By: Eileen Marable
The use of hydrogen as a clean energy source for the future is the subject of much R&D these days. We’ve long since figured out that hydrogen is an element that produces a lot of energy – the key is finding out how to harness it and store it in an efficient fashion so we can use if for everyday purposes like powering our cars or items in the home.
One of the cleanest ways to harness hydrogen is to separate it from a hydrogen heavy resource like water. In a process called electrolysis, an electrical current separates the hydrogen from the oxygen molecules in water. Our colleagues over at TestTube have created this awesome video explaining the process in detail.
So it’s relatively easy to harvest the hydrogen, the problem is how do you store it? The reason hydrogen holds so much hope as a fuel source is that it has a high mass energy density – that means it is powerful stuff compared to other fuels. The problem is hydrogen has a low volumetric energy density, which means it generally takes up a LOT of space to store.
In the past we’ve been able to deal with that given it’s large-scale industrial applications. In fact, NASA used it in the Space Shuttle programs. They used liquid hydrogen (produced when the hydrogen is super cooled) to power those massive rockets to get the Shuttle into space. In that case size wasn’t a barrier.
The key to using hydrogen for slightly less dramatic uses than launching rockets is finding that way to store it in fuel cells. NASA used early versions of hydrogen fuel cells on the Shuttle to power their electrical systems. The only by-product is water, which conveniently the astronauts used to drink.
The system has been improved upon so much over time that NASA is researching how to use it to power spacecraft to explore our solar system. On the smaller, more personal scale we now have cars like the Toyota Mirai that efficiently and cleanly use hydrogen fuel cells. The cars fill up with water, and utilize it's own air in-take to power the process of electrolysis. The hydrogen is stored in carbon fiber fuel cells and the only footprint it leaves behind is more water.
The Mirai is even more efficient because it combines existing electric car technology where electricity created by the braking mechanism is used to power the electrolysis process that creates the hydrogen.
As this car hits the market, the research on creating the next generation of hydrogen fuel use is underway. Creating new efficiencies in the fuel cells is one area of focus, looking both at what substances can most efficiently aid in the electrolysis process and help store them without corrosion.
One new study from McGill University in Montreal has demonstrated how existing technology of storing hydrogen atoms as hydrocarbons can be driven by ambient solar energy. Going a step further than electrolysis, some current storage applications create hydrocarbons by adding a catalyst chemical that bond with multiple hydrogen molecules. The trick is generating enough energy to “dehydrogenize” the hydrocarbon back into hydrogen to store in the fuel cells that make things go. It’s a process that can take a lot of energy and may be impractical on smaller scales, than say needing to power a rocket.
The researchers have found that plain old sunlight can drive dehydrogenization by using platinum based nanoparticles as the catalyst to pull the hydrocarbons apart without using high energy temperatures.
Some day soon things could be powered on a large scale by the very water and air around us, leaving nothing behind to corrupt the planet. We now have cars that can efficiently create and store hydrogen for clean transportation, and someday soon, huge solar farms could transform and store these high-energy molecules on a large scale to power entire city grids.
That’s a clean energy future we look forward to!
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