Belgium’s Calyos Demonstrates Passive Cooling Technology for High-Power Military Electronics.

Belgian thermal technology company Calyos presented its passive two-phase cooling systems for high-power electronics at the Brussels European Defence Exhibition and Conference (BEDEX). The pump-free technology aims to improve reliability, silence, and maintenance efficiency in defence platforms, aerospace systems, and critical digital infrastructure.

At the Brussels European Defence Exhibition and Conference (BEDEX), Belgian company Calyos showcased its passive thermal management technologies designed for high-power electronic systems used in defence, aerospace, and critical digital infrastructure. Founded in 2012, the firm develops two-phase cooling systems that dissipate heat without pumps, water circulation, or moving mechanical components. The technology relies on sealed phase-change loops to transfer heat efficiently, offering a silent, energy-efficient, and maintenance-free alternative to conventional cooling methods increasingly challenged by rising power densities in modern military electronics.
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Calyos’ two-phase cooling system dissipates several kilowatts of heat through passive fluid evaporation and condensation, providing low-energy, vibration-free cooling for high-power defence electronics. (Picture source: Calyos)

Calyos designs and manufactures several families of passive thermal technologies, including Heat Pipes (HP), Loop Heat Pipes (LHP), Micro-Channel Heat Pipes (MCHP) and Pulsating Heat Pipes (PHP). These systems operate on the principle of phase change. A dielectric refrigerant fluid absorbs heat generated by electronic components and vaporizes. The vapour then travels to a cooler section of the system where it condenses, releasing heat before returning to the evaporation zone through capillary forces. This closed cycle enables highly efficient heat transfer without requiring external energy input or mechanical devices. The absence of moving parts increases reliability and reduces maintenance requirements, which is relevant for military systems operating in remote or demanding environments.

These technologies address a growing challenge for modern military platforms. The increasing integration of advanced sensors, processors dedicated to artificial intelligence, electronic warfare systems and high-performance computing modules generates rising thermal loads within increasingly compact architectures. Temperature control is critical because overheating can degrade electronic performance, reduce system reliability and shorten equipment lifespan. Passive two-phase cooling systems allow engineers to manage high heat flux densities while limiting energy consumption and system complexity.

At BEDEX, Calyos highlighted the relevance of its solutions for defence electronics, command-and-control infrastructure and deployable data-processing capabilities. Modern military operations rely heavily on digital networks, secure communications systems and advanced data-processing capabilities. These functions often depend on data centres or high-performance computing platforms installed in fixed bases or mobile command posts. Cooling such systems traditionally requires large amounts of energy and water, which can become a logistical constraint in operational environments.

Calyos technologies aim to reduce these constraints by providing cooling systems that operate without water and without active pumping systems. According to the company, its passive two-phase systems can reduce energy consumption related to cooling by up to 50 percent compared with conventional approaches. In addition to energy efficiency, these systems operate silently and maintain stable thermal performance in environments characterized by vibration, dust and extreme temperatures. These characteristics are relevant for military equipment integrated into armoured vehicles, avionics systems, naval combat platforms or deployable command centres.

The company also highlights the role of these technologies in improving operational resilience and autonomy. By eliminating water dependency and reducing energy requirements, passive cooling solutions facilitate the deployment of computing infrastructure in remote or austere locations. This can support advanced command systems, edge-computing platforms and intelligence-processing capabilities that must operate reliably with limited logistical support.

Calyos was recently selected for the Defence Innovation Accelerator for the North Atlantic (DIANA) programme under NATO’s Energy and Power challenge. This initiative aims to identify and accelerate dual-use technologies that can strengthen the technological edge of the Alliance. Within this framework, Calyos’ passive two-phase cooling solutions are being explored for their potential to improve the energy efficiency and resilience of data-centre infrastructure used in both civilian and defence environments.

In parallel, the company is also involved in the OSYRYS project led by Safran Electrical & Power, which focuses on technologies related to cleaner aviation. The programme aims in particular to improve thermal management solutions for next-generation aircraft systems, an issue that is becoming more important as the electrification of aviation platforms increases heat dissipation requirements.

Calyos has established a position in the field of advanced thermal management. Its customers include Airbus, Honeywell, Valeo, Liebherr, Alstom and the European Space Agency (ESA). The company also receives support from the European Regional Development Fund (ERDF) and the Walloon Region, reflecting broader European efforts to develop technological capabilities in strategic industrial sectors.

Calyos also notes that its cooling solutions can be designed and manufactured entirely in Belgium and Europe. This supports supply-chain security and technological sovereignty in sectors such as defence and aerospace. In a context where armed forces are seeking to reduce dependence on foreign critical technologies, this European industrial capability represents an additional strategic factor.

The presence of Calyos at BEDEX reflects the growing importance of advanced thermal management in modern defence systems. As military platforms integrate increasing amounts of digital and electronic capabilities, effective equipment cooling becomes an important factor for maintaining performance, reliability and energy efficiency in the digital infrastructure that supports contemporary military operations.

Written By Erwan Halna du Fretay - Defense Analyst, Army Recognition Group
Erwan Halna du Fretay holds a Master’s degree in International Relations and has experience studying conflicts and global arms transfers. His research interests lie in security and strategic studies, particularly the dynamics of the defense industry, the evolution of military technologies, and the strategic transformation of armed forces.