Category Concentrating solar power technology

SOLREF reactor

A solar thermochemical reactor for the reforming of natural gas to hydro­gen was designed, fabricated and operated in the scope of the European project SOLREF (Fig. 20.7). Based on the experience obtained in a previ­ous project (SOLASYS), in which the ‘proof-of-concept’ of solar steam reforming was demonstrated, an advanced reactor was developed in the SOLREF project. The main purpose of this project is to develop and operate an innovative 400 kWth solar reactor consisting of a more compact and cost-effective reformer for such applications as hydrogen production or electricity generation.

Some of the aims of the SOLREF project were to achieve temperatures higher than 900°C to enhance the efficiency of the process and to enable the coupling of the reactor with the process for the prod...

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Aerosol flow reactors

The high temperature aerosol flow reactor (AFR) (Fig. 20.6) has been employed for the production of ceramics and for solar methane dissociation

20.6 image493
(a) Schematic of aerosol flow reactor (Weimer et al., 2001); (b) installed solar thermal aerosol reactor (Dahl et al., 2004).

(Perkins et al., 2008). ‘Proof-of concept’ experiments were carried out for the dissociation of methane for hydrogen and carbon black production and the dry reforming of methane for syngas production (Weimer et al., 2001). Use of an aerosol reactor for hydrogen production from water-splitting was presented in Funk et al. (2008) where Zn powder was introduced into a gas stream with the aid of a fluidized feeder and subsequently passed through an aerosol flow reactor...

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Rotating disk reactors

Another type of rotating reactor (Fig. 20.5) is the CR5 developed at the Sandia National Laboratories (Diver et al., 2008). The reactor is a receiver/ reactor/recuperator that consists of counter rotating rings or disks. Robo – cast redox material in the form of fin segments is adjusted on the rotating disks. With the aid of the rotating disks, the redox material is alternately exposed to solar radiation for the regeneration step and water vapor for the water-splitting step.

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Cavity dual cell reactors

A ‘rotary’ type system (Fig. 20.4) that was designed for two-step thermo­chemical water-splitting cycles, had separate dual cells for the water­splitting and the regeneration. It was developed at the Tokyo Institute of Technology (Kodama and Gokon, 2007; Kaneko et al., 2007) and consists of ceramic foams coated with the redox material and adapted on a cylindri­cal rotor. The reactor has two quartz windows through which the radiation

ZnO + CH4














3 8







Подпись: (b)(a)

20.3 (a) Vortex reactor (Steinfeld, 2005) that consists of: 1 cylindrical cavity, 2 windowed aperture, 3 inlet port, 4 outlet port, 5 window,

6 auxiliary flow of gas for cooling and clearing the w...

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Volumetric cavity reactors

Cavity solar reactors (Fig. 20.3) were introduced in the work of Trombe et al. (1973), for melting of oxides, Flamant et al. (1980) for calcite decom­position, and Steinfeld et al. (1998b) and Haueter et al. (1999) for oxide reduction. As the name suggests, concentrated radiation enters a cavity aperture via a window. In Steinfeld et al. (1998b), a 5 kW continuous-feed, ‘vortex’ cavity reactor was designed for co-producing Zn and syngas, while in Haueter et al. (1999), a 10 kW rotating-cavity reactor, similar to the aforementioned design, was used for the decomposition of zinc oxide.

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Multi-tubular solar reactors

For catalyzed reactions, reactors based on packed beds of porous solid cata­lyst particles are a standard approach in the chemical industry. Adaptation to solar operation via assembly of multiple tubes to form a receiver is an obvious approach. Stein et al. (2009) have followed this route for solar steam reforming, for example. Recently a thermal and optical analysis for the development of a multi-tubular reactor filled with mixed ferrite for hydrogen production via two-step water-splitting reactions by making use of mixed ferrites was reported (Martin et al., 2011). This concept has some similarities with the fixed-bed set-up employed in laboratory-scale experi­ments for the evaluation of the redox activity of ferrites...

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Solar-thermochemical reactor designs

The design of solar thermochemical reactors has been an issue of research over the last three decades. Some of the most significant reactor designs are presented in the following paragraphs.

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Solar hydrogen from thermochemical water splitting

Direct thermal water-splitting (Eq. [20.11]) is a reaction that requires very high temperatures (>2000°C).

2H2O + Energy ^ 2H2 + O2 [20.11]

The reduction of the temperature of the water-splitting reaction can be achieved via thermochemical cycles based on redox pairs.

One of the earliest investigations for multi-step hydrogen production from water-splitting was by Funk and Reinstorm in the 1960s (Funk and Reinstorm, 1966). They evaluated the energy requirements and the possibil­ity of employing two-step processes for water dissociation and hydrogen production by oxides and hydrides. The result of their investigation was that there were no compounds that could efficiently yield a two-step process for hydrogen production from water, provided that the temperature remained lower than 1100°C...

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