Ever since Toyota managed, with the Prius 2, to finally succeed in selling an alternatively powered vehicle in sufficient numbers for it to start to be taken seriously, the automobile industry has slowly been warming up to the idea of working on alternatives to diesel and gasoline/petrol, and people in general have started to also warm up to the idea of one day moving from internal combustion cars to alternative motorizations.
The main contenders for the moment seem to be 5, or rather 4 with one of them having two approaches.
1 - pure hybrid cars (like the Prius, or the hybrid Civic), and light hybrids like Mercedes and BMW among others are developing.
1.1 - the pure hybrids have a normal engines as well as a full electrical engine, so they can run on either, and then they have a number of systems to absorb the energy from breaking, slowing down, etc to load up the battery "for free". The idea is to run on electrical in the city, so you do not waste energy while stopped at lights, for example, (because an electrical engine does not stay running while the car is stopped) but then still have a normal fuel engine for long distances, so you avoid the problem of lack of range of batteries. In the end, clever systems allow the electrical engine to give extra whoompf to the fuel engine when needed, without putting pressure on consumption
1.2 - Light hybrids, on the other hand are basically normal cars which usually come equipped with two things. A small electrical engine attached to the gearbox or transmission, to feed extra power into the fuel engine when required while keeping consumption at its most efficient, much in the same way as the normal hybrids do; and a stop-go system which stops the main engine (which is a normal fuel engine) when the car is stopped, but allows it to immediately start again when you press the accelerator. By using these two systems and copying the energy efficiency system of full hybrids, manufacturers hope to provide full hybrid performances with a less complicated and cheaper system.
2 - fully electrical cars, like the Tesla, or the Volt concept car, and a number of models and concept cars currently being developed. These run only on an electrical engine, which therefore is at the same time much more efficient and responsive than a fuel engine. Besides not wasting energy running when not required, these vehicles also recycle energy from braking, slopes, slowing down and anything else is available to recharge the batteries, while accelerating faster and more smoothly than current cars.
One of the downsides is that batteries limit the range of these vehicles. To increase range they have to have more batteries, but this means they have to make the car bigger and heavier, demanding more energy to move the car, leading to less range. So, there is a limitation on how much more range manufacturers can pack into a car using current technology.
The Tesla avoids the lack of range by using light batteries similar to the ones in laptops and mobile phones, but this makes the car very expensive.
Most other cars stick to more traditional batteries to avoid the extra cost, but even so, electrical cars can be quite expensive.
So range has to be balanced out in relation to the cost of the whole system, and at the moment it is still difficult to achieve an attractive balance.
3 - Hydrogen fuel cells. A lot of manufacturers have been working on these, on and off, and governments have often cited the hydrogen economy as the solution to all our energy problems. Hydrogen fuel cells have probably gotten the most investment of all alternatives, because hydrogen is common in nature, namely in water, and it seemed like an infinite power source.
The idea is you feed hydrogen into the system, the system gets oxygen from the environment, applies a process called cataysis, and you get electricity on the one side, and water coming out of the exhaust.
There are other possible fuels that can be used instead of hydrogen, but the basic idea is more or less the same.
Despite all of the support, however, technical and safety issues have kept fuel cells from coming into the market, and I wouldn't be surprised if the development programs were put on the backburner to allow manufacturers to concentrate on hybrids and electrical cars, or simply on surviving the financial crisis.
4 - The aircar. The aircar is something that has been around for over a decade but has never really took off. It works, but it also has range problems, among others, akin to the probems of the electrical car.
The idea is simply that you put a tank of highly compressed air into the car, and use the pressurised air to run an engine. The engine is more complicated than that, but in essence this is what the concept boils down to. When the pressure in the tank gets lower, well, you just either plug it into a compressor and refill it, or you plug the car to a power plug and the actual car engine works in reverse to fill the tank.
There are currently a handfull of companies working on and selling this type of system, and Tata of India has signed an agreement with one of them to use the technology in India, so we'll see what that brings about, but for the moment the aircar is still pretty much an outsider.
Now, the main options are listed the big question is:
Are these cars cleaner?
and there are two answers to this: It depends. And, to a degree.
