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-   -   Electric Van Heat Pump/AC (and more!) (https://ecorenovator.org/forum/showthread.php?t=7264)

NiHaoMike 07-06-20 07:54 AM

Quote:

Originally Posted by AirConditioner (Post 62786)
I'm not sure why you are arguing. What you are talking about is in no way helpful or relevant to air conditioning a "van" or a Jeep. There is nowhere to store ice, and even if there was you would have to refill it. An air conditioning system provides cold air on demand at any time, and is unlimited for as long as you have power or gas.

The thermal storage can be "recharged" with an onboard heat pump. Most likely one based on a 5000BTU/hr window A/C since it's hard to go smaller with decent efficiency and still keep the cost of parts low, while going bigger increases weight and size. (And are you planning to have more than 500W or so of solar panels to be able to power a larger A/C constantly? Might be reasonable for a RV but not a van.)

4kWh of batteries would be overkill unless it's also being used for traction power. Could probably go that route fairly easily by replacing the alternator with a BLDC motor/generator.

AirConditioner 07-06-20 08:28 PM

Quote:

Originally Posted by NiHaoMike (Post 62787)
The thermal storage can be "recharged" with an onboard heat pump.

Thermal storage doesn't work on wheels. I am seriously baffled by your posts...

Where would you suggest one mount this thermal storage tank in a Van or Jeep? It is not even remotely practical, and moving all that mass just uses more energy.

Quote:

Originally Posted by NiHaoMike (Post 62787)
(And are you planning to have more than 500W or so of solar panels to be able to power a larger A/C constantly? Might be reasonable for a RV but not a van.)

I'm not planning on any solar panels, though the OP said he was going to have 1.2KW of panels, which is more than enough to run a ton of A/C and charge batteries at the same time.

I am planning on putting a 4KWH battery under the back seat, for numerous reasons portable power is extremely convenient. The OP says he has a 24.8 KWH battery. That can run a LOT of air conditioning, or other useful things like power inverters, lights, heating, cooking, fans, etc. With only 4KWH I can run a ton of A/C for 4 hours...or smaller A/C for even longer. The lithium battery will also be used to run the block heater in the winter without an extension cord, and removing the lead starting battery gives me more room under the hood.

I'm not trying to be rude but I honestly can't understand why your posts have anything to do with the topic. I don't think you understand the question. Onboard battery power is wonderful to have in any vehicle for numerous reasons. Thermal storage to any useful degree simply isn't an option on wheels. Thermal storage is a wonderful thing in stationary applications, but it is always very large and very heavy.

NiHaoMike 07-06-20 09:17 PM

Quote:

Originally Posted by AirConditioner (Post 62788)
Where would you suggest one mount this thermal storage tank in a Van or Jeep? It is not even remotely practical, and moving all that mass just uses more energy.

It takes energy to move batteries as well, although I suppose that can be largely offset with regenerative braking. It's down to the overall cost vs benefit of a large battery pack vs a smaller battery pack plus thermal storage.
Quote:

The OP says he has a 24.8 KWH battery. That can run a LOT of air conditioning, or other useful things like power inverters, lights, heating, cooking, fans, etc.
He's building an EV or plug in hybrid, a different use case. Of course there needs to be a sizable battery for that application.

jeff5may 07-07-20 01:22 AM

Sounds like you are on the right track already. A ton of a/c is literally enough for a Winnebago. In a Jeep, I'd probably go with half a ton of capacity, and get something energy star. They run part time pretty well and shut down the compressor before the fan to get the cool air out while the system bleeds down.

If you are running a bang bang unit (non vrf), make sure the power inverter has enough balls to start the compressor. It draws locked rotor amps for a few line cycles every startup. As close to pure sine wave as you care to spend will pay back in efficiency, extending the run time. At that capacity, I don't know if the price difference would justify a vrf unit. Sure, you'd save money for a smaller power inverter, but the half ton window shakers are selling for around 75 bucks used here. Maybe 150 or so brand new from the usual box stores.

AirConditioner 07-14-20 04:25 PM

Quote:

Originally Posted by NiHaoMike (Post 62789)
He's building an EV or plug in hybrid, a different use case. Of course there needs to be a sizable battery for that application.

A "future" EV. And that means less room and cargo capacity for thermal mass. Just drop it. You cannot have thermal mass in a vehicle. Jesus...you seem like a smart guy, but you're just talking stupid here. Lithium batteries and fossil fuel make more compact cold storage than anything else...except maybe a bottle of CO2.


Quote:

Originally Posted by jeff5may (Post 62792)
At that capacity, I don't know if the price difference would justify a vrf unit. Sure, you'd save money for a smaller power inverter, but the half ton window shakers are selling for around 75 bucks used here. Maybe 150 or so brand new from the usual box stores.

That seems to be an issue I run into a lot. Those cheap little units are SO hard to beat for the parts inside! I've been able to start a 5k BTU from as small as an 800 watt very old modified sine inverter. The compressor makes an odd humming noise on the inverter but I'm sure it would work better with a 2-3kw pure sine wave.

