The findings from a year of modelling, simulation and materials research
HydroCool follows a clear path from concept to prototype, covering sustainability, cost and market potential along the way. Work Package 1 sits right at the beginning of this journey. Its role is to answer some fundamental questions. Does the concept work? Under which conditions? And what are the key materials, performance targets, and constraints that will shape the system?
By the time WP1 is completed, the project is no longer dealing with an abstract idea. It has a validated concept, a clear understanding of its performance, and a solid foundation to move into design and construction.
This blog takes a closer look at that first step and the insights that are now guiding the rest of the HydroCool project.
The first challenge at the start of the project was to define how the HydroCool system should operate for all different use cases. This required building a detailed thermodynamic model capable of simulating real operating conditions.
The teams involved have developed a complete modelling framework that allowed them to explore different system configurations and operating models. These simulations made it possible to compare HydroCool with conventional refrigeration systems. The results are promising, and one deserves particular emphasis: the use of isothermal compression shows clear efficiency gains, with significantly higher coefficients of performance under certain conditions.
This work served a dual purpose: confirming the viability of the concept and identifying the most suitable system designs depending on the application.
A central innovation in HydroCool is the use of a liquid piston to compress CO₂ in a near-isothermal way, meaning the temperature remains nearly constant throughout the process and reduces energy losses compared to conventional compressors. This key distinction needed to be carefully validated.
To do this, advanced simulations were carried by Storage Drop and Universitat Rovira i Virgili (URV) out to study how CO₂ interacts with the liquid during compression. These analyses showed that achieving strong mixing between the gas and the liquid is essential. When this is done correctly, the system can reach pressures close to 80 bar while reducing energy consumption.
The results indicate that this approach can deliver energy savings of up to around 40 percent compared to traditional compression methods. At the same time, the work helped define important design requirements that will guide the engineering phase.
Another key aspect of the system is the liquid used in the piston. This fluid needs to perform reliably at very low temperatures and must not interact negatively with CO₂. This is important to ensure operation in demanding applications such as deep-freeze conditions down to around −40°C.
The teams behind this task, Centre National de la Recherche Scientifique and University Clermont Auvergne carried out an extensive screening process combining literature review and experimental testing. As a result, ten promising liquid piston fluids were identified. These include different types of aqueous solutions and organic mixtures.
The analysis highlighted the main challenges, such as CO₂ solubility, corrosion risks and potential formation of hydrates. These insights are crucial for selecting and optimising the fluid in the next phase of the project.
Beyond technical performance, HydroCool aims to offer clear environmental and economic benefits. To assess this, a preliminary life cycle assessment and cost analysis were performed by AristEng with the support of Storage Drop and URV.
The findings show strong potential. The system could reduce climate impact by around 50 percent compared to conventional cooling technologies. It also shows lower electricity demand and improved energy efficiency.
From an economic perspective, the estimated cost of cooling is significantly lower than current solutions. This combination of lower emissions and reduced operating costs strengthens the case for future adoption in industry.
To ensure that progress can be tracked consistently throughout the project, a comprehensive set of key performance indicators was defined by URV, Storage Drop and Inveniam Group. These indicators cover energy performance, technical reliability, economic viability, environmental impact and social aspects.
In total, twenty KPIs were established. They will be used from early modelling stages through to experimental validation and final system assessment. This ensures that every claim about HydroCool’s performance can be backed by consistent, traceable evidence throughout the project.
By the end of this first work package, HydroCool has moved from concept to a validated and well-understood system design. The project now has a clear view of how the technology performs, what challenges need to be addressed, and where its main advantages lie.
With this foundation in place, the project now moves into detailed design and the construction of a real prototype.
Authors: Guillem Figueras & Lucía Salinas
