A photovoltaic system for driving cleaner electric cars

Our Alsace reader Fabien wanted to get rid of nuclear power to drive an electric car. He made the choice of a self-consuming solar cell installation on the roof of his house. After 5 years of production, it draws a very positive balance.

Tesla Model S + Volkswagen e-Golf

Now regional manager of Tesla Owners Club France, Fabien switched to electric cars in 2016 after following Yoann’s adventures, the founder of our webzine Clean car.

Our reader started with a Hyundai Ioniq, which enabled him to confirm his choice of electromobility. Two years later, a child’s arrival at home made him decide to lease a Tesla Model S 75D. A Volkswagen e-Golf took over from the Korean electric car and became the second vehicle in a family that now counts 5 people in total.

However, its eco-citizen approach does not stop at the abandonment of thermal engines well in advance of the deadline set by national and European institutions.

A 4.2 kW peak installation

There are a number of reasons why Fabien had 4.2 kWp solar panels installed on the roof of his house. ” I wanted to produce my power, not consume too much on the network. Above all, I would avoid being told: “You drive electrically, therefore you drive nuclear power”. I could thus answer: “No, no, I am a producer of my electricity” Fabien explained to Max Freyss.

In our reader’s garage, the left wall is impressively equipped. Between the Tesla wallbox and the house’s electrical panel, there is a lightning protection box specific to the photovoltaic system and a two-way hybrid AC / DC Solax Power inverter. The latter is dimensioned to accept up to 5 kWp solar panels.

Just below that is an LG NMC (nickel-manganese-cobalt) lithium-ion battery with a gross energy capacity of 6.5 kWh. A value close to the energy that our readers’ electric car uses for its daily trips. The set is complete with a measuring unit, which gives the inverter information about the house’s electricity consumption.

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Operation in the summer …

When the house’s consumption is greater than the solar cell production, the battery makes the difference. Originally, the latter was intended to store the energy produced during the day, to recharge the car in the evening when returning from work. ” Since then, there has been a pandemic, incarceration, with still remote work today Fabien remembered.

This change in lifestyle allows our reader to recharge his electric car directly during the hours of solar cell production. However, the NMC package has not become useless. First and foremost because it is to be used to power other equipment and, at best, to provide the energy necessary for the operation of the house until the next morning.

The optimal period for this operation is the one we are in at the moment when the days are long, the sun is there in the morning very early to very late in the evening. “, Specified our interviewee.

… And in winter

In winter, the battery is too small to further supply the heat. In addition, solar production is down. ” In this case, I can decide to recharge the battery at night during the low season, with the return of energy during the day. It’s a completely different behavior. I do this every year for 3 to 4 months Fabien explained.

At present, our reader never resells his production. ” In 2017, it was not allowed with panels on top of the roofs, on a metal frame, without removing tiles. The law has evolved. It is now possible to resell with such an installation “, he concluded. What the Alsatian electric motorist has not done so far.

If he wanted to, he should just turn to his energy supplier Électricité de Strasbourg, on which his department depends. By optimizing the operation of his installation as well as possible in all seasons, he does not feel the need for it at the moment.

An investment return of 10 years?

Five years ago, Fabien’s installation mobilized an envelope worth about 20,000 euros. ” In 2017, I had calculated a repayment after 12 years based on an increase in the price of electricity of 5% per year. In February, we had a very large price increase. The situation should continue. My new calculations bring the break-even point back to 10 years, ie in 5 years “, He encrypted.

Today, the price of installations is falling, the price of electricity is rising. It became even more interesting «, He stated. Our interlocutor estimates that second-generation monocrystalline panels attached to its roof can be used for about twenty years. ” Even if tomorrow they only produce 60% of their original value, they will still be there and have been profitable. It will not necessarily be helpful to replace them at this time. ‘, He assured.

Until now, he relied on rainwater to wash these surfaces. Even when the sands of the Sahara came to cover them, which damaged electricity production. He’s leaving ” for industrial solar farms that need profitability ‘Expensive cleaning with mineral water using a dedicated device. ” Individuals rarely perform maintenance on their roof installations “, he argued.

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Small annual report

With the Tesla Model S, the Fabien drives about 20,000 km a year. e-Golf is a total of half as much: 10,000 km. There are a total of 30,000 km each year in electric cars. This corresponds to a consumption of 5,000 kWh or an average of 16.6 kWh per. 100 km. ” As luck would have it, these 5,000 kWh also represent exactly my annual solar cell production ‘, He turned.

The solar cell battery can be recharged several times during the day , ”He clarified. This means that the daily solar cell production is not strictly limited by the level of the package’s energy capacity.

When the weather is cloudy, the yield is necessarily reduced, without, however, being zero. Before covering the roof of your house with solar panels, it is necessary to make an estimate that takes into account this point, the sunshine of the place as well as the slope and orientation of the roof. Requirements for production level will then result in a quantification of the number of panels required.

Charging test

With its inverter, Solax Power delivers a smartphone application. During the visit of Max Freyss, the production of electricity was surplus (power of 3.2 kW). In addition to covering the low needs of the house (0.260 kW) and completing recharging of the buffer battery (almost 2.5 kW), a share was injected into the network free of charge with a modest power of 360 W.

Hence Fabien’s idea of ​​connecting our journalists’ Model 3 to the Tesla Wall Connector. The car system quickly indicated an output of the order of 4 kW (5 A on each of the 3 phases of the three-phase installation). The application showed the development of currents. First of all, the suppression of the injection on the network.

The power consumption for the house, including the charging station, increased to just over 3.8 kW, primarily supplied by solar energy production (3.2 kW), but also by pulling on the battery (more at 0.7 kW). ” This is how you can demonstrate the possibility of recharging your electric car with your own solar cell installation. “, Illustrated by our reader.

A story makes it possible to find the evolution of the characters over a given range. This makes it possible, for example, to observe that the passage of a cloud may result in a request for additional energy being drawn from the network.

Why not do the same?

With an optimistic hindsight of 5 years, Fabien can only invite us to follow his example. ” Because of the assessment that I draw from my own experience, I would be wrong not to recommend doing the same. Choosing such an installation has a cost. If electric car drivers can be producers of their electricity, it’s a step in the right direction. And for the car and for the future. Because we need to provide energy other than oil, coal and nuclear power “, he campaigned.

If it takes up space, it still reassures something in the conclusion: ” In your own consumption, just with a carport, a small parking space or a wall, you can already install 3 panels and produce electricity. So let’s go! “.

The whole team ofClean car heartfelt thanks to Fabien for his welcome and his testimony.

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