Once upon a time, buying a hybrid meant buying a Prius. But that was nearly 20 years ago when they were still the preserve of environmentalists and Hollywood stars. Today, hybrids are for everyone, and they come in all shapes and sizes, some of which you might find surprising.
The world’s most famous hybrid, the Toyota Prius, entered its fourth generation this year, and quietly hums toward five million copies sold since the first one were launched in 1997. No surprise that people think the Prius is the only hybrid. It isn’t, and not only do many car makers make hybrids, they use many radically different types. But they all share a basic principle: the power of the engine is supplemented by a buffering battery and electric motor/generator. When the car is slowing down, kinetic energy can be harvested by the electrical system into the battery rather than uselessly burning off as heat in the brakes – this is what we call regeneration. Then, when the car is moving slowly or cruising on a very light accelerator, the buffer battery feeds the electric motor and the engine can be switched off altogether. That saves fuel. Also, when the engine is at full power, the electric motor gives it a helping hand, so the engine can be smaller than in a conventional car of similar performance. Again, good for fuel consumption.
Finally, conventional petrol cars aren’t very efficient when going gently at part-throttle. The hybrid system increases the load by recharging the battery, allowing the engine to be shut down for a while later. This means the transmission can be programmed to hold the engine at its most efficient speed/load range or else shut it down, and the engine can be re-designed to work well at that regime. More efficiency gains result.
The energy storage medium doesn’t necessarily have to be a battery. Racing cars have experimented with flywheels and big capacitors. Both allow for very rapid input and output of energy – which, in other words, means extra power.
But by far the most common type is the petrol-engine hybrid. Petrol engines are the cheapest option, especially as the hybrid’s electric motor can in effect do the job of a turbocharger. In Europe, hybrids haven’t taken such a hold because the cheapest and most common fuel-saving option is a non-hybrid diesel engine. But in North America, Japan, and China, diesel are very rare, partly because of (recently highlighted) concerns over diesels’ NOx emissions, and partly because the necessary low-Sulphur diesel fuel isn’t always available. Petrol hybrids are very peaceful in town, because the engine is quieter than a diesel, and the electric motor quieter still.
Of course, hybrids have their drawbacks. They’re complicated, costly and heavy, thanks to the need for two power units (engine and motor) and two energy stores (petrol tank and battery). Those duplicated systems can be smaller than if they were doing the job alone, but not a lot cheaper.
Also, hybrids open up their biggest advantage in urban and suburban driving where the energy recuperation and engine downsizing do their bit. At a steady speed cruise, on the motorway, the battery buffer isn’t much use – a diesel engine tends to do better.
There has been controversy about the extra CO2 load of manufacturing hybrids’ batteries. But since most cars produce 85 percent of their lifetime CO2 in driving, and only about 15 percent during manufacture, the improvement in fuel economy easily outweighs any small extra manufacturing load.
Having developed the engine and hybrid system, further fuel savings are comparatively easy. Just make the battery bigger, and in most cases the electric motor too, and allow it to be hooked up to the mains. You’ve got a plug-in hybrid. Most of them can do 20-40 miles using the electric motor. The engine kicks in when the battery is nearly flat and they revert to regular hybrid operation. They appear to be fantastically economical (and hence low in CO2 emissions) in official fuel tests because they can run most of the cycle engine-off, and the depleting electrical energy from the battery isn’t counted. It’s like when your doctor asks you how much you drink each week, and you tell him about the beer but don’t mention the whiskey. Even so, running on UK electricity can be a low- CO2 option.
There’s another kind of mains-capable hybrid, known as the extended-range electric vehicle, or series hybrid. Here the engine doesn’t power the wheels directly – instead, it serves as a generator to top up the battery (while an electric motor drives the wheels).
Most dedicated hybrid cars tend to use all available factors to improve economy – low drag shapes, low-resistance tires, and lightweight materials. Whereas hybridized versions of regular cars have fewer of those tweaks, so they do less well on fuel economy. Taking a fundamentally thirsty vehicle such as a large SUV and then installing a hybrid powertrain might seem a contradiction – like butter on celery. But these big vehicles have most space to package the hybrid components, and the additional cost is small compared with the already high overall price. We will publish few blogs about some of the top hybrid cars. Keep your eyes on autopartstoys blog. Till then, stay green and get a hybrid.