Category Concentrating solar power technology

Reduction of carbon dioxide emissions from the metallurgical industry

Another sector that consumes a lot of electricity and heat and thus is also responsible for a large share of anthropogenic greenhouse gas emissions is the metallurgical industry. It was estimated (in Steinfeld and Meier, 2004) that by replacing the non-renewable energy in the technology used for processing of aluminum (which requires very high temperatures ~2200°C) by energy deriving from solar irradiation, the CO2 emissions produced would be reduced by ~90%. In that sense, solar energy either directly (by solar furnaces) or indirectly (through the production of solar fuels) could be applied to multiple industrial processes that demand high amounts of energy (usually electricity), high process temperatures or a combination of both.

20.6 Conclusions

The high power density, ease of transpor...

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Reduction of carbon dioxide emissions

Synergy with carbon capture and storage

The various endothermic reactions that have been discussed that poten­tially convert hydrocarbons to H2 and CO2 are also those that are proposed for potential CO2 emission-free processes. In this scenario, some of the fossil fuel itself is oxidized to provide the heat input for the reactions. CO2 is then scrubbed from the product gas for sequestration. The challenge in CO2 emissions is currently focused on finding storage sites capable of hosting quantities reaching annually 25 billion tons (‘Basic Research Needs for Solar Energy Utilization’, 2005). Such sinks, which could be geological for­mations, the ocean, saline aquifers, terrestrial ecosystems, etc...

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Waste processing

Besides solar fuels that can replace fossil fuels in various applications, con­centrated solar energy may also be used directly to satisfy thermal or power needs of various processes. For instance, solar energy could be incorporated in the sector of waste treatment that comprises another modern-day man­agement problem that deals with hazardous compounds. After basic pro­cessing, such products are usually disposed of in sites with limited storage capacity. Due to this space limitation, technologies that recycle hazardous materials and convert them into valuable products have been developed. The recycling technologies used require thermal processes with high energy demand and thus use huge amounts of fossil fuels...

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Other applications of industrial solar chemistry

20.6.1 Closed-loop energy storage systems

The utilization of the solar potential via thermochemical processes can be applied to closed-loop energy storage systems for the storage and transpor­tation of solar energy, as discussed in Chapter 11. The idea of closed-loop energy storage was first suggested in the 1970s and it involved gas phase reactions in endothermic and exothermic reactors with associated counter­flow heat exchangers. In this area of solar thermochemistry, the solar methane reforming (Abbas and Wan Daud, 2010b) and the ammonia solar dissociation reaction systems have received much attention (Dunn et al., 2012).

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Ongoing research into solar fuels

The ‘European hydrogen and fuel cell roadmap’ introduced by the Euro­pean Commission considers hydrogen as the most feasible solution to achieve independence from fossil fuels. However, currently hydrogen pro­duction employs fossil fuels (i. e., natural gas), and therefore has the undesir­able side effects of the use of carbonaceous materials. For this reason, the European roadmap (Fig. 20.18), which covers a timeframe until 2050, estab­lished the activities and strategies that should be supported for the develop­ment of the technologies for solar hydrogen...

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Solar-derived fuels

By employing solar energy, solar hydrogen and CO2, solar hydrocarbons can be synthesized. In this way solar hydrocarbons can play the role of a

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(a) Partitioning of the SSPS-CRS heliostat field at the PSA (Roeb et al., 2011); (b) focus of solar radiation on the dual HYDROSOL-II reactor (Konstandopoulos and Lorentzou, 2010).

renewable energy carrier since they utilize solar energy and consume waste CO2.

A very well-known technology that could be applied for the conversion of solar energy, hydrogen and carbon monoxide (e. g., from the solar decom­position of CO2) into solar hydrocarbons is Fischer-Tropsch synthesis. The term Fischer-Tropsch is applied in a rather large variety of chemical pro­cesses used for the production of synthetic hydrocarbons (e. g., paraffins,

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Chain growth ...

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HYDROSOL reactors

The hydrosol reactor was the first solar thermochemical reactor that pro­duced on-sun (Roeb et al., 2006b; Konstandopoulos and Lorentzou, 2010) solar hydrogen from the dissociation of water vapor via a redox-pair cycle.

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Gaseous products toward analysis

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window

 

(a)

 

(b)

Exit for the sweeping

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20.8 (a) Schematic of the 20 kW solar reactor and filter (Rodat et al, 2010a); (b) close look at a 20 kW SOLHYCARB reactor aperture during cooling at CNRS-PROMES test rig (Richter et al., 2008), (c) schematic of the 50 kW pilot solar reactor (Rodat et al., 2010b).

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Residence time (s) (a)

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T (K) (b)

20.9 (a) Temperature dependence of CH4 conversion and C2H2 off-gas mole fraction vs residence time (CH4 mole fraction in the feed: 20%) in the 20 ...

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SOLHYCARB reactors

As mentioned previously, the solar thermal cracking of natural gas can be achieved in two types of reactors. In a direct heating reactor (Kogan and Kogan 2003b; Kogan et al., 2005; Trommer et al., 2004; Hirsch and Steinfeld, 2004; Abanades and Flamant, 2008; Rodat et al., 2010b), the particles absorb heat from solar radiation and the reactor is seeded for the increase of the adsorption and nucleation sites. The disadvantage of direct heating is the potential deposition of particles on the window of the reactor. In the indi­rect heating reactor (Dahl et al., 2004; Wyss et al., 2007; Rodat et al., 2010b), the solar irradiation zone is separated from the reacting flow by an opaque wall that serves as a heat transfer medium that allows convection of heat from the solid wall to the gas flow...

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