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This is a reasonable desperation setup for emergency power, but not a great off-grid solution.

Highway cruise for a compact car needs around 7 to 20HP, so a reasonable target output is in that range. That's 5 to 15 KWh. Seems small, but as others have pointed out, auto engines have peak outputs far beyond their continuous rating.

1800 RPM 60Hz generators are available, and larger generators tend to run at 1800 RPM. Or you could do something with belts or gears to keep the engine RPM down, as others pointed out. Running at low RPM is good if you want to run for a long time.

Probably a good idea to have the system disconnect output power until the frequency reaches at least 50 Hz, because this thing needs quite a while to reach operating frequency. Bringing up something like a refrigeration compressor (a likely emergency load) from 0 Hz to 60 Hz over the course of a minute may burn it out. Under-frequency operation is very bad for AC motors; they draw way too much current and overheat, because the inductance of the motor isn't able to oppose the lower frequency. Put an ohmmeter across an AC motor and note how low the DC resistance is.

> A cars cooling system is designed around that and the case where you need all 150 horsepower for 5 seconds, then drive for 30 seconds at 20 horse power before slamming on the brakes

My old 2004 Opel 1.6, 105hp could deliver almost full load (car fully packed with passengers and baggage, with roof trunk also packed, going 140km/h uphill with fully open throttle, fuel usage was reported as 16L/100km, typical road usage was 8L/100km) for about half an hour without any problems.

In the end it’s all about the load not the horsepower. Doing the job of a 100hp engine with a 300hp engine doesn’t require 3x the cooling. So companies happily sell higher trim levels with more HP while keeping the same radiator.

Smaller engines are designed to operate at higher percentage of maximum capacity at lower speeds. Roll back to the days of 40hp engines and they max out highway speeds and can sustain that for hours. As you keep adding HP the maximum sustained load at a given speed doesn’t increase. So, 1000+ HP super cars can make use of that power at 200+ mph, but they don’t waste weight having radiators large enough to dissipate that heat continuously at 85mph because there’s no way the car is staying that slow while applying that much power.

External temperature also plays a role, cars need to be able to handle highway speeds at 45C adding headroom at lower temperatures. Trucks also need to be able to do that while towing a large load.

25hp = 19kW or ~1x standard 42U rack, 105hp = 78kW or 20x typical households. Cars are powerful machines!

That’s the useful work which represents ~1/3 of the energy in gasoline. ICE cars needs to deal with ~2x that energy in waste heat.

A good rule of thumb is 1/3 of the energy into mechanical work, 1/3 into the cooling system, and 1/3 out the tailpipe. The actual numbers are pretty close to this across a wide range of operating conditions.

With the caveat that in cars the very long exhaust system dissipates a great of the heat rather than all of that energy literally coming out of the tailpipe as hot gas.

Also catalytic converters provide more complete combustion and thus generate even more heat.

Well, heat your water with it.

In addition, I don't see why you wouldn't just buy a home battery pack and use that to store up energy. You can run the ice in the high power bursts to top off.

I just kind of like this post because there's going to be a lot of excess ICE engines out there once EVs take over the primary job of consumer transport.

Would be nice to have a DIY recipe to convert them over to leveling for your solar grid at home

IIUC the significant fractions of heat can't be absorbed, else it eats into efficiency, which is okay if part of the purpose of the engine is for heat - I think he's just pointing out the hydrocarbon-to-kinetic conversion ratio is around 1/3rd, which is a useful rule of thumb.

That seems a little bit nuts considering what they're doing with passive heat exchangers right now.

Waste heat from an ICE must be way more useful than a simple 10 or 20° gradient that they're trying to use for house heating and cooling

with 140km/h wind to cool it in addition to radiator fan

I don't think fan was engaged anyway, never noticed it working when moving, only when stationary. I don't think it would help anyway.

What I mean - cars can do fine for long periods under load as long as they are cooled appropriately, not only for 10s of full power.

You look under the hood to see your fan moving while you're doing 140km/h? ;)

No, but I can hear it easily when car is idle, also see a change of power used by engine (fuel usage goes from 0.8L/h to 1.2L/h, not a small change). I purposefully wrote that I THINK that it doesn't work at speeds, because indeed it can be hard to notice it when going highway speeds. I would have to verify it probably with some CAN reader, but I think at speeds >40km/h it's not worth it to start the fan, air should be enough.

It wouldn't on highway, only time where extra cooling would be needed if you were on actual track where you'd have far higher average power on top of slower average speed.

>Your *American car engine can typically...

Agreed, only in America; and thank goodness for that.

I literally stopped at the Ford dealer today; there, I told the sales lady trying to sell me on the F150 that, for a few more thousand dollars, I prefer the F250 because I don't want a dinky euroboost 2.7 L turbo V6.

Luckily the F250 has a 6.8L V8 base.

For what?

Basically sounds like your typical American that buys a massive car truck. Just a drive around suburbia with for no real practical reason and F-250 would be ridiculous for that.

