Solar Air Conditioner

[gnubie]

From what I understand the automotive industry is as we speak considering a move to 24 or 36 volt systems due to all the electronics in cars now.

Compressors in EVs are fed off the HV DC supply (300+) so I expect that will become the norm as EVs slowly become the defacto.

 

[Opusdei]

i am on board with this design.

i can mount all of this in my pickup truck bed, and i already have plans to mount 400w solar above the bed on a rack. and lithium bank in the bed as well.

what i want to see is the coil set and the interior cooling unit. i have cab access, but i am not cutting a hole in the roof of my powerwagon.

Sounds like a good project. Mini-split uses an umbilical hoses that pass the refrigerant gas so you need a 3" hole. I used Polyurethane foam to seal it.

 

[Opusdei]

I am able to run my coleman air conditioner in my truck camper from my LiFePo4 battery(271ah) using an inverter, of course. But when the compressor is running I'm using about 80amps of 12v. I have looked at mini split which could conceivably shave that down to a 50 amp draw.

How many cubic feet are you planning to cool? What is your target amp draw with the compressor running?

Coleman air conditioner is designed for RV with shore power. Not only the Colman but also the inverter draw a significant amount of current due to the AC-DC mismatch inefficiency. That’s why DC air conditioner is a better for the RV and trucks. As far as 12V DC air conditioner is concerned, I think it uses 30Ah of power considering 7 hours of operation out of 170Ah AGM batteries on sunny day above 100F. Keep in mind that I had (2) 200W solar panel trickle charging and it could have been turned on and off to maintain 70F inside the mini-van.

 

[powerwagon]

mini splits are by far the easiest to work with.

i wont lie, the Zero breeze in concept works. if i could better insulate the two front occupants with window covers and blanket, park in the sun, i could have all day no idle AC

Sounds like a good project. Mini-split uses an umbilical hoses that pass the refrigerant gas so you need a 3" hole. I used Polyurethane foam to seal it.

of course, i understand that, i can see the hoses in your install, and i have removable in floor cargo boxes that are plenty sufficient for any hoses..

just wondering what the evaporator setup looks like. water drainage? size? filter?

 

[Opusdei]

From what I understand the automotive industry is as we speak considering a move to 24 or 36 volt systems due to all the electronics in cars now.

Tesla uses 375V DC, correct me if I'm wrong

 

[Opusdei]

Any ideas yet as to what the $/BTU or the watts/BTU would be?

I don't have a final product yet. It is rated 6000 BTU of cooling power, 300W-795W of power consumption, so watts/BTU would be 0.05-0.13

 

[Opusdei]

mini splits are by far the easiest to work with.

i wont lie, the Zero breeze in concept works. if i could better insulate the two front occupants with window covers and blanket, park in the sun, i could have all day no idle AC


of course, i understand that, i can see the hoses in your install, and i have removable in floor cargo boxes that are plenty sufficient for any hoses..

just wondering what the evaporator setup looks like. water drainage? size? filter?

It is a typical mini-split evaporator. As shown in the attached photo, I attached it on the left side of window next to my daughter's seat. Evaporator has a dry mode operation and water drainage runs on the lower left corner as shown in the picture. Refrigerant hoses and AWG-4 size cable connect the evaporator and AGM batteries. There is a mesh filter inside the evap but it is not HEPA type.

 

[Freep]

Coleman air conditioner is designed for RV with shore power. Not only the Colman but also the inverter draw a significant amount of current due to the AC-DC mismatch inefficiency. That’s why DC air conditioner is a better for the RV and trucks. As far as 12V DC air conditioner is concerned, I think it uses 30Ah of power considering 7 hours of operation out of 170Ah AGM batteries on sunny day above 100F. Keep in mind that I had (2) 200W solar panel trickle charging and it could have been turned on and off to maintain 70F inside the mini-van.

If I could reliably consume only 30 amps at 12V and have the same or smaller footprint than the Coleman I'd be looking very seriously at swapping the Coleman out. A large number of RV owners would. The Coleman AC on a truck camper is ridiculously large and as you say, is meant for running on shore power, which means a large generator(and noise and vibration). Most truck camper owners do not like to camp at sites with electrical hookups.

Our strategy for keeping cool has been to just drive to higher elevations where it isn't so hot. It's just not worth the hassle to run a generator to cool off. Something like this would give us a lot more options.

I hope you're successful.

 

[svetz]

... It is rated 6000 BTU of cooling power, 300W-795W of power consumption, so watts/BTU would be 0.05-0.13

Apologies in that I asked the question backwards... was trying to get to EER to compare with other products. Please let me know if this math is wrong... EER = BTU / watts. So, 6000/300 to 6000/795 gives an EER from 20 to 7.6?

The 20 is great, the 7.6 not-so-much... is the design that variable or are there specific conditions that would cause the .13W/BTU draw (e.g., hotter interior when first turned on)?

