Sweden rolled out its first wireless charging buses earlier this month and has developed a tool for other cities to determine the environmental and financial benefits of introducing their own electrified bus networks.

Using the model to propose the optimal locations for installing chargers on Stockholm’s bus network, energy technology researcher Maria Xylia at KTH Royal Institute of Technology reported that the fleet could halve CO2 emissions while lowering energy consumption by 34 per cent, if the city installed 150 chargers to electrify 94 bus routes.

The 40 per cent savings in fuel costs would balance out the projected costs of investments in infrastructure such as chargers and connection to the grid, said Xylia, who developed the model in cooperation with the International Institute for Applied System Analysis (IIASA).

While that forecast is based on optimised energy usage, the model also offers users the option of cost optimisation. In Stockholm’s case, a cost-optimised scenario would mean fewer electrified bus lines, but lower energy consumption nevertheless – albeit with a slightly-less-extensive estimate of 40 per cent reduction in emissions.

Xylia says that the model allows for multiple bus charging technologies and even takes into account potentially rising electricity costs in the estimates. “But as long as electricity prices remain in this range, the infrastructure cost would balance the fuel savings.”

However, in order to gain the maximum environmental benefits of electrification, the electricity needs to come from renewable sources, she said. “If you look at the energy mix throughout the EU, you will see a difference – it’s a totally different story from Sweden. You have to have green energy in order to maximise environmental benefit.”

The model can be applied to any city as a basis for decision-making.

“As long as you have a detailed map of the bus network and a reliable bus schedule, then you can do this for any city,” she said. “London is much bigger than Stockholm, but if they have this data, then we can generate optimised energy and cost scenarios for that system.”

“Cities and urban areas will soon become the major driver for energy demand globally,” said IIASA researcher Sylvain Leduc. “Many cities are still using a combination of different kinds of buses and tramways. These combined road and rail urban grids can be assessed and optimised in an integrated way.”