We have been left to believe that hybrid cars will save our planet as well as our pocket.
However I don't see why people are so obsess with them, they are suppose to be very efficient however i cannot workout how can two engines could possibly be more efficient than one.
Hybrid (electric-gas ones kind like the Prius) cars have a gas engine which under the right conditions (e.g. driving at lows speeds, in city like environments) will use the gas engine to recharge the batteries which at the same time are used to power an electric motor.
The thing is that i cannot workout how can that process be more efficient. The fact of the matter is that gas engines have an efficiency of about ~20% (which means that 20% of the total chemical energy in gas will be readily usable) therefore a regular gas powered car has about 20% of the gas energy available to move around (less than 20% since energy is loss in electrics and in friction in the gearbox and shaft etc)
However an electric car which have that 20% available from the motor have to recharge the batteries which have an efficiency of about 75-85% (lead-acid battery) which drops to 45-70% when you include all the circuitry used to charge it. Just for the sake of the calculations less assume is a super efficient circuit and the total efficiency is about 80%. This means that 80% of the 20% of the original chemical energy available in gas can be "delivery" by the battery to the electric motor. Now, electric motors are very efficient (about 95% for 50HP+ motors which would probably what would be used to power a car). This means that 95% of the 80% of the 20 % of the original chemical energy available in gas can be used to power the car when the electric engine is running. This ends up being ~15.2% (which is actually less since more energy is lost as friction within the mechanical components and to power the electric accesories in the car, but since those are the same components that would be present in a regular car lets assume thats sums up to 0 energy for both hybrid and regular cars)
This means that hybrid cars (electric-gas type) are nearly 24% less efficient than regular cars (15.2/20*100=24.) And in top of that it weights more than the regular car since it has the batteries and an extra motor (2932lb for prius and 2822lb for corolla even though the corolla is a bit bigger -couple of inches longer and wider-, that is 100lb extra which translates into 1%-2%)
Now how does a Prius manages to get the 45mpg it claims that it can achieve. First, 45mpg is an estimate and unless you drive in a perfect world with not having to break and where there is no air and no slopes etc it wont do 45mpg, second the engine in a prius is minute (1.4 – 1.5L depending on the model, which generates about 110HP) which is a pretty small engine, and the second things that helps in fuel efficiency is the technology that charges the batteries when the car is breaking, however those are things that we could have in regular cars and help increase the efficiency of those without making them hybrid (e.g. use the breaking energy -same technology that the hybrid but without the extra batteries and the extra electric motor) to recharge the regular battery (or maybe one a bit bigger than the regular battery) this will reduce the load in the engine by running the onboard accesories (such as satnav, cd, onboard computer, lights, power windows, power steering wheel, powerbreaks, abs etc) from the battery and not from the alternator which would significantly reduce the engines load.
Anyway regular cars or hybrids wont be around much longer, check on the Honda's hydrogen cell electric car, now thats the future………
Also keep in mind that the hybrid car is about 4,000-8,000 more expensive than the equivalent gas powered and if you think you saving the environment, think twice since the batteries contain lead which is toxic, and rare earth metals are used to manufacture the vehicle (are rare for one reason) and in top of that materials have to be imported from all over the world, guess what kind of fuel planes use?
34356, did you even bother in reading what i said? you cannot get energy out of the thin air if the gas engine is inefficient then the gas engine + electric engine MUST be less efficient than the gas alone since the energy available for the electric engines = total energy in gas – energy lost as heat and friction due to gas engine inefficiency – energy lost while charging the batteries due to battery's inefficiency (e.g. heat) – energy lost by the electric motor due its own inefficiency (e.g. heat, however this last one is very little ~5%)