Innovative heating technology with AC•THOR 9s

Masonry stove and photovoltaic heat instead of a heat pump

The newly built single-family home impresses with environmentally friendly construction and innovative heating technology.

Facts about the project

Photovoltaic power and orientation
Heat storage size
Building type
Year of construction and number of square meters
my-PV product in use
System control

The framework of the special heating technology

The house of Nils and Isabell Burghardt is located in the Lower Franconian district, specifically in Neuschleichach. The construction of the newly built single-family home in 2023 is mostly ecological with natural building materials – the 275 m² living area (including the basement area with a basement apartment) is environmentally friendly.

In the open living area on the ground floor of the single-family home, there is a masonry stove with absorber technology, which heats the buffer storage with a circulation pump. Due to the massive construction of the heater, it stores heat for about 12 hours and releases it to the room with pleasant radiant heat. During the first cold season, approximately 8 cubic meters of hardwood were used for heating.

Of course, what must not be missing in environmentally friendly construction is a large photovoltaic system to use solar energy instead of fossil fuels. With a total of 25 kWp, divided into 17.6 kWp facing south and 6.4 kWp facing north (both sides tilted at 40°), there is a significant amount of surplus electricity that should be used rather than being unprofitably fed into the public grid.

Personal customer opinion and resumee

"I really am positively surprised at how well the system works. The control speed of the AC•THOR 9s, especially on cloudy days, is extremely fast. The installation and setup of the system went very quickly and was possible without any problems!" Nils Burghardt enthuses about the implementation of photovoltaic heat in his newly-built single-family home.

How was the way to photovoltaic heating solutions from my-PV?

"I found my-PV online on the search for an easy-to-use device that could also communicate quickly and easily with SMA products," describes Nils Burghardt his research. Thanks to the open system of my-PV, the SMA Sunny Home Manager 2.0 can be easily used as a surplus detector – the data from the SMA smart meter is sufficient to regulate the my-PV devices, saving the customer from needing a separate smart meter for power measurement.

An AC•THOR 9s was chosen, which regulates the surplus linearly via 3 heating rods (each with 3 kW power, integrated at different heights in the buffer storage) depending on availability. The intelligent photovoltaic power manager from my-PV supplies the buffer storage with heat during the day, using the photovoltaic electricity that is usually overproduced and would be fed into the grid. This means that the homeowners need to use less wood in the evening to heat the buffer storage with the masonry heater to achieve the desired comfort temperature in the house.

The large PV system can supply the three heating rods in the buffer storage with enough solar energy even during the transition period. A grid power draw (about 400 kWh), which can be additionally set for hot water supply, was only necessary in December and January. Through a stock market price-dependent electricity tariff (Tibber), which is billed hourly, hot water supply could be scheduled for the cheap, often windy night hours.

How is the house generally heated?

The buffer storage supplies the underfloor heating in the basement and the wall heating in the ground floor and upper floor, with the respective flow temperature being separately adjustable for both heating circuits. Through a separate fresh water station in the upper third of the buffer storage, warm domestic water is ensured at the tapping points, guaranteeing the highest comfort for showering, etc.

With this economically and ecologically smart heating system, it is ensured that the single-family home with 275 m² can be heated and supplied with hot water over 95% completely with sustainable energy (sun and wood)!

Were there any obstacles in the set-up?

Indeed, there were challenges in implementing the intended heating method. However, this was not due to product errors. "It wasn't easy to find a heating contractor who wouldn't immediately want to install a heat pump," says the homeowner from Lower Franconia, who lives in the house with his wife and a child. The fact that the switch away from the heat pump paid off is evident in the impressive heating balance over the first winter!

Good to know

What are the advantages of photovoltaic heat?

"Even without a battery storage, the self-consumption rate is over 90% on average in the cold season. In our case, we were able to completely forgo an expensive heat pump. The running costs, including maintenance of the system, are significantly lower compared to a conventional heating system with a heat pump," Nils Burghardt is convinced of the photovoltaic heat solution.

A few more details about the construction of the single-family house

The single-family house is built mostly ecologically with natural building materials, as can be seen on the photos. It was important to the owners to avoid chemicals and plastics as much as possible.

The exterior walls (ground and upper floor) are constructed in a glue-free solid wood construction (Nur-Holz system) with a thickness of 24 cm and an 8 cm wood fiber insulation. A ventilated, suspended facade made of Douglas fir serves as wood cladding. All interior walls are built in wood frame construction with diagonal paneling, covered with dry clay building boards, and plastered with fine clay plaster. Where necessary, water-conducting pipes are installed as wall heating.

The ceiling between the ground and upper floors is constructed as a solid board stack ceiling. Over 2500 clay bricks were laid under the system construction with 25 mm solid oak country house planks as mass. The roof truss is designed as an exposed roof truss with above-rafter insulation.

The basement is built with 36 cm thick solid bricks. Insulation was therefore not necessary.

"The entire interior construction, including electrics and all plastering work, was almost exclusively done by ourselves," says Nils Burghardt, showing a bit of pride in the work accomplished.

To the demo access of the my-PV Cloud

Real system data of this reference project
ACTHOR-9s Seitenansicht


in use

Simple & efficient: AC•THOR 9s controls up to 3 electrical heat sources depending on the availability of PV energy and heat demand – for both hot water, as well as for space heating. It ensures your personal living comfort fully automatically.

More infos about AC•THOR 9s

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