Electric Power Generation Needed for Decarbonizing the Transport Sector in the US
Question 4: Power Needed for Decarbonizing the Transport Sector In this question the goal is to quantify how much additional electric power will be needed in the US to replace (a) all gasoline-powered cars and light trucks with battery electric vehicles (EVs), and (b) all diesel-powered heavy trucks with hydrogen-powered fuel-cell vehicles. How can we calculate the total amount of new electric power generation required for this transition?
To calculate the total amount of new electric power generation required to replace gasoline-powered cars and light trucks with battery electric vehicles (EVs), we need to consider several factors. For gasoline engines, assuming an efficiency of 30%, only 30% of the fuel energy is converted into mechanical energy. Out of this baseline mechanical energy, 90% needs to be supplied by electric motors in EVs. Therefore, the effective energy conversion efficiency from fuel to electric power is 30% * 90% = 27%. Assuming a round trip efficiency for battery charging of 90%, and DC motors with 95% efficiency, the overall efficiency from fuel to useful electric power for EVs is 27% * 90% * 95% = 23.29%. To calculate the electric power needed, we can divide the total energy consumption of gasoline vehicles by the overall efficiency: Electric power = Gasoline sales (in gallons) * fuel energy density * overall efficiency = 140 billion gallons * 740 g/L * 44 kJ/g * 23.29% ≈ 1.678 × 10^14 kJ Converting this energy to terawatt-hours (TWh): Electric power (TWh) = 1.678 × 10^14 kJ / (3.6 × 10^6 kJ/TWh) ≈ 46.61 TWh Therefore, approximately 46.61 TWh of additional electric power generation would be needed to replace the gasoline vehicle fleet completely with EVs. For diesel-powered heavy trucks, assuming an efficiency of 40% in converting fuel energy to mechanical energy, the effective energy conversion efficiency for H2 fuel cell-powered trucks would be 40% * 25% * 95% = 9.5%. Following the same calculation as in part (a), using diesel fuel sales for on-road engines (40 billion gallons) and the appropriate energy density, we can estimate the electric power needed to replace the diesel truck fleet with H2 fuel cell-powered trucks. Electric power (TWh) = Diesel fuel sales (in gallons) * fuel energy density * overall efficiency = 40 billion gallons * 840 g/L * 44 kJ/g * 9.5% ≈ 1.343 × 10^13 kJ Converting this energy to terawatt-hours (TWh): Electric power (TWh) = 1.343 × 10^13 kJ / (3.6 × 10^6 kJ/TWh) ≈ 3.73 TWh Therefore, approximately 3.73 TWh of additional electric power generation would be needed to replace the diesel truck fleet with H2 fuel cell-powered trucks.