Recently, a research team led by Dawei Liang, associate professor of NOVA University of Lisbon, Portugal, announced that they had achieved 4.64% of the energy conversion efficiency from solar energy to laser energy using a new Ce: Nd: YAG rod solar pumped laser.
It is reported that the innovation of this research is that instead of using semiconductor laser arrays, the direct solar pumping technology of solid state lasers is used to overcome the current performance limitations and enable space borne lasers to operate stably and reliably for many years.
Specifically, the team used NOVA heliostat parabolic mirror system for solar energy collection and concentration. The system consists of a large plane mirror and two plane parts mounted on a two axis heliostat. The device rotates continuously to keep sunlight reflected to the fixed parabolic mirror installed in the solar laser laboratory.
Their heliostat has a reflectivity of 93.5% and redirects the incoming solar radiation to a fixed parabolic mirror with a diameter of 1.5 meters, a rim angle of 60 ° and a focal length of 660 mm. The back of the parabolic mirror is silver plated, and the reflectivity of the main mirror is 80%.
The solar laser head module is composed of a large fused silicon aspheric lens and three Ce: Nd: YAG rods with a diameter of 2.5 mm and a length of 25 mm (installed in a single tapered pump cavity). Then three small 1064 nm partial reflection output mirrors will be aligned with the corresponding laser rods respectively. Finally, silver plated aluminum foil with a reflectivity of 94% is used to protect the inner wall of the pump cavity.
The test results show that this method provides three continuous wave 1064 nm beams with high efficient synchronous emission, with a solar laser power conversion efficiency of 4.64%, a solar laser collection efficiency of 41.25 W/m2, and a calculated slope efficiency of 7.64%.
The research team pointed out that broadband sunlight can be converted into laser by solar pumping, which is a narrowband, collimated, fast pulse radiation source, and may have extremely high brightness and intensity. Dawei Liang said: "Since solar energy is the most abundant and reliable energy in space, 10 times more than that on the earth, space-based laser power generation will be an important step to meet the energy demand. Moreover, since there is no cloud cover, the intensity of sunlight in space is almost twice that on the earth, and the time when there is sunlight is 4-5 times that on the earth."
The semiconductor laser array has two obvious disadvantages: first, its performance declines over time, and second, its life is limited, and the loopholes in these two aspects will expand with the average output power level.
Now, the above research team points out that replacing semiconductor laser arrays with direct solar pumped solid-state lasers will hopefully help overcome these limitations. In the future, if such highly efficient and low-cost renewable lasers are successfully applied to laser material processing, their applications in ground scenes will become increasingly prominent.
Source: OFweek
