From Doug in another thread:
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1. There will be a range where your 32 percent efficient IC will have excess power over cruising, and yet your batteries won't accept the excess amps the generator will accept.
In this case, the generator will not operate at peak efficiency, or the generator will start cycling on and off.
A lot.
2. By the way, where do we purchase one of these 32 percent efficient IC engines? Sounds pretty neat.
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From DCB in another thread:
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3. Not only 32%, but, 32% air cooled gas engine. I was under the impression that liquid cooled gave a slight efficiency gain due to maintaining optimal head temps.
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1. I think this may be answered in my novel above. You are basically correct. There is a meaty part of the battery charge profile during which the engine is very close to fully-loaded. It takes many minutes to complete a cycle, unless the vehicle is just sitting in a parking lot -- although even then it takes a while -- it's charging at 1C, so it could take an hour if the batteries were flat and you wanted them full... but the microprocessor will not allow them to be full, because the load tapers off too much. Once the load drops, the engine shuts off. It won't cycle back on again until the driver pushes the start button. As I mentioned somewhere, this could be automated based on GPS, so that you always arrive at home with a low charge, given distance, terrain, etc. but I'm not going to do that. I think that drivers will be able to figure out their own desires re charging. Making the generator start up at automatically at 30% charge or any other SOC, would be simple for the same microprocessor, but I prefer driver control, because if you have a 40-mile commute, the engine would otherwise be starting up (maybe half the time) at distances of 10 to 0 miles from home, depending on things like temperature and traffic. A lot of people, I think, would prefer to say no to gas, other than for long runs (and will be willing to take the hit in overall battery life that the deeper cycles entail).
2. I think you already have an IC at about 32% peak efficiency with your Civic engine. Without a huge amount of work you could get it up to 36 - 38% peak efficiency, by modifying it for Atkinson cycle. You'd loose low end torque and the ability to idle smoothly. My engine has about the same cylinder volume as a Prius or your engine. It will be available only from me, as far as I know -- there has not been a strong market for efficiency in commercial engines, but at least closed loop injection is showing up. My mods effectively cripple the engine for other uses.
3. I think that water cooling makes emission control easier. Head temperature can be adequately controlled with good control over mixture and timing, without going outside the emission limits for motorcycles.