Most renewable heating articles describe what should work in theory. This one describes what has been running on our own rooftop for years. In a study published in Energy Proceedings (Vol. 61, 2025; doi:10.46855/energy-proceedings-12108), researchers from Necmettin Erbakan University, Solimpeks and its R&D start-up Innorma R&D evaluated the solar-assisted heat pump system that provides year-round climate control for a 1,637 m² administrative building in Konya, Türkiye.
What was built?
The rooftop carries 298 collectors: 78 photovoltaic modules (270 W each) and 220 PVT hybrid collectors rated at 270 W electrical and 550 W thermal each — an installed capacity of 21 kWe of PV plus 59 kWe of PVT. The collectors work with twelve 1 m³ thermal storage tanks and three 50 kW air-source heat pumps with fan coils to hold the building at a target indoor temperature of 24 °C across all four seasons, with surplus electricity exported to the grid.
Konya's climate makes this a demanding test bench: 1,028 m elevation, semi-arid, hot dry summers, cold snowy winters — and one of Türkiye's best solar resources at roughly 1,650–1,700 kWh/m² of annual irradiation.
How does the system handle winter and summer?
Two season-specific strategies keep the collectors productive year-round:
| Season | Strategy | Effect | | --- | --- | --- | | Winter | Warm water from the storage tanks circulates through the PVT collectors | Melts snow off the collector field, preventing shading losses | | Summer | Active PVT cooling draws heat away from the cells | Higher electrical yield and useful thermal output for the heat pump |
This is the PVT-heat pump symbiosis in practice: recovered low-grade heat from the collectors raises the heat pump's source temperature and lifts its seasonal coefficient of performance, while the cooled PV cells generate more electricity. How the coupling works in general is explained in our PVT-as-heat-pump-source answer.
What did four years of data show?
Between 2020 and 2023 the heat pump system fully met the building's heating demand — natural gas consumption, previously around 650 MWh, was eliminated entirely. Thermal production peaked in the coldest months (over 107,000 kWh in both December and January), tracking Konya's monthly average outdoor temperatures of 0.1–2.1 °C. In the summer months the system reached a SCOP of 6.2–11.4, and compared with conventional fossil-fuel systems the study reports an overall efficiency gain of about 66 % and a CO2 reduction of about 65 %.
A SCADA platform monitors and controls the whole installation in real time: storage tank temperatures, indoor zone temperatures, mass flow rates, weather data, fault status and seasonal operating mode, with remote adjustment of setpoints and flow rates. The study credits this monitoring layer, together with the temperature-controlled PVT cooling, for the system's stable performance across seasons.
Why does this case study matter?
First, it is measured, not modelled: the results come from four years of SCADA-logged operation, published in a peer-reviewed venue. Second, it demonstrates at building scale what the EPBD's zero-emission building requirements will ask of new construction across Europe from 2028–2030: fossil-free heating built on a solar-plus-heat-pump backbone. And third, it shows the approach scales beyond single-family homes — offices with four-figure square meterage can run entirely without a gas boiler.
The research was funded by the CET Partnership Joint Call 2023 (Cetp-FP-2023-00114), and the system continues to operate — and log data — on our rooftop in Konya. Future work extends the analysis to other climates and long-term techno-economic performance.
