Efficiencies of photovoltaic cell receivers for laser power transmission under the lunar environment
Major space activities in the next century will substantially increase the demand for power. The system of powering a very diverse set of remote missions will be an important infrastructure in space. Especially, the nighttime power supply to a space base placed on the Moon is a central problem in the development and utilization of the Moon, because the period of the nighttime on the Moon corresponds to 15 Earth-days. Photovoltaic cells could potentially be used as power receivers for several lasers at visible and near infrared regions. Several paper studies on the solar-cell response to laser illumination are available. However, the efficiency and response of cells would be quite different if these were used on the nighttime Moon surface since the temperature of lunar environment drops very low during the nighttime (about {minus}170 C). A feasibility of a laser energy transmission concept for a first stage lunar mission on 2005--2015 has been studied by NASDA. The lunar energy system consists of a small battery and a receiver (solar cell panel) on the lunar surface and a laser power transmission satellite on the moon orbit. In order to study the plausible lunar laser energy transmission system based on the state of the art of lasers and PV cell technologies, the authors report the cell efficiencies illuminated with several kinds of CW and pulsed lasers under the temperature range from {minus}190 C to 60 C. Solar cells of c-Si, GaAs for space use, CuInSe{sub 2} and infrared enhanced c-Si photodiode have been tested by changing the laser power from 3mW/cm{sup 2} to 1000mW/cm{sup 2}. The authors observed that the temperature dependence of the efficiency for YAG fundamental laser light is quite different from that for LD and Ar ion laser. In the latter cases, the efficiency increases with decreasing temperature. This is the general feature for the efficiency of conventional solar cells. In contrast with those, the PV cell efficiency under YAG fundamental light illumination drastically decreases with decreasing the cell temperature, due to the blue shift of Si band gap. This data indicates that Si cell efficiency for Nd:YAG fundamental laser light at the nighttime on lunar surfaces is much lower than that measured at room temperature. Furthermore, the authors have found that the laser power density on PV receiver surface assumed in the NASDA's feasibility study is far lower than the optimum laser power for the PV cells used in this study. Even in this condition they have obtained more than 40% conversion efficiency for pin-Si or GaAs cells illuminated LD. However, in view of the state of the art of beam quality of LD, it will be difficult to use LD's for long distance laser energy transmission missions in the near future. On the other hand, fundamental laser light of Nd:YAG laser will be used for the receiver system having narrow gap PV cells. However, it will take a long time to develop the high efficiency narrow gap PV cells for space missions. From the state of the art of both laser and receiving systems, the combination of GaAs cells and CW-mode Nd:YAG SHG light may be a choice for the lunar energy mission at 2,005--2,010 years considered here, because they have obtained more than 30% efficiency for GaAs cells illuminating Ar ion laser in this study, and will obtain higher PV conversion efficiency if the optimization of PV cells for the laser power density of missions is achieved.
- Research Organization:
- Tohoku Univ., Sendai (JP)
- OSTI ID:
- 20000380
- Resource Relation:
- Conference: 33rd Intersociety Energy Conversion Engineering Conference, Colorado Springs, CO (US), 08/02/1998--08/06/1998; Other Information: 1 CD-ROM. Operating system required: Windows 3.x; Windows95/NT; Macintosh; UNIX. All systems need 2X CD-ROM drive., PBD: 1998; Related Information: In: Proceedings of the 33. intersociety energy conversion engineering conference, by Anghaie, S. [ed.], [2800] pages.
- Country of Publication:
- United States
- Language:
- English
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