I am always fantasizing about having a energy efficient air conditioner for van life, anyone seen any concepts in tech news or anything?

[GSXR1000]

some use the reversing valve to pump heat back to defrost, some use a heating strip, right? i thought these two (admittedly compatible) approaches were both used in heat pump devices.

admittedly i am a total amateur so it could be my ignorance ?

the heat stripes are for the indoor. they are used when it is too cold outside and most of the time they turn on when the unit defrost when the reversing valve activate... which heats up the outdoor but also blows cold indoor for 10-15 minutes

 

[curiouscarbon]

thank you for helping me understand!

 

[Batvette]

Hey Im gonna revive this thread because I just saw something completely different:

https://www.amazon.com/gp/aw/d/B0BWFQNPJS

 

[eXodus]

Hey Im gonna revive this thread because I just saw something completely different:

https://www.amazon.com/gp/aw/d/B0BWFQNPJS

This is a great unit for temporary install in something small like a Van.

It doesn't really tell us how efficient it is. In the product description it says:

Wattage	‎656

Which would be rather bad for a 6500 BTU. My Midea U - Window unit is 12000 BTU and needs about 700-800W.

Efficiency is crucial for a battery solar operated system.

 

[curiouscarbon]

Hey Im gonna revive this thread because I just saw something completely different:

https://www.amazon.com/gp/aw/d/B0BWFQNPJS

thanks for sharing this interesting architecture device. adding pictures because it almost looks like a "micro split"

at 700 usd for 6,500 BTU/hr, it does seem on the more expensive side; the flexible connector would seem to enable more installation options as compared to e.g. midea's U-shaped rigid architecture.

6500 BTU translates to ~1900W of thermal pumping 6500BTU/(3.41BTU/W)
as mentioned, the listed power consumption is ‎656 Watts
this implies a Coefficient of Performance of about ~2.9, which is much better than 1, but still a bit behind some other devices.

cheers!

 

[Batvette]

thanks for sharing this interesting architecture device. adding pictures because it almost looks like a "micro split"

at 700 usd for 6,500 BTU/hr, it does seem on the more expensive side; the flexible connector would seem to enable more installation options as compared to e.g. midea's U-shaped rigid architecture.

6500 BTU translates to ~1900W of thermal pumping 6500BTU/(3.41BTU/W)
as mentioned, the listed power consumption is ‎656 Watts
this implies a Coefficient of Performance of about ~2.9, which is much better than 1, but still a bit behind some other devices.

cheers!

Thanks for your input. Im still looking for a practical AC solution for my Honda Odyssey minivan. This is my second odyssey, on my first one last year I had installed a small GE traditional portable unit inside the van, ducted the exhaust out a plywood plate at the side window behind the driver, (well sealed) and added an additional hose to convert the unit to dual hose operation.
It did work, albeit not as well as Id like, probably because it was GEs smallest portable. It was $300 at Lowes.
My biggest issue was the sheer size of it when the dual hoses were included, theres only 147 cu ft of space behind the front seats.

Options I am considering all have roadblocks.
For instance an RV type AC, either 120v or 12v, but every one I have seen seems to have pass through designed for the typical RV ceiling vent, about 14" square. I have less than that on the front-rear direction of the opening for mu sunroof. About 11"x22?
Ive considered another type of portable, industrial spot cooler portables, whereas the unit could sit on a trailer hitch rack, with a generator in a hush box next to it. The output hose could enter the van through a 5" hole cut in the well where the 3rd row seats would normally stow in, which Ive removed. These units are typically about $700.
Its drawback is the sketchy appearance of hanging off a trailer hitch rack.
The unit I posted about above isnt practical because theres no way to route the lines between the only place I could put the outside unit (trailer hitch rack again) and the inside unit. The lines arent removable so cant go through the floor. My van is white and Im tinting all the windows with max solar rejecting film, and its bearable in the shade but thats rare in my pseudo desert city. I wonder if it would be worth trying one of those automatic umbrella-car shade things. May not work real well as it still leaves the van sides exposed.

I still have the vornado window fan i posted about 2 pages back. Great for a fan but on those really hot days only AC will do.

