It would be interesting to try! until I get the chance I’ll believe the paper shared above.
My personal experience tells me I can move a lot faster than 0.1kmh at 270W, for sure fast enough to not fall over. Grade 11 math/physics would also tell me that if I move >0.1kmh at 270W, it will take <270W to move 0.1kmh. You can use whatever mathematical formula you want to get to 0.1kmh at 270W, and I can tell you with 100% confidence it is the wrong formula.
I still believe the formula is right, its just some of my assumptions for the numbers in the formula could be off. Probably the 0.32 I used for CdA.
If you’re Dan Bingham on a TT bike, it would literally be half the power required (I think I heard is CdA was 0.16! for his hour record run).
I have ridden into a 70 km/h headwind for hours. Tell me what power I was putting out according to your equation.
Sure, were you at sea level? what was your CdA? how fast were you riding? and what tires were you using? was it basically flat or much elevation change?
Geez, I agree @RChung! looks like the moderator set the topic as solved… the power you have…
Again.
There is no difference in aerodynamic drag experienced between riding 40kph on a calm day, and riding 20kph into a 20kph headwind. Otherwise wind-tunnel testing wouldn’t work, and we would not have modern airplanes.
The reason why it takes more power to go 40kph on a calm day then 20kph into a 20kph headwind is because of things like increased rolling resistance at higher ground speed. Not due to a difference in drag between the two scenarios.
There are also increased drivetrain losses at 40kph due to increased frictional losses within your drivetrain components at higher speeds.
I think this thread has somewhat devolved into an opinion piece on a physics problem, but I wanted to provide a couple of papers which suggest the paper being mentioned above is being interpreted incorrectly.
F. Malizia, B. Blocken. Bicycle aerodynamics: history, state-of-the-art and future perspectives
J. Wind Eng. Ind. Aerod., 200 (2020), Article 104134
Martin, James & Milliken, Douglas & Cobb, John & McFadden, Kevin & Coggan, Andrew. (1998). Validation of a Mathematical Model for Road Cycling Power. Journal of Applied Biomechanics. 14. 276-291. 10.1123/jab.14.3.276.
To avoid requiring you to access these papers, I have copied the formula for total power required here:
To explain the physics of what is going on (and which agrees with the papers mentioned above), the net wind (air speed + ground speed) creates an aerodynamic drag force which does not care whether you are moving at 0 mph in 40 mph wind or 40 mph in 0 mph wind. To compute work or power, you need the force you are applying and the distance you have travelled (or dx/dt for power). In the case of a bicycle, the distance needs to be computed relative to the thing you are applying power to (the ground), not the thing you are pushing through (the air). This is not the case in an airplane where the engine is pushing against the moving fluid to produce power. This also tracks with the knowledge that if you move from point a → b while overcoming a set amount of force, you have done a fixed amount of work regardless of how quickly you reach that point.
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I was at a few m above sea level, no idea at Cda I’m riding my bike in the real world. Put some numbers in your equation tell me what power I was putting out for hours.
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The equation above is only as accurate as the info that goes into it. If you don’t have accurate info for me to put in, I won’t have accurate info to output for you. If I just make up numbers to put some numbers into the equation it doesn’t prove anything. You haven’t even told me how fast you were riding, how would it be possible to estimate your power output?
Also, I’ll give you the benefit of the doubt, but riding into a sustained gale force wind for hours seems like a very unlikely. That wind speed is described as difficult to walk in.
No one knows their cdA unless they’ve been in a wind tunnel etc. I was riding at 22 Km/h, and I weighed 79kg at time, and height 1.79m.
Plug some estimates and tell me what power your equations come up with. We just want to sense check them we are not looking for exact as you’re not going to get it anyway.
You clearly don’t ride ultra distance
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I think @RChung might have something to say about that 
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Nice reply.
To bring back to the OP’s question, this is another (correct) post showing that it takes more power to ride at 40kph in still air, vs at 20kph into a 20kph headwind.
You can have a rough estimate but even that only applies for the position you maintained when testing. Your cdA on a different ride could be different again.