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Paris (France)
An engineer- developer of hyride vehicles of series- parallel type
Interests: Automotive, Energy
Recent Activity
Can be also very useful for a series-parallel architecture. In some innovative arrangements electric power is decreased below 10KW. Refer:
48 V battery is the best way to mitigate risk of high voltage in case of a car crash. It is why I have a close look at it. But it is not always necessary to get an electrical rear axle for driving traffic jam. Explanation: With a double planetary gear system, electric power in a series-parallel system (Prius or Volt family) can be decreased to 10 KW which is compatible with 48 V voltage. As you know in this architecture, the electric chain has a Generator and a Motor. Reversing the Generator you can get 20 KW for pure electric propulsion in traffic Jam while the two machines can work as usual in other conditions. Such device is described following link:
For me, the series- parallel architecture for hybrid vehicles is a good solution. With a double planetary gear set is a most. The difficulty is how to shift from one set to the other. Here we use clutches. Unfortunately clutches have well-known disadvantages. Particularly, we lose the rotation speed accuracy of the shafts provided by the synchronic motors. Some double gear set devices have roughly the same functions despite they are using a single dog clutch which in addition avoids torque disruption. Refer to:
It might be no good to increase battery capacity regarding costs but also efficiency. Global efficiency should be considered on the complete energy cycle, not only on the vehicle. In addition, energy conversions should be minimized to decrease the unavoidable associated losses and consequently battery should be small. I trust Toyota to well known the matter.
I am a fan of Toyota Prius because it is a real breakthrough in the automotive field this last decade. However, I am a little disappointed by how high voltage and battery risks are tackled. Despite a top control system in place, the risks are still there. One efficient way would be to reduce the electric power so the voltage for the same results on the Engine. Such improvement has already been proposed; in addition, you save money and increase vehicle performances:
@T2 Thanks for your comments, Electrical braking in a Prius is made with the Motor working as a generator. A 54 kW Motor! Even if electronic limits the recovered power up to 10KW for protecting the battery. In fact the braking torque of the Genset is mainly used to control and to limit the Engine torque through a planetary gear. The fatal generated power is then recovered in the battery or in the Motor. I you want vehicle performances; you need a powerful electric propulsion chain for balancing the Engine torque through the planetary gear. The purpose of my example is to demonstrate that it can be achieved with less electrical power provide some innovative arrangements. The wearing of the braking rotor is spectacular but it does not means that all braking power is recovered. A30 % limit for the energy recovering is usually admitted. We have two problems with electricity: -It should be produced and production is not clean yet. Having a small background in the field (35 years), I have the feeling that it will last. As soon as you call for electrical power you multiply energy conversions: thermal - mechanical- electrical - chemical - electrical – mechanical without considering daily leaks and transport losses. Each conversion has its own cumulative inefficiency. At the end, global result is poor. In addition, energy losses are costly because they have been generated by top cost equipment’s. For me, only the complete energy cycle should be considered regarding efficiency, emission and costs. What is genius in a Prius is that the electric power can be reduced as soon as the Engine has achieved its best working point.
I am happy to see that the 50 km/h usual limit for changing mode EV to HEV, slowly decreasing to 30-40 km/h for a better safety and costs. But not only, if you look behind the electric plug, and if you consider the complete energy cycles (regarding both efficiency and emissions). Even so, it is not the topic of the day. My main remark is that it is a new parallel architecture which will be added to an already long list. Few innovations are trying to challenge series-parallel architectures (Prius type). This last has a huge innovative potential. For instance, in a 10KW power electric propulsion chain, you can increase the rotor inertia of the Genset in order to store kinetic energy (150 KJ which can have the same usage than the energy in a battery). During the rotor acceleration, the braking power of the Genset can be easily increased to 20 KW, even 30KW. In addition, there are plenty of other interesting developments. Design is a little more complex but equipment’s are not.
My concern is that I have to use my car during day light when sun power is available, and I would prefer to have my battery full when I leave my home early morning.
@ Alex C It’s difficult to explain in few words. Usually, I have slides for supporting my presentations. I don’t use the same quadrants as the Prius. So both electric machines can participate in electrical mode in my configuration. Thank you for your encouraging wishes but for the moment, I only look for a feasibility study on an existing vehicle in an existing environment. Patents take time before to be accessible. In addition, their reading is not always easy. I am sorry; a planetary system is linear relations starting from the Willis formula. I know at least one project of a major car maker which has failed for forgetting this fact. You are right about voltage versus performances but performances depend on many parameters such as water cooling, distances between the machines, etc. My target is mainly to improve the complete energy chain. To use a battery multiplies the energy conversions and associated losses, whatsoever its price. I am also interested by information about Renault project.
