Due to its wide availability and low price (<10€/t), lime (CaO) has been long proposed as an energy intensive material to store energy in a chemical form by means of carbonation/calcination cycles. The challenge is, however, that lime tends to sinter at the high temperatures of the standard Calcium-looping (CaL) cycle for CO2 capture, which reduces dramatically its multicycle conversion.
SOCRATCES addresses this issue by proposing innovative operating conditions for CaL. Instead of the well-known operating conditions in carbon capture and storage applications (high temperature calcination and moderate temperature carbonation) SOCRATCES will reverse this sequence by using moderate temperature calcination and high temperature carbonation. Preliminary laboratory tests have shown promising results in terms of the sintering of the lime sorbent. Therefore, this is a promising technology for removing the main barrier of CaL for energy storage.
The project is developing an integrated system based on a solar tower (for concentrated solar energy harvesting), a CaL cycle (for energy storage) and a power block (for using the stored energy to produce electricity). The new solar-CaL integration allows storing a higher amount of energy per volume in comparison to current storage systems, which will favour the operation of the whole system in the absence of sunlight. In addition, the CaL-power block integration will allow achieving high thermal to electric efficiencies (>45%).
If successful, SOCRATCES will confer the EU a leading role in the development of efficient and non-toxic CSP with competitive storage cost (<12€/kWhth) and levelised cost of electricity (<7c€/kWh).