2. Solar energy conversion and storage via solar pumped lasers

Solar energy conversion and storage via solar pumped lasers

  • Institute of Innovation for Future Society

Tomoyoshi Motohiro [Professor]

Outline of Seeds

"Employing an off-axis parabolic mirror with an aperture of 50 mm in diameter, uniquely designed compact solar-pumped lasers (SPL) have been developed, and continuous stable lasing has been attained by tracking the sun. Sunlight is once converted to a monochromatic laser light by a 2D array of SPLs, and then it is converted to electricity at the efficiency over 60% using PV devices specially designed for the laser light. Taking advantage of the small beam diameter and good transmission performance of laser, the PV devices can be also small and located in a conditioned room apart from SPLs at outdoor exposure. This enables long-term high efficiency PV power generation.
Instead of coiling superconducting wires, compact superconducting magnetic energy storage (SMES) systems are formed by depositing superconducting thin films in the spiral trench formed on a Si wafer using MEMS technology. Consolidating a plurality of these Si wafers, a SMES unit is composed. Depending on the needs of energy storage, a plurality of the SMES units is arranged and combined with a refrigerating machine of corresponding capacity. At the refrigeration temperature over 20K, the system is expected to attain a storage capacity of 550Wh/liter which is comparable with the target value of Li-ion battery, and to have additional advantage of compactness, compatibility with mass production, low cost and high charge-discharge rate.
Although hydrogen storage solid state materials has been extensively studied, it seems there remains no possible candidate to substitute high pressure hydrogen tank. Hydrogen storage and release properties of some nano-structured materials may have still unknown future possibilities, detailed studies have been difficult because exothermic reaction at hydrogen storage destroy the nano-structures. To make a breakthrough in this situation, we are engaging in precise measurement of heat generation at hydrogen storage and permeation and in analyses of related accompanying phenomena.

Novelty and originality of this research

[1]the compact size of solar pumped laser of an aperture of 50cm in diameter in comparison with the conventional ones of 1-2m in diameter. Coordinated solar tracking of the compact solar pumped lasers. High PV energy conversion efficiency over 60% in comparison with 15-20% of solar-cells. [2]the compact size of superconducting magnetic energy storage system around several ten cm in comparison with the conventional ones around several m. High energy storage density over 550Wh/liter which is comparable with the target value of Li-ion battery. Local high density magnetic field generation as strong as 20T. [3]detailed studu of exthothermic reaction at hydrogen storage utilizing mesoporous materials.

Application and research area for Industry collaboration

same as above

Key Takeaway

We explore new technologies requested in future hydrogen energy society via nonconventional aproaches.


Solar-pumped laser,monochromatic PV, Superconducting magnetic energy storage, hyudrogen storage and release, exothermic reaction


  • Technology related to solar-pumped lasers
  • Technology related to solar-cells
  • Technology related to superconducting magnetic energy storage
  • Technology retated to evaluation of hydrogen storage and release


  • ultralowtemperature 5W refregerator


  • not dusclosed yet.

Monographs, Papers and Articles

  • "T. Motohiro et al., ""Consideration of coordinated solar tracking of an array of compact solar-pumped lasers
  • "N. Sugimoto and T. Motohiro,""Anisotropic I-V
  • T. Hioki et al.,"Inductively Coupled Plasma Mass Spectrometry Study on the Increase in the Amount of Pr Atoms for Cs-Ion-Implanted Pd/CaO Multilayer Complex with Deuterium Permeation",Jpn. J. Appl. Phys. 52, 107301(2013).
  • T.Motohiro, "Part II Theory and Practice:Sputtering Deposition of Functional Thin Films , 4 Computer Simulation",pp.143-294 in Handbook of Sputter Deposition Technology Second Ed.",edited by K. Wasa, I. Kanno, H. Kotera, Elsevier 2012.