Unlocking the Potential of Waste Heat Reuse: How Greece’s Growing Data Center Sector Can Benefit from MODERATOR’s Innovations

ITA S.A.

Greece is rapidly emerging as one of Europe’s most attractive destinations for large-scale data center investments. With hyperscalers and national, as well as international operators, announcing new facilities across Attica, Crete, and Northern Greece, the country is stepping into a new era of digital infrastructure. Abundant renewable energy potential, strategic geographical positioning, and strong governmental support have helped cultivate this momentum. This expansion is transforming Greece into a strategic node for cloud services in Southeastern Europe.

However, as data center capacity grows, so does the need to manage energy consumption, improve efficiency, and support national and European sustainability goals. In this evolving landscape, the ability to capture and reuse waste heat becomes a compelling opportunity—one that aligns with modern legislative requirements and advances environmental performance.

Across Europe, policymakers are sharpening their focus on the environmental impact of data centers. New and upcoming regulations increasingly require operators not only to use renewable energy and reduce electricity demand but also to manage noise levels in urban or peri-urban siting and, crucially, to recover and reuse a portion of the heat they generate. One of the most notable examples is Germany’s Energy Efficiency Act (EnEfG), which mandates that newly commissioned data centers must progressively increase their waste-heat reuse: 10% from July 1, 2026; 15% from July 1, 2027; and 20% from July 1, 2028. These requirements signal a clear shift in European expectations and provide a model that other EU countries, including Greece, are likely to follow as they update their regulatory frameworks for large digital infrastructure.

Within this changing context, the Horizon Europe research project MODERATOR offers a technological blueprint for the next generation of high-efficiency, low-impact data centers. The project aims to revolutionize energy management by demonstrating how immersion cooling and advanced thermal storage systems can dramatically increase both the capture and reuse of low-temperature waste heat. As Greece continues to expand its data center footprint, MODERATOR’s innovations point toward a path where digital growth and climate responsibility can go hand in hand.

At its core, MODERATOR is developing a fully integrated system that includes several groundbreaking components. First, the project is designing a high-efficiency immersion cooling architecture, meticulously engineered to maximize heat extraction at optimal temperatures. Unlike traditional air-cooling techniques, immersion cooling allows nearly all of the generated server heat to be captured directly through a liquid medium, significantly improving thermal efficiency.

Second, MODERATOR incorporates an innovative thermal energy storage unit based on phase-change materials (PCMs). These materials enable the system to store up to 500 kWh of thermal energy while maintaining stable temperatures, thus allowing heat to be transferred and reused even when demand does not coincide with peak data center operation. This is especially important for applications in agriculture, hospitality, and industry, where heat demand varies throughout the day or season.

Third, the project includes the development of a multi-layer insulation system composed of recycled materials. This advanced insulation minimizes thermal losses during heat recovery and transportation, improving overall system efficiency and reducing environmental impact. All these technologies are integrated into a fully automated 40-kW immersion-cooled data center prototype, representing a complete and operational demonstration of MODERATOR’s approach.

The potential applications of captured waste heat are particularly significant in Greece, where the agricultural, hospitality, and industrial sectors play a central role in the national economy. Reused heat can enable greenhouses to regulate temperature, support aquaculture farms, provide hot water for hotels and spas, power industrial drying processes, or contribute to heating buildings in the tertiary sector.  

Importantly, the reuse of waste heat also aligns with emerging legislative trends. As the EU pushes for stricter energy performance criteria under the Energy Efficiency Directive (EED) and the upcoming revisions of data center reporting obligations under the EU taxonomy, operators will be expected to demonstrate concrete actions on energy efficiency, renewable energy sourcing, and environmental impact mitigation. Requirements will increasingly mandate renewable electricity, compliance with strict noise-control regulations for data centers near residential or mixed-use areas, and transparent reporting of heat reuse potential.

Projects such as MODERATOR, therefore, not only drive technological innovation—they also help prepare the market for regulatory compliance. The immersive-cooling-plus-storage approach demonstrates how low-grade heat, traditionally wasted, can be transformed into a valuable energy resource. This is precisely the kind of systemic efficiency improvement envisioned by European legislation, and an essential step for ensuring that Greece’s accelerating data center expansion develops sustainably.

As Greece continues its digital transition, MODERATOR showcases a vision where data centers are no longer passive consumers of massive amounts of electricity but active contributors to circular energy systems. By embracing waste heat recovery, renewable energy integration, and smart design principles, data centers can become energy hubs that support communities, industries, and regional development. With strong legislative signals now emerging across Europe, and with enabling research like MODERATOR paving the way, Greece is well-positioned to lead in the creation of sustainable, next-generation digital infrastructure.