Click on any of the two images below to view them in fullscreen!
Let’s take as example a typical modern car having the main characteristics around the following ones: 2 l gasoline engine of 160 hp, 1650 kg (3634 lbs) overall weight (two persons and some luggage), coefficient of air drag 0.3, front area 2 sq. metres, and consumption as follows: 12.3 l/100km (19.1 mpg) at standard European urban driving cycle (ECE 15 Test cycle according to 99/100 EEC), 7.7 l/100 km (30.5 mpg) at standard European extra urban driving cycle (EUDC according to 99/100 EEC), and 5.9 l/100km (39.8 mpg) at steady 90 km/h (56 mph).
The necessary energy to move this car for 100 km at ECE 15 cycle is around 41800 kJ, but the consumed 12.3 l gasoline give around 432000 kJ. I.e. the overall efficiency of the power train (engine and transmission) of the car at this cycle is only 9.7 %. For 100 km of EUDC cycle this car needs about 48960 kJ energy, but it consumes 7.7 l/100km (30.5 mpg), which give 270450 kJ. I.e. the power train efficiency at EUDC is 19.1 %.
Where the rest energy is wasted :
The engine of the car is the most disappointing unit of the power train. Large amount of energy losses occur with its exhaust gases. The modern gasoline engines have minimal brake specific fuel consumption (BSFC) around to 250 g/kWh at so called “sweet spot”, which corresponds to certain load and speed of the engine. This value of BSFC corresponds to an engine efficiency of 30 %. The rest fuel energy is wasted as heat by the exhaust gases – up to 40 %, and by the cooling of the engine (30% and more). The situation is even worse at real driving conditions, where the engine operation regime declines from the sweet spot, and thus the real specific fuel consumption and engine efficiency are worse than the best ones. E.g. if the above sample car consumes 5.9 l/100km at steady 90 km/h, it means that the BSFC of its engine at this operation regime is more than 315 g/kWh, which corresponds to an efficiency of less than 24 %. So, the wasted fuel energy by the exhaust gases is even more. Known are turbo-compound systems, which recover some of these losses, by mounting on the exhaust pipe of a gas turbine, which adds extracted power to the engine crankshaft. But they suffer from number of problems, which reduce the efficiency and applicability, while significantly increase the cost. If interested in some details, you can visit the competitive technologies page.
Then, the mechanical energy of the moving vehicle, very often is lost by braking or simply decelerating. The main problem is in the frequency of such decelerations, and thus, the sum of corresponding losses. E.g. the above said sample car wastes about 49 % of its kinetic energy during the braking and decelerations prescribed by the urban ECE 15 Test. That is why the consumption of the car at the ECE 15 cycle (12.3 l/100km) is for 59 % higher than the consumption at EUDC (7.7 l/100km). The situation is similar with the American US FTP 75 urban driving test, where the braking losses of the same sample car are about 44 %. The modern trends to avoid these losses are hybrid vehicles, where the gas – electric hybrids (e.g. Toyota Prius), or hydraulic hybrids (e.g. Permo-Drive RDS and Ford’s HLA system) capture some braking energy and release it later on during the subsequent acceleration. There are variety problems, related to them. About details you can visit the competitive technologies page.
Any auxiliary hydraulic systems as such as Material Handling Equipment Cranes, Load Handling Systems, Power Steering, etc. drawn power permanently. For example, the ordinary power steering causes about 5% extra consumption and emissions due to the permanent driving of its hydraulic pump by the car engine. During the rest time, it is just “carried” as an useless load. The actual new trends in power steering – electric demand-responsive drive of the hydraulic pump and direct electric power steering – avoid the extra consumption and emissions, but they still are passive ballasts (and costs) most of the time.
That is why the idea to solve above problems by combining them, came. Let’s make an integral system providing all above operations. How? – visit concept, structure and operation.