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RE: Hybrid Dinghy that Improves Motorhome Fuel Economy?
One needs to really review what makes a hybrid work. There are 3 factors:
1)Braking is translated into stored energy.
The HDP does this.
2)The fueled engine is undersized, and since it runs at near maximum power, it is more efficient. When extra power is needed, both the electric and the fueled engine run in parallel to make up for the undersized engine.
The HDP also does this. It takes a certain amount of work to move a motorhome up a hill or to start from a stop. The quicker that work is done, the more power it takes. I don't know the battery capacity of the current Ford Escape Hybrid, but the prototype Escape Plug-in Hybrids carry 10 kW-hr of battery capacity. Just like on the current hybrid, that is a reservoir that can be used, and refilled, under various driving conditions. It just uses the energy stored from going down the hills/stopping to go up the hills/starting. We are not claiming 100% efficiency. But, current systems get back 0% of that energy. If the HDP can recycle 20%, or perhaps even 30%, of that energy, the HDP would make a difference - which it can given currently available vehicles.
3)The engine is optimized for a very specific RPM and power range and can be tuned much more radically than an engine that must perform at many different RPMs. (The Prius has a 14:1 compression ratio)
One could certainly use a Prius. However, we were thinking more along the lines of a Ford Escape or GMC Yukon. Class A owners seem to like to tow these larger vehicles. Besides, the electrical systems in the hybrid versions of these vehicles are getting to the size that they can now help a MH.
There are two ways to look at this. You apply full power in a MH to get up that next hill. The addition of the electrical horsepower provided by the HDP (up to 90 hp in the case of a Escape Hybrid or 80 hp for the Yukon Two-mode Hybrid) helps get the motorhome up the hill that much faster. Of course, there is no fuel savings in this case, you just get up the hill quicker. In the second scenario, you don't apply as much power to the MH and the (previously stored electrical) power of the HDP makes up the difference. In this case, you get up the hill in the same amount of time, but with a reduced fuel consumption.
If you notice, 2 significant factors do not apply to the hybrid pusher concept.
Doesn't look that way to me.
1. Hybrid vehicles themselves barely (if at all) make financial sense. Spending money on a hybrid concept (even using an existing hybrid vehicle) makes no sense at all in a vehicle that only gets driven 7000 miles per year or less----most of which are not stop and go miles on top of it.
Then why is Freightliner investing in a hybrid chassis for motorhomes? Talk about expensive. Ford and GM are both mass producing hybrid vehicles and they have the economy of scale. Why not take advantage of that economy of scale and apply that to MH's, which will never happen for a hybrid MH? The HDP takes that advantage.
2. The battery packs in current Hybrid vehicles (and any other likely hybrid toad) aren't nearly big enough to store enough energy to impact the mpg of a 26,000 lb. MH.
The electrical systems are not operating all the time. These systems merely assist the operation of the MH. The high rate of fuel consumption in a MH is when accelerating from stop or going up a hill. Those conditions are when the HDP steps in. The HDP would simply be tagging along when driving on flat interstate. So, 90 hp is not enough to help?
3. The "inventor" needs to take some thermodynamic courses and learn about entropy.
Funny you should say that. One of the inventors taught thermodynamics in Mechanical Engineering for about 10 years. As noted above, we are not claiming 100% efficiency. Nevertheless, claiming the HDP will not work is analogous to saying that a hybrid vehicle will not get better gas mileage in town than a regular vehicle. We both know that statement won't hold water. Let me give an analogy.
Suppose I could take a big rubber band (we're talking huge) and hook it to a big anchor. I now use that rubber band to bring a motorhome to a stop (think Wil-E-Coyote). The kinetic energy in the MH has been converted into strain energy in the rubber band. I now move that band to the other side, such that it is in front of the MH. Now, the strain energy in the rubber band is converted back into kinetic energy in the MH to get it going again. In all of this, I have not dissipated any energy through brake friction (heating) nor have I used ANY fuel to accelerate the MH. There are certainly viscoelastic losses in the rubber band and other frictional losses in this process. As a result, the final speed of the MH will not be the same as when we started this whole analogy. Nevertheless, I don't have to use near as much fuel to get the MH back to the desired speed. In effect, we have saved fuel. The HDP does exactly this process, except through the use of a moving electrical system - which is really no different than existing hybrids, it's just adapted to help a MH.
I suppose someone needs to contact the auto manufacturers (Ford, GM, Honda, Toyota, etc.) and tell them that because of "entropy" their hybrids won't work. We are not claiming to provide something for nothing. There is some added expense to an HDP over a regular vehicle. But, if someone is going to be towing a vehicle anyway and could benefit from driving the hybrid around town, why not an HDP?
I have been doing this for the past couple of years. We tow a Prius behind and since that increased my fuel mileage so much I got another one that we push. That took some effort to set up steering. We also put a couple of wind turbines on the roof to take advantage of the wind there. Now our only problem is that we have to stop 2 times a day to siphon out some of the excess gasoline produced.
Unfortunately, these sorts of analogies are exactly why some people believe the HDP will not work. We are not violating any laws of thermodynamics or physics - in fact, we are simply taking advantage of them.
