Interview with expert Dipl.-Ing. Gerd Pommerien, Consultant at pommerien solar, on the combination of solar power, storage technologies and e-mobility.

The combination of solar power, storage technologies and e-mobility is considered an important cornerstone of the energy and transport transition. You have been working as a planner for PV storage solutions for several years. In the meantime, e-mobility is also playing a role. What has changed technologically during this time?

We plan and install PV systems for private and commercial customers. The systems are coordinated and connectivity has improved. There are now intelligent charging boxes for electromobility, for example. However, care must be taken to use the surplus electricity from the PV system so that as little as possible is fed into the public grid. Work is also being done on bidirectional charging. However, there is currently still no regulatory framework for this.

What do you have to look out for in the combination?

We recommend that the electricity from the home storage system is not necessarily used to charge the car, because otherwise there are multiple conversion losses. With an intelligent charging box, it is possible to use only the surplus electricity from the PV system. For this, of course, the components must be coordinated with each other. With E3/DC, the energy management is included in the home power plant. However, there are also intelligent charging boxes that make it possible to measure the house consumption and the PV generation.

How large does a solar power system in a single-family home need to be to make such a combination worthwhile?

The normal annual consumption of an electric car is 2,000 to 2,500 kWh for 5,000 km of driving. A 5 kW system is sufficient for this. The degree of supply is then about 70 %, whereby it is important when charging takes place. If charging only takes place in the evening, the degree of utilization drops because the solar energy cannot be used directly. If, however, the car battery can be fully charged over the weekend, for example, and this is sufficient for the week, depending on the mileage, then I get a higher degree of utilization of the PV system. It depends on user behavior.

In your opinion, what has been the biggest hurdle to comprehensive utilization so far?

At the moment, a major hurdle is that there are too few qualified personnel for installation. Also, currently, the long delivery times.

So there is not too little support?

In terms of subsidies, I would say that at least the same amount that is now going into the subsidization of fossil fuels, namely through tax reductions on gasoline and diesel, should go into the subsidization of renewable energies, and there primarily into storage systems and charging boxes. In addition, there should be a subsidy for the installation of PV systems if the roof is occupied to a maximum, e.g. 150 euros/kWp. It would also be helpful for installers if meter applications were standardized, for example via a nationwide portal, in order to curb the rampant bureaucracy. A simplified Tenant Electricity Act would also help.