E-cars as an energy store ?: “They would have the capacity of 100 nuclear power plants”

Anyone who installs a photovoltaic system on the roof has a problem: cheap electricity is mainly produced when you are not at home. After sunset, only expensive energy from the grid remains in the evening. To optimize consumption, most solar systems are only sold with a home warehouse. By far the best energy storage devices are at your fingertips. However, in the eyes of Christian Rahn, Germany has so far failed to exploit the potential of electric cars. Local charging stations in particular are a problem. “Other countries show that it works,” says Managing Director of Otovo Germany at ntv’s “Climate Lab”. “There is no reason why this should not work in Germany as well.”

ntv.de: Please explain what “bidirectional loading” means.

Christian Rahn: It just means energy exchange in both directions. First and foremost, it is about electricity that can be stored somewhere and released again in different areas.

And we urgently need this in Germany to achieve the energy transition?

Christian Rahn, Managing Director of Otovo Germany

(Photo: Otovo)

It could at least be a design element. In the case of renewable energy, it is usually the case that solar energy, but also wind energy, produces electricity when the sun is shining and the wind is blowing particularly hard. But that doesn’t mean I need this energy right now.

The sun does not shine at night, as has been emphasized many times.

And also not in the early morning or evening. But maybe this is the time when I would like to use the electricity that I generate myself. This is where electricity is stored, both on a small scale and from a macro perspective, i.e. Germany. Part of the way it is today is that we produce more electricity than we can store when the sun is shining and the wind is blowing hard. In this respect, storage plays an important role in renewable energy.

But it is called bidirectional Load. What’s loaded in there?

In the case of solar systems, 85 percent of what is known as in-home storage is usually included in the energy storage unit in the basement. This allows me to store excess electricity throughout the day and use it again in the evenings. It is a kind of two-way charging or delivery: I charge the storage system and give energy to all consumers connected to the house.

And if you put electricity into the grid, will you get money?

I installed the solar system on my roof myself twelve years ago and have still been receiving a feed-in of over 30 cents since.

It is worth it.

Unfortunately, the feed-in tariff has continued to decline in recent years, while electricity prices have risen drastically at the same time. For every kilowatt hour of electricity you pay over 30 cents. The production costs of a normal solar system are between 12 and 14 cents per kilowatt hour. This means that I produce relatively cheap electricity. But out of memory, I only use 35 to 40 percent of it myself. With the right size memory, I can increase its consumption to 85 to 90 percent.

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So all people who are just now using solar energy are at a financial disadvantage if they supply electricity to the grid instead of using it themselves?

Exactly. The electricity it produces costs between 12 and 14 cents. You pay 30 cents for electricity from the grid. The strategy is therefore to store and use as much of the electricity it produces as possible and to minimize the amount of electricity drawn from the grid.

And how well does it work in Germany compared to other European countries?

In fact, we’re still at the very beginning. Especially in the field of e-mobility and storage devices that are installed in e-cars. It is a potential that could constitute an important building block in the energy transformation. This has to do with the fact that the storage devices used in solar systems typically have a capacity of ten kilowatt hours. The average storage capacity for e-cars is 75 kilowatt hours. This is a multiple of what is available in homes as home storage, enormous potential.

So e-cars are super good energy storage devices?

Potentially definitely. But of course it is assumed that the cars are connected somewhere on the network and sharing their memory. They don’t do it when they’re on the move. But of course we know that 95 percent of the time the cars are parked in front of the door. In this respect, it would make sense to use this potential in the charging infrastructure.

In Berlin, you can see charging stations more and more often, but also e-cars on the streets. Can it be used?

No, usually not yet. A field test is currently taking place in Schwäbisch Hall. There, the commune has made available a multi-storey car park with appropriate charging stations where you can connect your e-car with the appropriate technology.

Why? Is it not possible to retrofit cars and charging stations?

