The market for gasoline-electric hybrids and electric cars is expected to grow over the next few years, but they aren't the only energy-efficient vehicles expected to become more popular.

Also looking at an increase in popularity are micro-hybrids and mild hybrids, according to a Lux Research report.

According to MarketWatch, the Lux report expects the market for micro-hybrids to grow to 39 million vehicles by 2017, creating a $6.9 billion market for energy storage devices.

Europe and China will lead the race for micro-hybrids, and the U.S. market for the vehicles will rise from virtually nothing to 8 million vehicles by 2017.

Over the same period, sales of mild hybrids should grow by 1.5 million vehicles, or 1.6 percent of the market.

Micro- and mild-hybrids: What are they?

Mild hybrids are easy enough to explain. Honda has been selling them for several years. They aren't as efficient as full hybrids like the Toyota Prius, but still have the ability to use stored energy to drive a motor, assisting the regular gasoline engine.

That means a smaller, more efficient engine can be used, without compromising too much on performance. When coasting and braking, the electric motor turns into a generator, storing energy for later use.

Micro-hybrids are a half-way measure between regular vehicles and those equipped with stop-start technology, and mild hybrids. The report defines them as vehicles using a small battery to provide efficiency-boosting features.

They use a small battery or capacitor to store energy, generated by the heavy-duty starter motor and used for rapid stop-start systems.

Unlike a normal stop-start system, micro-hybrids don't drain the regular battery, and intelligent systems can stop the engine in a precise position to reduce fuel use when re-starting. The heavy-duty starter motor acts as a generator, and the energy produced is stored in capacitors or batteries.

Several manufacturers already offer micro-hybrids in Europe, where stop-start related systems offer more visible benefit on official fuel consumption tests. The lack of impact on EPA city ratings is why stop-start hasn't yet caught on in the U.S.

What does it mean for buyers?

For many, it will be a simple and inexpensive way of improving economy, particularly so in the city.

Without the need for expensive and heavy battery packs, the technology is also suited to sports cars, muscle cars and other enthusiast vehicles, where weight is a concern and drivers are less willing to forego a more traditional driving feel for that of a full hybrid system.

Being relatively easy to produce - in the absence of large battery packs and electric motors - they could also have the largest impact on reducing fuel usage and emissions, as they'll be available on a much wider range of vehicles.

For other consumers, and those who already drive hybrid vehicles, the extra demand for batteries should help bring down the price, making efficiency more affordable than ever.

And though micro and mild hybrids may not be the final solution for cutting down on fossil fuels and reducing pollution, they certainly have the potential to improve gas mileage in the meantime.


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