Cutting Carbon in Flight Training: Can electric planes offer a 90% reduction?

Aviation students are increasingly seeking ways to pursue their passion without the emissions associated with conventional flight training. Electric planes (e-planes) are being proposed as a solution, but how big of a reduction can they achieve?  

Flying electric planes is often called zero emission flying. However, we want to look beyond the direct emissions during flight to recognize the lifecycle emissions —those resulting from the production, transportation, and transformation of fuels. In 2023, the University of Waterloo partnered with Waterloo Wellington Flight Centre to introduce a Pipistrel Velis Electro to explore this question. In 2024, an additional Velis Electro was added at Waterloo and another at Sealand Flight on Vancouver Island. With two of the e-planes accumulating over 100 hours of flight time each, what have we learned about the associated reduction in emissions? 

The most significant change in operational emissions is the difference in fuels. AvGas is a refined petroleum product with a high carbon intensity. In contrast, electricity is a form of energy that can come from many sources. For example, if coal is being burned to generate the electricity, then the carbon intensity can be up to1000 gCO2e/kWh. However, if the electricity is from nuclear, hydro, wind or solar, it has a much lower carbon intensity—typically <50 g/kWh). 

While fuel type is a major factor in emissions, the production and transport of the fuel to the aircraft also play a role. Direct emissions occur during flight, and in the case of electric planes, electricity can claim zero emissions during flight. However, pollutants are emitted during other parts of the life cycles, for example, during the production and transport of the fuel or electricity. We can use lifecycle analysis to measure the emissions through the full cycle (well to wake). First, let us look at the conventional fleet. The Cessna 172 is the most common trainer and is used at both WWFC and Sealand. WWFC also offers other trainers, including the Cessna 152 and Diamond DA40. Annual data from WWFC operations give the fuel consumption values shown in Table 1. The emission values are calculated using standard carbon intensity values from CORSIA (Cabon Offsetting and Reduction Scheme for International Aviation). The life cycle emissions (well to wake) from AvGas are reported as 95 gCO2e/MJ or 2930 gCO2e/l with over 80% of emissions coming from the flight (tank to wake). The table illustrates that one way to reduce emissions is to choose a plane that burns less fuel. For example, flying the Cessna 152 instead of the Cessna 172 could reduce emissions by 29%.

Sources: WWFC; ICAO, CORSIA 

Next, let’s examine the carbon intensity of electricity supply for the Pipistrel Velis Electro. Since Ontario and British Columbia have different electricity sources, we will consider each separately. In addition, WWFC’s Hangar 7 also has a 30 kW solar array, which provides onsite electricity to run the 20 kW charger for the Velis during sunny charging times. Table 2 below presents the electricity sources for the e-planes and their associated emissions.

Sources: Sealand; Canada, NREL 

The electricity used was measured at Sealand Flight, where the average charge put 13 kWh in the battery, but drew 15kWh from the grid due to losses in the transformer and charging system. These values were adjusted to an hourly basis (18 kWh) as each flight averaged 50 minutes. The Government of Canada's Fuel Life Cycle Assessment (LCA) Model is a tool to calculate the life cycle carbon intensity (CI) of fuels and energy sources used and produced in Canada. The 2023 revision to the lifecycle carbon intensity of electricity in Canada revised the carbon intensity up (40gCO2e/kWh) in British Columbia to recognize the carbon emissions during hydro dam construction. The lifecycle carbon intensity of Ontario’s electricity system is about 15% higher (46gCO2e/kWh). The large share of low carbon sources (nuclear, hydro, wind and solar) creates this low value and demonstrates the achieved decarbonization of the Ontario grid since the reference year of 2005 when carbon intensity was five times higher.  

Finally, the US National Renewable Energy Lab reported the lifecycle carbon intensity of solar photovoltaic electricity. Table 2 illustrates that choosing lower carbon sources of electricity is another way to reduce emissions. 

The results from Tables 1 and 2 are illustrated in Graph 1. Lifecycle emissions from the fuel and plane choices listed show that pilot training emissions can be reduced by 99% (from 73 kgCO2e/hr to 0.7 kgCO2e/hr) for each hour that a Pipistrel Velis Electro is used instead of a Cessna 172 when using low carbon electricity such as the BC grid or solar electricity at the Innovation Hub. Even if a high carbon electricity source such as the coal-fired Alberta grid of 1990 was used, the e-plane would reduce emissions by 77% in comparison to the Cessna 172. By 2022 Alberta had cut the carbon intensity of its grid in half (470gCO2e/kWh), so if the trend continues, flying e-planes in Alberta will soon achieve a 90% emission reduction.

When comparing the greenhouse gas emissions of fossil fuel and electric powered trainers, the difference is clear. Emissions from the production, distribution, and use of electricity in the e-plane amount to approximately one percent of emissions from the conventional trainer—representing a 99% reduction in emissions. 

Did the electric planes achieve zero carbon flying? Yes, if we only consider the direct emissions during flight, but no, if we account for the complete lifecycle. Nevertheless, efficient e-planes can offer a 99% reduction in emissions, which represents a major step forward in climate friendly flying. 

What about the emissions beyond the fuel? For example, those associated with the production of major components like batteries?  

A 2017 study of the three most common lithium-ion batteries used in Chinese electric vehicles (EVs) found that the production of batteries generated approximately 3000 kgCO2 for a 28 kWh battery or 107 kgCO2/kWh of battery capacity. Assuming that the Pipistrel battery has a similar carbon footprint, its 20 kWh capacity would result in over 2000 kgCO2 emissions during production. Given the battery life expectancy of 1000 deep cycles, this represents 2 kgCO2 per flight or 2.3 kg CO2/hr of flight time.If the battery is replaced after 500 hours, it would represent 4 kgCO₂ /hr flown In other words, the production of the battery can contribute about three times the climate impact as the electricity used by the e-plane. These impacts can be reduced by greening the grid in China where the reference batteries were made or using batteries produced in low carbon jurisdictions like Canada. A fully electric lithium mine is being proposed in Manitoba and recycling facilities for lithium-ion batteries are making rapid progress. Each of these steps should further reduce emissions Despite the carbon emitted during the production of the batteries, the Velis Electro still represents a reduction in carbon emissions of approximately 90% in comparison to the Cessna 172 and we have not accounted for the carbon released during the production of the Cessna’s engine or replacement parts.  

All other components of the conventional and electric planes should be added and compared in a future comprehensive lifecycle analysis; these initial calculations certainly show the potential to cut hourly emissions by over 90%. 

The magnitude of the change is illustrated by the 70 kgCO2e/hr difference between the Cessna 172 and the Velis Electro. If a pilot used the electric plane for 100 of their 250 hours typically flown to complete a Commercial Pilot License (CPL), they could reduce their training emissions by 7 tonnes of greenhouse gases.  

This is a win-win result, with both environmental and economic benefits. The ‘fuel’ used in the e-plane results in a 99% reduction in emissions (from 73kg to <1kg CO2e/hr) and reduces fuel costs by 95% ($75/hr for AvGas (25l *$3/l) vs $3.60/hr for electricity (18kWh * $0.20/kWh).