How did you find my-PV?

The Wahl family's 500 m² multi-party house is located in beautiful Middle Franconia, more precisely in the district of Erlangen-Höchstadt. The house, which was last renovated in 1996, encompasses three apartments and an additional holiday apartment in the outbuilding. The building accommodates up to ten people and additionally up to six people to vacation in the holiday apartment. The attached hall is spacious enough to mount the 24 kWp photovoltaic system on the roof, which is aligned to the northeast with a 5 degree inclination.

The owner from Bavaria discovered the solutions from my-PV through the heating construction company Potenz and his own research on the Internet with the aim to optimize self-consumption and heating with environmentally friendly energy.Obstacles/specialities during the installation

In order to be able to efficiently design the heating with solar energy – despite the large PV system – the thermal renovation had to be carried out in a 2- to 3-person household. This insulation was carried out in 2020, so nothing prevented the implementation of the proactive heating engineer's idea.

Brief explanation of the system – what should be mentioned?

Three heating rods from ETA's primary heating system are installed in each of the two buffer tanks, each with a capacity of 800 liters. These are linearly controlled via the two AC•THOR 9s to load the photovoltaic yield into the buffer storage during the day. This way, the hot water for sanitary and household applications is heated and prepares it for space heating and heating purposes.

The control and thus the surplus information can be queried directly from the built-in inverter or the associated surplus detection in the sense of the system openness of my-PV. This means that there is no need to install a separate meter, which in turn saves costs for the customer. A total of three inverters from HUAWEI are installed as well as a blackout box for possible emergencies.

The surplus electricity detected from the photovoltaic system is first forwarded to the home consumers, then to a 15 kWh electricity storage unit (also from HAUWEI) and subsequently to the heating rods in the buffer storage tanks. The decisive factor is linear control. This is done by the two AC•THOR 9s, which control the surplus to the exact watt and thus distribute and control the fluctuating PV yields in a targeted manner. The operating mode M1 is used here.

Obstacles/specialties during the installation?

Of course, the connection of several systems sometimes may have a catch. In this case, it was up to the installers, as the owner Mr. Wahl admits: “After we did the installation together with a friend, we had to deal in particular with the surplus control – it was not easy to establish the connection to HUAWEI. In retrospect, however, it was just a mistake in our reasoning.”

Persons in the household - hot water demand etc.?

The five people, who are spread over the three residential units, live permanently in the Middle Franconian district. Even though only five people live there today, the three residential units were originally designed for up to 10 people.
Therefore, with the second 800 liter storage tank, a sufficiently large addition was created to be able to provide hot water for up to ten people and for the entire property at peak times.

Is hot water backup with mains power used?

The boiler heating – a biomass heating – with an output of 30 kW from ETA was newly installed. If there is not enough solar energy available, the room is either reheated and temperature is increased to a comfortable level. During the months of November to April, the peak loads must be supplemented by pellet heating.

Since mains electricity currently costs more than 40 cents per kilowatt hour, this type of hot water backup is more cost-efficient than reheating with mains electricity.