 

[Altide8]

This is a great unit for temporary install in something small like a Van.

It doesn't really tell us how efficient it is. In the product description it says:

Wattage	‎656

Which would be rather bad for a 6500 BTU. My Midea U - Window unit is 12000 BTU and needs about 700-800W.

Efficiency is crucial for a battery solar operated system.

How did you mount you midea unit in your van? I have one of the 12v mini splits. It works but efficiency isn't great as you mentioned. I'm looking into other options.

 

[eXodus]

Something very interesting on Kickstarter:

https://www.kickstarter.com/projects/940981776/comfyair-the-ultimate-window-air-conditioner

Two major advantages for Vanlife and RV Living I can see - the unit is small and pretty quiet - and it doesn't stick out the back and can be mounted vertical.

So you can basically just cut a hole on the wall mount the A/C against it. And put a grill on the outside. Or stick it through a sliding RV window

The efficiency is not great on paper, but that could be maximum numbers. My Midea U - states 800W - but mostly runs at 300-400w.

 

[JJJJ]

here ya go....extremely efficient, pet approved ;-

Aka 465, 470 depending upon the speed limit and number of windows open.

 

[Lt.Dan]

This is a great unit for temporary install in something small like a Van.

It doesn't really tell us how efficient it is. In the product description it says:

Wattage	‎656

Which would be rather bad for a 6500 BTU. My Midea U - Window unit is 12000 BTU and needs about 700-800W.

Efficiency is crucial for a battery solar operated system.

One of the reviews says he's never seen it over 5.5a, so that's a good sign.

 

[SupraSPL]

My mini split 12000 BTU cooling watts: 3500W runs of 600W of AC COP 5.8

Measured a friends Inverter 12000 BTU Window A/C from Midea = it runs of 700W COP 5

This is where the rubber meets the road and huge improvement over a standard COP of 3. A 15 CEER unit can almost match efficiency of a 33 SEER mini split, these "adjusted" EER values can be misleading in this case as someone else pointed out.

The measured wattage depends alot on outdoor temp of course and that directly affects effciency. My Midea U 8000 BTU pulls 850 watts during very hot weather and as little as 100 watts with compressor still on. These inverter units also have the benefit of high efficiency DC brushless fans inside and out and that power savings really adds up over time.

One downside is regarding power factor. The Midea U 8000 BTU unit ranges from .7pf at low loads to .78pf during higher loads. I assume that is due to harmonics in the power supply and if you are off grid that extra load comes out of your batteries.

It would be great if we could BYPASS the power supply and power these units with direct DC and probably simple for the manufacturer to add a DC input. I have done that successfully with other inverted DC devices. If it is a 24V system that would be about 40 amps but would be an awesome boost in efficiency, recovering 20 to 30% by eliminating power factor, another 10 to 15% eliminating the 120V to 24V conversion and another 10 to 15% eliminating inverter losses.

This same exact approach applies to inverted DC heat pumps, ceiling fans, inline fans, washing machines, dehumidifiers, fridges and freezers. DC brushless air handlers, water and well pumps should become the norm. The soft start would be a huge relief for well pumps, reducing inverter size. It adds up to so much savings it would truly make a huge dent in the world's energy problems.

 

[Hedges]

One downside is regarding power factor. The Midea U 8000 BTU unit ranges from .7pf at low loads to .78pf during higher loads. I assume that is due to harmonics in the power supply and if you are off grid that extra load comes out of your batteries.

It would be great if we could BYPASS the power supply and power these units with direct DC and probably simple for the manufacturer to add a DC input. I have done that successfully with other inverted DC devices. If it is a 24V system that would be about 40 amps but would be an awesome boost in efficiency, recovering 20 to 30% by eliminating power factor ...

The 0.22 to 0.30 difference between real power and actual power should not entirely, or even mostly, show up as power loss.

It is related to higher peak current part of the time (offset by no current part of the time) when powering these VFD.
In the case of inductive or reactive loads, it is current drawing power in-phase part of the cycle, and current returning power out of phase part of the cycle.

