There has been much talk in the past few decades about renewable energy and our societal need to transition away from fossil fuels in order to avoid the impending physical and social disasters promised by climate change. Every so often a study is published and some renewable energy technology leaps ahead of the pack and captures the public’s attention. There have been many of these instances— we have seen dreams of a fleet of U.S. cars powered by renewable biomass, or have been told of massive carbon capture technologies that can scrub our past environmental sins from the atmosphere, or even how tidal power, in all of its discreteness, will be the secret workhorse of coastal cities. These trends have been far from well defined, but one seemingly clear trend in the United States has been the rise and fall (and current rise) of the hydrogen fuel cell. So what is hydrogen in relation to renewable energy? What do you need to know about it?
Hydrogen is an element (H) on the periodic table. Without going too much into the chemistry (or physics for that matter), hydrogen is the smallest element there is (a hydrogen atom has only one proton!) and most always bonds to one other atom. When isolated, hydrogen commonly takes the form of H2, which means that it pairs with another hydrogen atom, and exists in the gas state at room temperature. This is important to understand, as H2 (“H-two”, or “diatomic hydrogen”) can be combined with oxygen (O) to form H2O (water!). This process of creating water using H2 is what a chemist might call energetically favorable: it releases energy! So this means that if you have H2 and some oxygen handy, and you combine them, you can make energy and water!
The fuel cell
The hydrogen fuel cell makes use of this concept. It is a device (similar to a battery) that uses the fuel (H2) and combines it with oxygen (commonly just from the air) to make electricity. The only byproducts of the process are water and heat! This has a wide variety of applications, cars being the most commonly cited. A hydrogen car would have an “engine” that uses hydrogen fuel (that you would buy from a place similar to a gas station) and emits only water from its “tail-pipe.”
Hydrogen fuel can be thought of as a form of energy storage. This is because initial energy is required to make H2, as it doesn't appear in nature by itself— not like oil or coal, which can be harvested and then used. The energy that is used to make H2 can be thought of as “stored energy” in the fuel, which a fuel cell can then recover and put to use.
There are many ways to make hydrogen, and some are more difficult and expensive than others. Some ways actually involve fossil fuels themselves which takes away some of the environmental consciousness that hydrogen fuel is often associated with. In fact, most hydrogen today is produced by refining natural gas. But this need not be the case! It is possible to harness the power of the sun to create hydrogen, although many of these technologies are still being developed for large scale production.
The limitations of hydrogen
Although a clean form of energy that has significant potential, hydrogen fuel has its limitations that are important to understand. Unlike solar, wind, or tidal power, hydrogen gas is a renewable energy that is combustible (meaning it can be ignited and burned, much like gasoline, wood, and oil). This has presented significant challenges to the scientists and engineers who are designing systems to store and transport the fuel. Hydrogen needs to be pressurized or combined with another element (such as xenon) to be transported and stored, and so designing systems that are safe and easy for anyone to use has been challenging. The same was true for early gasoline engines. But such concerns over safety and transport are being addressed through advancement. Hydrogen fuel cell vehicles are widely considered to be safer then their gasoline counterparts (despite public misconceptions)! Nevertheless, achieving the level of safety and convenience necessary for widespread use has been part of why hydrogen fuel has yet to be universally adopted.
The future of hydrogen
The future looks bright for hydrogen, although its story is not new. NASA has been using hydrogen fuel cells onboard spacecraft since the 1960s, and many times hydrogen has surfaced in the media as the sustainable fuel of the future. Advancements in hydrogen fuel technologies have begun to make this promise look more like a reality. In the past few years, increases in funding for hydrogen projects, along with the release of hydrogen vehicles from big car manufacturers, have breathed new life into this renewable energy.
The powerful potential hydrogen holds as a renewable form of energy storage should not go unrecognized. Along with the fuel cell’s applications in vehicles and home appliances, one day (perhaps soon) solar panels may be connected to systems that generate H2 during off-peak hours. In this sense, hydrogen fuel would replace battery packs (which are environmentally taxing to produce) as the go-to form of solar energy storage. Ultimately, there is still much work to be done— especially in the development of infrastructure— before hydrogen and its fuel cells are in every home, driveway, and business.
Article written by Eric West, Undergraduate at Cornell University
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