Innovating for the next generation of renewable electricity and heating technologies.
Calix is a member of the SOCRATCES Project, which is currently completing construction of an exciting new application of Calix’s technology at the University of Seville in Spain. Seville is one of the leading locations for concentrated solar power (CSP) research and operation globally.
The pilot plant comprises a solar field, a hybrid CSP-electric direct separation reactor (DSR) from Calix, a carbonator, and a power block. The facility is under construction and operations should begin in the next couple of months.
SOCRATCES is a European Commission-funded Horizon 2020 project which is investigating the use of ‘calcium looping’ as a form of concentrated solar power (CSP) energy storage. It runs from January 2018 to September 2021. It involves the design of novel reactors, their construction and operation, and finally their integration into a full working prototype.
It takes a lot of energy to calcine limestone (i.e. calcium carbonate) into lime (calcium oxide) and carbon dioxide.
However, the other side to this chemical coin is that you get the same energy back if you recombine them. So, if you can calcine limestone when energy is plentiful, you should be able to recover much of that energy when it is scarce. This cyclical process is called calcium looping.
CSP uses banks of mirrors to focus large amounts of sunlight onto a small receiver, increasing its temperature to a level where steam can be produced to generate electricity.
In SOCRATCES, instead of producing steam we calcine limestone using specially designed CSP direct separation reactors (DSR’s) from Calix. DSR’s are ideal for this process because they already operate with indirect heating, something which is highly desirable for SOCRATCES.
The lime and CO2 products are collected and stored in separate vessels. When the energy is needed (e.g. at night, or in winter) the two products can be passed to a carbonator reactor where they react. The resulting heat is removed from the vessel and used to produce the steam required for electricity generation. The limestone can be returned to the calciner, completing the loop.
The benefits of the SOCRATCES process are that the equipment does not use expensive and in-demand resources such as rare metals and lithium, and it does not suffer from the same gradual loss of stored energy over large timescales as electrical batteries. This makes it ideal for inter-seasonal storage, i.e. calcining during the sunny summer months and carbonating during the dark winter months.
Calix has provided the calciner design, as well as oversight of the construction work package. We are contributing to the experimental plan but due to current travel restrictions we are unable to attend site to assist with commissioning or operations.
While energy storage is one market for a CSP-DSR, it could also be used to make zero-emission lime products, or indeed any calcined material. There are several promising mineral extraction industries in countries with significant CSP expertise and infrastructure, such as Morocco.
While SOCRATCES has made good progress towards enabling CSP-DSR technology, more development work is required, especially looking at the design of full-scale calciners at megawatt scale, and overcoming some of the unique challenges that come with combining CSP and DSR technology.