Stefania Tescari

Thermochemical Solar Reactor: Simplified Method for the Geometrical Optimization at a Given Incident Flux

This paper aims to describe a simplified method to optimize the geometry of a solar thermochemical reactor. As a first step, this paper focuses on a purely thermal analysis. The chemical reaction is represented by a uniform heat sink inside the material. The heat transfer modes are radiation in the empty part (cavity) and conduction inside the reactive material. The aim is to find the optimal geometry of the reactor, by maximizing its efficiency, for a fixed value of the incident solar flux and of the total volume of the reactor. An analytical solution can be found thanks to some simplifying hypothesis. The influence of different operational parameters on the maximal efficiency and on the optimal shape is studied. A comparison between different reactor designs (cylindrical and cavity reactors) is shown. A 2D study, based on CFD software using a finite element method, allows for quantifying the effects of the simplifying assumptions. The constructal theory aims to optimize the internal structure of a system in order to provide easier access to its internal currents and increase the system efficiency. Thus, this study can be seen as the optimization of the elemental volume of the constructal approach. In a next step this optimization method will be used to optimize more complex reactor design, as for example, a honeycomb reactor obtained by the assembling of several cavities, in order to optimize a thermochemical reactor for hydrogen production or high temperature heat storage.

Thermochemical storage for CSP via redox structured reactors/heat exchangers: The RESTRUCTURE project

The present work provides an overview of activities performed in the framework of the EU-funded collaborative project RESTRUCTURE, the main goal of which was to develop and validate a compact structured reactor/heat exchanger for thermochemical storage driven by 2-step high temperature redox metal oxide cycles. The starting point of development path included redox materials qualification via both theoretical and lab-scale experimental studies. Most favorable compositions were cobalt oxide/alumina composites. Preparation of small-scale structured bodies included various approaches, ranging from perforated pellets to more sophisticated honeycomb geometries, fabricated by extrusion and coating. Proof-of-concept of the proposed novel reactor/heat exchanger was successfully validated in small-scale structures and the next step included scaling up of redox honeycombs production. Significant challenges were identified for the case of extruded full-size bodies and the final qualified approach related to preparati...

Experimental proof of concept of a pilot-scale thermochemical storage unit

An efficient heat storage system, which allows disposal of the energy independently of the weather conditions, is a key factor on the development of Concentrated Solar Power (CSP). In this respect thermochemical heat storage could play an important role. Despite being still at early development stage, the number of recent studies dealing with thermochemical systems for high temperature storage shows that the interest on this topic is largely increasing. Among the reactive materials studied, certain multi-valent metal oxides seem to be a promising option, especially for air-operated CSP plants.

Solar Aluminum Recycling in a Directly Heated Rotary Kiln

South Africa currently is experiencing an electricity constraint due to economic growth and lack of investment in generation capacity, resulting in power blackouts in 2008. With increased electricity prices, the economic sustainability of energy intensive industries is threatened. The aluminum smelting industry is a significant consumer of electricity.