Periodic Reporting for period 1 - THUNDER (THermochemical storage Utilization eNabling Data centre seasonal Energy Recovery)
Période du rapport: 2024-01-01 au 2025-06-30
Data centres (DCs) are the backbone of the digital economy, but they are also major energy consumers, accounting for 1–2% of global electricity use. In Europe, their electricity demand is projected to reach 98.5 TWh/year by 2030, corresponding to 3.2% of total electricity demand. Most of this energy ultimately becomes waste heat, which is typically released into the environment via cooling systems. Even with energy-efficient practices, the amount of waste heat generated is substantial—estimated at 50 TWh/year, enough to meet the heating needs of about 2.5% of the European building stock. Despite this potential, waste heat recovery (WHR) from data centres is underutilized due to the relatively low temperature of the waste heat, the mismatch between when heat is produced (often in summer) and when it is needed (mainly in winter), and technical, economic, and regulatory hurdles to integrating DC waste heat into district heating networks (DHNs). However, the political and strategic context is rapidly evolving, with the European Commission pushing for greater energy efficiency and sustainability in data centres, through new regulations and funding initiatives. Moreover, updates to the Energy Efficiency Directive (EED) and Renewable Energy Directive (RED) are making heat recovery mandatory above certain thresholds and the EU Taxonomy Regulation is setting sustainability criteria for investments, including waste heat recovery. There is thus growing pressure and opportunity for data centres to become active contributors to sustainable urban energy systems.
In this context, the THUNDER Project aims to unlock the untapped potential of data centre waste heat by developing and demonstrating innovative, efficient, and cost-effective seasonal thermal storage solutions based on thermochemical materials (TCMs), which offer high energy density, near-zero thermal losses, and modularity for urban environments. These storage systems will be integrated with high-temperature heat pumps to upgrade low-grade waste heat to useful temperatures for district heating. The full system will be validated in a real-world demo site in Varna, Bulgaria, including both fixed and mobile (“Heat on Wheels”) storage solutions, to overcome the challenge of direct DC-to-DHN connection. Replicability and scalability will be assessed by conducting pre-feasibility studies in 10 additional sites across Europe and novel business and financial models for DC heat recovery will be developed, including “energy as a service” concepts, and address regulatory and policy barriers. Co-design and training workshops will involve stakeholders and raise social awareness, supporting market uptake and replication. A holistic sustainability assessment (environmental, economic, social) will be delivered, ensuring alignment with EU Taxonomy and Sustainable Development Goals (SDGs).
Demonstration activities will provide operational proof of concept, with the goal of achieving:
• At least 70% storage efficiency
• Energy density of 120 kWh/m³ (double current commercial TCMs)
• Halved capital costs for TCM storage
• Significant energy and CO2 savings (e.g. 90 kWh/m³ and 24 kgCO2/m³ of TCM storage, compared to methane heating)
In this context, the THUNDER Project aims to unlock the untapped potential of data centre waste heat by developing and demonstrating innovative, efficient, and cost-effective seasonal thermal storage solutions based on thermochemical materials (TCMs), which offer high energy density, near-zero thermal losses, and modularity for urban environments. These storage systems will be integrated with high-temperature heat pumps to upgrade low-grade waste heat to useful temperatures for district heating. The full system will be validated in a real-world demo site in Varna, Bulgaria, including both fixed and mobile (“Heat on Wheels”) storage solutions, to overcome the challenge of direct DC-to-DHN connection. Replicability and scalability will be assessed by conducting pre-feasibility studies in 10 additional sites across Europe and novel business and financial models for DC heat recovery will be developed, including “energy as a service” concepts, and address regulatory and policy barriers. Co-design and training workshops will involve stakeholders and raise social awareness, supporting market uptake and replication. A holistic sustainability assessment (environmental, economic, social) will be delivered, ensuring alignment with EU Taxonomy and Sustainable Development Goals (SDGs).
