High Energy Advanced Thermal Storage Studies (HEATS)
Typical solar thermal propulsion systems require direct solar illumination at the time of propulsive maneuvers. A combined solar thermal propulsion and latent heat energy storage system has been proposed for use on a low earth orbit satellite to eliminate this issue. In this system, sunlight is concentrated on and melts a solid phase change material. When sunlight is no longer available, the melted material cools and solidifies, and the thermal energy that melted the phase change material leaves the system. The heat is converted to electricity through the use of thermophotovoltaic (TPV) cells. The propellant passes through a heat exchanger embedded in the phase change material for preheating prior to entering the nozzle for enhanced propulsive performance. The novel aspects of this work include the use of silicon as a phase change material and the coupling of energy storage and propellant heating.

Colored surfaces represent moving melt front during solidification of silicon

Related Publications:

Reid, M.R., Saleem, F.M., Scharfe, D. B., and Webb, R.N., 2013, “Preheating a Cold Gas Thruster Flow through a Thermal Energy Storage Conversion System,” Journal of Propulsion and Power, 29 (6), pp. 1488 – 1492.

Reid, M.R., Scharfe, D.B., and Webb, R.N., 2013, “Computational Evaluation of a Latent Heat Energy Storage System,” Solar Energy, 95, pp. 99 – 105.

Supported by: Air Force Research Laboratory and ERC, Inc.

mm-Wave Heat Exchanger Evaluation
The requirement that the propellants used in launch vehicle systems must also provide the thermal energy to be converted to kinetic energy in the rocket nozzle has plagued rocket designers since the dawn of the space age. Beamed propulsion systems, however, avoid this constraint by placing the energy source on the ground and transmitting the energy to the spacecraft via microwaves. This work computationally thermally and fluidically characterizes hydrogen flow through a heat exchanger with a beamed energy input.

Related Publication:

Gould, D.W., Hoff, B.W., Young, M.P., and Webb, R.N., "Numerical Analysis of a Single Microchannel Within a High-Temperature Hydrogen Heat Exchanger for Beamed Energy Propulsion Applications," submitted to the ASME 2013 Summer Heat Transfer Conference

Supported by: Air Force Research Laboratory and SAIC, Inc.

Enhanced Solar Collection Using Butterfly Wings
Diminishing natural resources, dependence on foreign nations for fuel, and pollution dictate the need for alternative energy sources. For renewable energy options to be viable, they need to be made more efficient. Due to structures on their wings, butterflies are incredibly effective solar collectors. Adding structures inspired by those on butterfly wings to existing solar collection and storage devices could enhance solar collection efficiency. This work proposes an experimental investigation of the radiative surface phenomena associated with these bio-inspired structures.

Related Publications:

Horvath, J.A. and Webb, R.N., 2013, “Experimental Study of Radiation Absorption by Minichannels of Varying Geometry,” Experimental Thermal and Fluid Science, 44, pp. 631 - 636.

Horvath, J.A. and Webb, R.N., 2011, “Experimental Study of Radiation Absorption by Microchannels of Varying Aspect Ratios,” Solar Energy, 85(5), pp. 1035 - 1040.

Supported by: UCCS Center of the University of Colorado BioFrontiers Institute