Demonstrated fossil-fuel-free energy cycle using magnesium and laser

We propose an energy cycle based on a renewable fuel. Magnesium is chosen as an energy carrier and is combusted with water to retrieve energy using many power devices. MgO, the combustion residue, is reduced back to Mg by laser radiation generated from solar and other renewable energy sources. We have achieved an energy recovery efficiency of 42.5 % for converting MgO to magnesium, using a laser. We achieved 11-14% slope efficiency of solar-pumped laser by Cr-codoped Nd:Yttrium Aluminum Garnet ceramic and Fresnel-lens focusing from natural sunlight. The laser output of 24.4 W was achieved with 1.4-m2 Fresnel lens. The maximum output for unit area of sunlight was 18.7 W/m2, which is 2.8 times larger than previous results with mirror collector.