9 Possible Alternatives to the Gas-Powered Engine

The search is on for alternatives to gasoline that consumers will accept in their cars, trucks, and SUVs. While gasoline prices are a lot lower now than they were at the beginning of the decade, environmental concerns are pushing automakers around the world to develop alternatives that generate fewer emissions -- or none at all.

Here are nine alternatives that are available or in development at some level today.

To date, the most popular alternative to gasoline internal-combustion engines has been the gasoline-electric hybrid. Vehicles like Toyota’s (NYSE: TM) huge-selling Prius combine a conventional gasoline engine with an electric motor and a battery pack. The battery is charged as the car drives, and the electric motor works in conjunction with the gasoline engine, saving gas. 

ALSO READ: Toyota is Finally Getting Serious About Electric Cars

Taking the idea of a hybrid one step further, some automakers have begun offering “plug-in” hybrids fitted with lithium-ion battery packs that can be charged up by external chargers. If you remember to charge up your plug-in hybrid, you can travel a limited way (typically 15 to 40 miles) entirely on electricity. If you need to go further, the vehicle operates like a typical hybrid.

General Motors’ (NYSE: GM) Chevrolet Volt was one of the first plug-in hybrids, and it remains a strong seller. 

More and more experts think that our automotive future will be fully electric. Battery-powered vehicles have been around for decades, but in recent times Tesla (NASDAQ: TSLA) has shown how lithium-ion batteries can be used to power fast, stylish vehicles.

In the last year, most automakers have announced plans to bring at least some battery-electric vehicles to market over the next several years. It’ll take some time for them to become widespread, however: Lithium is a key ingredient in most electric-vehicle batteries, and while there’s plenty in the ground, miners haven’t yet scaled up to produce enough to keep up with automakers’ production plans.  

What’s biodiesel? It’s diesel fuel manufactured from edible oils like animal fats or used frying oil from restaurants. When mixed with conventional diesel fuel, it raises the octane and helps it burn more cleanly.

Most diesel-powered vehicles offered in the U.S. can run on diesel fuel that includes up to 20% biodiesel. It’s possible to run vehicles entirely on biodiesel fuel, but the engines require some modifications. 

ALSO READ: How Biofuels Will Change the Trucking Industry

Vehicles powered by alcohol have been a thing for a while. Alcohol -- specifically, ethanol made from corn -- has a lower energy density than gasoline, but advocates have argued that its renewable nature makes ethanol a more environmentally-friendly choice.

There has been considerable controversy over that point. But while there are few vehicles that run entirely on ethanol, quite a few have been offered in recent years with engines that can take “flex fuel,” gasoline mixed with up to 15% ethanol.

How can you tell a “flex fuel” vehicle? The gas cap will be yellow.

Propane-powered cars and trucks? They’re out there: Propane, or liquified petroleum gas (LPG), is a by-product of oil refining that’s significantly cheaper than gasoline. That has made it appealing to some government and commercial fleet operators, and automakers like Ford Motor Company (NYSE: F) have responded by offering LPG-ready vehicles for these markets.

There are downsides that make LPG-powered vehicles unlikely to become widely popular: LPG-powered vehicles require special pressurized tanks that are heavy and bulky, and refueling stations are scarce. Those are challenges that can be overcome by a fleet operator, but they’re obstacles for ordinary customers. 

Can natural gas power a car or truck? Yes: Vehicles that run on compressed natural gas (or CNG) get similar mileage to gasoline-powered equivalents, but natural gas burns more cleanly than gasoline. To date, CNG-powered vehicles have mostly been limited to commercial fleets, and most have been trucks.

A few automakers have tried offering CNG-powered cars, including General Motors and Honda. But as with LPG, the lack of CNG refueling stations has so far made them a hard sell beyond fleets. 

Fuel cells -- devices that chemically convert the energy in hydrogen gas to electricity -- are probably the leading alternative to batteries in electric cars. They’re considered very green, as a hydrogen fuel cell’s only “emission” is water vapor, which can be collected and reused.

Fuel cells have been around for decades, but until recently they’ve been too expensive for automotive use. That’s changing, slowly: Toyota, Honda, and Hyundai all currently offer fuel cell electric vehicles, or FCEVs, for sale in a few regions of the U.S.

ALSO READ: Toyota Taps Fuel Cell Energy for California Hydrogen Project

Will solar panels ever be practical for automotive use? To date, most automakers have looked elsewhere for ways to power electric cars. But researchers keep tinkering, spurred on by an annual race called the World Solar Challenge -- and at least some automakers are watching.

The University of Michigan’s solar-car racing team, sponsored by heavy hitters like Ford and GM, is a perennial contender in the Challenge. 

John Rosevear owns shares of Ford and General Motors. The Motley Fool owns shares of and recommends Ford and Tesla. The Motley Fool has a disclosure policy.