If you read my recent article, you know I'm not the biggest fan of electric vehicles and their long-term viability. Not only are there issues with the current batteries being used, but there are also better solutions that could be game-changers when it comes to zero-emission cars. As a bonus, these alternative solutions could make investors a pretty penny.

The problem
Electric cars seem like a great idea. However, their limited range and expensive batteries have limited their appeal. According to Pike Research, consumer interest in electric cars has steadily declined over the past two years for exactly those reasons. The researcher also found that consumers are willing to pay more for an electric car, but only about 18.75% more, or around $23,750. That's a fair amount less than what current electric cars actually sell for.  

As for the lithium-ion battery used in General Motors' (GM -0.04%) Chevy Volt, Toyota's (TM 1.07%) fifth-generation Prius, Ford's (F 0.08%) third-generation hybrid system in the Fusion Hybrid and C-MAX, and Nissan's (NSANY -0.56%) Leaf, it's incredibly expensive. But that's not where the problems with Li-ion batteries end.

First, Li-ion batteries lose storage capacity over time, meaning you'll be able to travel progressively less on one charge. Battery warranties state that only an "abnormal decrease" in range is covered, meaning car companies know the declining power is a problem, but they don't say a whole lot about it to consumers.

Second, if Li-ion batteries are damaged, or if there's a defect, or if they're exposed to too much heat, they're more susceptible to short-circuiting and starting a fire than any other battery is. That's because Li-ion batteries use flammable liquid electrodes, which are susceptible to thermal runaway. For a recent example, look no further than Boeing's (BA -2.87%) Li-ion batteries, which forced the grounding of the entire fleet of 787 Dreamliners. Granted, manufacturers say electric cars use a cooling system and automatic shutdown to avoid such a problem, but the Dreamliner had similar safety features. Researchers are working on solid electrodes as an alternative, but there are a number of issues, and it's all still in the beginning stages.   

Third, lithium is an alkali metal and isn't naturally occurring. That means it has to be refined after being extracted through salar brines (the most common approach) and mined hard rock. In a recent study, the European Commission on Science for Environmental Policy stated, "Although there is no immediate shortage of lithium, its continued use needs to be monitored, especially as lithium mining's toxicity and location in places of natural beauty can cause significant environmental, health and social impacts." I don't know about you, but one of the reasons I like sustainable and alternative energies is that I'm a fan of the earth. That means I'm not a huge fan of things that mess up the pretty places.

The solutions?
There's a lot of hype around hydrogen fuel cells, and for one very good reason: Hydrogen is the most abundant element in the universe. Both Daimler AG's (MBGA.F -0.04%) Mercedes-Benz and Honda Motor (HMC -0.49%) are testing hydrogen fuel cell vehicles in California. While these cars can go 190 to 240 miles before needing to refuel -- and then refuel in just minutes -- with a price tag of $350,000 for the hydrogen cells per unit, these cars are probably a bit outside the average budget.  

There's hope for a cheaper method of developing hydrogen cells, but because hydrogen is the smallest atom and is extremely corrosive, storing it also presents an issue. That, in turn, requires costly solutions. Consequently, this isn't my favorite solution.

Another alternative, which Toyota is researching, is a magnesium-ion battery. Toyota believes that such a battery would be safer, as well as cheaper, since magnesium is more readily available -- it's the eighth most abundant element in the earth's curst. Toyota also argues that the batteries would have a greater range, because magnesium-ions have a positive charge of two, as opposed to lithium's one, making the battery more energy-dense. 

Unfortunately, commercial production of a magnesium-ion battery is still a way off. But as a long-term solution, it's promising -- and as we Fools like to invest for the long term, it's a potentially promising addition to your portfolio.  

Finally, cryogen, or liquid air-powered engines are re-emerging as an alternative energy option. As The Economist reported, Peter Dearman, a British inventor, found a solution to the expensive heat exchange that previously made liquid air engines unattractive.  

Dearman Engine, along with Ricardo, a prestigious global engineering consultancy, is quickly moving forward with an engine design, and they expect to have a "fully characterized demonstration engine [that] is scheduled to go into testing during mid-2013 to provide the groundwork for field trials." 

I'm a fan of this solution for a few reasons:

  • The engine uses traditional reciprocating engine processes, so there's less cost involved and it can hit the market more quickly than other alternative technologies. 
  • A proof-of-concept model has already been tested and deemed more efficient than any other previously built.  
  • Following an extensive study, Ricardo stated that "the technology is likely to compete with hydrogen fuel cell and battery electric systems in zero-emission applications." 
  • A liquid air engine would be a far cry cheaper than hydrogen or battery cars, making the car more affordable for consumers. 
  • Liquid air is less hazardous than batteries, hydrogen, or diesel. And it can be "produced and stored on site or delivered through pipeline or road tanker." 
  • Liquid air can be stored in non-pressurized insulated tanks. As a bonus, energy stored as liquid air would allow energy produced by wind farms and other alternative sources to be stored for later use, instead of being wasted. 
  • It's possible that the "fuel" used to power the engine could use existing industrial companies' distribution infrastructures. 

Basically, a liquid air engine is a lot like a typical combustion engine, except that instead of using a spark plug to ignite the fuel and cause an explosion to force the piston down, the liquid air itself expands into a gas as it reaches ambient temperature and forces the piston down. So while liquid air engines still have hurdles to overcome, they're promising, and they could be a viable and cheap alternative to current batteries.

Wave bye-bye to current EVs
The race is still going strong for an alternative energy solution. Yes, Li-ion batteries are popular right now, but given advances in technology, I'm not sure they'll stay popular. Some solutions aren't the most financially feasible -- hello, hydrogen -- but others have lots of potential and are relatively cheap. Those are the ones I'm keeping my eyes on.