@Alex C Thanks for your comments. Please find some answers. Q1 All electric driving: if you have 2 e-mootors of 2x 17 KW (as above), how much max power can they deliver to the wheels when ICE is turned off? A1 In e-mode, the Generator can work as a motor to support the Motor, so 34 KW is available. It is sufficient up to 30 km/h in a hyper-city center. If an extra power is required, the ICE can easily and quickly restart as described in another patent. The limit 30 km/h is based upon the fact that the efficiency and CO2 emission, from the pit to the wheel through a power plant, are not good even for an EV. To run in electrical mode the above limit is not so interesting in today conditions. Q2 This 17 kW for motors - is it continuous power or peak power? A2 17 KW is peak power; my target is 10 KW continuous to decrease hybrid extra costs and to decrease voltage for more safety. In addition (around 150 KJ), I use the inertia of the generator rotor to store some kinetic energy, which is directly available through the gearing system, mainly to boost vehicle performances. Q3 When braking from 50 kph to zero (using brake pedal), at what speed will the ICE be turned off? A3 The ICE is turnoff according the power requirement and, of course, according the speed diagram. Note that the ICE power can be accurately calculated from the behavior of the high inertia generator. This reference does not change during vehicle life and according to external conditions. Another patent. Q4 Max electric braking power - with ICE on and with ICE off? A4 The kinetic energy stored in the generator rotor can be used as the energy stored in a battery but, almost, without power limit Q5 How are capacitor and battery connected - in parallel, via a DC-DC converter or some other way? A5 As far as possible, the Generator and the Motor work at the electrical balance. So basically, we do not need a huge battery except for plug in operation. In that case, we use the Motor remaining capacity. In a good hybrid concept, the electric power is decreased as soon as the ICE gets its best working point, so plenty of capacities are available for the plug-in energy. Q6 Compared with Prius and Chevy Volt 2016 hybrid systems (or new GM HEV in Malibu, ie without big battery), what are the advantages od this system? A6 Usually, I never comment competitors. My strategy is basically to increase the efficiency regarding the complete energy cycle (from the pit to the wheels) and to decrease the power of the electric power chain. In addition, the transmission architecture gets five innovations and even opens the way to a new technology (pulsatile cycles at low power). Please refer to the following links: I am available for more information:
48 V is fine for safety in case of car crash, fire, maintenance and repair. In addition, it is cost effective. Nevertheless, stop and start system has some draw backs: •15 % efficiency improvement might be based on test cycles which have a lot of idle periods very far from the real world (25 % in NEDC cycle!), •Only one machine means that the electricity energy has to be stored in a battery and reused after many energy transformations and associated losses, •At each stop and start, the engine gets chocks: mechanical, thermal, lubrication, chemical (NOx). Some projects aim to reduce power of the two machines systems (like Prius) so their voltage and battery size to the level of the start and stop system. Refer to the following link and the good comments from T2:
Another limitation about vehicle architecture: The plug-in battery can be refilled from your roof PVs only during daylight and sunny days. Unfortunately, it is when you most probably need your car. It might be the same for your neighbors who also would like to avoid future taxes at their meter. To get a plug-in battery that you can leave from time to time at your garage while you use your car, which remains autonomous, can help. Such project exists: Note that the main purpose of this project is to decrease the laden weight (200-400 Kg) of the vehicle.
I come back to the choice of the vehicle architecture for using its battery to support the grid at home. For me, it is obvious that the battery should not be filled with “non green power” or “non efficient power” coming from the ICE when we plug it to the grid. Along side the series and parallel hybrid powertrain there is the series-parallel hybrid type (Prius type). Note that more than 4 millions of this last have already been sold over the world and may be, is the most interesting for this debate. In series architecture a large amount of the ICE power is stored in the battery after a lot of losses in the multi-energy conversions. So it is not very interesting regarding best efficiency and green power. With only one electrical machine, parallel does not have other solution to store its electric energy in the battery when ICE efficiency request to generate electricity. We are in the same situation but with smaller volume than here aboyé. Series-parallel have two electrical machines which give the opportunity to work at the electrical balance as Generator and Motor. In addition, the power of the electric propulsion chain can be reduced when the engine reaches the best working point. With some improvements we can insure that the plugin battery is never filled with the electricity generated from the engine but only from the grid while we get a better regenerative braking: (
I agree that the plug-in hybrid vehicle has a great potential. It can also limit energy fluctuations at home. But I regret for this last; that the following points have not been fully considered: The whole energy cycles from the source to the wheel should be assessed. Generally, energy transformations have to be limited in number of and volume of for the best efficiency. Some cycles are better than the others from this point of view. Thus to store energy in a battery involves many energy conversions (electric-chemical-electric), generates losses including daily losses and degrades cycle efficiency. By the way, all plug-in hybrid architectures are not equivalent. Series-parallel family (based on a planetary gear mechanism as a power split device) reduces the energy multi-conversions because the main part of the mechanical energy is directly transmited to the wheels without any electric transformation. The grid absolutely needs some powerful back-ups, which cannot be started or stopped in a minute even in a day. Dispersed and small batteries cannot replace them. The following links and associated ones could be interesting for the mater:
With a series–parallel powertrain and synchronous machines, the rolling cylinder deactivation seems simple. Please refer to: Note that the inertia of the generator can be used to store some kinetic energy like in a conventional battery without cycle number and power limitations. Moreover, it can also stabilize engine vibrations. Its inertia is 100 times more efficient than if it was installed at the crankshaft edge. Please refer also to:
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Jul 1, 2015