Cryogenic-temperature Cold Storage using Micro-encapsulated Phase Change Materials in Slurries

Cryogenic-temperatures cold storage is the Cinderella in thermal energy storage. According to the recent DOE global energy storage database, until now there are globally 166 thermal storage projects in operation or under construction for renewable energy time-shift/capacity firming or electric bill management, with a total capacity of 3365MW. However most of these projects are molten salt heat storage for concentrated solar power (CSP) plants (2552MW in total) and chilled water or ice slurry cold storage for demand side electricity consumption management (200MW).

Only recent years the potential value of cryogenic-temperature cold storage has been widely recognised for the much elevated exergy density and the capability of cogeneration of cold and power. The related UK leading technologies those under development including cryogenic engine for transportation, liquid air energy storage, pumped thermal electricity storage etc, in which cryogenic temperature cold storage is a key to improve the performance. Moreover, with efficient and cost-effective cryogenic-temperature cold storage, the operation of traditional cryogenic systems can be more flexible as an effective mean of demand side management (consumes more off-peak electricity and less peak electricity instead of constant load operation to save electric bills). In a long term it will contribute to the creation of 'cold economy'.

This project will develop Micro-encapsulated Phase Change Materials in Slurries (MPCMSs) as novel approaches of cryogenic-temperature cold storage. Slurries are excellent cold storage candidates as they can be transported by pumps (good fluidity), just like the molten salts in CSP plants. On the other hand with phase change materials (PCMs) encapsulated in the micro-size particles not only the equivalent heat capacity can be significantly improved, but also the temperature-dependent heat capacity can be designed easily by adding different capsules with appreciate freezing point core PCMs to minimize the exergy loss in charging/discharging processes.

The key challenge of this approach is the wide working temperature range of MPCMSs from room temperature to cryogenic temperature. Therefore this project will utilize the applicants' developed skills and sophisticated research facilities in Micromanipulation lab (within School of Chemical Engineering, University of Birmingham) and new launched Birmingham Centre for Cryogenic Energy Storage (BCCES) to formulate, characterize, and demonstrate the application of MPCMSs for cryogenic-temperature cold storage. Through this project we will gain the skills of MPCMSs fabrication depending on the applications as well as the capability of optimal design of related cold storage devices.

The impact of the research will be wide and varied. It is highly relevant to various sectors including: (i) Academics - This project will contribute to the creation of a new element of thermal energy storage that stores cold at cryogenic temperatures. It will dedicate significantly to the development of related disciplines such as cryogenic fluids formulation/fabrication, and the design and analysis of cold storage devices etc. (ii) Industry - With no doubt the success of this project will directly contribute the performance improvements of some developing technologies such as cryogenic engine, liquid air energy storage and pumped thermal electricity storage. It will have long-term influence on the cryogenic industry by enabling more flexible operations. (iii) Government - This project is a prompt response on the recent governmental 'the eight great technologies' investment which aims at accelerating UK unique technology development. Furthermore the potential of more flexible operation of large scale cryogenic systems will enforce the policy makers to consider the role and revenue mechanism of large scale energy storage and demand side management in Electricity Market Reform.

The academic impact will be achieved by article publications and conferences/events. We will keep publishing our findings in a timely manner in top peer-reviewed journals and conferences. We will also report our outcomes to other relevant programmes such as Grand Challenge energy storage programme to attract attentions in this new area and the ultimate goal is to establish a society for cold storage research to develop even other approaches. In addition we will be involved in developing a new master program in 'cryogenic energy storage' at the University of Birmingham by contributing in the aspect of cold storage. The industrial and governmental impacts will be achieved by direct industrial interaction and knowledge transfer. Dearman Engine Company as a potential user of the proposed technology is directly involved in the project. We will continue communicating results and engaging with potential industrial partners such as Highview Power Storage, Isentropic Ltd etc. Our outcomes will also be disseminated through various knowledge transfer networks as well as application-oriented magazines to maximize the impact.

The outcomes from the proposed work will be patentable, for which the existing exploitation mechanisms of the University of Birmingham will be used. Patents will be considered prior to any publications. We will also accumulate our expertise and secure high TRL funds (e.g. Horizon 2020 or Innovate UK) to carry out large scale demonstration (i.e. pilot-scale demonstration in a host institution owned liquid air energy storage test bed (350kW/1.5MWh)) at the late stage of the project.