July 21, 2022
◼ Massive dimensions in multi-generation house
In a Swiss multi-generation house, the photovoltaic yield of summer is taken into winter - with a 100,000-litre hot water storage tank.
Becoming Switzerland's first self-sufficient multigenerational house - that sounds like an ambitious goal. But that is exactly what has been realised in a small village in the Swiss canton of Aargau.
The building with 921 m² living space, which is partly a renovated old building and partly a newly built extension, has a lot of photovoltaics integrated on the roof and in the facade. On a total of eight sides of the building, including the roof areas, 144 kWp are installed. These are already striking figures. But the interior of the multi-generation house is even more impressing: a 100,000-litre hot water tank, four meters in diameter and 12 meters high, stores the solar energy of the warmer seasons for the winter months as well.
Increasing self-consumption with hot water
The builder, Markus Ursprung, wanted to ensure that the grid connection of the house was not too heavily burdened with his own feed-in from the 144 kWp photovoltaic system. Therefore, the way was paved for a higher self-consumption of the photovoltaic electricity. The owner achieved the higher self-consumption by installing five AC•THOR 9s in his multi-party house, so that the feed-in is reduced and the energy is stored or used directly at the "production site". This is because the AC•THOR 9s only ever heats the hot water tank with the surplus electricity from the photovoltaic system by adjusting the output every second - i.e. during the day, when there is too much electricity available for the house or the house consumers anyway. The AC•THOR 9s does not care how high the temperature is to be raised. The builder wanted to have boiling water, i.e. at about 95 °C, in the water storage tank. A heat pump cannot achieve this, because the temperature range can no longer be reached at higher water temperatures.
From summer to winter
"We store the energy for winter in summer because 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 in use with my-PV products.
Even with 12 people living in this multi-generational house, the seasonal storage tank is never emptied.
Why is the AC•THOR 9s predestined for this?
After more than a year of operating experience, the owner Markus Ursprung sums it up with the following quote: "In order to calculate the exact energy content of the water tank, I measure the temperature at each level. I have connected 4 temperature sensors to each AC•THOR 9s. The PV power often fluctuates between 20 kW and 60 kW; and it is exactly these fluctuations that the AC•THOR 9s can take over. What other consumer can handle such power fluctuations?"