Portable Electric Air Conditioning from Peter Schiff

[RCG571]

Has anyone purchased any one of the Peter Schiff portable AC units? I have a 182Q and Texas summers are brutal and the wife is very negative about sweating till altitude. I've tried the Arctic Air evaporative coolers and they just aren't suited for my mission. Lugging ice around and then draining at destination is pain. Then more ice is required at destination to come home. Booo.

Seems I'll need to upgrade to a 100A alternator since my plane is 12VDC, but I can't find any other suppliers for a solution like this. Not being STC'd, portable, and removable for the cooler months is a big plus in my book.

Any feedback or direction would be appreciated.

Portable A/C | Peterschiffaero

www.peterschiffaero.com

 

[bentmettle]

tangential question - would a portable battery like https://www.amerescosolar.com/simpliphi-phi-1-2-kwh-high-output-lithium-battery that has the energy (this example doesn't have a voltage match to the 12V plane) required to run the unit for ~1hr be cheaper than upgrading the alternator?

It "seems" like a battery powered unit for peak usage that is charged at a rate the existing alternator can handle would be a far easier installation and truly portable between different planes.

 

[Barrett50]

I started looking at electric only AC systems for my plane also. I sent a few emails to a different vendor because, I could never get the answers to the BTU calculations to work out with 12V 65amp power draw. The best I could determine with an 85% efficiency rating was about 2300BTU, but the vendor was advertising 8,000 BTU. They never got back to me with anything except marketing materials.

I'd like someone with HVAC expertise to walk through the power consumption vs BTU production of any elec portable AC systems. As an example, I had one of those old style boat AC that sits on the foredeck of a cabin boat. It was rated at 5,000BTU. Plugged in to a 120VAC outlet, and took 10.8amps running. That's 1300W for 5,000BTU. Hmmm, but the plane AC is rating it 8,000BTU?

I used this as just a handy quick way to figure it out.

BTU to watts (W) conversion calculator

BTU per hour (BTU/hr) to watts (W) power conversion calculator and how to convert.

www.calculatorx.com

8000BTU/hr works out to 2344W/hr. Maybe I'm doing it wrong?

 

[Jim_R]

I used this as just a handy quick way to figure it out.

BTU to watts (W) conversion calculator

BTU per hour (BTU/hr) to watts (W) power conversion calculator and how to convert.

www.calculatorx.com

8000BTU/hr works out to 2344W/hr. Maybe I'm doing it wrong?

That is reasonable to approximate the performance of an electric heater, which is converting electrical energy to heat energy.

That is not reasonable for your application. Because of the laws of physics (entropy), you can't directly convert electricity to cooling like you can to heating. (Even with piezoelectric devices.) Most cooling systems are just moving heat from one place to another. The energy required to do that is used in the motors driving the fans/pumps/compressors and there is not a universal relationship between power consumption vs. amount of heat transferred--it depends on the system design, working fluid, and environmental factors.

 

[Barrett50]

That is reasonable to approximate the performance of an electric heater, which is converting electrical energy to heat energy.

That is not reasonable for your application. Because of the laws of physics (entropy), you can't directly convert electricity to cooling like you can to heating. (Even with piezoelectric devices.) Most cooling systems are just moving heat from one place to another. The energy required to do that is used in the motors driving the fans/pumps/compressors and there is not a universal relationship between power consumption vs. amount of heat transferred--it depends on the system design, working fluid, and environmental factors.

Right, that's what I had decided, so I used another method that takes into account the efficiency of the conversion. Typical AC units are 83% efficient. Some are a bit more than that, and some a bit less. However, even the best of the best cannot come close to the best case Carnot engine conversion. Which is why I used the quick and dirty calc above.

If we use an efficiency of 85%, the vendor is promising 8,000BTU/hr. And, what will that be in terms of W/hr? My example of the boat AC is indicative that the conversion offered by the vendor is wildly optimistic. Anything else that can be provided for the conversion relationship in Carnot(entropy) terms will be appreciated. The different vendor I contacted didn't know, or didn't want to disclose.

 

[Jim_R]

Right, that's what I had decided, so I used another method that takes into account the efficiency of the conversion. Typical AC units are 83% efficient. Some are a bit more than that, and some a bit less. However, even the best of the best cannot come close to the best case Carnot engine conversion. Which is why I used the quick and dirty calc above.

If we use an efficiency of 85%, the vendor is promising 8,000BTU/hr. And, what will that be in terms of W/hr? My example of the boat AC is indicative that the conversion offered by the vendor is wildly optimistic. Anything else that can be provided for the conversion relationship in Carnot(entropy) terms will be appreciated. The different vendor I contacted didn't know, or didn't want to disclose.

Again, apples and oranges. You're not directly converting electricity into "cooling" like some kind of a reverse heater. That's why you don't hear AC vendors talk about their units being "85% efficient" and instead talk about more esoteric measurements like "SEER".

If you want to look at home air conditioners as a comparison, there are a bunch of HVAC sites that will give you ballpark electricity usage figures. Here are a couple:

How Much Electricity (kWh) Do Air Conditioners Use? (Calc + Chart)

How much electricity do air conditioners use? Quite a lot, actually. According to EIA, US households used 235 billion kWh (kilowatt-hours) of electricity just for cooling in 2021. Of course, we are usually most interested in how many kWh does our air conditioner use. Most of us already know that...

learnmetrics.com

How Much Electricity (kWh And KW) Does An Air Conditioner Use? | RenewableWise

But how much electricity does an air conditioner use exactly?

www.renewablewise.com

Even a low-efficiency 8000 BTU system would draw less than 1kW, and a typical modern system would more likely be closer to half of that.

Now, whether it makes sense to draw any comparison between a home AC system and the portable you're looking at using in your aircraft is another question. But the point is, you gotta stop thinking about direct conversions between BTU and watts times some efficiency factor. You need to know more about the mechanism the system is using to move the heat around, and some are more energy-costly than others.

 

[AV8R_87]

To add to what's been said above, an air conditioner can move more than twice the amount of heat energy compared to the energy they consume. That's why people use heat pumps instead of resistive heaters.

 

[Barrett50]

What I need, and I think the OP needs is the ampacity draw. If the 182 has a 12volt system, it's going to be rated at 12.5VDC which is the nominal voltage of a FLA cell at 90% SOC. If we use an EER of 12 which is a SEER(I don't need the seasonal, all I care about is the worst case summer number) of 13 - 14. We'll say it uses 850W, just to be safe, that's 850/12.5V = 68 amps. Finally something useful.

If we use the 80% rule for alternator loads, then a 68 amp draw by the AC would leave 32 amps left over for the remainder of the alternator output of 100 amp rating. However, the AC unit is advertised as being 'portable' and thus not subject to the 80% rule for aircraft alternator output. A plane with a 50A alternator would not work at all. A plane with an 80A alternator would work - barely and leave very little reserve for other loads on the plane.

For 68A load, we need 4Ga, or 2Ga wire would be better. The vendor says 35-75 amp draw for 12V system. It's doable, but I wouldn't want to try it on a 80A alternator. The time the AC is needed is on the ground, and on takeoff/landing. I'm going to need the 100A alternator, if there's an STC for that, and then add the big power cables from the batt to the AC unit.