Many engineers doubt that battery technology can ever be developed to a state in which it could give electric cars the same customer appeal as conventional cars.
There is more optimism about the hybrid, which uses a combination of electric power with a conventional engine – or even a gas turbine. Unlike battery vehicles, hybrids promise good fuel consumption and low emissions without sacrificing the range and performance of a conventional car.
Few have made it into production. However, two are now destined to reach the UK market next year. Toyota’s Prius has been on sale in Japan for nearly two years, and demand has been high enough to persuade the company to increase production to 2,000 monthly.
But it will be beaten to the European market by the Honda Insight. The Insight is about to go into production at Honda’s specialist Tochigi plant. With its lightweight and high aerodynamic efficiency, it comes close to achieving the goal of covering 100km on three litres of petrol. And the two-seater coupe, with its chassis and suspension designed to give it a sporty feel, is a clear attempt to send a signal that environmental credentials do not imply inferior performance.
Though both are hybrids, the Insight differs considerably from the Prius in its design philosophy. The Prius, a four-seater saloon, is a parallel hybrid, carrying enough batteries to give it a reasonable range when operating at low speeds in towns under electric power alone.
Elsewhere, it is driven by a petrol engine which also charges the batteries.
The Insight, however, is a series hybrid, in which an electric motor and an internal combustion engine are connected to the same drivetrain. The electric motor gives a boost to the internal combustion engine during acceleration. For cruising, the engine alone drives the wheels. During deceleration the electric motor acts as a generator to recharge the batteries. The petrol engine automatically cuts out when stationary and idling.
The Honda uses a 50kW (67bhp) petrol engine with a 10kW electric motor – enough to give acceptable performance because electric motors are capable of operating at higher than their rated power for short periods – while the Toyota uses a 43kW (57bhp) petrol engine and a 30kW electric motor.
Though the parallel arrangement gives more flexibility – power can be diverted from the petrol engine to charge the batteries while on the move – Honda’s series arrangement avoids the need for complex control mechanisms, large capacity batteries and a separate motor and generator. Honda also claims the Insight feels more like a conventional car.
Both share the characteristics of all hybrids. Regenerative braking – energy is recovered during braking and stored in the batteries – allows an improvement in fuel consumption.
Both power plants can be used together to deal with peak power demands such as hard acceleration. This allows the internal combustion engine to be sized closer to the average power demand – typically a quarter to a fifth of the peak. This `peak lopping’ also improves emissions performance, because nitrogen oxides and hydrocarbons are produced under high or transient loads.
Through its combination of the hybrid drivetrain, low weight and efficient aerodynamics, the Insight achieves fuel consumption of 3.4 litres/100km (83mpg).
The big disadvantage of hybrids is cost. The Insight is expected to be priced at less than £20,000, a figure significantly below its true cost.
The cost is partly due to the complexity of having two power plants, and partly because the Insight also has a sophisticated aluminium body to reduce weight. Many experts therefore doubt whether, even if produced in high volumes, hybrids will ever provide an acceptable match of performance and cost.
Nonetheless, the success of the Prius has prompted Toyota to start development on a range of hybrids, including a version of the Yaris City car, the Previa multi-purpose vehicle, and the Crown luxury model.
Copyright: Centaur Communications Limited