carson said:
Christian and Gary, I am no ECO-engineer nor a government-engineer. Something tells me there is something terribly wrong with all this conservation talk.
I will only use numbers that I can't substantiate. A gas/diesel compression engine is probably in the neighborhood of 70% efficiency in regards to fuel versus HP power output.
If you have a 10 ton RV +/- it takes x amount of horse power to keep you going. If you went to engine/generator/motor (like a locomotive), where does the power come from?
Between the engine and the generator there is a loss in power. From the generator to the drive-train motor there is an efficiency loss. There is no way to amplify power from the original source, the engine. Someone tell me where the savings are going to come from.
If you say, the batteries will take care of that...well, where does their power come from? Batteries don't generate power, they just store energy. Charging them at home will raise your home power bill; on the road...who pays. Charging them while driving uses engine power.
Who was it that said that energy cannot be created or destroyed, just changed.
The cost off batteries, their weight and their replacements in time, will negate any savings over time.
I am just rambling here, can someone explain why hybrids save money?
carson FL
Ok, you make many good points... where to start...
First, an internal combustion engine in a car/truck/motorhome is at best, about 20% efficient at turning chemical energy from fuel into mechanical propulsion. Furthermore, most combustion engines are "most" efficient at converting chemical energy into mechanical energy at or about their horsepower peak. Unfortunatly, most driving does not occur at that engine rpm. Most of the time, particularly when you are on the highway, an engine is at partial throttle and is even less efficient (let's say 15% for simplicity sake).
Hybrid: A hybrid has the same basic limitation except a) it uses stored electric power for added propulsion so the combustion engine can be smaller b) said engine will run closer to its peak efficiency more of the time, and c) recaptured kinetic energy from regenerative braking reuses "free" energy. As many have mentioned, this technology works best when regenerative energy can be captured from braking... otherwise, they are using engine power just like any other car, albeit a generally smaller more efficient engine. Clearly the best application is for city/stop and go use.
Diesel or Gas-Electric Propulsion: A diesel electric propulsion system (or gas electric) uses a smaller combustion engine to generate electricity and only electricity propels the car. The engines in these designs are more efficient because the ONLY have to run at their peak efficiency and can be designed to be very efficient at one RPM. They generate power to propel the car and any remaining power is used to charge batteries, which in turn help propel the vehicle when more power than is available from the engine is needed. In this application, the engine can approach 27-28% efficient overall and is much better for over the road (or rail) application. This doesn't sound like much, but 8-10% increase over 20% is a net gain of 50% overall...a huge net gain. The Chevy Volt, if it ever gets built, is designed on this concept.
Trolley Assist: A concept that I think merits consideration is the use of "trolley assist" for over the road vehicles. If we were to introduce an electric propulsion system as discussed above, you can then consider pulling power from an embedded rail system or overhead wire system, similar to an electric rail system as used in most subways and many east coast amtrac trains. Of course, using power from a rail or wire would introduce the question of "who would pay", which would have to be evaluated, but could be easily overcome by using electronic tolling similar to the RFID technology used in EZPass toll tags. To your question about the efficiency of grid-generated power vs. a vehicle...grid power is VASTLY more efficient from a thermodynamic and emissions perspective. Your average coal-fired power plant is roughly 35% efficient at converting chemical energy into electrical energy, a gas-fired power plant (combined cycle) can approach 45 -48% efficient. On top of that you have about 22% of power in the U.S. coming from Nuclear, 3% from wind, 10-15% from Hydro, etc. Overall, the grid can make power more efficiently than your car by a health margin due to economies of scale.
Anyway, now I am rambling. There are no perfect answers, but there are certainly some great ideas that merit consideration as we look for ways to reduce our oil habit...whether you only care for national security reasons or for environmental reasons, or both, at the end of the day, we need to start doing things differently and start thinking "big" when it comes to changes in our energy infrastructure.
