A Hybrid is never “just a Hybrid”.
The Parallel architecture has been quite popular, simply because it is cheap and easy to make. And you can actually make a wimpy Parallel that almost doesn’t qualify as a Hybrid, and still call it a Hybrid and sell it as such, as do certain makers that I shall keep unnamed. 😉
The Series architecture is the most efficient, but has been kind of expensive to build up to now, and it also kind of draws the attention of the public to the fact that you don’t actually need a combustion engine to make a car go…
Then there is that wonderful engineering achievement, the “mixed Hybrid” architecture, that stands in the middle of the classification: it is as much Series as it is Parallel – yes, I’m talking about the Toyota Synergy Drive again. If you’re contemplating the (disgrace of the) present car market, it is by far the best thing out there. But if you investigate the Electric Vehicle technology (including the Hybrids), you become shocked to learn that they have been around for well over 100 years, and that progress in this area has been interrupted continuously since then, solely because of the internal combustion engine and the big players behind it. It’s true that the Electric Vehicle has made many sporadic appearances in recent history – it is inevitable, because the best solutions are evident to any one who stops and thinks for a while – but only to be sent back into “the chest of forgotten things” by the forces of “business as usual”. To me, the Toyota Synergy Drive is just a mere representative of this mentality and way of doing things, just like the rest of them: keep the combustion engine as the star of the show for as many years as you possibly can, preferably until the oil runs out. Then, when there is no alternative, we can explore other locomotive means.
Well… not for me. I firmly believe that if we do that, it will be too late to change anything – the planet will no longer welcome us with warm predictable summers and rainy predictable winters – the planetary weather system will leave the present point of equilibrium and find a new one… which may be as alien to us as the weather on Mars or Mercury. And no one wants that. Really.
So, to answer the original question, I prefer the Series Hybrid any day. It is the best architecture because it completely decouples the power source from the locomotion system, allowing the vehicle to generate (or more precisely, transform) its energy in the most efficient way possible without being constrained by the sudden and unpredictable needs and desires of the driver. Objectively, the electric battery system acts as a temporary intermediate storage station that feeds the electric motor(s) as fast or as slowly as needed, leaving the generator alone to do its job in the most efficient way.
That generator can be pretty much anything, as long as it packs enough “punch” (power and energy): a gasoline or diesel engine, a gas turbine, a hydrogen fuel cell, a photovoltaic solar panel (if they ever get close to 100% efficient) , bicycle pedals, or whatever other gadget you can cram into the car and get it to cover the distance. Plus the energy storage itself, of course (the fuel tank, where applicable). It can even be a combination of any of those things. In an ideal world, the generator would not be inside the car; then you’d have the good old Electric Vehicle. In this class, I must bow down and tip my hat to the grand master of modern EVs, the Tesla Roadster, who is doing a great job of changing public awareness about EVs and killing the myth of thermal engine superiority. But we must be realistic, and we do need an on-board generator to make the typical car cover the expected 1000km with confidence (or at the very least, a good 500km).
So, its a Series Hybrid. What’s the generator?
Frankly, I don’t much care about that, for the time being. You see, my major beef with the current generation of hybrids is that they are still way too dependent on the Parallel model to really make a difference in the world’s wrongs. They are also so afraid of stepping away from the tried and tested solutions of the past (i.e. the mechanical transmission), that they don’t dare explore the great inventions of present times.
For practical reasons of feasibility, I will start with a normal (gasoline combustion engine) car, and step-by-step transform it into the green gem I dream about. Somewhere along that path, I will have to choose the right power source, but there is ample enough time for that. The first step is to install an electric traction system in the car, effectively turning it into a Parallel Hybrid. Then, after testing and tweaking, remove the entire mechanical transmission and use the combustion engine exclusively as propellant for the generator, effectively turning it into a Series Hybrid. And after that is tested and tweaked, I can go find the perfect green power source, which is going to take considerable planning and implementation effort. But by then, I will already have a far better car than I have now.
There is another reason why I’m not building a Hybrid car from scratch, and instead I am adapting an ordinary combustion car: Trash. Or better said, Recycling. I can’t stand the fact that everything we buy sooner or later ends up in the garbage dump, even if it is a car. Cars today are like 95% recyclable, but I doubt that even 30% of the actual cars are in fact recycled. So I’m recycling my own car, extending its useful life, and in the meantime creating an innovative public movement. Have I told you I hate waste? 😉
How’s that for a plan?