Ecologically and economically sound!
Photovoltaic heat during the gas crisis
In a semi-detached house in Münsterland, the AC•THOR from my-PV supports a condensing boiler with the power of the sun.
Facts about the project
- Builder/owner/planner
- Location
- PV power, orientation (direction, possibily inclination)
- Type of building
- Year of construction and number of square meters
- Heat storage size
- my-PV product in use
- System control by:
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Customer's preliminary considerations
A semi-detached house from the 1990s in the Westphalian community of Neuenkirchen (in northern Münsterland) was recently retrofitted with photovoltaic heat.
While considering the renovation of the heating system (switching from an atmospheric gas boiler as a hot water instantaneous water heater to a condensing boiler), the gas crisis arrived at the same time due to the war in Ukraine in 2022. This led to the decision in favor of a gas condensing boiler. However, this was not coupled as an instantaneous water heater, but rather with a hot water storage tank – with PV support for hot water preparation. Sustainability and cost-effectiveness were decisive factors, as well as the concern about rising gas prices. The hot water should therefore be generated using electricity from the newly planned PV system – but initially as support for the gas boiler in order to reduce gas consumption. A system for generating hot water from solar thermal energy is not available and is not planned. At that time the owner, Mr. Köppen, had no knowledge of the my-PV company.
Personal customer opinion and resumee
“My expectations have been exceeded! Since I had no knowledge of control systems when planning the electric heating, and I thought I'd have to intervene manually a lot, I'm thrilled with the automatic adjustment of the heating power to the PV production (surplus utilization). Manual intervention has not yet been necessary, so the gas boiler has not been emitting any CO2 for two months. “I’m also hoping for a support effect when heating water with gas in the winter months,” says Rainer Köppen, who is extremely satisfied.
How did you come to my-PV?
“The electrician who connected our newly installed PV system gave us the crucial tip in April 2022. We were able to obtain further information from the my-PV website. “This paved the way to a solar-electric photovoltaic heat solution,” says Rainer Köppen, summing up the further proceeding.
Were there any obstacles during the setup?
The technical support – from both the gas water fitter and the electrical installation company – was reduced to a minimum. “Appointments could not be obtained, the year 2022 was a chaos in this regard. “The demand for heating systems (in advance of the impending restrictive heating law in Germany) and for PV systems was skyrocketing,” says Rainer Köppen.
The owner of the semi-detached house was able to benefit even more from the detailed documentation of the my-PV products. There is a great overview of compatible manufacturers and third-party products with which the AC•THOR is compatible. The “Instructions for integrating AC•THOR® or AC ELWA®-E into the SMA Sunny Home Manager (SHM) or the SMA Energy Meter” were decisive for the customer's decision in favor of the AC•THOR from my-PV.
Installation and commissioning as well as initial experiences
The heating element was installed by a specialist company (gas fitter and plumber), the connection of a separately fused (16 amp) socket for the AC•THOR and the integration into the existing network were carried out in-house. Commissioning was problem-free and communication with the Sunny Home Manager from SMA was uneventful, according to the homeowner. “When planning the PV system, we decided not to use electricity storage. The purchase seemed too expensive to us at the current stage of life. We focus on the highest possible level of internal consumption,” says Mr. Köppen regarding his own considerations.
If the customer wants a high proportion of self-consumption, the AC•THOR plays into their hands. Its electricity consumption adapts exactly to the PV production (see Figure 1, blue curve: AC•THOR consumption, yellow curve: PV generation).
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Figure 1: AC•THOR power curve (blue) automatically adapts to the PV generation curve (yellow).
In times of normal weather, often a mix of clouds and sun, the target temperature of 60 degrees in the boiler is available around midday (observed months August/September after installation). “Our gas boiler has currently been completely switched off for two months. To our surprise, hot water production during this time is predominantly self-sufficient via the PV system. “Other electricity consumers (washing machines, dishwashers, etc.) also use solar power and there is still electricity left over to feed into the public power grid,” reflects Rainer Köppen, enthusiastically about the functioning of the system.
People in the household – hot water requirements etc.?
The children have already left the household, which means only two people live permanently in the 158 m² semi-detached house. However, when the children come to visit, they shower more often or even take a full bath. This can also be implemented with the AC•THOR, of course depending on the photovoltaic yield.
Is hot water supply used with mains electricity?
The “hot water backup function” is activated. This means that the owner has set two time windows during which the AC•THOR draws electricity from the public grid if there is insufficient PV generation to ensure a target temperature (here: 50 °C). In September 2023, this was only necessary on four days in one time window each (yellow columns in Figure 2). Switching off the hot water supply at a water temperature of 50 °C, time window for possible switching on: 2 p.m. – 3 p.m., 5 p.m. – 7 p.m., daily. This ensures the highest level of comfort (a warm shower or a bath in the evening) at all times.
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Costs of the system including savings
“I would like to give other interested parties a brief overview of what the system cost me and what it has achieved compared to last year,” says owner Rainer Köppen. The overview:
Purchase price of heating element: 189 euros
Acquisition price AC•THOR: 799 euros
Replaced gas output in September 2023 (comparative month of September in the previous year): 227 kWh, equivalent to 35 euros with a working price of 15.42 ct/kWh
Equivalent power from the photovoltaic system via the AC•THOR in September 2023: 183.20 kWh + 6.81 kWh from the grid
“It is already becoming apparent that, given our consumption patterns, hot water preparation with gas in the months April to September can be completely replaced by PV electricity via the AC•THOR control. We hadn't expected that in our preliminary considerations. At the same time, there are no CO2 emissions during this period and there are no production costs.
Given these findings, I am enthusiastic about the AC•THOR and am eagerly awaiting the full 2024 season,” sums up the homeowner from Münsterland.
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AC•THOR
in use
Simple & efficient: AC•THOR controls electrical heat sources depending on the availability of PV energy and heat demand. And that for both hot water, as well as for space heating.
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