David Ong

Oh man I discovered another error, turns out my oridignal analysis was correct because I didn't keep the energy density for gas constant between tabs. Paramotors are more efficient because they are bigger, they have more power density and energy fuel efficiency. The winner goes to BlackHawk Although it's based on the 60% power assumption for quoted fuel burn rate so it's just iffy. Noddyc's paramotor however we know is 46% well above gas generator efficiencies thus making generators undesirable.

You can build an induction motor instead of relying on magnets. Btw, what is your fuel burn rate at 15kw? Also is your 4 stroke EFI?

Ok I made a fatal error in my above analysis, looks like the generators are indeed much much more efficient than the paramotors which are extremely inefficient. The numbers for the paramotor efficiency had an error in it, I forgot to divide my Wh by the number of litres the engine runs on. The Wh number was reached by multiplying kW output by hours of run time associated with it (presumably half throttle is used to work out run time in hours before fuel tank is dry). Anyways after the correction is made Paramotors seem to be only 2-3% efficiency! That means 97% of the energy in the fuel is wasted as heat! Can someone confirm ? As for the generators their efficiency are much better: they are 10 over times better with an efficiency about 30%. Cars have an efficiency between the two extremes at 20%. So looks like there is still a use for the generators here! The only advantage of the larger paramotor engines is power density! They can output more power by consuming more fuel faster. I also had a brief chat with Noddyc privately and got some numbers off him to put in my spreadsheet. All the evidence is in the screenshot below of my spreadsheet. Can the efficiency of a paramotor be improved by turning it into an electrical generator as well as an engine? Or will this not change the fact that most of the wasted energy is heat? Also I am wondering if the above 2 mentioned paramotors im using in the screenshots below are 2 or 4 stroke engines and if they use carborator or fuel injection. I am hoping and guessing that they are 2 stroke carbs and that the newer 4 stroke fuel injected ones coming out such as blackhawk Intruder 250 EFI 4 stroke will have much better numbers. So far all I know is that it consumes 4.3L/hr and its max power is 35HP. If we maintain the assumption that all rated fuel burn rates are at 50% power then that would give it an efficiency of 4.62%. David

I have been following this thread and reading it and re-reading it for a week now. Noddyc can you draw a cartoon diagram of your proposal? I am seriously considering building it! I think in a nutshell (and correct me if Im wrong) the idea of this thread is Chance Waite has this idea of using electric portable generators to replace the paramotors themselves. But the problem I think is that he doesn't realize that paramotors are more efficient than portable generators as they are larger. Rule of thumb for internal combustion engines, the larger the engine the more efficient it is and portable generators are NOT efficient compared to larger motor cycle engines or paramotor engines. If you examine my attached screenshot of my spreadsheet of our Australian Gentrax portable generators I worked out the most efficient generator as well as it's power density of roughly 125W/kg. It's output is 3.5kW and it's weight 28kg. Compare that to a Flattop paramotor I have been closely researching to be my first paramotor for years now and you will see it has a power density of 800W/kg because it has a full power rating of 20kW and it weighs 25kg. Compare 125W/kg to 800W/kg !! The paramotor is has much much more power density! About 6 times more! While this doesn't prove higher efficiency it does show that the larger paramotor is more power dense. I can't work out the efficiency of a paramotor without the fuel consumption numbers at a specific wattage. And no paramotor website supply this information. Very strange. It's like there is a deliberate technical gap in this sports. So I make educated guesses. I assume that the "flight time" numbers used by the websites assume 50% of max thrust/power. Using this assumption you can see in the second attachment that it shows that the paramotor in general has about only 2-3% more fuel efficiency. So if going by my "educated guess" is correct the main advantage in paramotor is it's higher power density which still means that if the fuel efficiency is still roughly equal, it would mean that paramotors still maintain higher overall efficiency because of it's vastly higher power density. Your idea Noddyc, is to have a normal paramotor engine (large internal combusion engine) and use it as a generator because then it will be more efficient if it is running at the peak efficiency RPM and torque correct? That will increase it's efficiency as an electric generator and the electricity can be used to power the propealar to boose efficiency. I would think that in such a situation you probably want to have some lithium ion batteries and super-capacitors (with a voltage booster) to act as a buffer. And as you pointed out need to make sure the buffer doesn't get overloaded with voltage when it's full. Have I understood this thread so far? What I don't understand is why you would choose to go 3 phase AC? Is that the most efficient configuration as a generator? Also would that same generator be used as a motor? Or would the motor be a seperate device also connected to the propellar? (Is the prop connected to one or two electric motors/generators? I am not too keen on creating a propelar that is powered by both Internal Combusion Engine as well as electricity. But I want to try. But as a minimum what I really want is the ability to use the paramotor as a high output electric generator so that when I land on my "base camp" I can use it as an electric generator to supply power to the camp site. At least in the order of a few kW but ideally about 20kW which is about the same power as the mechanical output from combustion. David