Thermochemical storage: successful proof of concept
The RESTRUCTURE project, deals with thermo-chemical heat storage for solar power plant. The storage system absorbs the heat coming from the concentrated solar radiation and releases it during cloud or night period. This allows a continuous operation of the turbine and therefore a continuous production and delivery of electricity.
The project, which officially ended in January 2016, performed the validation at a semi-pilot scale system of about 74 kWh capacity and was constructed and operated at the Solar Tower Jülich (STJ), Germany.
Although the storage capacity was relatively low, this was the first time that such a concept was validated under near-realistic conditions for thermochemical heat storage applications.
The novelty of the RESTRUCTURE reactor design relates to the use of a monolithic honeycomb ceramic structure as its building block, in which the active material is incorporated.
In a multi-scale approach the suitable storage material was defined and its structure and composition optimised, first at the gram-scale, then at the 100 grams-scale to conclude with the semi-pilot at 100 kg-scale. At each scale, extensive tests were carried out to characterize the material and to define the characteristics of the next scale system.
An extensive experimental campaign carried out at the solar tower in Jülich, showed the concept feasibility. During charge, the system could absorb efficiently heat from air at 1000°C first in sensible form (by increasing its temperature) and then chemically (undertaking the chemical reduction). During discharge, cold air could be heated up by the system, which released almost completely the heat previously stored. More than 15 charge-discharge cycles were carried out without any lose in performance.
In the last step of the project, an overall plant configuration and its preliminary techno-economic assessment indicated that the technology is promising.