Problem 83 - Chemistry: An Atoms-Focused Approach

Question

Methane can serve as the fuel for electric cars powered by fuel cells. Carbon dioxide is a product of the fuel cell reaction. All cars powered by internal combustion engines burning natural gas (mostly methane) produce \(\mathrm{CO}_{2}\). Why are electric vehicles powered by fuel cells likely to produce less \(\mathrm{CO}_{2}\) per mile?

Step-by-Step Solution

Answer

Answer: Electric vehicles powered by fuel cells are likely to produce less CO₂ per mile because they have a higher efficiency at converting chemical energy from methane into usable electricity, compared to internal combustion engines, which have lower efficiency and generate more waste heat. This means that fuel cell electric vehicles require less methane fuel to produce the same amount of power, resulting in lower CO₂ emissions per mile.

Step 1: Understand the fuel cell process in electric vehicles

Electric vehicles powered by fuel cells convert chemical energy from hydrogen and oxygen into electrical energy. These fuel cells operate by combining hydrogen with oxygen to produce water, heat, and electricity. Methane, as a fuel source, can be reformed into hydrogen and used in these fuel cells. The process of converting methane to hydrogen and using it in a fuel cell is generally more efficient than burning methane directly in an internal combustion engine.

Step 2: Analyze the efficiency of internal combustion engines

Internal combustion engines powered by natural gas (mostly methane) burn the fuel in the engine to produce mechanical energy. In this process, CO₂ is produced as a waste product. Internal combustion engines are known to have lower efficiency compared to fuel cells, partly because a significant portion of the energy generated is lost as waste heat. This means that more methane fuel would need to be burned per mile to generate the same amount of power as a fuel cell electric car, leading to more CO₂ emissions.

Step 3: Compare the efficiencies of fuel cells and internal combustion engines

Fuel cells are more efficient at converting the chemical energy of methane into usable electrical energy compared to internal combustion engines, which convert the energy into mechanical motion. This higher efficiency in fuel cells means that they can generate the same amount of power while using less methane fuel. Consequently, this results in lower CO₂ emissions per mile compared to internal combustion engines.

Step 4: Conclusion

Electric vehicles powered by fuel cells are likely to produce less CO₂ per mile because they have a higher efficiency at converting chemical energy from methane into usable electricity, as opposed to internal combustion engines, which have lower efficiency and generate more waste heat. This means that fuel cell electric vehicles require less methane fuel to produce the same amount of power, resulting in lower CO₂ emissions per mile.