Coimbra already has a fleet of electric minibuses, purchased with the help of €6.4 million in European funding

Coimbra scientists develop intelligent charging model for electric buses

Optimises charging and increases life-cycle of batteries

A team of researchers from the University of Coimbra (UC) has developed an intelligent model that optimises the charging of electric bus fleets by 30 to 40% and reduces operating costs.

In a press release sent to Lusa on Monday, the UC explains the study – called “Electric Bus Coordinated Charging Strategy Considering V2G And Battery Degradation” – shows the model also contributes to increasing the life cycle of batteries.

The study has been published in Energy magazine and was conducted at the Institute for Systems Engineering and Computers of Coimbra (INESC Coimbra) at the University of Coimbra, funded by the Foundation for Science and Technology (FCT).

Quoted in the press release, researchers Jônatas Augusto Manzolli, João Pedro Trovão and Carlos Henggeler Antunes explain that the decarbonisation of public transport is essential to increase energy efficiency, mitigate climate change and reduce urban pollution.

However, “there are still challenges to overcome to enable the mass adoption of these vehicles in cities – namely limitations at the infrastructure and operational level.”

“Currently, the electric grid is not ready for full electrification of public transport. Therefore, it is necessary to find solutions that overcome these obstacles.” 

The model proposes a mixed approach “considering the sale of energy to the grid through V2G (vehicle to grid) technology and the degradation of batteries”.

Carlos Henggeler Antunes and João Pedro Trovão, also professors at the Faculty of Science and Technology of the UC (FCTUC) and the Polytechnic Institute of Coimbra (IPC), respectively, stress: “what distinguishes this model is precisely the fact that it takes into account the degradation of batteries.

“The main novelty of the model is to include a battery ageing framework to assess degradation costs, which increases the life cycle of batteries, which are currently still expensive,” they explain adding that “not all vehicles need to be fully charged to operate daily”.

“This aspect is relevant as it reduces the cost of charging and plays a role in improving the life cycle of batteries.”

To evaluate the model’s effectiveness, the team conducted a case study using actual data from the fleet of electric minibuses circulating in Coimbra.

Several analyses were also done to understand how the model would operate optimally in fleet management.

The results obtained showed that “comparing the worst possible scenario – for example, charging the fleet at the time when energy is most expensive and charging all the buses at the same time, without any kind of coordination – with the model, an improvement of between 30 and 40% was achieved, a very high percentage, showing that, if the charging is coordinated, the cost reduction is very significant”, highlighted Jônatas Augusto Manzolli.

The team also conducted sensitivity analysis tests to assess the possibilities of trading energy with the power grid and found that currently, it would not be advantageous, but in the near future, it could be economically profitable.

The researchers explained that the system assesses the “possibilities of energy transactions with the grid, considering scenarios of battery replacement price and electricity price variations”.

“Looking at battery degradation and energy sales, our study indicates that in 2030, operating costs can be 38% lower. Therefore, the approach presented in this work provides a tool that public transport operators can use to assist in decision making regarding the electrification of bus fleets.” 

The UC also mentioned that the next phase of research will focus on developing a more detailed version of the optimisation model, allowing a forecast in minutes to respond, for example, when an accident happens and forces a reorganisation of the entire fleet and its charging.

Source: LUSA