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We have fabricated a functional prototype of an ultralight power converter tile; a modular building block for a space-based solar power system. The tile is $\sim 10\mathrm \times 15$ cm in area, and weighs $\sim 1.5$ kg/$\text{m}^{\mathbf {2}}$. It comprises a photovoltaic (PV) solar energy collector, a radio-frequency (RF) power converter, and an array of transmission antennas. The PV collector subassembly utilizes $\sim 15\mathrm {x}$, 1D parabolic trough reflective concentrators with triple-junction (3J) solar cells. It has areal mass of $\sim 0.8$ kg/$\textbf{m}^{\mathbf {2}}$, 74% optical efficiency, and a peak specific power of $\sim 230\mathrm {W} /$kg. We demonstrated wireless power transmission over a distance of $\sim 50$ cm in our lab. Analysis of the sources of mass and inefficiency suggest a path towards achieving dramatically higher performance with future designs.

Concentrator photovoltaic systems can provide supplementary shielding against high energy particles. In this paper we compare the radiation environment that the same solar cell would experience in a flat-plate module versus in a parabolic mirror concentrator system. We have observed that the shielding provided by the concentrator system is remarkable. In order to obtain an accurate prediction of the overall shield needed in our concentrator system triple-junction space solar cells have been irradiated on the edge with 350-keV protons at a fluence of 1012P + cm−2. A mild degradation of the open circuit voltage was measured (~70 mV).

Lightweight parabolic mirrors for solar concentrators have been fabricated using carbon fiber reinforced polymer (CFRP) and a nanometer scale optical surface smoothing technique. The smoothing technique improved the surface roughness of the CFRP surface from ~3 {\mu}m root mean square (RMS) for as-cast to ~5 nm RMS after smoothing. The surfaces were then coated with metal, which retained the sub-wavelength surface roughness, to produce a high-quality specular reflector. The mirrors were tested in an 11x geometrical concentrator configuration and achieved an optical efficiency of 78% under an AM0 solar simulator. With further development, lightweight CFRP mirrors will enable dramatic improvements in the specific power, power per unit mass, achievable for concentrated photovoltaics in space., Comment: IEEE Photovoltaic Specialist Conference (PVSC), DC, USA, 2017

We report the design, fabrication and characterization of ultrathin metasurfaces that exhibit wideband 300 K thermal emissivity. The emissive behavior of these structures is almost independent of the emission angle. Our ultralight subwavelength-thickness metasurfaces can be fabricated relatively easily and are excellent candidates for radiative cooling in space applications.

We report the effects of high energy electron and proton radiation on perovskite solar cells. For irradiation with 1 MeV electrons, at fluence from 1012 to 1016 cm−2, there are no significant changes in the morphology and the crystal phase in the perovskites, and the perovskite solar cells show only slight degradation in photovoltaic performance and spectral response. The results from Monte Carlo simulations show most of the electrons completely penetrate through all of the layers of solar cells with little scattering. In addition, 50 ke V proton radiation with fluence of 1012−2 has no significant impact on the open-circuit voltage or short-circuit current, and degrades only the fill factor. We have further found that the fill factor can be restored with a vacuum annealing process. The results suggest that perovskites have superior electron and proton radiation tolerance, and thus hold particular promise for space applications.

The Space Solar Power Initiative (SSPI) seeks to enable reliable, cost-effective baseload power generation from large-scale solar power stations in space. We propose an ultralight, modular power station, having specific power in the range of 1–10 kW/kg for the photovoltaic (PV) collection subsystem. The building block of the power station is the ‘tile,’ a self-contained element that performs PV energy collection, conversion to radio frequency (RF), and transmission to earth. To minimize PV mass, we select a 1D, 10-20X parabolic trough concentrator geometry, which provides cooling and radiation shielding for the cells, and which folds flat for deployment. Here, we discuss the design, fabrication, and testing of the initial PV tile prototypes.

An optical amplifier followed by a bistable element is statistically analyzed. To this end, the birth-death-immigration model and the coupled mode theory are used to characterize the amplifier and the bistable element, respectively.

We use the 3D vectorial Gaussian beam tracing method to model millimeter wave propagation. We simulate the propagation of Gaussian beams in a large scale environment at 62.4 GHz. First, a known far field pattern of the transmitter antenna is expanded into a set of Gaussian beams. We chose Gabor expansion based method to expanding radiating field into Gaussian beams. Then, a Gaussian beam tracing model considering reflections and transmission is used to represent urban microcell propagation. We use a phase matching method to find reflected Gaussian beam The results of the Gaussian beam tracing simulations including line-of-sight (LOS) and non-line-of-sight (NLOS) propagation are compared with the results of the ray tracing method. The results are in good agreement with results of ray tracing technique on the same geometry. Overall coverage map shows the dominant effect of shadowing in the millimeter wave band. The tracing technique is faster and more promising compared to exhausted ray tracing methods.