Basic Research Needs for Solar Energy Utilization - Office of ...
Basic Research Needs for Solar Energy Utilization - Office of ...
Basic Research Needs for Solar Energy Utilization - Office of ...
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An overview <strong>of</strong> solar thermochemical processes is provided by Steinfeld and Palumbo (2001).<br />
Some topics addressed by recent studies are<br />
• Evaluation <strong>of</strong> novel processes <strong>for</strong> fuel synthesis (Möller et al. 2002; Dahl et<br />
al. 2004) and material production (Murray et al. 1995; Wieckert et al. 2004);<br />
• Development <strong>of</strong> novel solar reactors (Anikeev et al. 1998; Osinga et al. 2004);<br />
and<br />
• Catalyst development <strong>for</strong> solar-driven high-temperature gas-gas reactions<br />
(Berman and Epstein 1997).<br />
The development <strong>of</strong> fuel production using solar energy is in a relatively early stage. Progress in<br />
the above topics is crucial to assess the technological viability <strong>of</strong> such processes prior to<br />
estimates <strong>of</strong> their economical feasibility.<br />
Present long-term projections suggest that the solar fuel production processes described above<br />
will probably be two to three times more expensive than present high-emission industrial<br />
methods. However, they also predict that solar fuel production can be competitive if carbon<br />
emission cost is considered (Steinfeld and Palumbo 2001).<br />
Low-temperature <strong>Solar</strong> Thermal Systems<br />
Low-temperature solar thermal systems have the potential to supply a significant number <strong>of</strong> U.S.<br />
households and commercial buildings with heating, cooling, and refrigeration; refer to the <strong>Solar</strong><br />
Thermal Technology Assessment <strong>for</strong> further details. To overcome the current barrier <strong>of</strong> high<br />
initial cost, there is a need <strong>for</strong> new materials in a number <strong>of</strong> roles. Durable polymeric materials<br />
or films are sought that provide high transmittance in the visible spectrum and protection from<br />
ultraviolet light, which is crucial in the successful development <strong>of</strong> polymer collectors (Davidson<br />
et al. 2002). The viability <strong>of</strong> polymer heat exchangers and absorbers depends on the development<br />
<strong>of</strong> extrusion-grade thermoplastic polymers with high strength to minimize the required thickness<br />
<strong>of</strong> the polymer structure and resistance to hot chlorinated water.<br />
Low-cost methods to improve the thermal conductivity <strong>of</strong> polymers are desirable. Some methods<br />
are proposed by Danes et al. (2002) and Davidson et al. (2002), but further work is required. An<br />
understanding <strong>of</strong> the mechanism leading to crystal growth on polymeric surfaces is required to<br />
develop strategies to avoid such growth. Of key interest are chemical differences between<br />
polymers, which influence their interaction with water; the mechanism <strong>of</strong> calcium carbonate<br />
nucleation; and scale morphology and structural differences (e.g., surface roughness), which may<br />
affect calcium carbonate nucleation and adhesion (Sherman 2001; Wang et al. 2005).<br />
Other needs are found in the development <strong>of</strong> low-temperature solar thermal systems that can<br />
supply both hot water and space heating. Cost-effective thermal storage is sought <strong>for</strong> seasonal or<br />
annual rather than daily energy requirements. Chemical or phase-change materials may provide<br />
per<strong>for</strong>mance superior to that <strong>of</strong> water-based storage options. Initiatives to develop systems that<br />
are part <strong>of</strong> the building envelope should be supported <strong>for</strong> both existing and newly constructed<br />
buildings. The solutions will be different. New buildings represent an opportunity <strong>for</strong> major<br />
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