 

[Opusdei]

Of course, it is a number game and I'm new to HVAC business. SEER depends on the test condition and 12V DC air conditioner uses VFD technology so it is complicated. I would rather give a metric based on how many hours of operation can be maintained at standard test condition.

 

[Dzl]

Of course, it is a number game and I'm new to HVAC business. SEER depends on the test condition and 12V DC air conditioner uses VFD technology so it is complicated. I would rather give a metric based on how many hours of operation can be maintained at standard test condition.

Can you explain how you will (or are) defining standard test conditions?

 

[Opusdei]

Can you explain how you will (or are) defining standard test conditions?

Think a black box. Let’s apply a thermodynamic steady state. Set the outside temperature at 100F and target is to keep inside temperature at 70F. Then we can measure how many hours the air conditioner can maintain 70F for a given battery power. I would call it a standard test condition.

 

[lisalizajohn]

So are you just gauging interest? Or are you prepared to put them together to people currently in the market for an air conditioner?

The unit I'm most interested in is a Mitsubishi 6000btu minisplit that rates at 33 SEER. If I needed something a little bigger, there is a Carrier 40 SEER option at 9000btu. The former 'should' max out at less than 200 watts, and the latter should max out at less than 250 watts. They run at 208/230vac, so I have to account for a split phase inverter setup when considering both up front costs and power consumption. They're both ~$1500 - slightly less than the DC units I've found. The consumption on those, though, is prohibitively high - I can't spend a fortune for the same consumption as a cheap window unit. I'm definitely interested in hearing more about what you're developing.

If I had more money to play with, I'd love to test the units above, the commercial DC air conditioners, and a window unit in your black box setup.

 

[Trukinbear]

Tesla uses 375V DC, correct me if I'm wrong

I'm not sure. My Prius's batteries are 200+ volts and the inverter bumps it up to 400-500VAC - but there is a 12V battery in the back, and all the computers, hvac blower, stereo and other car electronics are 12 VDC. You know not that you guys are mentioning electrical automotive AC, I leave my dogs in my Prius with the AC on (and a sign that explains they are ok, a thermometer people can see, and my PHONE NUMBER) - it uses an electrical AC compressor. My Mercury Mariner Hybrid had AC that only worked while the engine was running, I was glad the Prius went the other way. What I meant was the automotive systems like the computers, controllers, stereo, nav etc are going to 24-36V. If I'm not mistaken the Tesla has a 12V battery, and 12V stereo etc... I could be wrong, but I doubt stuff runs on 375VDC, they might invert that to 120VAC and run computers... but I'm pretty sure they are 12VDC.

 

[Opusdei]

It is still DIY project until I have a listing on Amazon. Black box is a hypothetical setup because it is nearly impossible to make a fair comparison between ac and DC air conditioners.

 

[Opusdei]

I'm not sure. My Prius's batteries are 200+ volts and the inverter bumps it up to 400-500VAC - but there is a 12V battery in the back, and all the computers, hvac blower, stereo and other car electronics are 12 VDC. You know not that you guys are mentioning electrical automotive AC, I leave my dogs in my Prius with the AC on (and a sign that explains they are ok, a thermometer people can see, and my PHONE NUMBER) - it uses an electrical AC compressor. My Mercury Mariner Hybrid had AC that only worked while the engine was running, I was glad the Prius went the other way. What I meant was the automotive systems like the computers, controllers, stereo, nav etc are going to 24-36V. If I'm not mistaken the Tesla has a 12V battery, and 12V stereo etc... I could be wrong, but I doubt stuff runs on 375VDC, they might invert that to 120VAC and run computers... but I'm pretty sure they are 12VDC.

That's interesting. Prius had a solar option. I'm wondering if the Prius solar panel provided 12V electricity for the A/C without the need of idling - for your dog.

 

[Jims94vmx]

Very interesting. Good luck. Plenty of mobile people traveling this great land. Should be a market.....following.

 

[Trukinbear]

That's interesting. Prius had a solar option. I'm wondering if the Prius solar panel provided 12V electricity for the A/C without the need of idling - for your dog.

Perhaps in the later ones (though I doubt it). I'm sure in my 2nd generation the AC compressor pulls from the HV traction battery - the AC will run for about 20 minutes with the engine not running, then will crank up and run for about 5 minutes to bring the HV battery back up.

 

[Opusdei]

Aha! Sounds like Prius has an electric motor to run A/C. It takes 20 minutes to drain the auxiliary battery before the alternator starts to re-charge the battery.

 

[Texhub]

It is a typical mini-split evaporator. As shown in the attached photo, I attached it on the left side of window next to my daughter's seat. Evaporator has a dry mode operation and water drainage runs on the lower left corner as shown in the picture. Refrigerant hoses and AWG-4 size cable connect the evaporator and AGM batteries. There is a mesh filter inside the evap but it is not HEPA type.

As a owner of a 40ft class A. Living in Texas Ac is required. Can you make a system that will operate at 40 DB. Current Ac systems operate at 72 Db.