Heating with the sun

Renovated single-family house in Austria

Two large heat storage tanks are heated during the day with the own photovoltaic power via two 9 kW immersion heaters.

Datos sobre el proyecto

Type of building:
Year of construction:
Photovoltaic power, orientation:
Heat storage size:
Used my-PV product:
System control by/with:
Stoeger PV Projekt

Customer statement

The family lived in this bungalow until its enlargement and renovation in 2021. A 5.5 kWp photovoltaic system had already been installed on it before, and the AC•THOR 9s from my-PV used surplus energy to load the two 1,000 liter buffer tanks.

Even before the photovoltaic system was enlarged, the client Markus Stöger, himself a specialist in high-quality electronics, created the right conditions in his hydraulic heating system for the planned system expansion. For example, by installing two 9 kW screw-in heaters, the subsequent increase in photovoltaic heat generation capacity was already considered from the outset.

With over 35 kWp of installed photovoltaic power, it is now a true solar power plant that naturally provides immense excess power. These surpluses from the photovoltaic system can be used sensibly on site for heat generation thanks to my-PV's solutions, instead of being unprofitably fed into the grid.

In the new 18 kW operating mode, two electric heating elements are supplied with surplus power from the photovoltaic system. One of them can be controlled continuously, the second one is switched on as soon as sufficient surplus is available.

Since both 9 kW heating rods were already available, the effort to upgrade the photovoltaic heating was limited to the installation of a three-pole relay and a minimal adjustment in the wiring. The necessary firmware update for the AC•THOR 9s was simply imported by my-PV via the Internet. All AC•THOR 9s already installed by our customers can also be made suitable for this operating mode by updating the software.

In addition to the surplus detection at the house connection point by means of my-PV Power Meter, Markus Stöger uses (as an optional extra) a second my-PV Power Meter for power measurement at the switched heating rod. Thus, this consumption is also shown in the power display on the display and on the web interface and can also be taken into account in the energy recording of the data logger.

Enormous advantages for the customer

The AC•THOR 9s has been in use in the new operating mode since summer 2021. By mid-November, it had not been necessary to heat up the biomass heating system even once, and this despite the fact that the existing high-temperature heating system with radiators was retained on the first floor during the refurbishment.

The immediate economic benefits are already obvious. The costs for the chimney sweep have been significantly reduced and the storage space required for logs has also been massively reduced. Both in front of the building and inside it. In the future, the family will have an entire basement room at its disposal, once the existing firewood stocks have been used up. Whether this will happen in the coming winter is highly questionable, however, because the heating season for the Stöger family has now been reduced to the months of December and January thanks to photovoltaic heating from my-PV.

Opinión personal del cliente y resumen

In this operating mode, it is expressly recommended that both the AC•THOR 9s control and the power measurement at the switched load are each carried out with a my-PV Power Meter!

Stöger PV Projekt von oben
my-PV PowerMeter
Stoeger PV Projekt 2
my-PV AC THOR 9s
Stoeger PV Projekt
PV Projekt

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