Hybrid cars explained
OK, here’s your starter for 10: what was the first hybrid car to go on sale in the UK? It was the Toyota Prius, wasn’t it? Of course it was; this was the car that all around the world went on to become synonymous with hybrid technology. Except the Prius wasn’t the first hybrid to be sold in the UK; it was actually the original Honda Insight, now forgotten thanks to less than 200 having been sold here. Meanwhile the second-generation Insight has come and gone and the Prius continues to sell in huge numbers, now in fourth-generation form.
However, the Prius was the first hybrid to go on sale in its native Japan, more than two years before the Honda arrived. Toyota had realised that conventional petrol and diesel-powered cars are just too inefficient; too much energy is lost in everyday driving, leading to poor fuel economy. What Toyota did by inventing the first practical, usable hybrid, was to come up with a way of reducing the amount of energy wasted through driving – or more specifically, a way of capturing the energy that would otherwise be lost every time the car slows down.
To understand the point of a hybrid, a short physics lesson is needed – but we’ll keep it simple. The key point at the heart of the hybrid is that you can’t create or destroy energy, you can only convert it from one form to another. Some of the different types of energy include light, heat and motion, with the last one known as kinetic energy. In a conventional car an engine generates lots of heat and the rest (the minority) is converted into kinetic energy by getting the car up to speed.
Every time the car is braked, kinetic energy is converted into heat and that energy then disappears into the atmosphere. What a hybrid car does, is to convert that kinetic energy into electricity which is then stored in a battery pack; it does this through a regenerative braking system.
So to summarise, a car uses a petrol or diesel engine to burn fuel which then produces the power to produce forward motion. It’s just the same in a hybrid, but when you slow down a battery pack is topped up with electricity from the regenerative brakes. At low speeds the batteries power an electric motor which allows the car to be an electric vehicle at low speeds and for short distances. Then as the speed and distance increase, to save the batteries being depleted too quickly, the engine cuts in to drive the car conventionally.
The next generation
When Toyota introduced the Prius, a hybrid was all about boosting economy by making the car more efficient. But things have come on since then. The next step was when Toyota subsidiary Lexus started to build hybrids that focused on increasing performance by supplementing the petrol engine with an electric motor. In essence it was the same principle as before; providing extra power without having to burn so much fuel, but for the first time the focus was on performance rather than ultimate economy.
However, as rival brands started to develop their own hybrids, they were still selling them on the premise that they squeezed more miles out of every gallon of fuel (which by now wasn’t always petrol, as some diesel hybrids started to be developed). All of them suffered from the same limitation; a small battery pack that allowed an electric-only range of typically just four miles. So in urban driving the engine would kick in and start burning fossil fuel once you’d barely started your journey.
The answer to increasing the electric-only range of the hybrid seemed simple enough – fit a bigger battery pack. But keeping this charged up would have meant the engine acting as a generator, which defeated the object. So what if you could charge the enlarged battery pack from your domestic electricity supply? You could have the best of both worlds; an electric car for short trips and the convenience of a petrol or diesel for those longer journeys. And so the plug-in hybrid was born, typically offering a range of up to 30 miles if you didn’t go too crazy with your right foot. The key issue was that many urban dwellers didn’t have any way of charging their transport unless they draped cables across the pavement, but for anybody with a drive or garage it was a way of enjoying reduced fuel costs and the potential to achieve a real-world fuel consumption figure of more than 100mpg.
The fundamental flaw
Hybrid technology relies on lots of slowing down to keep the battery pack topped up. While a plug-in hybrid suffers less from this to a point, if you just thrash up and down the UK’s motorway network the battery pack will soon get depleted and that 70mpg potential will be closer to 40mpg in reality. Don’t rush into buying a hybrid on the assumption that your fuel bills will automatically plummet – only some drivers see the benefits.
Urban drivers or anyone regularly caught in traffic is likely to benefit from this technology. But if you somehow avoid the worst of the jams and your journeys tend to consist of high-speed motorway miles, you’ll end up paying a premium for a hybrid without seeing your fuel bills slashed. So before jumping in feet first, assuming that you can decimate your fuel bills, consider how you drive your car and whether or not you’re likely to reap the benefits of all that tech.
Richard Dredge
