Johannesburg - As the beloved internal combustion engine gets ever closer to possible extinction within the next few decades, the race is on to find the most suitable alternative energy source to power future cars.

One day, our grandchildren will look back in horror at the pollution-spewing cars we drove with little regard for the ill effects this has on the planet.

But what are our nature-nurturing, tut-tutting descendants likely to have under the hood of their emission-free cars on their commutes and family holidays?

There have been many ideas advanced for alternative energy cars over the years - compressed air and nuclear power being among the quirkier ones - but right now in pole position is electric power.

Unless someone invents Star Trek-style teleportation which would make cars obsolete, our future transport needs will be met by electricity and it’s basically a two-horse race between batteries or fuel cells as to how that electricity is generated.

Battery Electric Vehicles

BEVs (if you want to use the ‘in’ lingo) use chemical energy that is stored in rechargeable battery packs to produce electricity, which powers an electric motor.

Lithium-ion batteries, the same type that power your cellphone, are the most popular in both handheld electronics and cars as they’re able to pack a large amount of energy into a relatively small space.

The advantages of BEVs is their quiet running, lack of emissions, the instant torque of the electric motor, and their cost per kilometre being a fraction of that for a petrol or diesel-powered car.

There’s also a widespread electric infrastructure and you can charge the car at home, at work, or anywhere there’s a 12-volt power socket.

Expensive batteries

Their main disadvantages, and which is why you don’t see a Nissan Leaf or BMW i3 on every street, is their limited range and their long recharging times.

The first-generation electric cars claimed ranges of about 160km but in reality achieved just over 100km at best, while they took around eight hours to fully charge at a regular wall socket.

Their batteries are also expensive and a battery pack for the electric i3 is a whopping R339 616 - more than half of the vehicle’s R631 700 pricetag. But as with any budding technology, the cost will eventually decrease as performance improves.

The next generation of BEVs are to offer up to 400km of range, and quick-charging stations will soon be able to charge electric cars for the next leg of a long-distance journey in around half an hour - the time it takes you to eat a burger at a rest stop.

Building the supporting infrastructure is key, and electric cars will gain popularity once quick-charge stations become widespread.

Indirect pollution 

BEVs aren’t as zero-emission as they’re purported to be and indirectly cause pollution due to most electricity being generated by burning coal, and going green clearly requires a holistic approach that includes clean power stations.

Just like we didn’t go from horse-drawn wagons to Ferraris overnight, it will take a couple of decades for the transformation to take place, but the prospects for BEVs are good.

With improving range, quicker charging times, and cheaper batteries due to economies of scale, they look most likely to take hold as the most popular types of future cars.

Tesla, the Nissan Leaf and the BMW i3 were the early BEV adopters that blazed the trail, but now most auto companies have followed suit and will soon introduce electric cars of their own.

Hydrogen fuel cells

This is where hydrogen and oxygen are mixed inside a fuel cell stack to produce electricity, which powers an electric motor.

A small number of car companies are investing in fuel cell vehicles, including Honda which in 2008 launched its FCX Clarity as the first hydrogen fuel cell vehicle to reach the market (only in the USA, Europe and Japan).

Its successor, the Honda Clarity Fuel Cell (pictured above), was launched in 2016 and at 589km it is reputed to have the longest range of any zero-emission vehicle in production.

Like BEVs, hydrogen fuel-cell cars are locally pollution-free and the only exhaust byproduct is water, but their main advantage is that they have a longer range than BEVs and don’t need recharging; they are quickly refuelled at a hydrogen filling station in around three to five minutes.

The technology’s very expensive however, with FCVs around double the average new car price.

Splitting water

And while hydrogen is abundant and can be made from water, producing the stuff is expensive and can create pollution. It isn’t a naturally occurring element and has to be created through either electrolysis or cracking hydrocarbons.

Electrolysis involves splitting water into its constituent components of hydrogen and oxygen, an inefficient process that takes an enormous amount of energy (much less efficient than creating electricity using batteries).

Cracking hydrocarbons involves making hydrogen from non-renewable natural gas in a process that creates enormous CO2 emissions.

The major stumbling block will be the high cost of building a widespread infrastructure of hydrogen filling stations. This puts HCVs initially at a distinct disadvantage to BEVs which can be charged (albeit slowly) at any wall plug.

Nevertheless, a number of automakers including Audi, BMW, Honda, Hyundai, Mercedes-Benz and Toyota, are forging ahead with the technology and are selling HCVs (in limited numbers and not in South Africa).

Hydrogen internal combustion engine

This is another concept that was in the running a few years ago, but has failed to gain traction. Unlike with electricity-producing hydrogen fuel cells, here the hydrogen is burned - just like petrol - to run a combustion engine.

BMW introduced a hydrogen-powered 7 Series in a limited production run from 2005 to 2007, as the world’s first car to use an internal combustion engine modified to run on both petrol and hydrogen.

Like BEVs and HCVs it was virtually pollution free, with water vapour being the main exhaust gas, and it could be refilled in a relatively quick eight minutes.

Like a regular car

BMW believed the concept would take hold with buyers seeking a non-polluting vehicle that still drove and sounded like a regular car.

Unlike fuel-cell and electric cars which are silent, the engine can be revved and there’s an exhaust sound to listen to.

The big problem was its sky-high fuel consumption. Hydrogen has a much lower energy density than petrol, which saw the BMW Hydrogen 7 burning through around 50 litres of hydrogen per 100km (compared to about 14 litres per 100km when running on petrol), and due to the size of its tank it had a hydrogen-fuelled range of just 200km.

No wonder the idea didn’t take hold.

Drive360