Plants have long harnessed sunlight to create ‘food’ for themselves, and now a joint American and Swiss team have created a device that can duplicate the process! The team recently unveiled their prototype, which uses captured sunlight and a metal oxide called ceria to break down CO2 and water and create fuels which can be stored, used or transported to those who do need them.
The details of this remarkable machine were published in the latest issue of Science, where the team explains in detail how their device works. Whereas normal photovoltaic panels must use the electricity they generate instantly and cannot deliver power at night, the prototype device is designed to store energy for later use. It does this using a quartz window and cavity, which concentrates sunlight into a cylinder lined with cerium oxide. This oxide, also known as ceria, has the ability to ‘exhale’ oxygen as it heats up and ‘inhale’ it as it cools down.
In the prototype, CO2 and/or water are pumped into the vessel where the ceria then strips them of oxygen in order to create hydrogen and/or carbon monoxide. This in turn can then be used to fuel hydrogen fuel cells or ‘syngas’.
There is one drawback, however — the current prototype is extremely inefficient, harnessing only between 0.7% and 0.8% of the solar energy taken into the vessel. It would appear that a large amount of the energy is lost as heat is transmitted through the reactor’s wall or through the re-radiation of sunlight back through the device’s aperture.
The researchers are confident that efficiency rates of up to 19% can be achieved through better insulation and smaller apertures. “The chemistry of the material is really well suited to this process,” says Professor Sossina Haile of the California Institute of Technology (Caltech). “This is the first demonstration of doing the full shebang, running it under (light) photons in a reactor.”
+ Science