The higher total current draw causes greater loss in the inverter due to I^2 x R power dissipation in resistance. Loss maybe about inverter efficiency multiplied by that excess current. Perhaps 10% ... 15% loss multiplied by 22% to 30% higher current than an ideal load?

The higher current also reduces how many W or VA are available to drive other loads.

I would like to have PF corrected front ends. That is basically a switcher synthesizing sine wave current drawn from grid, similar to the switcher VFD has synthesizing sine wave current into motor. At work we got some 1500W Lambda/TDK PFC modules which take in 85V to 250V rms and output 360VDC. Spec says 20V ripple, which depends on added filter capacitors and power draw. We measured about 0.95 PF.

To power direct from DC would be nice, but the front-end takes in 120Vrms, rectifies it into a capacitor. That will produce 170VDC under no load, or draw down lower during the dead time between each AC phase. I think you would need to boost from battery voltage to make that work. A square wave inverter could be ideal, or MSW, or tap the HV bus of such an inverter.

We simply fed DC into AC input of SMPS. That contains an AC fuse, so I would want to either replace with DC fuse or simply short it out and use an AC fuse before the PFC module.

 

[AntronX]

I have Midea 12000 BTU. I seen it pull 1150Wac on max cool setting on a hot day. You cannot assume constant BTU output from variable compressor speed air conditioners. Assuming at max cooling the unit was making 12000 BTU then the COP was (12/3.412)/1.15 = 3.06 at full load. At partial load COP may be higher due to heat exchanger coils becoming effectively oversized which should increase COP. But the fan speed is reduced as well, so it may not be getting any more efficient at low compressor speeds.

 

[SupraSPL]

So we could probably say COP of 3 in worst case scenario and surely it would be much higher when outdoor temps are lower. But yea that is very hard to measure and compare to other units with so many variables, indoor temp, humidity, outdoor temp, variable BTU output and variable power consumption.

My 8000 BTU Midea unit is at 350W most of the time and cycles down to 200W then back up to 350W, in a much larger room than recommended spec, outdoor temps in the 80s indoor setting is 75F. It can easily make 1000 sq ft comfortable and sips power compared to my aging 3 ton R22 central air which has ~600 watt air handler plus ~2500W condenser.

 

[SupraSPL]

To power direct from DC would be nice, but the front-end takes in 120Vrms, rectifies it into a capacitor. That will produce 170VDC under no load, or draw down lower during the dead time between each AC phase. I think you would need to boost from battery voltage to make that work. A square wave inverter could be ideal, or MSW, or tap the HV bus of such an inverter.

We simply fed DC into AC input of SMPS. That contains an AC fuse, so I would want to either replace with DC fuse or simply short it out and use an AC fuse before the PFC module.

Great info thank you. I will try to get a clamp reading on the inverter input to compare against the AC power and power factor to see how much if at all it affects current draw from the batteries. That would be great if it is the type that doesn't pull extra power!

Dang my battery system is 24V so if the compressor is running 170VDC.. overall sounds like 120 AC is the way to go for now oh well

 

[Hedges]

I was thinking I could power an inverter-drive minisplit (or other VFD) just fine from my MSW inverter.

But then I realized MSW waveform tries to yank voltage from zero to 170V, to zero, then dead time, then to -170V ... Problem is, that is connecting a transistor between 170V HV caps in inverter, and partially discharged caps in VFD. Near infinite inrush current every cycle. Square wave inverter would be better than MSW.

Voltage like staircase in middle:



That is OK into a resistor or inductor, not OK into a capacitor.

Would be better to tap the HVDC bus, not the AC output.

 

[culty]

I sell a lot of ac equipment. I have commercial coolers, I have a sub-zero cooler set.
I think combined with an inverter ecm driven compressor i can custom build a system that will sip power, and be very efficient...

Did you ever do it?

 

[eXodus]

At this point I'm just looking at those Hybrid from Signature

EG4 Hybrid Solar Mini-Split Air Conditioner Heat Pump AC/DC | 12000 BTU | SEER2 22 | Energy Star Certified | Plug-N-Cool Do-It-Yourself Installation

Signature Solar provides solar panels, off-grid solar systems, grid-tie, and hybrid systems. Quality solar inverters, bifacial solar panels, complete solar kits, solar batteries. Featuring brands such as EG4 Electronics with their solar battery, LifePower4 and EG4 LLifePower4 and EG4 LL

signaturesolar.com

They can run on AC or DC - directly off solar.