Demonstration activities will provide operational proof of concept, with the goal of achieving:
• At least 70% storage efficiency
• Energy density of 120 kWh/m³ (double current commercial TCMs)
• Halved capital costs for TCM storage
• Significant energy and CO2 savings (e.g. 90 kWh/m³ and 24 kgCO2/m³ of TCM storage, compared to methane heating)
Key Technical and Scientific Activities that will be carried out by the THUNDER project and related results will include:
• Analysis of the market, technical, and regulatory conditions for waste heat recovery from data centres, focusing on both the demonstration site in Bulgaria and broader European replicability.
• Development of the overall THUNDER conceptual design, defining a strategy for utilizing thermal energy storage systems to improve the energy efficiency, economic feasibility, and environmental sustainability of recovering waste heat from data centres and reusing it in urban district heating networks.
• Identification and adaptation of best practices for integrating waste heat recovery, seasonal storage, and district heating networks.
• Selection, characterization, and testing of innovative thermochemical materials that can store heat efficiently for long periods with minimal losses.
• Design, implementation and testing of laboratory and real-world prototypes of thermochemical storage systems with a modular and scalable design, suitable for different urban settings and space constraints.
• Development and optimization of high-temperature heat pumps specifically designed to upgrade the temperature of waste heat, making it suitable for storage and district heating.
• Development of advanced algorithms using model predictive control (MPC) and machine learning to optimize when and how heat is stored, transported, and used, minimizing costs and maximizing efficiency.
• Integration and demonstration of all system components at a real data centre and district heating network in Varna, Bulgaria.
• Installation of a comprehensive monitoring system to collect operational data, enabling continuous optimization and impact assessment.
• Assessment of the environmental and economic impacts of the solutions throughout their life cycle, from material sourcing to operation and end-of-life.
• Identification and analysis of at least 10 additional sites across Europe where the THUNDER solution could be replicated, conducting feasibility studies to support future deployments.
• Analysis of the market, technical, and regulatory conditions for waste heat recovery from data centres, focusing on both the demonstration site in Bulgaria and broader European replicability.
• Development of the overall THUNDER conceptual design, defining a strategy for utilizing thermal energy storage systems to improve the energy efficiency, economic feasibility, and environmental sustainability of recovering waste heat from data centres and reusing it in urban district heating networks.
• Identification and adaptation of best practices for integrating waste heat recovery, seasonal storage, and district heating networks.
• Selection, characterization, and testing of innovative thermochemical materials that can store heat efficiently for long periods with minimal losses.
• Design, implementation and testing of laboratory and real-world prototypes of thermochemical storage systems with a modular and scalable design, suitable for different urban settings and space constraints.
• Development and optimization of high-temperature heat pumps specifically designed to upgrade the temperature of waste heat, making it suitable for storage and district heating.
• Development of advanced algorithms using model predictive control (MPC) and machine learning to optimize when and how heat is stored, transported, and used, minimizing costs and maximizing efficiency.
• Integration and demonstration of all system components at a real data centre and district heating network in Varna, Bulgaria.
• Installation of a comprehensive monitoring system to collect operational data, enabling continuous optimization and impact assessment.
• Assessment of the environmental and economic impacts of the solutions throughout their life cycle, from material sourcing to operation and end-of-life.
• Identification and analysis of at least 10 additional sites across Europe where the THUNDER solution could be replicated, conducting feasibility studies to support future deployments.
The THUNDER project is expected to produce significant impact in the EU by developing sustainable waste heat recovery and seasonal storage solutions available to data centres in urban environments, to supply heat to neighbouring DHNs. The project will generate scientific impacts, by providing high-quality knowledge about thermal energy storage using TCMs, usable in different applications for medium long terms, ensuring a low land/space footprint due to high energy density and using abundant and no critical raw material. From a societal standpoint, THUNDER will broaden available energy savings options by offering a viable way to recover waste heat from data centers, not limited to land availability or specific waste heat characteristics, as high temperature. THUNDER will also generate positive economic impacts by providing a consistent methodology for DC cooling to DHN optimization with seasonal storage, and will also guarantee a reduction of actual costs of the seasonal storage under 30€/kWh and comparable with water tank thermal energy storage.