Well-to-Wheel: explained step by step
The Comparison Between Petrol Vehicles and Electric Vehicles: "Well to Wheel" Efficiency
Electric vehicles (EVs) and petrol vehicles (VBs) represent two completely different approaches to road mobility. While gasoline vehicles are powered by internal combustion engines that burn fossil fuels, electric vehicles use electric motors powered by rechargeable batteries. One way to compare these two types of vehicles is to look at "well to wheel" efficiency, which takes into account all the losses in the process, from power generation to vehicle movement.
"Well to Wheel" Efficiency for Petrol Vehicles
Efficiency of Oil Extraction
The initial step in obtaining energy in gasoline vehicles is the extraction of oil, a non-renewable energy source. Efficiency at this stage is usually very high, as crude oil is extracted with relative ease. However, including all losses along the way, we can assume an efficiency of 90% for this phase.
Oil Refining Efficiency
After extraction, the oil must be refined into fuel. Refining involves energy losses, with a typical efficiency of 85%.
Efficiency of Fuel Distribution to Pumps
The refined fuel then has to be transported to distribution pumps, which leads to further losses. We assume 90% efficiency at this stage to better represent the losses associated with fuel transportation and distribution.
Internal Combustion Engine Efficiency
Internal combustion engines in gasoline vehicles have a typical efficiency of 20-30%. Let's use the average value of 25% as an example.
Summary of Efficiencies for Petrol Vehicles
We can now calculate the overall "well to wheel" efficiency for gasoline vehicles with these efficiencies:
Overall Efficiency for Gasoline Vehicles = Oil Extraction Efficiency x Oil Refining Efficiency x Fuel Distribution Efficiency x Internal Combustion Engine Efficiency
Overall Efficiency for Gasoline Vehicles = (0.90) x (0.85) x (0.90) x (0.25) = 0.17
The overall "well to wheel" efficiency for gasoline vehicles is 17%. So, about 17% of the energy initially present in oil extraction is actually used to move the gasoline vehicle after all losses at all stages of the process.
"Well to Wheel" Efficiency for Electric Vehicles
Efficiency of Energy Generation from Methane Power Plants
Energy for electric vehicles can come from several sources, including methane power plants. Let's assume 60% efficiency for power generation in a methane power plant.
Transfer Efficiency from High Voltage to Medium Voltage
During the transfer of energy from power plants to charging stations, some losses may occur. We assume 94% efficiency when transferring from high voltage to medium voltage.
Efficiency of Conversion from Alternating Current (AC) to Direct Current (DC) in the Charging Station
In the charging phase, electric vehicle charging stations perform a conversion from alternating current (AC) to direct current (DC) to recharge the batteries of electric vehicles. Let's assume 90% efficiency for this conversion.
Car Charging Efficiency with 40 kW Battery
Car charging efficiency is how efficiently the car battery accepts electrical energy. Let's assume 95% efficiency at this stage.
Efficiency of the Electric Motor for Movement
The electric motor used to propel the car has a typical efficiency of 90%.
We can now calculate the overall "well to wheel" efficiency for electric vehicles by taking these efficiencies into account at each stage:
Overall Efficiency for Electric Vehicles = Efficiency of Energy Generation from Methane Power Plants x Efficiency of Transfer from High Voltage to Medium Voltage x Efficiency of AC/DC Conversion x Efficiency of Car Charging x Efficiency of the Electric Motor
Overall Efficiency for Electric Vehicles = (0.60) x (0.94) x (0.90) x (0.95) x (0.90) = 0.29
The overall "well to wheel" efficiency for electric vehicles is 29%. So, about 29% of the energy initially present in the methane power plant is actually used to drive the electric car after all losses at all stages of the process.
"Well to Wheel" Efficiency for Electric Vehicles with Energy from Solar Panels or Renewable Sources
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Efficiency of Energy Generation from Solar Panels
Since solar energy is free and requires no additional energy input, 100% efficiency is considered for this phase.
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Transfer Efficiency from Generation to Medium Voltage
During the transfer of energy from the solar panel generation to the medium voltage electricity grid, some losses may occur. Let's assume 94% efficiency at this stage.
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Efficiency of Conversion from Alternating Current (AC) to Direct Current (DC) in the Charging Station
In the charging phase, electric vehicle charging stations perform a conversion from alternating current (AC) to direct current (DC) to recharge the batteries of electric vehicles. Let's assume 90% efficiency for this conversion.
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Car Charging Efficiency with 40 kW Battery
Car charging efficiency is how efficiently the car battery accepts electrical energy. Let's assume 95% efficiency at this stage.
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Efficiency of the Electric Motor for Movement
The electric motor used to propel the car has a typical efficiency of 90%.
Now we can calculate the overall "well to wheel" efficiency for electric vehicles with energy from solar panels, considering all stages from the solar panel to the car's wheels:
Overall Efficiency for Electric Vehicles = Efficiency of Solar Energy Generation x Transfer Efficiency from Medium Voltage Generation x AC/DC Conversion Efficiency x Car Charging Efficiency x Electric Motor Efficiency
Overall Efficiency for Electric Vehicles = (1.00) x (0.94) x (0.90) x (0.95) x (0.90) = 0.72
The overall "well to wheel" efficiency for electric vehicles with power from solar panels is 72%. In this case, 72% of the collected solar energy is actually used to drive the electric car, taking into account all stages of the process.