Sustainable thermal management in Croatia
Topusko, located approximately 100 km south of Zagreb, is known for its geothermal resources, among the highest quality in Europe. The Top-Therme complex includes indoor and outdoor pools, therapy centres, and hotels, all of which rely on stable and efficient access to geothermal water.
The objective of the project was to renovate four geothermal wells originally drilled decades ago, optimising their output and upgrading the piping infrastructure to better serve the resort’s renewable energy goals.
Geothermal system overview
The four geothermal wells collectively supply approximately 175 litres per second of thermal water, with source temperatures ranging from 68°C to 72°C. Distribution temperatures decrease to between 27°C and 34°C at the point of use. Each well supplies specific areas:
- TEB-1 (15–17 l/s): Serves the health and regeneration centre, including indoor/outdoor pools.
- TEB-4 (100 l/s): Located behind Hotel Petrova Gora, with water at approximately 68°C.
- TEB-2 and TEB-3: Feature higher source temperatures.
Modernisation of these wells supports the municipality’s long-term objective of becoming a smart, thermally powered community.
Why Polybutene-1 (PB-1)?
Geothermal water is typically high in mineral and gas content and can be chemically aggressive. Polybutene-1 was selected for its outstanding material performance under such conditions:
- Excellent chemical resistance in geothermal environments
- High flexibility, allowing installation in difficult terrain and reducing mechanical stress
- Efficient jointing options (socket fusion and electrofusion) for long-term reliability
- Thermal stability and low thermal conductivity for efficient heat transfer
These characteristics make PB-1 particularly well-suited for high-temperature, chemically aggressive applications like geothermal water transport.
Project scope and system architecture
The upgraded system supplies multiple interconnected facilities, including:
- Hotel Toplica
- Hotel Petrova Gora
- The health and regeneration centre
- The municipal library
- The therapy centre
- The mud bath facility
Heating network features:
- Closed-loop system filled with potable water, eliminating the need for complex water treatment.
- Heat exchangers integrated within a central energy station.
- Two 100 m³ concrete buffer tanks store water at 30°C and 60°C.
- Flow temperature maintained at 58°C, distributed via pre-insulated PB-1 Flexalen® pipes.
Geothermal water supply lines:
- Hot water line (60°C): Distributed through insulated PB-1 service pipes.
- Cold water line (30°C): Circulated through uninsulated PB-1 pipes.
The system operates daily from 07:00 to 15:00 and allows on-site temperature control depending on facility requirements.
Outcomes and benefits
The use of Flexalen® 600 and Flexalen® PU SL pre-insulated PB-1 piping led to several key improvements:
✅ Thermal performance and consistency: Enhanced thermal delivery to wellness facilities.
✅ Durability and chemical resistance: Reduced incidence of leaks and damage due to geothermal water chemistry.
✅ Sustainability and efficiency: Lower environmental impact through energy-efficient piping and reduced thermal losses.
This project reinforces the role of PB-1 as an optimal material choice for geothermal and district heating applications, particularly in locations aiming to transition toward renewable energy.
Conclusion and more information
The renovation of Topusko’s geothermal system demonstrates the performance and sustainability benefits of Polybutene-1 piping in demanding thermal applications. With its combination of flexibility, chemical resistance, and thermal efficiency, PB-1 enables long-term reliability and reduced operating costs in geothermal infrastructure.
For more information, visit the Thermaflex website.
Sustainable thermal management in Croatia
Topusko, located approximately 100 km south of Zagreb, is known for its geothermal resources, among the highest quality in Europe. The Top-Therme complex includes indoor and outdoor pools, therapy centres, and hotels, all of which rely on stable and efficient access to geothermal water.
The objective of the project was to renovate four geothermal wells originally drilled decades ago, optimising their output and upgrading the piping infrastructure to better serve the resort’s renewable energy goals.
Geothermal system overview
The four geothermal wells collectively supply approximately 175 litres per second of thermal water, with source temperatures ranging from 68°C to 72°C. Distribution temperatures decrease to between 27°C and 34°C at the point of use. Each well supplies specific areas:
- TEB-1 (15–17 l/s): Serves the health and regeneration centre, including indoor/outdoor pools.
- TEB-4 (100 l/s): Located behind Hotel Petrova Gora, with water at approximately 68°C.
- TEB-2 and TEB-3: Feature higher source temperatures.
Modernisation of these wells supports the municipality’s long-term objective of becoming a smart, thermally powered community.
Why Polybutene-1 (PB-1)?
Geothermal water is typically high in mineral and gas content and can be chemically aggressive. Polybutene-1 was selected for its outstanding material performance under such conditions:
- Excellent chemical resistance in geothermal environments
- High flexibility, allowing installation in difficult terrain and reducing mechanical stress
- Efficient jointing options (socket fusion and electrofusion) for long-term reliability
- Thermal stability and low thermal conductivity for efficient heat transfer
These characteristics make PB-1 particularly well-suited for high-temperature, chemically aggressive applications like geothermal water transport.
Project scope and system architecture
The upgraded system supplies multiple interconnected facilities, including:
- Hotel Toplica
- Hotel Petrova Gora
- The health and regeneration centre
- The municipal library
- The therapy centre
- The mud bath facility
Heating network features:
- Closed-loop system filled with potable water, eliminating the need for complex water treatment.
- Heat exchangers integrated within a central energy station.
- Two 100 m³ concrete buffer tanks store water at 30°C and 60°C.
- Flow temperature maintained at 58°C, distributed via pre-insulated PB-1 Flexalen® pipes.
Geothermal water supply lines:
- Hot water line (60°C): Distributed through insulated PB-1 service pipes.
- Cold water line (30°C): Circulated through uninsulated PB-1 pipes.
The system operates daily from 07:00 to 15:00 and allows on-site temperature control depending on facility requirements.
Outcomes and benefits
The use of Flexalen® 600 and Flexalen® PU SL pre-insulated PB-1 piping led to several key improvements:
✅ Thermal performance and consistency: Enhanced thermal delivery to wellness facilities.
✅ Durability and chemical resistance: Reduced incidence of leaks and damage due to geothermal water chemistry.
✅ Sustainability and efficiency: Lower environmental impact through energy-efficient piping and reduced thermal losses.
This project reinforces the role of PB-1 as an optimal material choice for geothermal and district heating applications, particularly in locations aiming to transition toward renewable energy.
Conclusion and more information
The renovation of Topusko’s geothermal system demonstrates the performance and sustainability benefits of Polybutene-1 piping in demanding thermal applications. With its combination of flexibility, chemical resistance, and thermal efficiency, PB-1 enables long-term reliability and reduced operating costs in geothermal infrastructure.
For more information, visit the Thermaflex website.
