The SUSHEAT project has released two new infographics that explain, in a concise and visual way, key technological solutions being developed by the consortium:
(1) the functionality of closed-loop waste heat recovery for industrial heat, and
(2) the design of Thermal Energy Storage (TES) tanks for higher energy efficiency.
The infographics translate complex engineering concepts into clear process flows, helping researchers, industry stakeholders, and the wider public understand how SUSHEAT’s technologies capture, upgrade, store, and deliver renewable and recovered heat for industrial use.
These visuals reflect the core ambition of SUSHEAT: to make high-temperature renewable heat technically viable, economically attractive, and operationally reliable for sectors that today still rely heavily on fossil fuels.
Strategic Importance of Reusable Heat in Industrial Decarbonisation
Industrial processes account for a large share of global energy use and CO₂ emissions, largely because many of them require high-temperature heat for operations such as steam generation, drying, pasteurisation, distillation, and chemical reactions. Much of this heat is still produced by burning fossil fuels, and at the same time, vast quantities of thermal energy are released as waste heat into the environment.
From an efficiency perspective, this is a missed opportunity. Waste heat is already paid for in energy and emissions terms, yet it is often too low-grade, too variable, or too poorly integrated into plant operations to be reused. Recovering and upgrading this heat can directly reduce fuel consumption, cut CO₂ emissions, and improve the overall energy productivity of industrial systems.
Sustainability goals reinforce this need. To align with European and global climate targets, industry must significantly reduce emissions in the coming decades. Electrification alone is not sufficient if high-temperature heat cannot be delivered efficiently from renewable or recovered sources. What is required are systems that can:
- Capture waste and ambient heat,
- Upgrade it to useful temperature levels,
- Store it when supply and demand do not match,
- And deliver it reliably to industrial processes.
SUSHEAT is built around this challenge. The project focuses on enabling renewable, circular heat flows that replace fossil fuel boilers and reduce dependence on imported energy, while maintaining the reliability and temperature levels industry needs.
Technological Scope and Objectives of the SUSHEAT Project
SUSHEAT brings together 14 partners from 10 countries to develop and validate a new class of high-temperature renewable heat systems. The project integrates three technological pillars into a coherent energy concept:
The SUSHEAT heat pump is designed to upgrade low-temperature heat sources, such as waste heat from processes, ambient air, or solar thermal input, into the 150 °C to 250 °C range. This temperature range is essential for many industrial operations but has historically been difficult to reach with efficient, low-carbon technologies. By using advanced thermodynamic cycles and low-GWP working fluids, the SUSHEAT heat pump enables electrified heat production at temperatures previously dominated by fossil fuels.
Because renewable and waste heat sources are often intermittent or variable, storage is essential. SUSHEAT uses phase change materials (PCMs) to store large amounts of heat in compact volumes. PCMs absorb and release heat at nearly constant temperatures, which is ideal for industrial processes requiring stable thermal input. SUSHEAT advances this technology by improving heat transfer inside the storage tanks, overcoming a key limitation of conventional PCM systems.
SUSHEAT includes several innovative technologies to facilitate the integration of renewables into industry at the temperature range of 150-250°C. Apart from the harvesting energy from waste heat, the SUSHEAT concept includes concentrated solar heat through a Linear Fresnel Collector (LFC) to support the heating process when weather conditions allow for it.
The entire system is coordinated through digital and AI-based control tools. The CIT uses real-time data and predictive models to decide when to store, upgrade, or deliver heat. This allows the system to respond to changes in energy availability, process demand, and electricity prices, maximising efficiency and operational flexibility.
Together, these components form a closed-loop, smart heat system designed to operate at Technology Readiness Level 5, validating performance in relevant environments and preparing the ground for future industrial deployment.
Advanced TES Tank Design Based on Bio-Inspired Heat Transfer Principles
One of the new infographics focuses on Thermal Energy Storage tank design, specifically using phase change materials. PCMs store energy in the form of latent heat, which means they absorb or release large amounts of energy during phase transitions (for example, from solid to liquid) at nearly constant temperature.
