Photovoltaic panels (PV) generating power from sunlight, have become a very common sight. As of 2017 over 401.5 gigawatts of PV capacity had been installed on the earth’s surface. However this cumulative electrical output produces only 1.8 per cent of the world’s energy demands.
Advances have been made in the efficiency of photovoltaics with energy conversion rates of 20 per cent as the norm. Some models can even reach as high as 45 per cent. Energy storage, for times of low production, is an issue still plaguing the alternate energy field. However, inroads are continually being made with technologists investigating various perceptive solutions.
Batteries are one avenue of research, but using the electrical energy produced by solar or alternate means to make the storable and environmentally friendly gas, hydrogen, has been the dream of many scientists and entrepreneurs.
One idea being scrutinized for energy storage in a number of research laboratories around the world is the conversion of sunshine in to fuel using artificial photosynthesis. One research group in particular has come up with a rather unique tangent on a problem that has beleaguered the advancement of this technology for some period of time.
The focus of a research group at Lawrence Berkeley National Laboratory, or Berkeley Lab, and the Joint Center for Artificial Photosynthesis (JCAP) is a hybrid of the photovoltaic panel. Lead author, Gideon Segev, along with Jeffrey Beeman, Jeffrey Greenblatt, all with JCAP, and Ian Sharp professor of semiconductor Physics at the Technical University of Munich, came up with a unexpectedly simple solution to a “water splitting” device that address the shortcoming of the materials used in their manufacture.
What they have invented is a “hybrid photoelectrochemical and voltaic cell” (HPEV), which splits water into hydrogen while simultaneously using sunlight to produce electricity. Computer simulations led to a prototype which converts 6.8 per cent of the solar energy into storable hydrogen, but also generates electricity at a conversion efficiency of 13.4 per cent. The combined efficiency of both processes in the same HPEV cell totals some 20.2 per cent. This is three times the rate of the conventional solar hydrogen cells currently being investigated.
Water splitting devices use stacks of light-absorbing materials. Different materials in each layer absorb different spectra of light and as it does so it generates an electric current used for the hydrolysis of water. The front surface is usually dedicated to fuel production and the back surface generates usable electricity. Efficiency is affected as the materials that don’t produce as well as the silicon restrict the amount of current harvested.
What Segev and his team came up with was an additional electrical contact on the back of the silicone component resulting in an HPEV device with two contacts instead of one. This simple rearrangement allowed the electrons that were previously contained by the inefficient materials, a route to travel too where their energy could be utilized.
One day the solar arrays in our yard may be used to fuel our vehicles as well as power our house. Time will be the ultimate judge.