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It works with the sun instead of with gasoline. How to use the panels for cheap travel

Jan Staněk has photovoltaic panels on the roof of his family home with a maximum installed power of 10 kWp. The photovoltaic system can cover a significant part of the household’s electricity consumption, including heating. Since 2018 it has also been charging two electric cars with the electricity it produces on the roof.

It is not obvious. The battery of a normal electric car needs a good amount of electricity to be charged. “It logically follows that the car has to be charged when it’s sunny and our photovoltaic system is producing at full capacity”, he says at the very beginning of the tenth part of the series. Domestic photovoltaic Jan Stanek.

It is not possible to charge the car from the battery

While the batteries we normally buy for the home as part of a photovoltaic system have an average capacity of 10 to 12 kWh, cars powered by an electric motor usually carry a battery with a capacity of around 75 kWh. Therefore, charging the car in the evening from the home battery, from which we want to “feed” the family at the same time, is not a good idea.

However, the Staňkas use the house’s battery to cover fluctuations in PV power during the day.

So load only on weekends? That does not make sense. “And from November to January, you simply won’t load the car. The little you do on the roof will be consumed by the family,” Staněk says flatly. To sum it up, the cooperation between domestic electric and photovoltaic cars will make sense for those who can work in the office or just charge their car on weekdays.

ElectroDad for the message list

  • Jan Stanek is a well-known advocate of electromobility and sustainable energy in a broader context. The Brno BUT graduate previously worked for eBanka, worked as an IT consultant at Deloitte and later represented Moravia IT in China.
  • Today he heads Purple Ventures, a company focused on startup investments. His video channel ElectroDad, through which he describes the theme of the transition of families to sustainable energy in a fun and informative way, is viewed by over 25 thousand subscribers on YouTube and Stream.cz.
  • Exclusively for Seznam Zprávy, independently of Seznam’s business partners, he has produced a series of ten videos on the topic of domestic photovoltaics.

If your PV system isn’t producing all the electricity you need at any given time, it’s time to consider priorities. What I want to charge, what I want to use the electricity produced for.

“It happened to us when we switched to heating the house with a heat pump. On the fringes of the photovoltaic season, by which I mean for example March, when the panels still do not produce much and, moreover, we still have to heat them, we have to make a choice. Car overflow charging or heating, “says Staněk. The priority is probably clear, so in late and early winter the electric car will lose the taste of electricity from the roof. So the solution is to charge the battery with electricity from the distribution network in times of advantageous rates.

Modern electric cars have a battery large enough to cover several days of basic appliances at home, in a cottage or on a campsite.

Jan Stanek

The technical side of things

In order for an electric car to be significantly charged with a photovoltaic system, the system must operate in three stages. This is possible if we have a three-phase distribution system in the house (for example a 3x 25 A circuit breaker). And, logically, charging the electric car ideally takes place in the same way in three stages, which is already the standard today. When each of the phases supplies a current of 16 amperes, the total power of the charger reaches 11 kW.

An important feature of today’s electric cars is the ability to adjust the charging power as needed, that is, according to the source that currently provides us with energy.

“In the summer, your roof will give you maybe 7 kW immediately when the sun shines. But the car would like eleven. Therefore, it is necessary to adapt the charge, to reduce the required power. Otherwise, you would buy the rest from the grid. And you don’t want it, “explains Staněk.

The charging power can also be adjusted via the wallbox, which should, in collaboration with the inverter (you already have it at home, it is part of every photovoltaic system), be able to charge the car, like an inverter and a domestic hot water, only if you have excess energy.

Home photovoltaic video series

In general, it can be said that it is possible to recharge an electric car with the electricity produced at home. In summer, on a sunny day, you can definitely charge an electric car for a range of 50 to 100 km. However, regular or at least frequent recharging requires a lot of “care”, which mainly consists in organizing time. It is not for everyone.

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