The true facts remain. If you use brakes to stop a motorhome, that energy is lost forever in the form of heat. You can never get that energy back. If, however, you use electrical motors as generators for braking and store that energy in batteries, you can get some of it back later. You can run that energy back through the motors, acting now as motors, to help get the system moving again. No, you don't get all of that energy back, but you do get enough back to make a difference.
THEN, if you want to run those "wind turbines" on your roof, you'll probably about break even :)
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tundracamper
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04/10/09 07:24am |
Class A Motorhomes
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RE: Hybrid Dinghy that Improves Motorhome Fuel Economy?
Seems that with all the batteries that our motorhomes have (we have 10 batteries in ours) that a hybrid system could be put in the motorhome itself as shown in the following article.
Personally, I would MUCH rather have the hybrid built-in rather than having something pushing or holding me back.
MM.
Yes, wouldn't it be great to use those batteries that you ALREADY have to improve fuel economy. Otherwise, you are going to have to guy a new hybrid motorhome to use them. What if you could buy a $30k hybrid SUV that would do the same?
It is that "pushing" and "holding" back that helps improve fuel economy and acceleration. That is exactly what a hybrid motorhome would do.
The biggest issue I see is the lack of power from the yukon. ... That 16% increase in hp is overstated in my opinion, I'm thinking it's closer to 1% or less.
So, the Yukon uses 9 hp to start from a stop in all electric mode?
Since Yukon's are typically priced $40k to over $50k, that could sure buy A LOT of fuel. $50,000 vehicle / by cost of today fuel $2.50 = 20,000 gallons of fuel! :h
Not a valid comparison. If you don't get the hybrid, that means you would have to buy the $40,000 non-hybrid. Remember, this is for folks that already tow a dinghy. Now you are only talking 4,000 gallons of fuel. We both know the actual costs are not as high as you stated. According to GM.com, the Hybrid Yukon lists for about $3k more than the loaded XL. Go to a Denali, and the cost difference is not even that much. Now that 4,000 gallons just became much smaller. Raise fuel to $4/gallon and your math just got blown out the window with all that extra fuel costs.
I think the whole "pushing" aspect of the OP's theory may be difficult to bring into fruition....legal hurdles, etc. Saying that there are no legal problems, because the system doesn't exist is akin to putting one's head in the sand!
My point was not to downplay this issue. The point was that the added hp is not that significant, in terms of pushing the MH off the road. We just feel that issue would be easy to overcome. However, it's hard to address the "legal issues" when there is no hardware to break the law. Is there any law about pushing? This is a whole new approach that has never been considered. Isn't it worth considering?
I find the idea interesting. However like other have said, my tow bar is a tow bar, not a push bar.
My dad used a "tow" bar to push his $45k+ pound motorhome into a gas station. No, it wasn't designed for that, but what if it was?
On the other hand the Op said it would be like an outboard, I wonder if I can use it to power my boat, and I would save even more money. :C
Sorry, the HDP won't work in the water :->
How about putting some kids on bikes in front PULLING
If they can generate 90 hp, I'd love to have them pull my FW setup when I'm driving around town.
Wow, just wow...
We think so too!
What have the ideas being discussed here to do with an industry in crisis because it has run out of ideas people actually WANT to buy?
That's the whole point of this post. We are hoping people, particularly motorhome owners, would be interested in buying this. Would that not improve sales?
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tundracamper
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04/06/09 07:57am |
Class A Motorhomes
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RE: Hybrid Dinghy that Improves Motorhome Fuel Economy?
Thanks for all the interesting feedback, I think. I certainly didn't expect so much negative feedback, but perhaps I shouldn't be surprised. As noted in the original post, this is not a product that is currently available. There are a lot of details on the technology not provided in the link. The point is that we believe the overall concept is sound. I am wondering how different the feedback would be if diesel was back up to $4.70/gallon.
In terms of "pushing it off the road," I'm not sure how to respond to that. We are not talking about enough power to propel the motorhome down the road. This is not like backing a travel trailer down the interstate!! Consider just the masses and forces involved and you will quickly see that the travel trailer dynamics approach gets quickly thrown out the window. The wheelbase of many motorhomes (three axles spread of a large distance) makes those issues significantly less important (not that they wouldn't need to be considered). We are not proposing to just turn on the hybrid full blast and go. We are talking about an "assistive" technology that helps improve fuel economy and acceleration. The HDP would help smaller motorhomes even more, given the increased hp/weight ratio.
Of course, there would have to be some communication between the MH and dinghy. When you think in terms of the complexity of anti-lock braking, stability control, and other safety systems, the hardware needed for safety in an HDP system would be fairly trivial and inexpensive.
In terms of the "kids on a bicycle" pulling comment, that gave me a good laugh to. If your kids can generate close to 90 hp of free energy, let's get a rope and hook'em up. I would love to have that free energy to help reduce my fuel consumption, particularly when stopping at all those stop lights in my town. Yes, there are some all-electric cars that would be ideal candidates for an HDP. While that can be done, we think the primary interest at this point would be in currently available hybrids.
