Today, parallel gasoline-hybrids are often touted as a cleaner, greener alternative despite the simple fact that avoiding purchasing a new car and sticking with your old one saves more energy and environmental impact in almost all cases. Rather than using the new technology to simplify the vehicle, hybrids are more complicated than their predecessors, and the results are not positive. The added weight of the electrical system means that the vehicle is either unusually heavy, or unusually expensive due to the necessity of balancing weight and crash safety. And the hybrid power system, most especially the batteries, comes at a substantial cost premium as well as substantially increasing environmental impact.
Let's make sure we all know what we're talking about here...
We're talking about gas hybrids here; there are also air-electric hybrids1, and human-electrics (think bicycles) and so on. They're not so interesting to me because in general they aren't suited for all types of driving, so we won't be talking about them here.
The first gasoline-hybrid to be sold (at least on a major basis) was the Honda Insight, a sort of clean-green successor to the Honda CRX (which came in a 55mpg freeway "HF" model.) Even its styling is clearly CRX-derived. Its nerdy styling and cookie-cutter wheels won it few friends but you can see these on the road any time. This was followed by Toyota's Prius, and now both Honda and Toyota make several models of non-nerd hybrids. Most other automakers planning a hybrid vehicle license Toyota's technology.
A parallel hybrid is a vehicle in which the multiple power systems are each capable of driving the vehicle. In all cases this means that the vehicle has both electric and liquid fuel, internal combustion engines - typically burning gasoline, although some diesel models are now appearing. It is possible for one motor to drive the front wheels and the other the rear, or for both to be connected into a complex transmission. Parallel hybrids are simpler in some ways than series hybrids, and may require less battery capacity.
A series hybrid is kind of an interim step between a parallel hybrid and a pure electric vehicle. They use an engine to run a generator in order to charge batteries, and then use an electric motor to propel the vehicle. Sans batteries, we have all seen this type of system moving; the common "diesel" locomotive is actually diesel-electric. Adding batteries into the mix permits us to perform regenerative braking, and to start out with stored power. Usually the motor-generator pair can generate at least enough power to maintain cruising speed; in an aerodynamic vehicle this might only be about 25 horsepower, even at freeway speeds! Any time you're running the vehicle under this, the battery can be charged. The major benefit of this system is that it eliminates the transmission. The generator might be as much as 90% efficient, and the drive motor perhaps 85%; total driveline losses in an automatic vehicle can easily reach 20%, so this is not as bad as you might imagine. And as the number of driven wheels increases, driveline loss increases, so this is even more useful technology in an all-wheel-drive vehicle. Eliminating the transmission also eliminates a significant number of parts and a common source of leaks.
The interesting thing about series hybrids, however, is that they don't need to run an internal combustion engine. They could literally be run with any source of motive power. One option is to use a turbine, which is much more efficient than a typical gasoline engine. Chrysler actually experimented with turbine-driven cars (with a transmission) in the 1960s but never went into production. They reportedly had problems with transmissions (the gear drive for taking the turbine output down to a usable speed was heavy, noisy, and failure-prone) and they were dealing with a large, heavy car. Even so, they achieved unheard-of efficiency for their day, getting over 40 miles per gallon on pump gas in a full-size sedan. If a generator were integrated into or closely coupled to a turbine, you could get maximum energy out of your fuel with minimal mass. Another benefit of using turbines is that they can more easily run on a variety of fuels than internal combustion types, potentially allowing the use of gasoline, alcohol, diesel fuels, vegetable oil, and even others in the same vehicle.
Not a third category but an attribute that can apply to any hybrid with a battery or a regenerative fuel cell, plug-in hybrids can be charged not only through driving or running their motor but also by plugging them into wall current. They still have a gasoline (or similar) engine but if you only make short trips it will never start. The up side is the increased range, the down side is lugging the gasoline engine around with you. Of course, for most people it is not practical to have a gasoline car for long trips and an electric for around town, so this may be the best solution. It's especially compelling because charging from the grid is cheap, especially if you use a time-of-use meter2 and charge at night. You also have the option to charge from some alternative source of energy, like wind or solar.
