In early United States history, transportation consisted largely of what was possible by the power of man or horse. However, upon the discovery of steam engines and locomotives, long-distance transportation shifted to the faster and more reliable train. For the better part of the last century, if someone wanted to get from one place to another, the likely mode of transportation increasingly became the automobile following a sharp increase in ownership and usage. However, when it comes to trains and, more specifically, automobiles, the primary source of energy for these modes of transportation lies in harnessing the power stored in fuels such as coal and oil. Until only recently, this increased reliance on the burning of fuels that release harmful chemicals into the atmosphere was the only choice available to auto manufacturers. Today, rapidly emerging technologies seek to topple these trends as more and more companies compete in an even more competitive automobile market with the two largest emerging technologies aimed at preventing automobile CO2 emissions lying in electrical and hydrogen fuel cell vehicles.
Powered by Lithium
Fig. 1 Wharton. Nissan Leaf
Largely popularized by Tesla Motors, all-electric vehicles have seen a large spike in popularity over the past decade. These vehicles are designed to use a lithium-ion battery in order to store chemical energy in a rechargeable and renewable state as opposed to gasoline-powered vehicles which combust a non-renewable fuel in order to provide energy. Provided that the energy used by the electric vehicle comes from renewable or lower-polluting sources, this analysis holds true which is why Tesla has been investing heavily in solar technology with ideas such as the Tesla Solar Roof. Currently, however, a large fraction of the energy grid still relies on non-renewable energy, so the impact of these electric vehicles from all different companies is rather stunted. With that said, electric vehicle manufacturers have been making leaps and bounds in the improvement of electric vehicles, expanding the effective range of a single charge from an average of around 80 miles in 2010 to the mid 200s today. This large increase has subsequently made the technology stand on par with that of many gasoline vehicles in terms of usage for both short and long trips. However, electric vehicles are not without their downsides.
To begin with many of the downsides, lithium-ion batteries are very dangerous for the environment when the chemicals are leaked. The chemicals can affect ecosystems and wildlife when uncontrolled, leaving issues with handling these cars following an accident or when scrapping the vehicle. Further, lithium-ion batteries can become highly combustible during accidents when punctured, leaving safety concerns for the heightened risk for a fire, forcing the driver and passengers to flee the vehicle. Finally, a current concern for electric vehicles is simply their cost; many electric powered cars cost far more than an average gasoline car, prompting many people to see these vehicles as more of a luxury rather than a smart economic purchase. Though these downsides may be the case as it currently stands with electric vehicles, the future looks bright for the potential positive impacts they could have in the long term as the energy grid slowly becomes more sustainable and many of the technological complications are resolved.
Powered by Hydrogen
Fig. 2 U.S. Department of Energy. Hydrogen Fuel Cell Electric Car
To begin analyzing the option of hydrogen fuel cell powered vehicles, one must begin by looking at the underlying power source of the car: hydrogen gas. As the lightest element on the periodic table, hydrogen has some significant advantages over gasoline in both performance and environmental impact in the automobile sector. To begin, hydrogen stores approximately three times the energy as gasoline per unit of weight. A hydrogen fuel cell vehicle, therefore, would require one-third the weight of fuel in order to travel the same distance as a gasoline powered car. However, at the same time, hydrogen gas, even when compressed, takes up significantly more space within the hydrogen fuel cell vehicle. As a result, the effect is largely neutral. Compared to lithium-ion batteries, however, hydrogen is significantly more energy dense than current battery technology. When it comes to other factors at play in hydrogen fuel cell cars, some downsides come to light, namely the scarcity of refueling stations nationwide and the questionable environmental benefits they provide in the first place.
Although hydrogen fuel cell vehicles promise a sustainable mode of transportation using hydrogen gas which can be easily obtained and only produces water as a byproduct, due to current limitations, a significant amount of CO2 is still produced in the formation of the hydrogen gas used by fuel cells. This gas can be formed in a variety of ways with the two most popular being natural gas reforming and electrolysis. Of the two, electrolysis is considered to be the most sustainable since it merely requires energy input from a preferably renewable source in order to split water into hydrogen gas and oxygen where the hydrogen is then combusted in a vehicle to reform water and restart the cycle. However, the vast majority of hydrogen gas available commercially comes from natural gas reforming which releases CO2 as a byproduct, rendering the switch to hydrogen-powered vehicles to be rather pointless. Finally, hydrogen-powered vehicles currently suffer from rather large efficiency losses compared to their electric vehicle counterparts due to the fact that energy is lost at each step of the process from formation of the hydrogen, to compression into the storage cells, to transportation to refueling stations, to the efficiency of the mid-tier efficiency of the hydrogen fuel cell engine itself. Overall, hydrogen-powered vehicles certainly have a place in the transition away from gasoline-driven vehicles, but, as with electric vehicles, share a host of drawbacks that must be overcome during the transition.
Although non-gasoline vehicles are far from perfect in their current states, the importance of them grows as time passes on. The potential of these vehicles to combat a significant source of US CO2 emissions head-on provides a popular solution to achieve net zero carbon emissions in the long-term future of the country. Though the technologies have many flaws in their current states, future research and engineering aims to mitigate the environmental and convenience concerns of both technologies as the world progresses to a more sustainable future.