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Chapter 3

Direct Solar Energy

Concentrated Solar Energy


H2O Splitting


Fossil Fuels (NG, Oil, Coal)

Solar Thermolysis

Solar Thermochemical Cycle

Solar Electricity & Electrolysis

Solar Reforming

Solar Cracking

Solar Gasification

Optional CO2/C Sequestration

Solar Fuels (Hydrogen, Syngas)

Figure 3.8 | Thermochemical routes for solar fuels production, indicating the chemical source of H2: water (H2O) for solar thermolysis and solar thermochemical cycles to produce H2 only; fossil or biomass fuels as feedstock for solar cracking to produce H2 and carbon (C); or a combination of fossil/biomass fuels and H2O/CO2 for solar reforming and gasification to produce syngas, H2 and carbon monoxide (CO). For the solar decarbonization processes, sequestration of the CO2/C may be considered (from Steinfeld and Meier, 2004; Steinfeld, 2005).

atmosphere or other sources in a synthesis reactor with a nickel cata- lyst. In this way, a substitute for natural gas is produced that can be stored, transported and used in gas power plants, heating systems and gas vehicles (Sterner, 2009).

Solar methane can be produced using water, air, solar energy and a source of CO2. Possible CO2 sources are biomass, industry processes or the atmosphere. CO2 is regarded as the carrier for hydrogen in this energy system. By separating CO2 from the combustion process of solar methane, CO2 can be recycled in the energy system or stored permanently. Thus, carbon sink energy systems powered by RE can be created (Sterner, 2009). The first pilot plants at the kW scale with atmospheric CO2 absorption have been set up in Germany, proving the technical feasibility. Scaling up to the utility MW scale is planned in the next few years (Specht et al., 2010).

solar fuel conversion (technical photosynthesis) with an efficiency of 10% (Sterner, 2009) and via solar-driven thermochemical dissociation of CO2 and H2O using metal oxide redox reactions, yielding a syngas mixture of carbon monoxide (CO) and H2, with a solar-to-fuel effi- ciency approaching 20% (Chueh et al., 2010). This approach would provide a solution to the issues and controversy surrounding existing biofuels, although the cost of this technology is a possible constraint.


Global and regional status of market and industry development

This section looks at the five key solar technologies, first focusing on installed capacity and generated energy, then on industry capacity and supply chains, and finally on the impact of policies specific to these technologies.

In an alternative conversion step, liquid fuels such as Fischer-Tropsch diesel, DME, methanol or solar kerosene (jet fuel) can be produced from solar energy and CO2/water (H2O) for long-distance transporta- tion. The main advantages of these solar fuels are the same range as fossil fuels (compared to the generally reduced range of electric vehicles), less competition for land use, and higher per-hectare yields compared to biofuels. Solar energy can be harvested via natural pho- tosynthesis in biofuels with an efficiency of 0.5%, via PV power and


Installed capacity and generated energy

This subsection discusses the installed capacity and generated energy within the five technology areas of passive solar, active solar heating and cooling, PV electricity generation, CSP electricity generation, and solar fuel production.


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