Fossil fuels may be running out, and to many people, that’s good news. These fuels can pollute the air and water, contribute to global warming, and damage habitats when the are mined. The lingering question, though, is how the world will power itself as it begins to turn away from fossil fuels? Forms of renewable energy, such as wind, solar, and geothermal power, are all popular options. Among the newest of renewable energy sources is solar fuel, a technology that could someday produce enough fuel to cleanly power a large portion of the world.
What is Solar Fuel?
Researchers have been able to use the geothermal energy of the sun to convert carbon dioxide and water into hydrogen and other fuels, such as methane, methanol, and ethanol. This fuel can be stored for later use, unlike other types of renewable energy. Solar fuel can therefore solve one of the major roadblocks to widespread adoption of renewable energy sources.
The fuel can be produced through direct or indirect processes. A direct process uses the energy of the sun to produce fuel without any other energy conversions, while an indirect process converts solar energy into another form of energy, such as biomass or electricity, before using that secondary energy to produce fuel. While indirect processes have been easier to implement, they are less efficient due to the intermediary conversion stage.
Solar Fuel Production
Solar fuel production has often been compared to photosynthesis. A photoelectrochemical cell combines the powers of a traditional solar panel and an electrolyzer to make the process possible. The solar panel portion collects sunlight and uses a semiconductor to generate a certain level of voltage. This voltage then powers an electrochemical reaction that separates water molecules into hydrogen, which is the fuel produced, and oxygen, the only byproduct of the production process.
Scientists are currently looking for ways to make this process even more environmentally sound. The materials used in the electrodes within the photoelectrochemical cells should be abundant in the earth, low cost, and stable in order for solar fuel to catch on as a viable method of producing energy.
Solar fuel is still a new technology, and reactors are not currently available for widespread use. Researchers are currently working to develop low-cost, effective methods of producing solar fuel. The photoelectrodes currently used represent a major breakthrough in the development of affordable solar fuel reactors, with more research underway.
Efficiency is the main issue for scientists to solve when it comes to increasing solar fuel production. While the indirect method of producing fuel is effective, it is far from efficient, and the technology does not currently exist to make direct solar fuel production a large-scale solution. Current electrodes use materials that are not particularly effective at facilitating the chemical reactions necessary to make solar fuel. This wastes voltage that could be used to produce more fuel. If scientists begin using a more powerful material in electrodes, this extra voltage can be used to create fuel instead of power the reaction.
Current Uses for Solar Fuel
Hydrogen is the main form of solar fuel being produced today. This fuel can be used in a range of applications that currently use hydrogen power. Hydrogen-fueled cars, while not particularly popular, are excellent candidates for solar fuels. These cars have more efficient engines that provide larger driving ranges, allowing drivers to fill up less often and use an environmentally friendly fuel in the process.
Hydrogen fuel is also used to produce electricity. Fuel cells combine hydrogen with oxygen to create electrical currents, and there are several types of these fuel cells currently available for purchase. Small cells can be used to power laptops and cell phones, while larger ones can power entire buildings.
One of the most exciting — if not common — uses of hydrogen fuel is in space exploration. NASA has used hydrogen fuel to launch space shuttles and other rockets since the 1970s. These vessels use hydrogen fuel cells to power their electrical systems while in orbit, producing only water as a byproduct.
Future Applications of Solar Fuel
Before solar fuel can truly become a viable source of renewable energy, it must be made more affordable and efficient. Hydrogen made from sunlight is almost 10 times more expensive than the same product when made from fossil fuels, and until solar fuel is more affordable, making the switch will be difficult.
Solar fuel can be used on an even larger scale in the future if production increases. It can power entire electrical grids for communities in a way that current renewable resources cannot. Solar fuel can also be used in heavy-duty trucks, ships, aircraft, and other commercial vehicles, which currently use about 40% of transportation fuels worldwide. Continued research into the production and usage of solar fuels could lead to a major step forward in the continued effort to leave fossil fuels behind for good.