Electric mobility: you can perfectly use the solar energy that is produced to power your electric car The methodology of this study

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Recharge your vehicle at home with solar electricity and without intermediate storage, even if you are traveling during the day?What seems to be only a dream is a reality, as shown by a recent study by EPFZ.

par

Jan Graber

In addition to the fascination for new technological advances, it is more generally ecological consciousness that plays a decisive role when buying an electric car.And this desire to drive a climate -friendly vehicle continues to grow: currently, around 70,000 purely electric cars and 200,000 hybrids are circulating in Switzerland - and these figures are increasing quickly.

But motorists concerned about the environment now want to know with what current their car is recharged. Si la Suisse produit presque exclusivement de l’électricité renouvelable, une partie du courant qui sort de nos prises provient tout de même de l’étranger et donc, entre autres, de centrales à charbon qui émettent beaucoup de CO₂.

One solution exists, however: recharging your car thanks to a solar installation placed on your own roof.That said, as soon as we use a photovoltaic power plant without intermediate storage, we find ourselves confronted with being on the move during the day, just when the sun shines the most.A question therefore arises logically: under what conditions could an electric car be recharged thanks to the solar energy that one produces yourself without it being necessary to modify your driver behavior?

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The evening and morning light is enough

This question caught the attention of a team of researchers from the EPFZ Cartography and Geoinformation Institute.The latter has reached a surprising conclusion: an electric car can largely be supplied by solar energy, even if it is only loaded in the evening and in the morning.The condition is to have a smart charger.

This research reviewed four scenarios.In the first, the vehicle is simply connected when you are at home.In this case, unsurprisingly, "solar electricity does not cover needs," explains doctoral student Henry Martin, member of the research team.The reason is due to the fact that electric cars take care as quickly as possible and draw electricity from which it comes, therefore largely from the network rather than the solar installation.

The second scenario uses the use of an intelligent load system: it slows the load and favors electricity from the solar installation."We found that the car can thus be recharged at 56% through solar electricity, especially thanks to the light of the evening and morning.But there are of course large differences according to the seasons, ”notes Henry Martin, who specifies that the data used were collected for ten months.

Have your own solar installation: a good choice

The third variant made it possible to reach an impressive 90% renewable electricity from its own roof.In this case, you have to have the courage to drive even with an almost empty battery and to load only when solar electricity is available."We overestimate the energy that an electric car needs on weekdays," said Henry Martin.Over a week, the study participants have only traveled on average only 250 kilometers with their electric car.

Le quatrième scénario – avec l’utilisation d’un accumulateur intermédiaire – permettrait certes d’utiliser 100% d’électricité solaire, mais le gain serait nul, eu égard aux émissions de CO₂ liées à la fabrication de l’accumulateur.

According to Henry Martin, this study highlights two types of advantages: with regard to the owners of electric cars, it is wise to consider an individual solar installation with an intelligent charging system, even without intermediate storage.As for manufacturers of intelligent charging stations, this study must encourage them to develop intelligent systems which also also take into account weather forecasts.

The study was conducted by the EPFZ Cartography and Geoinformation Institute, under the direction of Professor Martin RAUBAL.For ten months, the behavior of 78 drivers of electric cars (generally owners of individual houses who used their car mainly during the day) was recorded.Virtual solar installations of power between 5 and 25 kW were installed on the roofs of the houses.This research did not take into account the use of solar electricity for other purposes, for example for household appliances or the heat pump.