Solar power, while a limitless resource, poses the challenge of storage and delivery when the Earth’s sun isn’t up and shining.
A team of scientists from Stanford University recently experimented with rust to build a solar-powered battery, which could make large-scale solar power storage possible.
The team led by assistant professors William Chueh and Nicholas Melosh harnessed rust and other metal oxides, fashioning them into solar cells that can split water into hydrogen and oxygen and store energy for night use.
The photons, or packets of energy, captured by the solar cells are converted into electrons providing the energy for water-splitting. At night, recombining the hydrogen with oxygen reclaims the energy and delivers power back into the electrical system, free of carbon release and unsustainable effects of fossil fuels.
The Stanford team found that metal oxide solar cells are better in energy storage than silicon solar cells. Contrary to previously thought, the former more efficiently converted photons into electrons as they grow hotter, while the latter turn less efficient while heating.
"We've shown that inexpensive, abundant and readily processed metal oxides could become better producers of electricity than was previously supposed," says Chueh.
The team tested rust (iron oxide), bismuth vanadium oxide and titanium oxide, looking at how efficient these are in the photon-to-electron conversion and in water-splitting at various temperatures.
All three tests led to greater hydrogen plus oxygen production at increased temperatures, with bismuth vanadium oxide demonstrating the most efficiency. The greater temperatures, too, enhanced the cells’ carrier mobility, or the speed of electrons as they cross the metal oxides.
Co-lead author Xiaofei Ye explains that heating up the metal oxides using sunlight potentially doubles the rate of hydrogen production.
The team added that it’s simple engineering at work for heating solar cells for greater performance, with no need to add externally sourced energy. One of the researchers, Andrey Poletayev, said one can simply concentrate solar radiation through the use of parabolic mirrors or magnifying lenses.
For Chueh, the findings offer not only cost-effective, 24/7 solar power storage, but also hydrogen gas from the water-splitting, which could power machines and vehicles sans pollution. According to him, this type of energy cycle can enable people to store gases, transport them via pipelines and avoid the release of added carbon.
The findings were published in the journal Energy and Environmental Science.