I'm glad every American male feels compelled by Ford and GM's advertising to buy 70 and $80,000 trucks because we'll be that much easier for them to budget out for EVs when they start coming out

Honestly? On the remotely unlikely event that I have an opportunity to switch on the high idle switch if some extinction folks block the road on the way back from soccer practice two miles away.

Opel basically does not exist in the US.

Opel was General Motor's European brand until 2017.

They sold very different cars in Europe than they did in the USA, but it was the same company.

>A cars cooling system is designed around that and the case where you need all 150 horsepower for 5 seconds, then drive for 30 seconds at 20 horse power before slamming on the brakes (6 horsepower to run the AC) for the next red light where you wait for 10 seconds (again 6 horse power for the AC).

I'm no expert, but I can't imagine that this is true. I agree that is "average driving conditions", but there are plenty of times you're driving way outside of those conditions. That can't be how the cooling system is designed. I've never seen a car even tick up in temperature, under all kinds of tom foolery.

The limiting factor in average horsepower output over time is definitely the cooling system on most cars. It's just that most people don't run their car at 80% of rated output for extended periods, otherwise you would absolutely overheat it.

I've towed large loads up extended grades (hello shasta and grapevine) and you absolutely will overheat on a hot day. And that's with an uprated towing rig that had a radiator sized for the job - imagine that same horsepower of engine in a passenger car with 1/3rd the radiator surface area.

Subaru engines are sometimes used in DIY small airplanes and they work well without overheating.

This, it can be done.

The airflow differences between airplanes and cars are pretty significant, much higher near ground level and much lower at altitude, so they're kind of a different beast than a static generation setup.

Yeah but they're basically always derated.

Amusingly, this is also true for modern laptops.

Makes me wonder what a "portable desktop with integrated screen and input" like I had in 2004 would be like these days. I think it was 16 pounds? with a pentium 3 desktop processor in it and about 4 screaming fans. Loved that thing.

Depending on your route, there's some big mountains leaving Los Angeles, if you've got a lot of stuff in your car, it's pretty easy to get the engine and transmission warmer than usual. Engine heat isn't too hard to manage if it's just for a little while --- roll down the windows, turn the fan to high and the heater to max. May be unconfortable, but better than overheating.

Afaik, that won't help your transmission though. If you run that at high loads often, you'll want enhanced cooling for that; often part of a factory tow package, but often available from the aftermarket as well.

I don't recall seeing an automatic transmission in a car or truck that doesn't have a transmission fluid cooler in front of the radiator for the 25 years I've been paying attention.

You can instal a transmission cooler if you live in that region.

> max power means your engine needs a full rebuild every 20 hours of operation

Top fuel drag racers need a rebuild after every run, which typically lasts 4-5 seconds. Their engines can produce 10,000 HP, which is about 7.5 MW.

https://en.wikipedia.org/wiki/Top_Fuel

And other race cars get the best of both worlds.

Le Mans cars and other touring cars are famous for holding up 24hrs under very high loads, even with the engine strung out beyond its street legal spec, but I think the most impressive feat is the Baja 1000.

Modern trophy trucks make ~1000 horspower, and the load is insane. The engines are running a pretty high average throttle, at high RPM, pushing a giant, heavy truck through sand, in a blazing hot desert. The fine dust can clog the filter, radiators, and get in all sorts of crevices. The whole drivetrain is constantly being shocked as the wheels leave the ground then jolt back to the correct RPM when the truck lands. And the whole truck is constantly being G-shocked, crashing into terrain you wouldn't even want to hike over at highway speeds, over and over again, for 1000 miles.

This was impressive back when the trucks were making a mere 300-600 horsepower, but honestly I have no idea how the modern turbocharged monsters even hold up.

Also, the engine throttle is open for a long time on the flat, barren stretches.

That seems minor, but there are no paved racing leagues where a 1000hp+ engine can run flat-out for a long time. Le Man's formerly 6 km straight was the extreme, and they eventually shortened that with chicanes.

Not 1000HP, but Nascar several years back was running something near 800HP, and at a couple tracks (Daytona and Talladega) they were wide open the whole way around if they were in front. Those races last several hours, with some number of short breaks due to cautions.

Yeah, NASCAR engineering is underappreciated too, but I didn't know they could do a lap with an open throttle around Talladega. That's crazy.

Fun fact: the Porsche 917 still holds the lap record at Talladega, even though it was set in 1975, because no one else is crazy enough to run a 1200HP 1700lb car around it. And it got so hot (running an open throttle?) that it spontaneously caught on fire when it stopped in the pits without any airflow.

Baja 1000 trucks are amazingly light compared to street trucks.

Like 5,100lb?

https://www.jimcoracing.com/pages/fastball-racing-spec-troph...

I dunno if that counts the spares, the fuel cell and such, but thats in the ballpark of an F150.

Depends on… well, everything, but towing a 1-tonne trailer up a long hill is far more taxing on a car’s cooling system than this. I’d expect any decent car to be designed to handle continuous running at peak torque, if not peak power.

