Multidisciplinary analysis of indirectly-heated particles receivers/reactors for so-lar applications in extreme conditions (ARROPAR-CEX).
Subproject 3. Methodology and characterization of materials and components for receivers for solar applica-tions under extreme conditions (RESPACE).

Participants: IMDEA Energia (Coordinator), Centro de Investigación en Nanomateriales y Nanotecnología (CINN) and CIEMAT.
Contacts: Manuel Romero,; Alfonso Vidal,
Funding: 180 k€ (Subproject 3); Programa Estatal de Investigación, Desarrollo e Innovación Orientada a los Retos de la Sociedad, en el marco del Plan estatal de Investigación Científica y Técnica y de Innovación 2013-2016. Ref. ENE2015-71254-C3-2-R.
Duration: January 1, 2016 – December 31, 2018.

Background:The research program ARROPAR-CEX proposes a multidisciplinary analysis on novel concepts of indirectly heated receivers/particle reactors for solar applications under extreme conditions. Extreme operating conditions are understood to be those which involve the combination of high irradiance, in excess of 1000 kW/m2, and very high temperatures, typically above 800 °C.
ARROPAR-CEX is divided into three sub-projects in order to achieve significant advancements in several scientific and technological knowledge areas, which together will lead to the development and subsequent commercial deployment of new devices, materials and methodologies in concentrating solar thermal energy, responding to the "Safe, Efficient and Clean Energy" challenge of the Spanish Strategy for Science, Technology and Innovation: Within objective 2, CIEMAT will study new multifunctional ceramic materials for solar applications under extreme conditions, focusing on the development of ceramic components that are adapted to operating conditions beyond the current state-of-the-art. The development of new materials is generally the starting point for outstanding technological advances. In this case, the development will be fully aimed at providing solutions to the needs that have been identified in the field of concentrating solar power generation systems. For this, the development of novel multifunctional composite materials is envisaged, which will enhance the stability of the component under pressure/vacuum at high temperatures and reduce its losses by thermal emission.

Achievements in 2015:
In particular, thermochemical processes require thermally and chemically stable reactor wall materials, which can withstand severe operating conditions suitable for specific solar fuels production. Several unresolved issues are involved in predicting the effect of environmental degradation on the long-term behaviour of innovative materials for next generation solar chemical reactor appliances. Changes in degradation mechanism are possible in the long-term exposure.
In addition to these scientific issues, uncertainties regarding the limitations of existing test procedures, the variability of existing suitable materials and the lack of information on the effects of such variability on the reliability of test-derived predictions of material performance constitute problems that require solution. 

Fig. 1. Vacuum chamber and vacuum pump on test table.

For the purpose of proposing a durability test methodology for predicting the lifetime of innovative materials for next generation solar chemical reactors, our work during this period have been focused to the following items:

  • the description of the equipment needed for the lifetime prediction  methodology;
  • the procedures to carry out the ageing tests;
  • the procedures for processing and interpretation of the results of the ageing tests.

The methodology will have to be adapted to the existing experimental set-up available at CIEMAT (Solar Furnace SF60 and Electrical tubular furnace).