CRE Group BV

How our hybrid solutions saves fuel

For most city-busses around the world, improved fuel efficiency ranks pretty high on the list. But there are more playgrounds in the market for us when we consider the advantages of saving fuel using the hybrid driving or propulsion techniques. While it’s clear that the technology can improve fuel efficiency (this is after all one of the main drivers pushing commercial vehicles/boats to new systems), few people in the industry understand how it does so. Is it like a hybrid-electric car? No. Is "electric" horsepower somehow different from diesel or petrol horsepower? It would seem that, if anything, adding a generator between the wheels and engine (no matter how efficient they are) would simply be introducing additional losses which would not otherwise be there. How can adding more power conversions and the losses associated with it improve fuel efficiency? As you will see in the exploration that follows, what hybrid driving or propulsion technology does is to create the potential for fuel saving. It does not, in and of itself, automatically provide it. Understanding the technical issues that affect fuel economy is important for the potential buyer since not all hybrid systems take advantage of this potential. To get started it should be acknowledged that placing an engine and generator between the wheels the ICE (s.c. internal combustion engine) does indeed introduce new losses into the drive train. These losses can range from relatively minor to very significant and are directly proportionate to the efficiency of the ICE, controller, drivetrain and generator. Different technologies result in products of widely varying performance. Similarly, saving energy in the controller or weight means spending more on the electronics that control the flow of power or new lighter building techniques (carbon alu). It’s not only a matter of spending money, but also one of developing and applying the most appropriate technologies. Some ICE designs are quite efficient at one speed/load condition (s.c. sweet point) but drop off quickly as soon as the speed or load changes. Others have a much flatter efficiency curve. The collective impact of these differences can be huge with real operational efficiencies varying from better than 98% to as low as 72% for ICE’s and typically between 98% and 82% for generators. This means that for every 100 HP (74,6 kW) out of the ICE you could obtain as much as 95 HP (70 kW) at the wheels or as little as 61 HP (45,5 kW). At the high end this compares favourably with the 3% to 7% loss typical of a mechanical transmission. Considering these general accepted losses, is it really possible to improve energy efficiency? The answer is clearly yes, so long as the basic efficiency of your ICE + generator and controller is high. What you are relying on is that you can improve the efficiency of other parts of the system by more, than the new losses you have introduced. Fortunately, if your system losses are relatively low, this isn’t too hard to do. It turns out that there are many limitations inherent in conventional direct ICE drives that waste fuel. By making more efficient use of the ICE and transmission, it is possible to add more than offset the used conversion losses. The foundation for this saving comes from the fact that, in a well-designed hybrid system, the power required by the wheels (or propeller) is "decoupled" from the vehicle speed. In other words, in a hybrid system, the ICE/generator could theoretically be running at full speed (100% output) while the wheels/propeller is only tuning at 50% of peak speed so long as the ICE is sized to handle the power. Similarly, if the wheels/propeller were lightly loaded, the ICE/generator might only need to turn at low speed to provide enough energy to drive the vehicle at full speed, or switch off completely. This means that hybrid systems can be much better at "self-optimizing" to accommodate varying loads than are conventional ICE systems. At the road or river/sea, load conditions change by the trip (number of weight, by the hour, hills, wind and tide) and by the minute (going up a hill/wave or idling/surfing down). These variations provide a significant opportunity for fuel savings and as a result lower pollution. Same issue in other markets as for the drive in city busses, such as propulsion for rhine ships, mega yachts, agriculture and many other power traction solutions worldwide as in new economic arias.

Mission: our innovative goal is connecting existing systems, to optimize fuel consumption and reduce pollution. Building together for a cleaner future. We are engineers in the field of re-using energy in connection with low(er) use of fossil fuels. We are experimental on bi-fuel technology. CNG, LPG/GPL, biogas and hydrogen used in our ICE’s.

We are running at this moment a very small highly efficient automotive ICE (cons. 83gr/km) giving the power needed running on the sweet-spot, bolted to a newly designed high rev generator (98% efficiency). We ad flywheel technologies to store energy to re-use. Focussing on a zero polluting energy pack. CRE stands for common rail energy.

CREGROUP bv, Industrieweg 14-a,1422AJ Uithoorn, 0031(0)297-255 193 The Netherlands  

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