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Originally Posted by Old Mechanic
Is it fair to compare a factory electric hybrid to a conversion HH?
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It's better than claiming a HH is superior to a HEV when there are no viable examples of it in production, while there are many viable HEVs. On the same note, I'd probably put PHEVs in the same category as HHs in this context. Both will improve mileage, but at ~$15,000 a pop they aren't viable compared to HEVs. Even w/ mass production, it isn't likely that costs will lead to wide adoption of HHs give the EPA's projections regarding long term cost.
Quote:
Originally Posted by Old Mechanic
Accumulators are very simple. Think of a bottle of nitrogen you get from the welding shop. Then place a very strong balloon inside the bottle. Precharge the balloon to 1000 PSI. Pump fluid into the bottle and collapse the balloon.
Life expectancy is measured in thousands of hours of continuous operation, and when the balloon fails, you buy a rebuild kit, that is basically a new balloon, for less than $100 bucks.
Been around forever. Very mature technology. Used as backups for landing gear in aircraft. Virtually impervious to temperature variations. Used in excavators. and other heavy equipment.
In the same way your shock absorbers smooth out the ride in your car, and accumulator smooths out the huge variations in energy demand and recovery in a HH vehicle.
Why do we need huge batteries and capacitors to do what the simple accumulator has been doing for decades, even centuries.
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Because accumulators are heavy, and don't store a whole lot of energy compared to batteries. When batteries were relatively expensive/heavy, it was conceivable that a HH could compete in a cost effective manner. W/ NiMH/Li chemistries, that isn't the case currently. The EPA
placed the energy density of composite accumulators, which are a tenth to a fifth of the weight of steel piston type accumulators, at about 50kWs/gallon. 50kWs/gallon is about 14Wh/gallon, so even w/ 22 gallons that's only ~.31kWh, and it still weighs ~240lbs. The battery pack in a Prius for instance stores ~1.3kWh and weighs ~120lbs. My guess is that an order of magnitude difference in energy density is why HEVs have proven popular/successful and HHs haven't. There are certainly applications where weight isn't an issue, the system can be sized to meet specific driving patterns, and a greater number of stops/starts means that there's an advantage to a more robust energy storage device. Stuff like yard hostling and grabage delivery comes to mind. But for the most part energy density is why we see a ton of HEVs but not many HHs.
Quote:
Originally Posted by Old Mechanic
Look at this objectively. Pulse and glide is proven to be efficient. it's simple and totally effective. When you pulse and glide, your car is the accumulator.
To incorporate P&G into the vehicle, you need to accumulate energy and apply it consistently. The accumulator allows you to do this, when you combine it with an Infinitely Variable Transmission that has no fixed gear ratios.
This allows you to pulse and glide the accumulator and engine, while applying the exact same amount of power to the wheels by constantly increasing the displacement of the in wheel IVT as the accumulator pressure declines.
No vehicle speed changes necessary.
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There's also no need for P&G when an engine is geared to always run near peak efficiency. Continually using an accumulator to load level an engine is moot when appropriate gearing can do the same at a similar levels of efficiency, and an electric motor can provide plenty of acceleration until the engine revs high enough to make the rest of the power, all in a system that weighs hundreds of pounds less and costs thousands of dollars less, all things being equal of course.