For a utility with 22,000 km of overhead power lines that replace its helicopter-based inspections with drones, 258 tons of carbon emissions can be reduced every year, with the prerequisite that the drone pilot drives an electric car and charges it in Sweden.
One benefit of using drones for the inspection of overhead power lines is the environmental gains, such as reduced noise and carbon emissions. At Airpelago, one common question from our customers’ is how much carbon emissions can be saved and how these can be calculated. In this article, we try to answer this question. Below, you find a series of assumptions and calculations on how much carbon dioxide emissions can be reduced by replacing helicopter-based inspection of power lines with drones. distribution networks, and we acknowledge that different inspection types, flight patterns, and characteristics exist for both helicopters and drones.
To calculate the emissions reduced with drone-based inspections, we first need to know how much emissions are generated by helicopter-based inspections.
Some of the most common helicopter models used for power line inspection are:
The Bell 206 JetRanger is one of the most commonly used helicopter models for power line inspection in the Nordics. Therefore, we chose to base the following calculations on this model. It has an average fuel consumption of 92 liters of Jet A1 per hour.
To calculate the carbon dioxide emissions from the combustion of helicopter fuel, it's necessary to know the fuel's density and carbon dioxide coefficient. Jet fuel, commonly used in turbine helicopters, typically has a density of about 0.81 kg/L. The combustion of 1 kg of jet fuel (usually Jet A or Jet A-1) generates approximately 3.15 kg of CO₂.
These figures are approximate and may vary depending on the exact composition of the fuel and the combustion conditions. We also acknowledge the difference in fuel consumption and carbon emissions between helicopter models.
Using these figures, the CO₂ emissions can be calculated as:
Carbon emissions from helicopter
As a start, the helicopter must fly to the inspection area from where it is based. Once at an inspection area, the grid is not outlined in a perfectly long and continuous line but rather divided into several disconnected lines with multiple forks. The grid’s structure and how it is scattered through the landscape affects the overall inspection efficiency to a large extent.
Average flight speeds during various parts of the inspection are:
Due to the nature of the network, a significant amount of time is spent on transportation between the disconnected power lines that are to be inspected. Overall, from when the helicopter take-off, day one to when it lands on the last day, the average effective speed over power lines, including the flight to and from the inspection area, is assumed to be 40 km/h.
Helicopter inspection efficiency
The helicopter flies at an average speed of 40 km/h. Assume it must travel 2 km for every 1 km of power line it inspects due to the gaps between lines and the distribution grid's many forks and dead ends.
Emissions per inspected kilometer are calculated as:
Carbon emissions from helicopter-based power line inspection are estimated to be 11.74 kg CO₂/km of power line.
The drone pilot often uses a standard passenger car for transportation to, from, and within the inspection area of the grid. Therefore, the emissions produced when driving a car need to be calculated.
When gasoline is burned, approximately 2.31 kg of CO₂ is generated per liter (95 octane).
The fuel consumption for an average passenger car is 0.60 liters/km.
Passenger car carbon emissions per km
For drone-based inspections with standard off-the-shelf drones, the drone pilots must relocate several times each day. The inspection range varies with terrain, flight permit, type of inspection, the type of power line, grid construction, distribution throughout the terrain, and more. Based on our data from inspecting over 15´000 km of power lines, we have seen that this figure is close to 2 km by car for every 1 km of power line the drone pilot inspects.
CO2-equivalent emissions from an average passenger with a combustion engine are therefore calculated to be:
Emissions during drone inspection and gasoline-powered car: 2.772 kg CO₂/km inspected line.
The carbon intensity of electricity produced in Sweden is around 50 g CO₂/kWh.
Typical energy consumption for modern electric cars ranges between 13 to 20 kWh/100 km, varying by model, driving conditions, etc.
The electric car consumes 15 kWh/100 km (on average) and is charged with electricity with a CO₂-intensity of 50 g CO₂/kWh. This gives us the CO₂ emissions as follows:
Also, this car needs to travel 2 km for every 1 km of power line the drone pilots inspect (as per Assumption 5). This results in a total direct CO₂ emissions per inspected kilometer of line:
Carbon emissions of drone-based inspection with an electric car charged in Sweden is 15.0 g CO₂ per inspected kilometer of power line.
Please note. Actual emissions may vary with factors like exact consumption of the car, charging infrastructure efficiency, and variations in electricity production CO₂ intensity. The initial CO₂ load from manufacturing should also be considered and spread over the car's lifespan. In this comparative example, the CO₂ load from manufacturing is neglected for both the passenger car and the helicopter.
For a network owner in Sweden, with a grid size of 22,000 km, the carbon emissions reduced by replacing helicopter-based inspections with drones is an astonishing 258 tons annually, given that the drone pilot uses an electric car.