Great info thank you. I will try to get a clamp reading on the inverter input to compare against the AC power and power factor to see how much if at all it affects current draw from the batteries. That would be great if it is the type that doesn't pull extra power!

Dang my battery system is 24V so if the compressor is running 170VDC.. overall sounds like 120 AC is the way to go for now oh well

when you look at the voltage spec from the EG4 hybrid unit - it seems like the Compressor might be running even higher and lower in a Inverter driven Unit.

We might be seeing anything between 90VDC and 380VDC at the output of the inverter stage.

I think the issue is that - a low Voltage DC would have giant windings - which are hard to fit into a compressor. 24V at 1000W those are 40A - pretty massive wires.

In a home setting - it would be:
AC - line voltage - Inverter to high voltage DC - Compressor - done

RV/Van - Offgrid:

DC-Battery - Inverter to 115V - AC - line voltage - Inverter to high voltage DC - Compressor - done


What we would need is a low voltage DC - to variable high voltage DC converter. But those things are expensive and rare.

 

[Supervstech]

Did you ever do it?

Nope… it’s all sitting on a shelf in my warehouse… but time is short, and customers are plentiful…

 

[Swamplizard]

Agree with above however, I was on a budget and found the slightly used roof A/C for $300 and wanted it to be a low profile as possible, already planned on LV2424 all-in-one, and I found 280AH LIFEPO4s for relatively cheap ... built TWO 280AH 24V with quality bluetooth BMSs for a total of $1,400. I have yet to install the second 24V as I have not needed it for the overnights we do. Once we go boondocking and stay a week we will need all the juice we can store. Not sure what the split costs and if it can be as stealthy but pretty happy with my system so far.

 

[eXodus]

Found something new:

120V Inverter Roof Unit ECO-Cool by Gree:

ECO-COOL

<meta name="trustpilot-one-time-domain-verification-id" content="64f3e1f0-e077-4ee8-a1c7-1e93d20e2f6e"/>

ecocool.premierproducts.net

https://www.premierproducts.net/images/custom/gree-ecocool-brochure.pdf

Looks like those heatpumps are silent and pretty efficient according to their data sheet.

Since it's Variable-Speed Inverter - it does not need soft start for small systems.

 

[Vigo]

This appears to be the same unit:
TOSOT branded for $1299

I also found this interesting with a $400 coupon bringing it down to ~$500 for a small portable 6000btu inverter driven air conditioner with a 48vdc input!

EENOUR PA600

 

[SupraSPL]

It does look like that TOSOT unit. Specs put EER at 8.5 which is less than half the efficiency of the most efficient inverter mini splits. For example even the Midea U inverter window unit is 15 EER. I'll try to find a more clear and detailed spec sheet.

Cooling
Output 15K BTU 4440W
Input 1550W
4400/1550 = 2.84 or 284% efficiency at 95F
2.84 * 3422BTU = 9.7 EER

So 15K BTU must be the maximum output not rated output.

 

[Supervstech]

It does look like that TOSOT unit. Specs say EER 8.5 which is less than half the efficiency of the most efficient inverter mini splits. I'll try to find a more clear and detailed spec sheet.

Cooling
Output 15K BTU 4440W
Input 1550W
4400/1150 = 2.84 or 284% efficiency at 95F
2.84 * 3422BTU = 9.7 EER

So 15K BTU must be the maximum output not rated output.

Typo?
You state 1550, then put 1150 in your calculation.

 

[SupraSPL]

Typo?
You state 1550, then put 1150 in your calculation.

Fixed thank you. Yes I've been trying every different number they have provided but none of them are quite as low as 8.5 EER.

I'm guessing that they are rating at a relatively high BTU, because of the relatively small radiators, reducing rated efficiency. But more importantly it does not appear to have an economy mode (limiting compressor to 60%) leaving a lot of actual efficiency on the table.