How come water powered cars are not common?

To get to the bottom of this, we need to take a look at some of history’s more recent attempts to *go* with *h20* The idea became especially popular a century after Jules Verne’s prediction, during the American oil crises of the 1970s. A prolific inventor named Stanley Mayer patented a vehicle that he said could drive cross country on only 75 liters of pure water. It was a beautiful vision, but the science didn't quite back this idea up, and he ran into some legal trouble because of it. In the late 2000s, the internet was inundated by simple kits that promised to transform your car into a “water-burning hybrid” and increase your fuel economy by up to 300 percent. That same year, a company called Genepax began marketing a water-powered car they claimed was going to save the world from global warming. In the end, though, these prototypes ran into a teensy-tiny problem: the first law of thermodynamics. Energy cannot be created or destroyed. So, what's the problem here? Well, water on its own is simply not a fuel; similar to CO2, it’s only the product of a real fuel combusting. But water still carries energy locked up in its bonds, and Mayer’s invention, like many others, is based on splitting these bonds in a process called electrolysis. 

By separating the hydrogen and oxygen molecules in water, the hydrogen can be used as fuel, and fed back into the engine, or if it is an electric car, the fuel cell. Even better, this consumed hydrogen only produces water as waste. So! A super clean zero emissions fuel attached to zero guilt. Except not really. Because water is very stable, and splitting it up requires a lot more work than it’s worth, kind of like climbing up a steep slide. 
Mayer thought he’d figured out an easy way to do it, with far less energy wasted than a normal electrolytic cell, but what he created consumed more energy than it produced. Today, after decades of research, the electrolysis of water has yet to prove itself a viable way to produce hydrogen fuel. And if we can’t get hydrogen fuel from water, it’s not really clean energy at all. Currently, only four percent of all hydrogen produced comes from water electrolysis, some of which is generated by renewable electricity. The rest mostly comes from fossil fuels. 

Still, some scientists are desperate to make hydrogen energy sustainable, and in recent years, efforts have more than doubled the efficiency of water electrolysis. In turn, researchers at Stanford claim they’ve figured out a way to generate hydrogen fuel using solar power and saltwater. So, who knows maybe there’ll come a day when you can just pull over to the side of the road and fuel up on the ocean, but until then, maybe just try and ride your bike or take the bus as much as you can! Or ride your whale with legs to the local market and watch everyone screams. Whichever you prefer! So, if you could power your car on anything imaginable, what would it be?