When looking at the best ways to meet humanity’s energy needs, there is little doubt that the sun is the ultimate answer. In one hour, the Earth receives enough energy from the sun to meet all of our needs for a year. Despite this fact, the world currently only gets about 1% of its energy directly from the sun.
Our technologies for converting solar energy into electricity keep getting better and keep getting cheaper. However, none of them gives us a steady supply of energy because the sun doesn’t always shine.
For solar energy to meet all our needs, there needs to be an efficient and economical way to store the sun’s energy. Battery technology represents one solution to the problem that in principle can provide the electricity grid with the continuous supply of electricity that it needs. Batteries can provide energy for transportation as well, but charging times for electric vehicles represent a stumbling block.
A more universal approach is the use of solar fuels: turning the sun’s energy into a fuel that can be stored, transported, and used to both generate electricity and power vehicles. Hydrogen is the most attractive solar fuel since it is carbon-free.
Today’s technologies for making solar hydrogen require two steps: generating electricity from sunlight and then using electricity to produce hydrogen from water. This two-step process, known as photovoltaic electrolysis, is currently neither cheap nor efficient.
The Holy Grail is a one-step process: a device that would use sunlight directly to produce hydrogen, otherwise known as a photoelectrochemical cell. We are still far from having a practical, scalable technology for doing this sort of artificial photosynthesis, but if we are ultimately successful, it will make a huge difference in the world.
Photo, posted April 26, 2008, courtesy of Lima Andruska via Flickr.