity Beats Hydrogen for Fueling Cars,
Says Study

by Staff
Clean Edge News, June 29, 2004

A new study finds that major uses for hydrogen envisaged in hydrogen economy scenarios could be more efficiently accomplished with technologies that use electricity directly.

“In key roles envisioned for H2 as an energy carrier, transmission of remote renewable resources, storage of intermittent renewables and vehicle fuel, electricity offers more energy efficient options that might preclude mass-scale emergence of H2 technologies,” concludes the study issued by the Institute for Lifecycle Environmental Assessment and funded by the John D. and Catherine T. MacArthur Foundation.

Carrying the Energy Future: Comparing Hydrogen and Electricity for Transmission, Storage and Transportation finds that the energy penalties incurred in manufacturing hydrogen place it at a competitive disadvantage vis-à-vis electricity. The full report and an executive summary are available at .

“The first and most important understanding about the proposed hydrogen energy system is that hydrogen is not an energy source,” write study authors Patrick Mazza and Roel Hammerschlag. “It is an energy storage medium and carrier. And like the only other commonplace energy carrier, electricity, hydrogen must be made.”

The study compares the actual energy available when hydrogen and electricity carriers are employed and finds that electricity delivers substantially greater end use energy.

Hydrogen advocates portray it as a means to transmit abundant renewable energy resources located distant from markets, such as Southwest sunlight or Great Plains wind. Electricity generated in solar panels or wind turbines would be converted to hydrogen via electrolysis, a process that uses electrical current to break the bonds of hydrogen and oxygen in water. Electricity would be recovered through electrochemical reactions generated when hydrogen and oxygen join in a fuel cell. However, when energy penalties are taken into account, only 45-55% of original energy remains compared to 92% if transmitted as electricity. Electrical transmission provides roughly twice the end use energy.

Hydrogen is envisaged as a medium to store energy generated by intermittent renewable sources such as sun and wind, making power available on demand. However the same energy penalties apply while other energy storage technologies deliver comparatively more energy. Hydrogen storage returns around 47% of original energy, while advanced batteries return 75-85% and established pumped hydroelectric and compressed air technologies return around 75%. A wind farm which stores at 47% efficiency would require 160 turbines to generate the amount of useful energy produced by a 100 turbines which store at 75% efficiency.

Hydrogen as clean vehicle fuel, as projected in President Bush’s hydrogen car initiative, is the most prominent of its foreseen uses. But relative inefficiencies of hydrogen vis-à-vis direct electricity play out in vehicle technology too. Using electricity to charge electric vehicles (EVs) provides twice the miles per kilowatt hour than employing electricity to make hydrogen fuel. While conventional wisdom has it that the EV is a technological dead- end hobbled by limited range and extended recharging times, advanced battery technologies substantially extend ranges and could meet the needs of a more substantial share of the market than is commonly understood. Lithium ion batteries developed for portable electronics are now working in prototype EVs that go nearly 400 kilometers (250 miles) between charges.

A chart on p23-24 of the study shows that batteries outcompete hydrogen in price, safety, calendar life and gross material availability. On cycle life, recyclability and toxicity, fuel cells do not show decidedly superior performance. One developing option near market competitiveness today that faces no range or charge time limitations while capturing EV advantages is the plug-in hybrid electric vehicle that runs on batteries charged from both an on-board engine and the power grid. It could reduce fuel consumption 85% over a comparable conventional car.

The relative inefficiency of hydrogen as opposed to electricity has implications for global warming emissions. The study calculates the carbon dioxide (CO2) emissions reductions from employing clean, renewable energy in various applications. Directed to displacing electricity generated by advanced technology coal plants, renewable electricity eliminates 2.6 times more CO2 than if it is used to displace gasoline by making hydrogen fuel for cars. Charging EVs removes twice the CO2 of making hydrogen fuel. The study calculates similar results for use of natural gas, which also has been proposed as a source of hydrogen energy.

“These results strongly suggest that priority use for new renewables should be to eliminate demand for coal-fired electricity,” Mazza and Hammerschlag write. “If for some reason this is not an option, use the power to charge EVs.”

The study distinguishes between hydrogen and fuel cells. While a hydrogen fuel system is hindered by multiple inefficiencies, fuel cells can form an important part of highly efficient systems that convert biofuels or fossil fuels to electricity. Fuel cells can operate as stationary electrical generators, potentially at significantly higher efficiencies than central power stations or other distributed generators. Emergence of a substantial fuel cell market is in no way conditioned on mass application in vehicles or development of a hydrogen network.

The study recommends that hydrogen and electricity advocates focus on complementary development that can support both pathways. This includes rapid expansion of renewables, improvement in hybrid vehicle technology, vehicle-to-grid applications that employ parked vehicles as grid energy storage, and development of biomass supplies from which liquid vehicle fuels and hydrogen can be made.

Electricity Beats Hydrogen for Fueling Cars, Says Study
Clean Edge News, June 29, 2004

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