Natural Gas System Efficiency

Well-to-wheels fuel efficiency. The total well-to-wheels efficiency of converting natural gas to electricity for a BEV and to hydrogen for a FCEV is summarized in this chart, assuming that both the battery EV and the fuel cell EV are designed for 250 miles range.  The top row of this chart shows that 1.29 million British Thermal Units (MBTU) of natural gas energy would be required to make electricity in a natural gas combustion turbine to charge the batteries for a BEV to travel 250 miles.

The second row shows that the natural gas energy required would be reduced to 0.86 MBTU’s if a more efficient combined cycle power plant produced the electricity.

Finally, the last row shows that only 0.67 MBTU’s of natural gas would be needed to make enough hydrogen to propel a FCEV for 250 miles. Therefore converting natural gas to hydrogen provides between 1.3 and 1.9 times greater fuel efficiency than using that natural gas to make electricity for a BEV, so a given quantity of natural gas will provide 1.3 to 1.9 times more vehicle miles traveled in a FCEV than in a BEV.

Total system efficiency vs. range. The advantage of the FCEV over the BEV in natural gas utilization decreases for shorter range vehicles, since the battery banks become lighter and less energy is needed to accelerate the lighter BEV.  As shown in this chart, a BEV with only 100 miles range would have approximately the same well-to-wheels efficiency (natural gas utilization) as a FCEV, assuming that the electricity is generated by a high efficiency natural gas combined cycle plant. The FCEV would still have a slight efficiency advantage over a BEV charged from an older natural gas combustion generator.

Note that approximately the same analysis would apply to coal plants. Thus hydrogen made from either natural gas or coal would use less energy than electricity made from those fossil fuels when used in a BEV.

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