Eco-design to reduce environmental impact of electric vehicles
Cristina G. Pedraz/DICYT Eco-design is a practice incorporating environmental factors into the decision making process during the development of a product, as an additional factor to those traditionally taken into account such as cost and quality. In order to include this outlook to electric vehicles, Cartif, a technological center in Valladolid (Spain), has coordinated an European project called Green Car Eco-design, an initiative born at the project Interreg IV-B SUDOE involving seven Spanish, French and Portuguese partners. This project, finished in the first week of April, has been carried out during the last two years with a 1.17 million budget.
As DiCYT was told by the project coordinator and researcher at Cartif, Nuria García Rueda, the ultimate objective has been to add the environmental variable in the designing stage of the main components of electric vehicles and charging points and to increase awareness of their environmental impact throughout their life cycle. In this regard, Cartif has worked with some partners: Mondragon Unibertsitatea, Fundació CMT Centre Tecnològic, Fundación Instituto Andaluz de Tecnología, Instituto Tecnológico de Aragón, École Supériore des Technologies Industrielles Avancées, Instituto Politécnico de Setúbal and a consulting committee by companies concerned.
For the first stage, they selected electric vehicle components to be eco-redesigned, specifically batteries, converters, charging points, brakes, air conditioning and auxiliary systems powered by renewable energy. Furthermore, they designed a prototype to conduct studies with some specifications: 2,600 pounds, a single occupant of 155 pounds, particular use and urban travel of approximately 65,000 miles in a 10-year useful life, 5 seats, a battery-life of around 85 miles, an average speed of 20 miles per hour and a top speed of 75, able to climb slopes of up to 20%.
Using this information and after studying each component, the researchers proposed some eco-design measures implemented in later prototypes in order to validate with real data theoretical results.
Regarding the battery, Nuria García Rueda explains, the study aims to reduce its mass, a task by the Instituto Politécnico de Setúbal. “We tested a 420-pound lithium and iron phosphate battery and we found the greatest contribution to environmental impact lies on materials stage, that is the reason why we decided to reduce its mass as a strategy, without compromising its life that is critical in an electric vehicle. A new component has been added to extend its life: a very interesting system because it does not get activated in short distances, but when charge is depleted, it can provide that extra energy. The extender and battery set is lighter than the original battery and its life is longer; with a 3 gallon tank of gasoline, the car can achieve some 280 miles,” she underlines.
Regarding the converter, a component studied by the Mondragon Unibertsitatea, it is the element providing a greater contribution to environmental impact. Eco-design strategies have focused on “the enhancement of efficiency, combining the inverter and the charger, a new method increasing end power by two and a half times,” the researcher states.
The air-conditioning system is an auxiliary component “that has a lot of impact on the vehicle’s consumption, accounting for 5-10% of the total power consumption of the battery”. One of the measures proposed, in this case by the Instituto Andaluz de Tecnología, was a selective air-conditioning system and heated seats.
Regarding the brakes (a caliper, two pads and a disk), preliminary studies at the Fundació CMT Centre Tecnològic proved that breaks’ use is not the only stage producing an impact, materials lead to consequences as well. “Materials were analyzed and we proposed to use lighter materials such as aluminum instead of gray iron (to produce calipers);” although the theoretical analysis showed no environmental benefit at 65,000 miles, but up to 120,000 miles. Brake pads’ glass fiber was superseded by a less toxic friction material such as cellulose fiber, although the reduction of impact “was only a 2%”.
As for the charging point, studied by Cartif, “it is no included in the vehicle, but it is necessary to analyze it into the electric vehicle system. We studied two different technologies and found the life-cycle stage was the most important in terms of impact; as an eco-innovation measure, we proposed to integrate electronic components. This way we could get an improvement by decreasing energy loss in cables and connectors and by reducing raw materials, weight, etc. We have validated through an experiment the new energy consumption and, even if outcomes were not as positive as we expected, we have enhanced impact categories such as carbon footprint”, she explains.
Finally, the École Supériore des Technologies Industrielles Avancées was to analyze auxiliary systems powered by renewable energy and has developed a power-recovery system in shock absorbers in the patent stage. This system was first implemented at a 1/5 scale and at full-scale in a test-bed representing a quarter of the vehicle. “During trials, the power retrieved by each shock absorber was around 10 watts. Moreover, by feeding auxiliary systems close to shock absorbers and not to the battery, we can save wires, therefore copper, improving the overall impact”, she adds.
The final stage was to digitally sculpt the entire vehicle incorporating eco-redesigned components. Therefore, simulations have been performed with two vehicle models (a mere electric car and another with series configuration), three battery models, two models of traction motors and several configurations of brakes, vehicle loads, cooling intensities and temperatures, taking into account three route patterns and comparing results of equivalent energy consumption, energy loss and efficiency of systems used in several forms depending on the different driving cycles.
Besides prototyped measures, others have been depicted in a small eco-designed electric vehicle guide book, another “outcome of our project”, Nuria García Rueda states.