It depends on where you get the energy and this choice will define to what degree they are cleaner. They are also cleaner in terms of smog generating particles, but not really effective as a means against global warming.
The big problem with all of these "responses to global warming", is that they assume that energy comes out of nowhere. All of these systems have to be "fed", and this uses energy.
What I mean is, an electrical engine might emit nothing while running, but it still needs electricity. And eectricity has to be produced somehow. Therefore, your electrical engine will have zero emissions when running, but not if count the emissions of generating electricity to run it.
Only if your electricity production is emissions free will your car truly have zero emissions.
If you power up your electrical engine with electricity from a coal plant, you will still be generating loads of emissions in the process, only they will be only indirectly coming from your car.
On the other hand, if you happen to have a green energy supply, you will be completely clean.
Therefore, a Hybrid or an electrical car will only be as clean as the electricity you give it.
And the same goes for Hydrogen and pressurized air.
Hydrogen is really not a fuel. It is what they call an energy carrier. When you use energy to separate the Hydrogen from the Oxygen in water, you can get most of that energy back afterwards by putting them back together and making water again. It's as simple as that. If you feed it energy, then you can get it back later. But you do need to use energy to get the Hydrogen in the first place. So, where do you get that energy? If you get it from burning fossile fuels, you don't really get much of a benefit out of it.
So basically it's the same as the electrical car, only you get more steps in between, which will actually probably mean there are more inefficiencies.
Pressurized air is more or less the same. You need energy to create that pressure in the tank. You will never get more than that energy back, and in fact, you will probably get less. So, again, it depends on where you get the electricity from in the first place.
Comparison with current cars
According to coal power industry sources themselves, some older models of coal-powered plants will only use up about 30% of the energy existing in coal. Newer designs are able to provide top efficiencies of 40%-45%, and are getting close to 50%. Improvements are hoped to be able to reach as far as the high 60%s, achieving levels close to 70%, which is more or less where gas power is at the moment.
Naturally, there will be some loss of power until it gets to you, through dissipation, conversion losses, etc etc, but let us say that the efficiency of the electricity you get at home, which will come from a mixture of old and new plants, if it is coal sourced is somewhere between 35%-40%.
This will be the energetic efficiency of your electrically run car. Hydrogen and pressurised air will probably be a couple percent lower.
To compare, I can tell you that if you run a late generation diesel engine with electronic injection, peak efficiencies run around 40%-45%. Of course, average efficiencies will be lower. On an average day, your diesel engine will be making use of about 37% of the energy within the fuel.
A petrol/gasoline engine will be less efficient, using up only 25%-30% of the energy in its fuel.
On the other hand it will be lighter, compensanting for a small part of the lower efficiency, but it will never even come close to a diesel.
As you can see, if we take into account the source of the energy used to power alternative engines, a big part of the benefits disappear, unless, of course, you use green energy.
Conclusions
In a nutshell, alternatively powered cars will help fight global warming if they are powered using electricity, pressurised air, hydrogen, or any other 'fuel' generated using renewable energy.
If they are powered from the grid, using traditional sources of electricity, then most of the global warming benefits ebb away, and these cars are not much cleaner than a good Diesel car. Especially nowadays when we see smaller and smaller diesel engines, allowing smaller cars and higher efficiencies.
This fact allows for the cleaner cars in the market right now, and here I'm just speaking of end-of-the-exhaust emissions, not even including the emissions for the electricity used, not even being those popular hybrid cars, but rather small internal combustion cars with small but more efficient engines, like the Smart fortwo and the Toyota iQ.
The alternative types of engines are indeed cleaner in the sense that they pump out less particles into the air of our cities, so they leave the air cleaner there.
But they are not going to help much against global warming unless renewables make up a larger proportion of our primary electricity production.
In the end, we still have no free lunchs, and the only real way to decrease emissions from transportation is to simply be more organised and more modest in the way we travel:
- use public transport and bikes if that is an option
- travel less Kilometres or miles,
- travel less often,
- travel in smaller vehicles,
- share vehicles by travelling in the company of more people.
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