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District heating and geothermal energy synergies

How geothermal and district heating integration improves urban energy efficiency and emissions reduction

03 February 2025

The Organic Rankine Cycle (ORC) technology represents a cutting-edge solution for efficient geothermal resource exploitation. This article explores the potential of ORC systems in the geothermal field, with particular focus on their possible integration with district heating networks.

ORC Applications in Geothermal Field

ORC systems have revolutionized the exploitation of geothermal resources thanks to their thermodynamic versatility and energy efficiency across a wide spectrum of operating conditions. The technology has proven particularly effective in valorizing geothermal resources with different thermal characteristics, opening new possibilities for climate change mitigation through sustainable exploitation of this renewable source.

Characteristics and Advantages

ORC systems are distinguished by their ability to operate efficiently with geothermal resources at various temperature levels. They can generate electrical power from a resource with a minimum temperature of approximately 110-120°C. At temperatures below 110-120°C, electricity production is still possible albeit with lower efficiencies, therefore in these cases heat-only production is preferred (as in district heating applications). Above 120°C, combined heat and power configuration is always feasible, with various possible integration layouts between thermal and electrical power generation.

The ORC cycle, through the use of organic fluids with boiling points lower than water, enables significant conversion efficiencies even with moderate-temperature geothermal sources.

Performance and Reliability

The system architecture, based on a closed thermodynamic cycle, ensures high and consistent performance over time. The ORC plant can operate with remote control, guaranteeing availability above 98% with minimal maintenance requirements, ensuring efficient plant management over the long term. The inherent robustness of the technology translates into a long useful life of the installation, a particularly valued aspect in geothermal investments.

System Configurations

The implementation of ORC systems in the geothermal field can follow different configurations, optimized based on resource characteristics and plant objectives. In real applications, ORC systems are primarily implemented in two configurations: for electrical power generation only or in combined heat and power mode.

Power-Only Configuration

Optimized to maximize electrical power generation, this configuration is ideal for high-temperature geothermal sites or where no significant thermal users exist in the vicinity.

Heat and Power Configuration

Enables the exploitation of geothermal resources for both electrical and thermal power production. Particularly effective when integrated with district heating networks.

Integration with District Heating

The integration between geothermal ORC systems and district heating networks represents one of the most promising applications of this technology, offering significant opportunities for energy optimization and decarbonization at the system level.

Integration Benefits

The combination of geothermal ORC systems and district heating networks enables maximizing geothermal resource exploitation through flexible production management. The ability to adapt to seasonal demand variations, coupled with optimization of overall system efficiency, allows for significant CO₂ emissions reduction.

Turboden Application Examples

The Holzkirchen plant in Germany represents an exemplary case of a geothermal ORC system integrated with district heating. The ORC unit, powered by a medium-temperature geothermal source, demonstrates the effectiveness of this technology in valorizing geothermal resources for combined applications.

Similarly, the Traunreut plant shows how ORC systems can effectively exploit moderate-temperature geothermal resources (110-130°C) in heat and power configuration, adapting production to seasonal thermal demand variations.

Future Prospects

The continuous development of ORC technology in the geothermal sector opens new application frontiers, with particular attention to high-efficiency cogeneration and smart grid integration. A progressive evolution toward solutions capable of exploiting increasingly lower temperatures is observed, while integration with smart energy networks and implementation of advanced control systems are significantly expanding this technology's field of application.

Conclusions

ORC systems represent a key technology for efficient geothermal resource exploitation. Their ability to operate across a wide temperature range, combined with the possibility of integration with district heating systems, makes them an ideal solution for maximizing geothermal resource value in sustainable energy projects. As demonstrated by numerous successful installations in Europe and worldwide, choosing an experienced energy solutions partner with proven expertise is fundamental for ensuring optimal performance and long-term reliability.

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