An electric vehicle doesn't have an internal combustion engine. It uses a fuel cell and/or battery bank as a source of power. Batteries have poor energy density compared to liquid fuels, and long charge times, which is probably the single largest drawback. Fuel cells are seen as a possible solution, but so far they are only efficient at high temperatures and in general are expensive to produce both in terms of energy cost and environmental impact.
Ideally, however, we could eliminate the liquid fuel motor entirely. While the debate between liquid fuels and batteries is a very complicated one, one debate that is not complicated is the merit of the electric motor as opposed to any current internal combustion engine design, even a very simple one like the Wankel rotary engine. They simply do not have parts to wear out, especially in the case of brushless3 motors. An electric motor has four major parts: Two bearings, a case, and a rotor. No combustion engine is so simple! Jay Leno has an electric car from the 1920s which he drives on a regular basis, and to this day it requires no major maintenance. It even has the original batteries, although their power output is not useful in propelling a modern electric.
Either type of vehicle is vastly simpler than a hybrid with an internal combusion engine. Some all-electric vehicles still have a transmission, but in general it has only two speeds or so, and is thus much simpler than any automatic transmission which has a vast multitude of fiddly little parts, or even an ordinary five-speed manual which still has a good number of them. The Tesla Roadster utilizes a two-speed sequential gearbox (plus a reverse gear) which is smaller, simpler, and lighter than a transmission for a gasoline car in spite of the Tesla's amazing torque.
Fuel Cell Electrics
Fuel cells permit the use of a liquid fuel to propel electric vehicles. While some designs are capable of working in reverse and thus performing regenerative braking and the like, they don't switch back and forth as readily as batteries and they aren't as efficient at it, either. On the other hand, mediocre liquid fuels store around twice as much energy per kilogram as the best batteries ever will, and they can be refueled as quickly as liquid can be poured into the tank. The likely solution is some combination of the two, or possibly a combination of fuel cell and capacitors.
Why Batteries are Bad
You may have noticed that I am using the term "liquid" fuel, and not chemical. That's because batteries work by a chemical process as well. For example, in a normal wet cell car battery you've got six cells of 2.1 volts each. Each cell contains a suspension of sulfuric acid in water, and a lead plate coated with lead phosphate. This combination creates an electrical potential. As you draw power from the cell, the sulfuric acid reacts with the lead phosphate, producing lead sulfate and releasing hydrogen gas. When you recharge it, the process is driven in reverse and you get back sulfuric acid and lead phosphate. Note that I am not a chemist or physicist, and this is about my total knowledge of the process - but a similar sequence of events operates every chemical battery.
The batteries used in electric cars basically come in four types. The oldest use car batteries, good old lead-acid. The energy density is poor and the replacement interval is short under heavy use. The second-oldest (and some newer vehicles) use "Ni-Cad" or Nickel Cadmium composition. Newer vehicles use Lithium-Ion or Lithium-Polymer batteries.
Incidentally, anyone who argues that batteries are somehow less safe than gasoline should consider the merits of driving around with a big tank full of combustible fuel around behind them. While there have been issues with batteries on multiple occasions (witness the Sony laptop battery fiasco) the problems are not unsolvable. Many manufacturers, including Tesla Motors, would tell you they've solved them already. This isn't a reason why batteries are bad, but a reason why they are good - although frankly we could be using much better fuel tank designs in our gasoline cars. We don't, because in general people care more about low cost and cargo room than safety.
All heavy metals are bad for humans and most other creatures, but the refining of Nickel in particular is very nasty. In addition, the materials for making Ni-Cad batteries come from different places around the world, so these batteries and their parts may cross the ocean several times during their production. As this involves loading them into containers, putting the containers behind diesel trucks, taking them to a port and loading them onto a ship driven with bunker fuel4 which crosses an ocean, unloading them and putting them behind more diesel trucks, and shipping them off to another place to have more work done - and then doing this two more times! - you can easily see that the environmental impact is not as low as hybrid manufacturers would have you believe.
