I have to admit I am not sure what you are saying when you say Reading this verbatim this does not make sense to me. I am not familiar with measuring the potential "power" of electricity, diesel or gasoline in terms of "potential" HP production capacity.
Perhaps it is just in the wording. I will openly admit to not being an engineer but what you are saying does not sound any different than what I am saying. If the ultimate goal is to have output power that is measured at 100 HP then I acquiesce to your statement (at least to what I think is your statement). It will take a 105 HP electric motor and a 350 HP IC engine. Which is what I was saying.
An electric motor is approximately three fold more efficient than an IC engine. I discuss the issue of efficiency because it is this efficiency that is important to know about when you end up "sizing" a particular engine for the amount of output needed for the application. If one needs 100 HP output one needs to know how efficient a particular setup is at producing that 100 HP. If one knows that the IC engine rated for 350 HP will only be able to produce the needed torque when that engine reaches the 100 HP mark then one will have to chose this "oversized" power plant for the task. This is because that engine will end up running at 30% of its maximum HP output rating when operating at its optimum torque output range.
On the other hand if one knows that the efficiency of an electric motor is 98% of the rated output HP then one chooses a 105 HP electric motor. This motor can produce the needed torque while running at 100% of its maximum HP output rating. Both scenarios get you the needed 100 HP output. One just does it much more efficiently than the other.
Now this discussion holds true if you measure efficiency in terms of the ratio of energy input to energy output. The reality is efficiency can be defined with many other variables as well. Perhaps one wants to look at efficiency in terms of how much an operator knows about the system and how easily can he work on that system. Then the efficiency would take on a different meaning.
Perhaps if we define efficiency in terms of the capability to supply electricity to a moving airplane then maybe we would define efficiency differently. At present it is much more efficient to supply diesel or gasoline to an IC engine in an airplane than it is to supply electricity to an electric motor in an airplane. We do not have practical mechanisms in place to feed electric motors in such a mobile platform. Therefore the overall "efficiency" of the electric motor for an airplane power plant is not very good right now even though the "energy conversion" efficiency of electric motors is still much higher than IC engines.
These last examples of "efficiency" are reasons why we currently are not able to put electric motors in airplanes. However when attempting to "size" a power plant for a stationary ground based operation, the efficiency of the input/output energy ratio is going to be an important one to consider.
Hmmm, I think I just stated it poorly.
An IC engine runs at something like 33% efficiency. To get 100 hp out in the form of mechanical power (that is; work per time) you need to put in 300 hp worth of chemical energy. A fuel has a certain energy content per kg, this is what determines how many kg of fuel you need per second. The engine converts about 67% of the chemical potental energy of the fuel into heat (hot exhaust and cooling heat) and 33% into mechanical work.
An electric motor runs at something like 95% efficiency. To get 100 hp out in the form of mechanical power (again, work per time) you have put in 105 hp worth of electricity. The electric motor converts about 95% of the potential energy of the electricity into work, and 5% into waste heat.
An electric motor that is producing an output of 100 hp of mechanical power (essentially just torque X rpm) isn't doing anything different than an IC engine producing 100hp of mechanical power, it's just that the IC engine is using alot more energy to make 100hp than the motor.
If you pick a steady state operating point where an IC engine is rated at 100 hp, then it can be exactly replaced at that point by a 100 hp electric motor, no more, no less. That's just how much power it takes to turn your pump a certain speed (or a certain prop at a certain speed).
Now I agree that if you can take an IC engine that's rated at 300 hp peak at 5000rpm (which would be the rating in the procure) that only makes 100 hp at 2000 rpm and replace it with a 100 hp, 2000 rpm electric motor. If your application only requires 100 hp at 2000 rpm, you could just replace the 300 hp engine with one that's rated at a PEAK of 100hp at 2000 rpm. I guess the point I'm trying to make is that the load (the irrigation pump, the prop, etc) doesn't know anything about how the power is produced. IF you are able to replace a 300 hp (peak) IC engine with a 100 hp motor, it's not because the power produced by elec. motors is different, it's because whoever originally designed the system did a bad job of matching an engine to the load.
(...I think you understood this, and were just misunderstanding me, but i had to hash it out for myself, anyway...)
Edit: I re-read your last post, and now I understand. You are confusing "efficiency" (energy in/energy out) with "usability" (usable power/power available). In my example, the last 200 hp in the engine is unavailable at 2000 rpm because it can only be produced by the engine above that rpm. This is totally separate from the fact that the motor is ALSO more efficient.
