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|1. Some facts||2. Sources of usable energies on a vehicle||3. Hybrid architectures||4. Specifications overview|
One will be able to download here (in french) a more precise document on this topic as well as some elements of presizing.
- the chemical energies to basis of hydrocarbons (coal excluded)
They are numerous and, for most, used nowadays extensively. One can mention :
o gasolines : 'supercarburant", "without plomb" used for controled ignition motors.
o oil and heavy oils destined to the motors with spontaneous ignition (Diesel)
o the gas of liquefied oil (GPL) used as alternative fuel for gasoline engines. Their introduction in France at the end of nineties proved to be a failure since the rate of equipment of the vehicles gas is lower to 5%, although their emissions of pollutants are reduced and that the State, in his big goodness, limits the taxes on this type of fuel, not really ecological since the GPL is an essentially fossil origin hydrocarbon.
o The "green" fuels: methanol, esters. that put well a long time to pass the stage of the experimentation, but which are not THE solution, but contribute to improve the balance carbon of the road transportation. Biofuels are not ecological to the strict sense because they require energy and chemical fertilizers to be produced and raise a lot of agricultural problems (Do farmers make fuel for rich countries or food for poor people?...)
As one signalled it higher, they are extremely energizing (heat released by combustion of the order of 30 000 kJ / kg of fuel), but polluting.
- Pci is the calorific power of the fuel in kJ / kg of fuel
- Pco is the air consumtion power of the fuel in normal temperature and pressure conditions
Pco = [mas of air required to burn the mass of gaseous fuel] / [mass of gaseous fuel]
The conversion of this chemical energy is irreversible: it means that one only can "déstocker" this shape of energy inside a terrestrial vehicle. One exploits the chemical energy of the hydrocarbons schematically as indicated below :
chemical energy irreversible combustion pressurized hot gases: expansion mechanical energy with air (4N2O2) in a deformable volume thermal and pneumatic energies with thermal losses
- the chemical energies stocked as electrolytes or gases (non hydrocarbons)
They are used under the shape of electric accumulators, of which most widespread is the accumulator to plomb used in the batteries of cars (electrolytic accumulators). They are based on reactions of oxydoreduction to create an electric current. Their big interest resides in the reversibility of these reactions, that is to say that one can, while applying it a tension, reload the accumulator. However, the number of load / discharge cycles is limited, but important (of the order of 2000 according to the used technologies). The increase of the number of load / discharge cycles of the accumulators is the subject of active researches, the applications are indeed numerous (batteries of portable, of cars, of aerospace shuttles).
One notices the double arrows: it means that one can load and discharge this chemical energy within the vehicle, and it in 2 ways: either the thermal motor make turn a generator that loads the batteries, either the kinetic energy of the vehicle is converted in electric energy at each deceleration of the vehicle (Fig. 3.). This is how a car is going to be able to brake without manipulating the mechanical brakes: the energizing gain is very important since a big part of the kinetic energy of the vehicule, usually completely lost in heat with the mechanical brakes, is recovered here (fig. 3.). This recovered energy is particulary useful to reaccelerate again the vehicle, etc...
start / acceleration /
stabilized run / deceleration / slow motion
Finally, one can mention oxydoreductions in gaseous phase like the particular case of the fuelcell with dihydrogen / dioxygen which actually know a renewal of interest after having endured for many years the clutter of the reservoirs and of various devices.However, a big scale industrialization of such devices shouldn't start not before several years.
These 2 shapes of energy have a neighboring behavior and reversible features like the oxydoreduction chemical energies :
can therefore them also to be used to brake or to accelerate the
vehicle while limiting the losses Joule to the level of the brakes.
The 2 big types of mechanical storage are :
* The wheels of inertia thrown previously to big speed that, connected to a transmission, assure the traction of the vehicle. In the phases of acceleration, the wheel slows down, in the phases of deceleration, the wheels accelerate its rotation (kinetic energy recuperation).
* The springs put under tension in storage and whose relaxation frees the stocked (recuperation of elastic potential energy) energy.
* Without forgetting the vehicle in itself which the mass in movement constitutes a very big storage of kinetic energy, currently wasted to every slowing down in most of the vehicles.These are the solar and wind energies. They cannot be used to propel the vehicle, except if it is ultralight (less than 300kg with embarked passengers), what is not generally the case. On the other hand, the solar energy via photovoltaic cells can provide power for the electric accessories or to reload some batteries, whatever the vehicle do. For example, one can mention a solar car having crossed Australia in the South / North direction. Unfortunately, the solar panels cannot be very big on a car (surfaces limited at the roof, to the motor hood and to the lateral sides), and they are expensive and fragile.