A new heating system improves the autonomy of electric vehicles

FGUSAL/DICYT A research project developed at the Polytechnic School of Zamora from the University of Salamanca proposes a better heating system for electric cars. The engines of these vehicles are very efficient, but when the heating is connected by electrical resistances, they lose a lot of energy and, therefore, quickly lower the battery charge, thus decreasing the autonomy of the car. The new prototype addresses this problem.
Engineers had not faced this challenge before the irruption of electric vehicles, since conventional cars, powered by thermal engines, waste a lot of energy in the form of heat and partly redirect it to the heating system.

In fact, the efficiency of thermal motors vehicles, the most commons, is very small, since they actually just use between a 20 or 30% of the energy that they consume. "The performance of a car with its engine running standing at a traffic light is zero because no useful energy is obtained from it. despite that it continues to consume fuel," says Juan Ramón Muñoz Rico, a researcher at the Department of Mechanical Engineering and director of this project.

On the other hand, electric vehicles performance reaches a 95% or more, so they lose very little energy. This high efficiency is very positive, but it limits the use of heating since all the energy required has to leave the battery and this causes a decrease in the autonomy of the vehicle.

Very few electric models so far, use a resistance in their heating system in order to avoid an electricity consumption increase. Approximately, although the numbers can vary greatly depending on the use, in a vehicle that had an autonomy of 200 km., it would be reduced to 135 km., a very important decrease.

However, all-electric vehicles also have an air conditioning system, so it is feasible "to introduce a four-way valve that reverses the direction of circulation of the refrigerant and makes the systems work just the opposite," he explains.

In fact, it is a common solution used by home air conditioning equipment that also includes a heating function. Therefore, the idea of Juan Ramón Muñoz Rico is totally viable. Introducing this innovation involves reversing the roles of two of the heating system elements, the evaporator, and the condenser so that the air conditioning system becomes a heat pump.

A cheap solution

In addition to the four-way valve, a very cheap device that can be purchased for just 20 euros, it is only necessary to have heat exchangers that can respond to the two configurations. Therefore, incorporating this innovation would be quite inexpensive.

The researcher has built a prototype with the usual elements of a vehicle and has made the appropriate calculations. A car that loses 60 km. of autonomy with electrical resistance would reduce that decrease to only 15 or 20 with the heat pump, depending on its efficiency.

This project is part of the Proof of Concept call from the General Foundation of the University of Salamanca, within the TCUE program of the regional government of Castilla y León co-financed with FEDER funds.

A bet for the future

The system can still be upgraded. "For example, we can think about improving comfort, making the heating system reach the seats. There are many doors open, that needs to be research ", states Juan Ramón Muñoz Rico.

In any case, the proposed solution seems optimal. "In the future, the heating of electric vehicles will happen here, unless alternatives are developed that are only incipient at the moment," he says. In fact, until now the proposals that are implementing some commercial brands are more complex solutions.