Preliminary Analysis of a 100-kW_th Mini-Tower Solar Field With an Integrated Optical Waveguide Receiver for Solar Chemistry

Solar-driven thermochemical hydrogen production, CO₂ abatement technologies and production of solar fuels and chemicals in general, are candidates in the near future to be scaled-up at solar thermal concentrating facilities in the framework of demonstration projects. Chemical demonstrators undoubtedly will be more demanding in terms of temperature and solar flux than current applications oriented to electricity production. Some of the more promising H₂ production technologies are already in the position to scaling reactors up to the 1-MW_th level. Demonstration scale useful to develop new solar chemistry processes usually considers input thermal powers between 100 kW_th and 1,000 kW_th. In this range, the best option is making use of mini-towers with heliostat fields. Then, the challenge is to efficiently introduce high fluxes (above 2,000 kW/m²) with a small field of heliostats in solar chemical reactors (usually requiring high temperatures, above 1,000 °C, and high pressures). In order to overcome it, some authors have proposed the use of light waveguides collecting systems for directing concentrated solar light towards a reactor cavity (1, 2, and 3). This solution makes possible the use of a large variety of reactor geometries and to guarantee the reactor tightness even working at high pressures. However it becomes the critical component of the plant design since it largely governs the facility efficiency and configuration due to its optical properties. This work presents the design of a 100-kW_th demonstration plant placed in Mo´stoles, Spain (40° 20^′ N, 3° 52^′ W) with the concepts mentioned above, in which the light waveguide system is formed by a set of units that are composed by a secondary concentrator and a bundle of optical fibers. This study has paid special attention to optical performances of the facility by analyzing the coupling between solar heliostats field layout and the solar receiver composed by light waveguides. In addition, the paper provides information on sizing, efficiencies and expected investment cost based on light waveguides specifications.