I don't understand the thinking that hybridizing a motorhome, with very limited production numbers, would EVER be cheaper than adapting hybrid SUV's to do the same thing. The available horsepower in these hybrid SUV's is increasing with time. There is a massive reduction in cost with the numbers of vehicles produced by the automotive industry that is not present with the motorhome industry. Besides, a hybrid SUV can also be used for in-town driving. It just gets used more and is cheaper to produce. The payback is much quicker.
No, we wouldn't expect someone to rush out and buy a hybrid vehicle just to tow as a dinghy. However, if someone is going to buy an SUV anyway, it seems logical (at least to me) that they would look at hybrids given the potential to improve the fuel economy/acceleration of their motorhome.
Again, diesel was close to $4.70/gallon just last year. What positive impact did that have on MH sales? Let's hear it from the folks that have an expensive motorhome. Do you care at all if diesel is $4, $8, or even $10 a gallon? Some folks apparently think not. If you are going to tow a dinghy, would you consider spending $3k more on a hybrid SUV over a regular SUV, that would help improve your fuel economy? Or would you rather spend $25k to $50k on a hybrid system on the motorhome that gives marginally better performance?
50pascals: Thanks for the feedback. Note that the paint scheme on an HDP doesn't have to match the motorhome, like shown in your photo :->
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tundracamper
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04/06/09 07:30am |
Class A Motorhomes
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RE: Hybrid Dinghy that Improves Motorhome Fuel Economy?
The point of my post was not to determine all the issues that would need to be addressed. The point was to see if there was any interest, which there appears to be some. There are definitely challenges that have to be addressed. However, those all appear pretty minor and could be addressed during R&D, which shouldn't really take that long.
Some of the comments...
- If made into an HDP, any hybrid would work. Those with larger motors and batteries would work better. You get more electrical power and battery capacity to provide assistance to the motorhome. Note that we are not violating any laws of physics. This is just using a hybrid SUV to make a motorhome a hybrid. You don't have the added cost of hybridizing a motorhome, though.
- "Payback." We don't have real numbers since one doesn't yet exist. (See the brochure for estimates on fuel savings. Those are based on real numbers.)
- Size? The Yukon seems like an ideal candidate for this, and a hybrid already exists.
- Legality? These don't exist, so there are no laws that govern this area. The system will obviously have to monitor itself so it doesn't provide too much help. The HDP would have to communicate with the motorhome. It would be no different than using umbilical cords to control brakes in a regular dinghy. There might be other communcation signals, though.
- Towbar? Perhaps a new one would need to be developed. Again, this is a concept. I do know that current tow bars can be used to push a 50,000 lb motorhome into the gas station from a stop! Getting ahead of myself, though.
- PapPappy's comments - The generators for charging the batteries are ONLY engaged when stopping or going down hill. This would be activated just like a conventional jake brake. Flip the switch to HDP instead of jake brake. Let off the gas on the motorhome, and the HDP starts charging the batteries providing a braking force. The energy stored from that braking would LATER be used to drive the HDP motors and push the motorhome, either from a stop or up a hill. That is a huge savings! With this approach, the 90 hp of free electrical propulsion, from say an Escape, is used to assist the motorhome engine. That's a real savings!
- No, this is not a late April Fool's joke. I hope it is real obvious how SIMPLE this technology is. It doesn't require any leaps in technology, uses mainly existing technologies, and can be developed on a fairly short fuse (if we can find someone interested in helping us develop it - or buying the technology and developing it themselves).
Thanks for the questions and interest.
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tundracamper
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04/03/09 12:29pm |
Class A Motorhomes
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RE: Hybrid Dinghy that Improves Motorhome Fuel Economy?
OK. If it's allowed, here it is.
http://www.me.ua.edu/stal/xtras/HDP_UA.pdf
Note that this is a newly developed technology that does not currently exist. I am trying to gauge interest from motorhome owners.
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tundracamper
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04/03/09 10:37am |
Class A Motorhomes
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Hybrid Dinghy that Improves Motorhome Fuel Economy?
For those of you that tow a dinghy, would you be interested in having a hybrid SUV dinghy (i.e. toad) that helps improve your motorhome's fuel economy?
This dinghy hybrid vehicle would use its electrical system, while being towed, and provide propulsion assistance. It could also be used when going down hill as a braking mechanism (replacing the Jake brake). The batteries would store the energy from braking, obtained through the dinghy motors (generators), and then use that energy to help push the motorhome up the next hill. As a result, it would improve motorhome fuel economy and acceleration in-town AND on the highway. Note that the gas engine in the hybrid dinghy would not be used during towing, just the electrical system. It would provide assistance to the motorhome engine. Think of it as an "outboard" hybrid for motorhomes utilizing an existing hybrid SUV or sedan.
We have defined this technology as the Hybrid Dinghy Pusher. I have brochure on this technology that I could link, if anyone is interested. I don't suspect anyone here is interested in helping develop this patent-pending technology. However, I am trying to gauge the interest of its potential users.
On Edit: Here is the link listed below...
http://www.me.ua.edu/stal/xtras/HDP_UA.pdf
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tundracamper
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04/03/09 10:23am |
Class A Motorhomes
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