(Why peak torque? Because that’s peak efficiency, for petrol engines at least. Makes sense if you think about it.)

Cars are not built to run at peak torque for long as nobody does that. Cars are design for maximum power for long enough to get up to speed, and which makes for a lot more power at peak torque than they need for running at highway speeds.

Sometimes a truck will be designed to run near peak torque while towing uphill on a hot day (AC) with a headwind, but when you do that it takes a long time to accelerate to highway speed and so truckers typically just buy more peak power (trucks are already notorious for slow acceleration). Running at less that peak torque isn't too much a loss (and diesel engines don't suffer nearly as much from running at less than peak torque so the savings doesn't add up very fast for trucks)

This actually sounds like quite the argument for electric trucks.

If only batteries were not so heavy. Trucks need a lot of power when towing a large load.

Trains can use overhead wires, but running that on roads is tricky when people expect to pass.

"Your car engine can typically deliver 150 horse power to the wheels, but after 6 seconds of that you are at freeway speeds and then your engine is only delivering about 25 horsepower."

Unless you're in Colorado doing 80 mph, uphill for ten miles, fully loaded with cargo - then you engine brake (ie dissipate your KE into the engine block) on the way down. Or you take you car to the track. In both situations your cooling system is still expected to deliver, and does, since its not that big an issue to size it properly and a massive reliability issue if it isn't.

25hp is probably enough to power your household (18kW or 170A at 110V). It's certainly well over the mean summer usage, but peak usage is probably higher in hot climates (I couldn't find any typical peak usage numbers).

Peak potential usage is way higher than peak convenient usage after a couple of trivial optimisations. Just “don’t run the dryer, the kettle and the toaster at the same time” will knock 4-5kW off the max. Schedule your hot water system to only run off peak and that’s another 2.4-3.6kW.

Most houses in Italy are only getting 3 kW, +10% of tolerance for a few hours, and if people can increase the maximum power they can draw, it is still very uncommon.

25 HP would be enough to power a small apartment building.

In many European houses the main power line into the house has a 35A fuse at 230V, so that's only 8kW maximum load.

Heating (and water) comes from natural gas, or a high efficiency electric heatpump.

In the US I've seen one house with 30amps at 240V (I also heard about a house from that era getting 30 amps at 120 volts), and it was from the 1930s with no updates. Even in the 1950s houses were getting 60 amps at 240V - which allowed for an electric stove to draw 40 amps 240V, and have enough for the rest of the house. These days small houses get 100amps, while large ones get at least 200. Very large houses sometimes get 400 amps. If you install geothermo you get 300 amps because even though geothermo is highly efficient in the worst case it can draw 80 amps at 240 volts (you only see those worst cases when doing the max power test at install time).

Unless it is a tiny house I wouldn't not expect 35amps to be enough to run a heat pump any everything else in a house (at least none of the houses I've seen in Europe, though I've only been there for a few weeks total so there is much I have not seen). Large RVs in the US get 50 amps at 240volts, while small ones get 30 amps at 120 volts - both compare to a tiny house in size.

There are millions of houses like that over here. An 8 kW heatpump is enough to heat the house, and with the high COP that would electrically only be a 2 to 3 kW load.

Isn't that 35A fuse at 400V?

No, it's 35A single phase at 230V or you get a three phase connection which would have 3x 25A and the possibility to get 380V if using multiple phases. But those are getting rarer in newly built houses.

A car alternator is typically 2kW-3kW at most, and is very roughly 50% mechanically efficient, so it uses 4-6kW of mechanical power. Ie: 1/18th of the 150hp (111kw) engine's capacity...about 5%.

Cars are already designed to run A/C and alternator almost continuously, and the AC not only generates load, it pumps a lot of heat into the air coming through the radiator because the condenser is in front of the radiator. They're designed (if the manufacturer did their environmental testing properly) to do that even in ~110+ degree weather.

Methinks you should stick to things you know something about.

PS: Many cars, even regular passenger cars - can handle being driven around a track, where you can go through a full tank in under an hour's worth of driving, and are either on the gas or braking during most of the session.

There are also things called hills and mountains, which may take minutes to climb, or more. Plenty of cars make it up the Mt. Washington auto road (where the challenge is making it back down without overheating one's brakes; engine braking must be used.)

There's something called "towing", which lots of people do the world around with minivans and passenger cars (not just pickups and SUVs.)

This is an interesting and informative comment, but it would have been much better without the condescending snarky tone.

Even on the track you get some cooling time while on the brakes. And cars do overheat on the track if the driver is not careful. You are correct though that cars are designed for up a mountain on a hot day with the AC on - which uses more than 25 horsepower - but that is still less than max power. That leaves a lot of headroom for racing on a level track, but you do need to watch the temp gauge (or update the cooling system is done on the track if the race rules allow)

Even 25 hp is large compared to the generator output shown (about 5 kW or about 7 hp).

I learn so much on HN.