A study recently claimed that due the the battery energy factor, a Hummer (original, not a smaller version) is actually more environmentally friendly than a Prius! However, it made this claim based on the idea that the Hummer's lifetime was three times as long before it would be sold off and replaced with a new model. Putting that claim aside then, the lifetime energy consumption of the Hummer still ends up near parity with the Prius, solely because of the batteries involved. More compellingly, there are a number of gasoline-driven vehicles which are not hybrids which get the same or even better mileage than any hybrid, for example Volkswagen's TDI5 vehicles get as much as 50 mpg on the freeway in real-world driving, and they can do it on carbon-neutral biodiesel.
True Costs of Fossil Fuels
I live in the United States, where it's easy to have a skewed view of the actual cost of gasoline. Look around the world, and you will see people paying four times as much at the pump, especially in Europe. Other places you see Gasoline for pennies per gallon, but those are major oil-producing nations which produce more than they consume. Here in the US it is very much the other way around; while we do produce oil in the states (especially Alaska - though ironically this is threatened by global warming6) we consume far more than we are producing.
In order to secure our sources of oil, we have gone to war (not so recently - the current war is based on other financial motivation) to secure it. How many have died to keep gas prices down? The economic value of this practice is difficult to measure, because putting a value on human life is probably possible, but equally probably undesirable. Other nations which don't engage in war for oil have higher prices at the pump; we pay higher prices when tax day comes, and in the loss of our children.
Of course, this is not to mention the environmental repercussions of taking carbon that's been sequestered for thousands of years, and putting it into the atmosphere. We know from ice core samples that through the last four ice ages, there has never been so much CO2 in the atmosphere. Not once. In fact, we are something like an order of magnitude above it already. We don't know for certain what the repercussions will be, because this has never happened throughout history, but using all living things as guinea pigs in an industrial experiment in search of profit seems more than slightly shortsighted.
What conclusions can we draw?
Obviously, the upshot of this article is that fossil fuels are not the solution - and thus, the current hybrid vehicles are equally not the solution. Also, it is clear that hybrids are not necessarily any less detrimental to the environment, and may actually be moreso - especially when compared to a small gasoline-burning car. The hybrids are purchased by wannabe hippie-hipsters who want to feel like they're doing something to benefit the environment, but who can't live with the slow acceleration of a single-engined car which gets the same or even superior mileage. These hippie-o-crites would do more for the planet by sticking with their current small car for a decade, but that vehicle doesn't allow them to be a snob.
A far better solution than a hybrid would be to use an ordinary type of internal combustion vehicle based on biofuels. While I won't go into it here, when done properly biofuels have a negative carbon footprint. Algae-based biodiesel is made with sunlight and can use salt water, so it can be grown almost anywhere. There's also butanol, which can be run in gasoline engines without modification and at any ratio with gasoline. Interesting stuff.
Batteries are not necessarily very clean, especially based on the way they are made. This tendency could be mitigated though, and it probably will be (at least in this country) by our falling currency; it will become more sensible to produce more products in the country. And a huge benefit of using electric power systems is that you can potentially eliminate the fuel-based engine completely. The complexity of an internal combustion engine is astounding! Just considering the average push-rod type motor, there are more parts than you would ever consider. Let's consider a push-rod (overhead valve) V8; the basic shape and structure of the motor is provided by the block, two heads, intake manifold, and oil pan; that's at least four parts, plus a gasket for each part but the block on which all the parts go - that's seven there alone. Remember, the electric motor has four. Power is transmitted out by a crank (8) with hopefully a bearing per cylinder plus one (17) and valves are controlled by a cam - which hopefully has as many bearings as well (26). Each cylinder has a piston (34) and a piston ring (42); the pistons are connected to the crank with connecting rods. (50) Each rod is actually made of two parts plus two bolts (so make that 74) and has two bearings, one at each end7 (90). Each valve (98) is controlled by a push rod (106), a rocker arm (112), a lifter (120), and a valve spring (128) which is attached to a bolt or stud in the head (136) and held down with a nut (144). And we've only just finished describing a minimally complicated engine, without discussing lubrication, cooling, fuel delivery, et cetera. More meaningfully, over 100 of those parts are in motion! Even a Wankel rotary engine has a block (at least two pieces), a rotor (one piece), three rotor seals (we're up to 6 so far), two main bearings (8), two main seals (10), and again that's just major parts.