Technically anything is possible. There are many infrastructures in Utrecht, the Netherlands, that connect cars to the electricity grid in both the private and public sectors. In Asia, too, as is often the case, many countries are much further afield in this respect. So do car manufacturers. Basically, you need software that controls some intelligent charging and discharging processes and the appropriate hardware. In the end, it all comes down to having the right plugins.

Does this mean you can upgrade your charging stations?

Yes. Many cars are also designed for this. In many areas, it would be enough just to adjust the infrastructure on the hardware side.

Is it not because the technology is too demanding? Or are the legal obstacles too high?

In any case, there is still a long way to go in terms of regulation. But basically other countries are already showing us that it works. There is no reason why this should not work in Germany as well.

Is it on the political agenda? Have an idea where the problem is?

There is now a new funding program from the federal government. This provides for the promotion of two-way charging for almost 100 million euros. So you’ve got it on your screen. I am also convinced that many things will start in this field, because the potential is huge. There are many predictions about the spread of electric cars. It is said that up to 15 million vehicles will be in use in Germany by 2030. If that extrapolates, they will have a capacity of 100 nuclear power plants. It’s gigantic. In this respect, everything indicates that we are using this capacity.

How expensive would it be now to buy a solar PV system, a storage box, a wall box for a garage and an electric car?

The electric car is by far the most expensive. A photovoltaic installation for a four-person household costs between 12,000 and 15,000 euros, depending on the demand for electricity. The more modules installed to produce energy, the more expensive it is. When it comes to storage, you have to reckon with another 5,000 euros plus x. Charging wallboxes are now very cheap, you can get them for well under 1000 euros. However, if the wall box is to be adapted for bidirectional charging, the situation is different due to the rather thin distribution. They currently cost around 10,000 euros.

So a higher five-digit sum, if not six-digit sum. Is there a high demand for photovoltaic systems from Otovo despite the costs?

Yes, very high. This has acquired a special dimension, especially as a result of the crisis in Ukraine. However, the demand is very high due to the constellation of the last few years: electricity prices have risen significantly, while the cost of solar systems has dropped sharply at the same time.

And how long is the waiting time now?

It depends a bit on what system you order. If you order today, expect it to take three months to install on the roof.

Because installers are missing? You hear it more often.

The shortage of skilled workers basically plays a major role in our industry. There is an imbalance between demand and plant capacity. At Otovo, we focus on the private sector, which means homeowners. There are around 15 million homes in Germany that are suitable for solar installation. Of these, only less than 10 percent currently have a rooftop system, although demand is high. But with the existing capacity, we are currently only able to install 250,000 to 300,000 systems per year. Much more could be happening.

What do you have to pay attention to when deciding to buy a solar system?

Not so much so when you have a competent partner to advise you. First of all, we conduct a needs analysis and carefully look at how high the demand for electricity will be in the next few years in order to optimally dimension the systems. Next, we will look at the conditions on the roof. The storage tank is of course one way to optimize self-consumption as much as possible. Then you need a local partner to install this system. These are specialist companies. In agreement with us, they also register the system with the network operator. Of course, the electrician also needs to check that the power lines in the house are up to date so that I can connect the system.

We don’t want to burn the building down.

Exactly! That’s a lot of things, of course, but nothing that I, as a customer, need to deal with actively. There is also a register in which all solar systems are recorded and registered. But that’s not rocket science either. Basically it is enough to enter the system with the performance values. That’s it.

Juliane Kipper and Christian Herrmann spoke to Christian Rahn. The conversation has been shortened and smoothed out for better understanding.

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What helps in the fight against climate change? climate laboratory is a ntv podcast in which Clara Pfeffer and Christian Herrmann analyze ideas and claims that sound great but rarely are. Climate-neutral companies? lied Climate Killer Cow? Deceptive. reforestation? It exacerbates the problems. CO2 prices for consumers? Inevitable. wind turbines? They are systematically held back.

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