SBIR Phase II: Solar Thermal Collector Using Advection Enhanced Nano-Porous Insulating Media

The broader impact/commercial potential of this Small Business Innovation Research (SBIR) Phase II project will profoundly improve the economics of solar water heating (SWH) systems. Little innovation has occurred in this area since the advent of evacuated tube solar thermal collectors in the 1980s. Despite these advances the cost of SWH systems is much higher than the cost of fossil fuels in the U.S. Thus while there exists a flourishing global market in excess of $20B, the market for such systems in the U.S. is virtually nonexistent. The solar thermal collector technology under investigation has demonstrated performance in terms of efficiency vs. output temperature that is already superior to that of state-of-the-art collectors. Economic modeling further indicates that in high volume production the collector would be substantially less expensive than commercial products. This combination of improved performance and reduced cost has the potential to make SWH economically viable in more than 40 states in the U.S. An outcome which could provide a solid economic foundation for the revival of a domestic industry, and accelerate the proliferation of these systems worldwide. This Small Business Innovation Research (SBIR) Phase II project will extend the performance envelope of two solar thermal collector architectures identified during the Phase I effort. Current solar thermal collectors exhibit non-economic price/performance metrics and are constrained to water heating applications in only a few markets worldwide. The first architecture utilizes advection to improve the insulating properties of a granular nano-porous medium. The Phase II effort will transition this architecture from prototype to the fabrication and characterization of an engineering scale collector. It is expected that increasing the size and solar simulator output (currently below reference standard) will increase efficiency significantly. Material dopants, heat transfer fluid dynamics, and optical absorber thermal properties will be examined computationally and experimentally to further improve performance. The second architecture significantly extends the operational range. This effort will explore techniques to expand this range including the use of material dopants to modify optical characteristics and the development of passive technique for concentrating optics. Computer simulations suggest that outputs comparable to that of a parabolic trough are possible.