I have heard people claim that when using compressors that were not designed to be mounted on vehicles they die early because they can't handle the vibrations as well. I've seen this as a complaint on RV forums with mini splits. With that said I have no idea what would make an "RV" compressor different, but I know they cost a lot more.

I really like the new DC powered compressors I've seen from China...but, they still seem to cost $500 or more for very very small, incomplete system.

Also if someone is doing something like a van, they're making pure DC mini splits now for direct solar applications in pretty small sizes. Gotta pay to play though.

NiHaoMike 07-14-20 10:50 PM

Quote:

Originally Posted by AirConditioner (Post 62823)
A "future" EV. And that means less room and cargo capacity for thermal mass. Just drop it. You cannot have thermal mass in a vehicle. Jesus...you seem like a smart guy, but you're just talking stupid here. Lithium batteries and fossil fuel make more compact cold storage than anything else...except maybe a bottle of CO2.

For the batteries, a mere 4-5x per pound compared to ice which actually gets reduced to about 2.5x after derating the batteries. Doesn't seem like a huge improvement compared to the cost. On the other hand, you cannot regen into ice storage at any meaningful rate or use it for anything other than cooling, so that's where there's value in batteries.

It's hard to beat the energy per weight of running a generator, but there are a number of obvious disadvantages to that which relegate it to more of a backup application. The real game changer would be fuel cells - quiet and efficient, just needs the cost to come way down.
Quote:

That seems to be an issue I run into a lot. Those cheap little units are SO hard to beat for the parts inside! I've been able to start a 5k BTU from as small as an 800 watt very old modified sine inverter. The compressor makes an odd humming noise on the inverter but I'm sure it would work better with a 2-3kw pure sine wave.

I have heard people claim that when using compressors that were not designed to be mounted on vehicles they die early because they can't handle the vibrations as well. I've seen this as a complaint on RV forums with mini splits. With that said I have no idea what would make an "RV" compressor different, but I know they cost a lot more.

I really like the new DC powered compressors I've seen from China...but, they still seem to cost $500 or more for very very small, incomplete system.

Also if someone is doing something like a van, they're making pure DC mini splits now for direct solar applications in pretty small sizes. Gotta pay to play though.
You can take a look at repurposing a Prius compressor, you'll probably want the Gen3 since that includes the drive circuits.
https://openinverter.org/forum/viewtopic.php?f=14&t=258
There is a disadvantage in that they need about 200V to work, you can either build the battery to run in that voltage range (good idea if you want to be able to regen at high rates without dealing with really high currents) or use a DC/DC converter to get that voltage. It helps that the DC bus in a 120V inverter will be about 180V which probably will work.

Elcam84 07-20-20 07:26 PM

FYI the AC system in the average car is around 3 tons. Some smaller some larger. For a van you will be on the larger end. So you would need 3+ tons of ice per hour to cool it...

So to keep the van cool for say 8 hours you would need 24 tons of ice to do it. Actually more since some of that ice will have melted before you got to use it. So if it's a bigger van you could end up needing say 30 tons of ice. It would be more efficient to go back to hauling ice from frozen rivers up north on ships and using it to cool than it would to produce the ice and then haul it in a trailer behind the van.


If you want to cool it and your power source is electricity the solution is simple. Order a Sanden electric compressor. Sanden is the top brand of automotive AC compressors on the market. Used in everything from production vehicles to big dozers and other heavy equipment.

NiHaoMike 07-20-20 08:16 PM

Quote:

Originally Posted by Elcam84 (Post 62850)
FYI the AC system in the average car is around 3 tons. Some smaller some larger. For a van you will be on the larger end. So you would need 3+ tons of ice per hour to cool it...

Tons per 24 hours, and only for the short time it takes to cool down. As mentioned, 1 ton is plenty for a fairly large RV.

Elcam84 07-20-20 10:41 PM

My goof and typed that wrong.

The typical factory AC in a car is usually rated at around 3 tons. Now if you are doing a van and it's been insulated etc then yeah you can get away with less. Production cars have no real thermal insulation so massive amounts of heat gain to them.

Rooftop RV units are usually around 15Kbtu.

jeff5may 07-30-20 01:56 PM

This debate about ice storage versus battery range is getting ridiculous! The number one challenge for current BEV solutions is range. More range=better is the rule. Anything that adds mass adds drag on the range, period. So consider this, Batman: manufacturing ice on the fly at max capacity would cost you less range than carrying a big ice cube from the starting point. With a ton or two of capacity, it doesn't take an hour to make 100 gallons of ice. NO EXTRA BAGGAGE!

I have an idea, we could go to the dollar store and buy a whole row of the 6 dollar magic air conditioner EVAP and mount them on the roof. That could subcool the refrigerant while parked or driving and DOMINATE! Or hey, why not just put PCM sound deadening interior panels everywhere, with a heat soak range of 70 to 75 degrees. I dub thee" sta-cool" interior panels.

Just kidding, don't listen to my ideas...


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