How did you come to my-PV?

To prevent the house's grid connection from being overloaded with its own feed-in from the 144 kWp photovoltaic system, the client, Markus Ursprung, wanted a power limit on the grid feed-in. Of course, a stronger feed-in would have led to additional costs - another argument for higher self-consumption of photovoltaic power. Due to the higher self-consumption achieved by the 5 AC•THOR 9s, the feed-in has also been greatly reduced, which means that the energy is now stored or reused directly at the "production site".

A special aim by the owner was to produce boiling water (95 °C). A heat pump cannot do this, because the temperature range cannot be achieved here at higher water temperatures. The AC•THOR 9s, on the other hand, doesn't care at all: if there is enough surplus electricity, it can simply use it to heat the hot water tank until the desired temperature is reached - even the 95 °C is no problem there.

Obstacles/pecularities regarding the set-up?

It requires a well thought-out coordination with regard to the technical design to supply a multi-generation house with, for example 250m² of shared living space, two kitchen areas and the various private rooms with sufficient heat. There was a high degree of complexity and therefore the right support was very important! The manufacturer has to be able to provide exact specifications. This proved to be the biggest but manageable challenge with my-PV.

Brief explanation of the system – what should be mentioned?

"We store the energy for winter in summer because this way we don't need more energy in winter than in summer," Markus Ursprung explains the idea behind the system. Hence the seemingly oversized hot water tank design – with 100,000 litres, probably the largest hot water tank currently in use with my-PV products.

A total of 5 AC-THOR 9s control the photovoltaic power coming from the façade and the roof, which is generated from the power of the sun from all 8 sides (four side surfaces and four roof surfaces) of the building envelope and the roof surfaces. The excess power is then used during the day to heat the hot water, which would allow the large storage tank to bridge even weeks-long "lulls in the sun". In winter, there is still some of the residual heat left over from the 25 cm thick insulated storage tank, creating a self-sufficient environment.

Persons in the household – Hot water requirement etc.?

The 12 people who live in the barrier-free and age-appropriate multi-generation house, manage the garden together, use many areas together and are also very different in age. With the large hot water storage tank and the power of the sun, which is fed into the storage tank via AC•THOR 9s, the 12 residents of the house in the canton of Aargau always have enough hot water available.

After more than a year of operating experience, the client Markus Ursprung summarizes the project with the following quote: " I measure the temperature at every height so that I can calculate the exact energy content of the water tank. I connected 4 temperature sensors to each AC•THOR 9s. The PV power often fluctuates between 20 kW and 60 kW; and it is precisely these fluctuations that AC•THOR 9s can take over. What other consumer could handle such fluctuations in performance?”

An example of these fluctuations can be seen here:

Is hot water backup being used with mains power?

The potentially available hot water backup, which can always be activated with the my-PV units on days with low solar radiation, was not activated in this case.

In contrast to a heat pump, which should also have a long or preferably continuous running time for a long service life, AC•THOR 9s can be activated quickly, depending on the surplus power. This means that even short-term yields caused by different cloud formations or sunshine duration can be precisely reproduced in the hot water by the AC•THOR 9s at any time, i.e. they are available for heating water. The large fluctuation peaks are efficiently used in the house itself and not fed into the grid. This way, the feed-in peaks of the public grid are decreased because the surplus is used in the house.

Or, as the building owner sums it up: “I can use the surplus sensibly!”