Could laptops run on spinach?
Solar cells turn over a new leaf.
28 June 2004
Spinach power is not just for Popeye, it could work for computers too. US researchers have made electrical cells that are powered by plant proteins.
Spinach photosynthetic power can create electricity.
The biologically based solar cells, which convert light into electrical energy, should be efficient and cheap to manufacture, says co-creator Marc Baldo of the Massachusetts Institute of Technology. They could even be used to coat and power laptops, providing a portable source of green energy.
Baldo's team isolated a variety of photosynthetic proteins from spinach and sandwiched them between two layers of conducting material. When light was shone on to the tiny cell, an electrical current was generated. Their discovery is reported in Nano Letters1.
The proteins come from the chloroplasts of spinach leaves; tiny structures that help plants convert light into energy. As the reaction proceeds, electrons move around and create electrical currents.
But extracting the proteins was not easy. The molecules are delicate and tend to stop working when removed from their natural environment. So the researchers preserved them by mixing them with soap-like molecules called peptide surfactants. The protective molecules appear to form a shield around the energy-producing proteins, fooling them into thinking that they are still part of the plant.
The proteins were layered on to a thin gold film, attached to a sheet of transparent, electrically conducting metal, and then covered with a top layer of organic, conducting material. When light is shone on to the unlikely sandwich, the proteins spit out electrons, which pass into the lower layer in the form of an electric current.
The prototype cells still need a little refinement. At present, they can generate current for up to 21 days; then they give up. So alternatives that last longer are needed.
The cells also convert only about 12% of the absorbed light energy into electricity. Still, the researchers believe that it should be possible to reach 20% efficiency, which is better than typical values for commercial silicon solar cells.
1. Das, R. et al. Nano Letters, 4, 1079 - 1083, (2004). *