Ceria Mimics Plant Life
Newer and more exciting devices are being invented to harness renewable energy – especially solar energy. One such device is a prototype which uses one of the rare earth metals – ceria, otherwise known cerium oxide – utilizing its natural propensity of alternatively exhaling and inhaling oxygen as it heats up or cools down.
A new prototype
Formulated by US & Swiss researchers, this prototype has a quartz window and a small cavity to focus sunlight on a ceria-filled cylinder. With water and/or carbon dioxide being pumped into the vessel, hydrogen and/or carbon monoxide are created. Hydrogen by itself is used in hydrogen cells and by mixing hydrogen and carbon monoxide, fuel syngas can be produced.
As against the conventional photovoltaic cells, hydrogen and syngas are fuels which can be stored, are portable and can be used any time. The metal ceria is abundantly available being the most commonly found rare-earth metal. Professor Sossina Haile, from California Institute of Technology, has claimed that ceria is most suited for this process and fit for massive-scale production of fuels like hydrogen and syngas. She also said that saying that this prototype mimics plants’ photosynthesis is too generalized and over simplistic though the basic ingredients and working may be the same.
The fact that only some 0.7-0.8% of solar energy is being harnessed for fuel production with the rest being lost through heat or re-radiation makes this device rather inefficient. But improved insulation and smaller apertures are expected to make it a commercially workable option increasing the efficiency to some 19% or so.
Daniel Davies, from Solar Century, a British firm called the research as ‘exciting’. The possibility of large-scale production and portability of the fuel are the plus points of this device according to him. But Professor Haile strongly contends that making or marring of this and other such prototypes depends very much on national and state-level carbon policy.
Cost efficiency, storage/portability and production efficiency are three main challenges that need to be met by the hybrid technology devices such as these prototypes. Various methods are deployed to meet these challenges like using an array of mirrors for focusing sunlight on receivers, molten salts to store heat for up to 15 hours. But the search is still on for the most cost effective, efficient and continuous renewable energy providing device.