District heating and cooling (DHC) networks are centralized systems for distributing thermal energy designed to climatize buildings and urban infrastructures with higher efficiency than conventional decentralized systems. These urban energy systems come in various configurations, among which low-temperature or 5th-generation district heating and cooling networks (5GDHC) stand out. They represent a fundamental technological advancement for decarbonizing the thermal sector and optimizing energy flows from low-temperature waste heat.
Differences from conventional networks
Conventional district heating and cooling networks operate at high temperatures (70–120°C for heating and 6–8°C for cooling), which leads to significant transport losses and limits the integration of renewable and waste energy sources.
In contrast, low-temperature networks operate within a more efficient range: between 30–60°C for heating and 10–20°C for cooling. These temperatures reduce thermal losses, improve synergy with low-energy heat sources (usable thermal energy), and increase the efficiency of heat pumps connected to the system.
Technical and operational advantages
Low-temperature DHC networks offer numerous benefits:
- Higher energy efficiency: They reduce distribution losses and increase the overall performance of the system.
- Integration of renewable and waste energy sources: They enable the use of low-enthalpy geothermal energy, solar thermal energy, and the recovery of waste heat from industries and data centers, among others.
- Reduction of carbon footprint: They contribute to the energy transition and climate neutrality goals by supplying renewable thermal energy.
- Cost optimization: They reduce the need for initial investment in the distribution network and the connected systems, and extend the lifespan of network materials.
- Compatibility with high-efficiency buildings: They improve building energy performance, facilitate compliance with nZEB (Nearly Zero Energy Buildings) standards, and can be easily integrated into energy renovation projects.
Real-world applications of DHC networks
Recently, many headlines have highlighted the environmental impact of Artificial Intelligence (AI), whose societal use is rapidly growing. The increase in data processing has caused a surge in the energy demand of data centers, which currently consume 3% of the EU’s electricity. Their environmental impact is expected to grow significantly unless renewable energy sources are prioritized, particularly for cooling systems.
Data processing centers (DPCs) generate large amounts of waste heat, which can be reused through low-temperature networks to heat buildings or support industrial processes.
At Aiguasol, we have participated in pioneering projects in this field, such as RENEWIT (2016), in collaboration with IREC, aiming to develop innovative strategies to improve data center efficiency. Among the highlighted solutions, we analyzed the recovery of server waste heat to feed urban district heating networks.
We also worked on the Miramón Data Center project (2017), where airflow inefficiencies were identified. Through low-cost solutions such as rack reorganization, the implementation of hot and cold aisles, and server containment, energy demand was reduced by 10–15%.
The ideal solution for each data center depends on factors such as geographic location, construction year, and available technology. For instance, in colder regions, free cooling (use of outside air) can be maximized, while in urban or industrial environments, synergies can be established to reuse waste heat.
A look into the energy future
Low-temperature DHC networks are a high-performance technical solution for urban and industrial energy management. Their ability to integrate renewable sources and reuse waste heat positions them as essential energy infrastructure for the energy transition.
To promote them, it’s vital to implement economic incentives, create supportive legal and regulatory frameworks, and foster public-private collaboration. Additionally, investment in professional training and raising public awareness about the benefits of these systems are key. They must also be integrated with renewable energy sources and properly planned within urban design. Their implementation contributes to the creation of new economic opportunities and local employment—an essential factor for social cohesion during the transition.
At Aiguasol, we continue working on developing business models to drive them forward through initiatives such as the LIFE European project, focused on preparing investment plans for low-temperature DHC projects, consolidating them as a key technology for smart cities and future energy sustainability. Along these lines, we have also participated in various national and international DHC network development projects, including the planning and implementation of systems in the Ecodistrict of Mercedes (Barcelona), the Seda-Paperera district in Prat de Llobregat, San Pedro (Costa Rica), or the hotel districts in Varadero and Cayo Largo (Cuba), contributing to the global expansion of this cleaner and more efficient energy model.