2025/2026 Hybrid Powerunit speculation

[wuzak]

The problem is the volumetric density is appalling. Hydrogen at 750 bar is ~42kg/m3, so if they need roughly 110kg of fuel to complete a race now, they would need roughly 34kg of hydrogen for a fuel cell with a 60% efficiency vs a 50% efficiency PU currently, which means you need a roughly 800L tank of hydrogen to complete the race, which would be a packaging nightmare.

Well, yeah. But it's workable. I'm more skeptical about safety viability. A 750 bar tank bursting would be quite an explosion.

The latest generation of Space vehicles use Methane, mostly because of the density difference with Hydrogen, plus the amount of cooling needed, and pressure. Is it likely any F1 teams would look at it? (produced by solar so 'green')

You mean SpaceX uses methane?

SLS uses liquid hydrogen for the main stage and solid rocket boosters.

I would think the main reason to use Methane is cost.

[wuzak]

my (first 2) suggestions above - can someone explain what would stop them working ?

Race fuel allowance?

[Big Tea]

Well, yeah. But it's workable. I'm more skeptical about safety viability. A 750 bar tank bursting would be quite an explosion.

The latest generation of Space vehicles use Methane, mostly because of the density difference with Hydrogen, plus the amount of cooling needed, and pressure. Is it likely any F1 teams would look at it? (produced by solar so 'green')

You mean SpaceX uses methane?

SLS uses liquid hydrogen for the main stage and solid rocket boosters.

I would think the main reason to use Methane is cost.

Its mostly due to long term wanting to produce fuel from atmosphere (mars) and sun power, but partly because of much less weight and bulk of the tanks needed. Also stores at -160 odd

It produces less power, but takes up less room and weight, as would be needed on a car

[Cold Fussion]

Methane also burns much cleaner than RP1, useful considering the multiple use nature of engines.

[Just_a_fan]

SLS uses liquid hydrogen for the main stage and solid rocket boosters.

I would think the main reason to use Methane is cost.

SLS uses rehashed Space Shuttle main engines (RS-25) which means they have to use liquid H2. NASA are paying something around $100m per engine which is a lot of money - $400m per flight - to just throw away but then each launch costs something like $2bn. Very old-school thinking, sadly, but they are using the usual suspects like Boeing who just always charge a fortune and just do the "same old same old".

[Big Tea]

SLS uses liquid hydrogen for the main stage and solid rocket boosters.

I would think the main reason to use Methane is cost.

SLS uses rehashed Space Shuttle main engines (RS-25) which means they have to use liquid H2. NASA are paying something around $100m per engine which is a lot of money - $400m per flight - to just throw away but then each launch costs something like $2bn. Very old-school thinking, sadly, but they are using the usual suspects like Boeing who just always charge a fortune and just do the "same old same old".

The Blue origin RB4 engine also uses it and there are a couple of other companies intending to use RB4

Edit
OOps, I've done it again

[gruntguru]

. . . . In principle couldn't a 'throttle' reduce air drawn by the compressor without causing the usual 'throttling' loss of power ?

. . . where possible the "throttle" would reduce output to the wheels by loading the guk and charging the es. This would have the benefit of eliminating lag - the turbo is at full boost with ice charging es at 350 kW. Application of full throttle could increase output to the tyres by 700 kW without any change in ice output.

I think this is sort of what you were getting at.

[wuzak]

. . . . In principle couldn't a 'throttle' reduce air drawn by the compressor without causing the usual 'throttling' loss of power ?

. . . where possible the "throttle" would reduce output to the wheels by loading the guk and charging the es. This would have the benefit of eliminating lag - the turbo is at full boost with ice charging es at 350 kW. Application of full throttle could increase output to the tyres by 700 kW without any change in ice output.

I think this is sort of what you were getting at.

How much will the race fuel restriction impact that?

Remembering that the race fuel will be something like 70% of the energy that is used now.

And the engine is tied to the rear wheels, and potential engine power is controlled by the fuel flow, which is restrcited below 10,500rpm depending on rpm. Not sure what rpm would produce 350kW.

And if that system can be used, recall that the storage is only 4MJ. or 11.7s at 350kW. So long straights, like Spa, will have a lot less power available than now.

[Red Rock Mutley]

How much will the race fuel restriction impact that?

Think more in terms of per lap energy budget. The ES permits greater flexibility in the timing of the conversion between fuel energy and mechanical energy. Doing things like improve drivability is an important part of maximising the ruleset to improve lap time

And if that system can be used, recall that the storage is only 4MJ. or 11.7s at 350kW. So long straights, like Spa, will have a lot less power available than now.