So assuming that we use clean batteries, pure electrics look like a very clean solution. They don't even generally have fluids to leak (although the Tesla uses a battery heating/cooling system, and a two-speed transmission which I think we can safely assume to contain some kind of lubricant) which makes them much easier on the environment, easier to service, et cetera. Because they have dramatically fewer moving parts (see previous paragraph) and involve rotary instead of reciprocating motion, they are less prone to needing repair than piston engines.8 Because they don't use fossil fuels, they have the potential to have a reduced carbon footprint. And no one has to die for them, which I feel is a significant selling point, at least in this country.
For longer trips, series hybrids are the obvious win. They permit the use of optimally efficient motors, because they need only run at a single speed and load. And combining a series hybrid with plug-in functionality probably makes for the most efficient car for general use possible today. Carrying a powerplant with sufficient power to run the car at cruise reduces the amount of batteries you have to carry, and providing the plug-in can significantly reduce the amount of fuel you actually use. Being able to recharge on-the-go also allows you to discharge the batteries further before having to start up the engine, which increases the likelihood that you'll be able to run solely on the plug-in charge. But including the batteries provides for regenerative braking, which is definitely a win in city-type driving. For anyone with almost all highway miles, the most environmentally friendly thing you can do today is to keep driving your current car! It takes an awful lot of energy to produce any car. If you're going to replace your car anyway, and it's all highway, then do everyone a favor and just buy a small car with a small engine, which will get the same mileage regardless. Current hybrids with their huge packs of batteries are best suited to use as taxicabs, where they are involved in a great deal of stop-and-go driving.
The following is a jumble of related facts that I had no better organization for.
- Chevrolet is planning a series-hybrid plug-in known as the Volt. They are reportedly waiting for battery technology to become available.
- Toyota claims they will soon release a performance hybrid competitive with a high-end Corvette (0-60 in four or five seconds, and a high top speed to boot) but with mileage like a Celica (high twenties.) It looks fairly stupid (which hopefully will change before they bring it out) but is supposed to be under $40,000.
- Subaru has a concept (which they claim to be interested in producing) for a performance hybrid powertrain using a flat diesel motor and an automatic transmission, replacing the torque converter with an electric motor. This permits the electric and gasoline motors to work together to power the vehicle through the ordinary9 AWD drivetrain - and also to perform regenerative braking from all four wheels.
- The MDI Air Car uses high-pressure compressed air as a means of storing power. Energy density is even poorer than batteries, but it is absolutely clean (everything-neutral) and filling is very fast. They also have an electric motor/generator connected into their transmission which generates power to run onboard accessories, and which can be connected to wall current in order to drive the air motor through the transmission and use it as a compressor to fill the tank.
- 1. A company called Moteur Developpment International (MDI) has designed several air-propelled vehicles and has sold them for limited use in Spain - and is about to build more.
- 2. An electric meter that keeps track of when you use electricity. However, if you use more than a certain amount, you no longer get off-peak rates for off-peak use.
- 3. Instead of using brushes which contact an armature on the motor shaft (or someplace similar) a brushless motor uses sensors and electronics to control the coils in the motor.
- 4. A very dirty grade of diesel.
- 5. Turbo Direct Injection. Diesels with electronically-controlled injection. More or less all 2007 and later diesels (except "heavy" trucks) have catalysts to handle unburned hydrocarbons (unused fuel) so that they are very clean.
- 6. Rising temperatures cause melting of permafrost, which results in an unstable footing for the Alaskan pipeline.
- 7. Each bearing is actually made up of an outer race, an inner race, and a bunch of bearings or rollers, but we'll count them as one part anyway to be charitable.
- 8. Rotary engines need even more frequent service, although they are less likely to actually destroy themselves.
- 9. Okay, so Subaru's AWD is not ordinary.