The storage process has two main phases:
- Charging (Heat Storage):
The PCM first warms up to its melting temperature. At this point, it absorbs heat while changing from solid to liquid. During this phase transition, temperature remains nearly constant while energy is stored in the material’s structure. Once fully melted, the liquid PCM can continue to absorb sensible heat as its temperature rises.
- Discharging (Heat Release):
When heat is needed, the liquid PCM cools. As it reaches its solidification temperature, it releases the stored latent heat while changing back into a solid, again at nearly constant temperature. This makes PCMs well suited for applications that require stable heat delivery.
The major technical challenge with PCMs is their low thermal conductivity. Heat moves slowly through the material, limiting how fast the storage can be charged or discharged. SUSHEAT addresses this with a bio-inspired TES tank design developed by researchers at the University of Lleida.
The design is inspired by branched vein networks found in nature, such as blood vessels in the human body or the phloem structure in plant leaves. These branching patterns distribute fluids and energy efficiently across large areas. In the SUSHEAT TES tank, a similar internal structure enhances heat transfer between the heat exchanger and the PCM, increasing the effective surface area and shortening heat pathways.
The result is faster, more uniform charging and discharging of the storage tank, improving its usefulness in real industrial conditions where heat demand can change quickly. This concept has been published in Applied Sciences and represents a key innovation in making PCM-based storage viable for high-temperature industrial use.
The infographic explains these mechanisms step by step, helping viewers understand not just what PCMs do, but how design choices directly affect system performance.
Closed-Loop Waste Heat Recovery Architecture for Industrial CO₂ Emission Reduction
The second infographic explains the closed-loop heat recovery concept at the heart of SUSHEAT. Three novel key technologies are being developed and validated up to Technical Readiness Level (TRL) 5:
- An efficient, heat temperature upgrade (150-250°C) using a Stirling-based high-temperature heat pump working with low-global-impact-potential fluids to achieve the target high-temperature heat upgrade.
- A newly designed and bio-inspired highly efficient Thermal Energy Storage (TES) system using a Phase Change Material (PCM) that is adaptable to the heat requirements at target temperatures which can provide system flexibility.
- A digital twin smart Control and Integration Twin system based on AI and fed by industrial demonstration data.
In conventional systems, waste heat is often vented to the environment. In SUSHEAT’s approach, this heat becomes a valuable input.
The system works through several coordinated stages:
- Collection:
Waste heat from industrial processes, ambient sources, or solar thermal systems is captured, typically at temperatures below 100 °C.
- Low-Temperature Storage:
This energy is stored in a first TES unit designed for lower temperatures. This acts as a buffer, allowing energy to be accumulated even when it cannot be used immediately.
- Heat Upgrade:
The high-temperature heat pump raises the temperature of the stored or incoming heat to the level required for industrial processes.
- High-Temperature Storage:
Upgraded heat is stored in a second TES unit, using PCMs with higher melting points (up to around 180 °C and beyond in SUSHEAT’s design).
- Delivery to Process:
Heat is supplied on demand for steam generation, drying, or other thermal operations.
- AI-Based Control:
An intelligent control system continuously optimises the flow of energy between sources, storage, and processes, balancing efficiency, availability, and cost.
This two-battery approach, one for low-temperature and one for high-temperature heat, allows SUSHEAT to manage the mismatch between intermittent energy sources and continuous industrial demand. It also enables the system to operate flexibly under varying conditions, making it suitable for different industrial sectors.
The infographic shows how this closed loop reduces CO₂ emissions by replacing fossil heat with upgraded renewable and recovered energy, while still meeting the strict temperature and reliability requirements of industry.
SUSHEAT Contribution to the EU Climate Ambitions
SUSHEAT directly contributes to the European Union’s ambitions to reduce CO₂ emissions, improve energy efficiency, and strengthen the sustainability of the industrial sector. By enabling renewable and recovered heat to replace fossil-based thermal energy in high-temperature processes, the project supports the EU Green Deal and the transition toward a climate-neutral economy.
To learn more about the latest progress, technologies, partners, and demonstrations behind these infographics, we invite you to further explore the SUSHEAT website. It provides in-depth information on system development, publications, events, and opportunities for collaboration across research and industry.
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