2 points there -
Firstly, the 4MJ is the delta between ES minimum and maximum for the session, it's not a per lap limit. Even when used all in one go, the ES can be refilled during the remainder of the lap, and used again in that lap. There is a per lap input limit, 9MJ but no limit on the output.
Secondly, the 350kW is not a single define value. It is a function of car speed and tapers above 300kph (essentially long straights)

2026 PU Regs
5.4.6 The electrical DC power of the ERS-K may not exceed 350kW.
5.4.7 Additionally, the electrical DC power of the ERS-K used to propel the car may not exceed: • P(kW)=1850-5* car speed (kph) when the car speed is below 340kph
• 150kW when the car speed is equal to or above 340kph
5.4.8 The difference between the maximum and the minimum state of charge of the ES may not exceed 4MJ at any time the car is on the track.
5.4.9 The energy harvested by the ERS-K in each lap must not exceed 9MJ.
This limit applies to the energy going out of the CU-K and going into the ES.
5.4.10 The maximum mechanical torque of the MGU-K may not exceed 500Nm. The torque will be referenced to the crankshaft speed and a fixed efficiency correction of 0.97 will be used to monitor the maximum MGU-K mechanical torque.

[wuzak]

And if that system can be used, recall that the storage is only 4MJ. or 11.7s at 350kW. So long straights, like Spa, will have a lot less power available than now.

2 points there -
Firstly, the 4MJ is the delta between ES minimum and maximum for the session, it's not a per lap limit. Even when used all in one go, the ES can be refilled during the remainder of the lap, and used again in that lap. There is a per lap input limit, 9MJ but no limit on the output.

Right, but the battery capacity is 4MJ.

Means you can only deploy a maximum of 4MJ without recharging. Which is 11.7s at 350kW.

Or 23.4s at 175kW.

But I would think that 350kW would be used at the exit of the corner.

[mzso]

On their own, sure, but you ignore all the ancillary equipment needed to make a viable FCEV.

Again, you're generic without providing any basis. You need a tank, a fuell cell, and a small amount of battery, power electronics which all EVs have.

[djos]

On their own, sure, but you ignore all the ancillary equipment needed to make a viable FCEV.

Again, you're generic without providing any basis. You need a tank, a fuell cell, and a small amount of battery, power electronics which all EVs have.

And BEV’s don’t need the 2 largest, hardest to package items. Seriously mate, go have a look at the specs of the latest FC tech.

Eg Toyota’s latest Mirai uses the latest polymer electrolyte fuel cell with a power output of 114 kW and 330 cells. It has a Volume power density of 3 kW per litre.

That means the 114 kW fuel cell takes up around 38 litres of volume! To get 500 kW of power output, you’d need around 160 litres of fuel cells. And that doesn’t include the tanks or battery etc.

There is simply no scenario where you could make a decent F1 race car with the current tech. Even an LMP car would be grossly uncompetitive and they likely have room for more powerful FC stacks etc.

[mzso]

Remembering that the race fuel will be something like 70% of the energy that is used now.

Did the 100kg allowance stay the same I don't remember reading that information.

[mzso]

And BEV’s don’t need the 2 largest, hardest to package items. Seriously mate, go have a look at the specs of the latest FC tech.

Eg Toyota’s latest Mirai uses the latest polymer electrolyte fuel cell with a power output of 114 kW and 330 cells. It has a Volume power density of 3 kW per litre.

That means the 114 kW fuel cell takes up around 38 litres of volume! To get 500 kW of power output, you’d need around 160 litres of fuel cells.

There is simply no scenario where you could make a decent F1 race car with the current tech. Even an LMP car would be grossly uncompetitive and they likely have room for more powerful FC stacks etc.

First, you generalize something about fuel cells based on the plainest dumbest hydrogen fuel cell tech.
Then you provide some data, that actually is contrary to your point. 160 liters is not a huge volume, it could be spread around an F1 car. Hell F1 cars had bladders in the 80s that were around 160 liters larger than now...
The actual problem would be the hydrogen tanks.

But yet again: fuel cells doesn't just mean hydrogen. More suitable to F1 would be SOFCs or other direct carbon fuel cells. With a more practical fuel.

[mzso]

my (first 2) suggestions above - can someone explain what would stop them working ?

Stu mentioned the accelerator pedal and injector regs. I've looked, but I'm not seeing them as limiting the ICE to MGU interaction. Perhaps he can help point out the specifics?

5.14 & 5.15 (2026) define the relationship between the pedal map and the +ve torque to the rear wheels. However, they are framed in terms of net PU output. So, for the accelerator pedal at 0%, it's possible to run the ICE at +350kW and the MGU at -350kW for a net zero PU output.

The benefit is as you say, the turbine is already producing boost when the driver goes on the throttle, so all that problem with lag goes away.... plus you're harvesting energy for the later acceleration phase. All, in all, it seems very attractive to aim for running the ICE at full power for 100% of the lap, and modulating PU output using the MGU (at least in qualifying).

Braking is a point of contention, and there's a design choice of when to bring the ICE "on power". It's perfectly possible to do it early in the braking phase when the revs have dropped sufficiently for the output from ICE to balance the harvest from the MGU.

I already hear the crying about how strange the cars sound with the engines always screaming at least on 350kW.

I wonder if anyone could actually calculate how much power can be generated in total. Obviously only break and part-throttle phases are in play, which might count for very little in Monza or Spa and such. But I guess the extra 350kW would be always available in monaco/hungary, on tracks where you least need it. The battery would be completely full after every turn...