The provision of cold is a vital foundation of modern society to underpins many aspects of modern life, consumes up to 14% of the UK's electricity, and is also responsible for around 10% of UK's greenhouse gas emissions, including both CO2 associated with their power consumption and leakage of refrigerants with high Global Warming Potential (GWP). In order to achieve net-zero emission target in 2050 in the UK, we must significantly decarbonise the cooling sector.
The decarbonisation of the cooling section requires to tackle two key challenges. Firstly, the leakage of traditional, refrigerants with high GWP is a key issue of the greenhouse gas emission of the cooling sector. It is, therefore, necessary to substitute them with low GWP natural refrigerant such as CO2. Secondly, the high-power consumption of the cooling sector also results in greenhouse gas emission if non-renewable power is consumed. Hence, cost-effective cold storage capacity will need to be deployed to maximise the use of intermittent renewable energy and cheap off-peak electricity. The recent study concluded that the addition of cold storage can potentially provide a 43% decrease in peak period consumption.
In response to the challenges identified above, this project aims to develop a novel integrated system for cold energy generation and storage using CO2 hydrate as both refrigerant and storage material, contributing to the decarbonisation of the cooling sector in the UK and more widely the global. The multidisciplinary consortium, consisting of six leading researchers from the Universities of Birmingham, Glasgow and Heriot-Watt, processes a wide range of well-balanced expertise including chemical engineering, thermodynamics, heat transfer, CFD, and economics to address several key scientific and technical challenges, and is further supported by several leading industrial partners to maximise knowledge exchange and impact delivery.

Potential Impact:
The GREEN-ICEs project aims to contribute to net-zero emission target in 2050 in the UK by developing an integrated approach for cooling power generation and storage with the development of CO2 hydrate. A novel method to rapidly, continuously and economically produce the CO2 hydrate slurry by spraying subcooled liquid CO2 into the pressurized reactor, and a new method for ice slurry production through the throttling expansion process of high concentration CO2 hydrate, as well as a dynamic and reliable modelling code for simulating the GREEN-ICEs system, will be developed. This research will help reduce the current cold energy demand from fossil sources and facilitate within the UK a healthier and more sustainable energy system and low carbon energy market. The research will also accelerate the development of the next generation refrigerant and the deployment of carbon capture and utilization in the UK.
Through the implementation of this project, the following groups will benefit from the research:
- Academic communities working on research areas of cold energy storage, cold chain, CO2 capture and utilization, chemical reaction and process, heat exchanger design, system optimization, etc. Both the experimentalists and modelling researches could benefit from the project outcomes directly. These outcomes involve new scientific discoveries, understandings, and methodologies of CO2 hydrate formation, transportation, and dissociation process; knowledge concerning the heat transfer process of transcritical/supercritical CO2 flow for the optimal design of devices; and new knowledge on system modelling and the related techno-economic performance.
- UK industry associated with refrigeration, cold energy storage and cold chain applications (food, medical protective and transport), etc. They will benefit from the novel results in terms of new refrigerant production, CO2 utilization, heat exchanger and system design and performance optimization, to improve their competitiveness and maintain a leading position in the market.
- UK Energy policymakers. This project outcome will offer future technology options in cold energy storage towards decarbonisation of cold supply, and can also offer a broadened range of technologies for deployment of CO2 capture and utilization. These impacts will be achieved by engaging with stakeholders and policymakers as planned.
- UK Environment. This project will develop novel environment-friendly slurries through the dispersion of CO2 hydrate in water which is capable of carrying cold in secondary loops, then reducing the refrigerant amount in the cold system. This will benefit the availability of hydrofluorocarbons and also the fossil sources reduced in the UK. In addition, it will play a significant role in developing net-zero emission cold energy storage technology, benefitting for fighting global warming.
- UK Economy and Society. The addition of cold storage can potentially provide a 43% decrease in peak period consumption. Chilled water storage is most commonly used but only on very large projects (typically over 5,000m3). Ice storage (both ice block and ice slurry) is more compact but requires an additional heat transfer system that uses ethylene (or propylene) and also consumes more chiller energy due to lower refrigeration temperature. This project aims to develop new CO2 hydrate based cold energy storage technology which will help support the role out of cold energy in the UK that potentially contribute to a sustainable and low carbon society, and also help public understand the development of new cold storage science and technology.
- The PRDAs, PhD students and engineers involved in the research teams and industry partners. They will receive critical training that related to the CO2 hydrates formulation, transportation and dissociation processes as well as system numerical modelling and experimental skills during the project, benefiting UK's future research capacity in this regard.