A new buffer tank replaced the outdated one, providing space for two 9 kW screw-in heating elements for water heating, which are connected to a fresh water module. The buffer tank is optimally supplied with a layered charge, ensuring maximum storage capacity with efficient thermal stratification.

A key aspect of this setup is that the two 9 kW heating elements require precise, linear control to utilize surplus electricity (which would normally be fed into the public grid) for heating. Two AC•THOR 9s control each 9 kW heating element in real-time based on the surplus PV electricity. In total, this provides 18 kW of controllable power. The AC•THOR 9s also regulate the speed of a WILO pump (Varios PICO-STG model), ensuring energy is efficiently layered from top to bottom in the buffer tank. Compared to a conventional direct heating element installation in the tank, this approach ensures the target temperature at the hot water outlet is reached much faster.

The actual domestic hot water is then heated through an attached fresh water module, drawing energy from the buffer tanks. When solar yield is insufficient, the devices can maintain a minimum temperature, eliminating the need for conventional heating systems. Between October 2022 and September 2024, the club continued to use the remaining gas for backup heating. By September 2024, the gas supply will be fully depleted. Since October 2022, gas has only been used when the water temperature fell below 36°C, during bad weather or darkness, and could be easily managed by manually starting the gas heating system. Soon, the fossil fuel-based system will be dismantled, and if necessary, mains electricity will ensure the minimum temperature to avoid cold showers for the athletes! 😉

How does the system detect surplus electricity?

The surplus detection at the grid connection point is handled by a my-PV Power Meter (now the my-PV WiFi Meter), which communicates with the two AC•THOR 9s over the local network. This ensures that only the surplus electricity – the amount that would otherwise be fed into the grid – is used for heating. The electricity stays within the building and is converted into heat where needed. This guarantees that hot water is always produced from surplus electricity. "Self-consumed electricity is always the most economical option!" says Wolfgang Wührleitner, the club's treasurer.

System performance data from solar heating

Throughout 2023, the my-PV solution produced 4,688 kWh of heat. Comparing this to the previous gas consumption, it’s clear that nearly half of the energy needed for hot water was supplied by surplus PV electricity. Even higher coverage could have been achieved with a larger buffer tank (limited by space constraints in the heating room) or by setting a higher water temperature.

The revamped system, with its layered charging and improved insulation, paired with a lower required temperature, has significantly reduced energy consumption. Replacing the 30-year-old boiler also contributes to the system’s improved efficiency, proving that solar-powered heating can offer the same comfort with less energy.

The resulting cost savings will allow the my-PV components to amortize in under three years. With the sharp drop in feed-in tariffs, these savings would not have been possible without using solar-powered heating. It’s worth noting that the club often sets the target temperature for the my-PV devices between just 50 and 57°C, though the buffer tank could easily handle target temperatures over 80°C. Thus, the system could store double the amount of energy from solar heating, increasing storage potential.

The PV system's performance, including hot water production, is impressive. Detailed visualizations and analysis can be viewed in the slider below.

High electricity consumption at the sports club?

Between March 2023 and February 2024, the club's PV system generated exactly 24,608 kWh. Approximately half of this was sold to the Energy AG, the buyer of the PV electricity. The club consumed 12,031 kWh of the electricity for various uses (7,220 kWh for general consumption and 4,689 kWh for hot water from surplus PV electricity). The PV system itself required 122 kWh, representing system losses.

The high self-consumption is due to various demands: laundry for 150 youth players and two adult teams, refrigerators and freezers for the clubhouse bar, and power for three clubs (football, tennis, and stock sport) to run their facilities. Additionally, the club's rooms are heated electrically, powered by the PV system during transitional periods and sunny days.

As feed-in tariffs drop further in September 2024, the club aims to increase self-consumption. "Selling electricity at low tariffs no longer makes sense when buying electricity costs significantly more. So, we’re focusing more on solar-powered heating and optimizing appliance use," say the club officials.

The conclusion on solar-powered heating?

"The performance data speaks for itself. We are convinced by the reduced operating costs! Sure, a photovoltaic system is an investment, but the extra effort for solar-powered heating is manageable. Then you just let the sun do the work instead of dealing with gas purchases," sums up Wolfgang Wührleitner, sharing his experiences.

The my-PV Cloud's data visualization makes it easy for clubs to monitor and adjust the heating system via a mobile app. "I'm fascinated by how well the system works. It helps us save on operating costs – a crucial factor for every club. The easier it is to save, the better," says Wührleitner, treasurer of ATSV Vorwärts Neuzeug.