Solar-assisted air conditioning

[lana]

Dear All,

Please have a look at : http://sednaaireusa.com/How%20it%20works.htm

In this system a solar collector is placed in front of the condenser and compressor discharge gas passes through it therefore, it gets more superheated .....
They claim that this method saves energy .....

Above explanation is what I understand and it might be wrong.

Can anybody explain how it actually works? How this heating of the gas saves energy?
When gas is heated it gets superheated with constant pressure but they claim that the pressure also increases.


What is the thermodynamics behind that?

Thanks

[MikeHolm]

I hope someone could explain how adding more energy (solar or otherwise) prior to the condenser, while in cooling mode, will help to increase efficiency? To me this would just increase the load and make the entire system run longer. I see no way, on first look, that the system makes any sense.

Further, the vacuum collector cannot dissipate heat the same way a flat copper collector can at night (Which we sometimes do to shed heat). What would this do to the refrigerant? What is the effect of sustained 100C+ on the refrigerant, long term?

[Brian_UK]

My simple mind thinks they they use an under sized compressor that cannot generate enough discharge pressure/temperature.

The solar device then increases the temperature and therefore pressure? before going through the air cooled condenser.

Simple, use the sun to increase the pressure.

Nah, can't see how that would work because the increased solar pressure has got to feed back to the compressor discharge so it still has to work as hard.

End result? Still don't get it.

[MikeHolm]

The big problem with this system is that the sun is not controllable.....and would you design a system where the pressures could go sky high (HP switch cannot turn off the solar) or be ineffective when there is no sun?????

[Brian_UK]

Someone's taken the top of the snake oil bottle again.

[mikeref]

Someone's taken the top of the snake oil bottle again.

I had a look at the video they provided on the "tube", lacks quality and info. Still don't get it.

[MikeHolm]

It's hard to tell but is appears as though they are trying to cool the building when the ambiant is 20-22C. Then again, it is Florida.

[mad fridgie]

It may be that they are isolating the solar collector, filling with refrigerant, allowing the pressure to rise, releasing the pressure through a small TVR (thermal vapour recompressor) "not the car", which would elevate the the condensing pressure, but keep the discharge pressure low, or combinations there of. and if they are smart they would be using 2 TVRs
The drawing shows that the suction and comp discharge pass through a heat exchanger, indicating they they do over feed the evap, this would happen with above. Or they could have a very small liquid pump that continually pumps through the solar panel!

[MikeHolm]

MF, do you have a product example of a small TVR and I don't know what you mean by "not the car"? The video states that the refrig is throughout the system without any glycol to refrig HX at the panel. Also, they state something about an oil in the glass tubes which is not possible as the two layers of glass are under vacuum so that makes me wonder what they are talking about.

They would need a HX to have a liquid pump on the solar side which is something I was thinking of doing in one of my many day dreams

[mikeref]

Ah, now this explains it..http://http://ecolinegroup.com/index.php-p=1_14_Our-Technology.htm

[mikeref]

Page won't load. ..http://http://ecolinegroup.com/index.php-p=1_14_Our-Technology.htm

[MikeHolm]

get rid of the extra HTTP:/

[lana]

Dear All,

Thanks for the reply.

As far as I have found out, there is an ejector in the system and a liquid pump. BUT the puzzle is where is the compressor??????????


Solar.jpg

[mad fridgie]

TVR a sports car made in Blackpool UK, now owner bt the Russians
TVR yes is a type of injector.
I think their desciption is marketting spin.

They have adapted a old technology "JET refrigeration" very clever if it the the way I think it is done.

I will try and expalin

Refrigerant from evap into a normal compressor.
Compressed to a pressure lower than normally condensing pressure,
This where it gets tricky.
A small "liquid" pump increases the pressure of a small amount of liquid, this forced into the solar array. The liquid boils with the heat, we have high pressure vapour "Motive force"
This motive force is pushed into the TVR (like a venturi) it cause suction, now read carefully, the discharge of the compressor is connected to the suction of the TVR (so in effect is 2 stage compression) the 2 gas streams mix at pressure lower than the motive force, but higher than the suction. this becomes your new condensing pressure.

[lana]

ٰThanks a lot.

This make sense. My thinking is this : this system is more efficient because the condensing temperature which compressor feels is lower than say 50°C therefore, compressor capacity increases (like using water cooled condenser instead of air cooled.) Am I right?

Cheers

[mad fridgie]

Not so much more capacity but less power draw,

[MikeHolm]

Won't the system be undersized? There cannot be any heat rejected in the solar panel so it cannot be used as another parallel condenser. There is a company called "Swensen" that seems to be doing this on an industrial scale but not with solar. There is some math and discriptions on their website.

In the words of the great Homer Simpson..."DUH". I didn't put 2 and 2 together about the car. I've driven TVRs and I still didn't think of it.

[mad fridgie]

The solar panel, does not reject heat it absorbs it, it is if I am correct an evaporator, it is mixing 2 refrigeration technolgies, which is good, if this is how they are doing it

[rice_man]

mad fridgie, seem like you understand this process . . . please explain again how adding external heat to the compressed refrigerant can cause it to reject more heat at the condensing coils. Does not seem to comply with laws of thermodynamics. Thanks in advance. Here's a better diagram of the process:
http://www.solarcool.com/?page_id=26

[MikeHolm]

One problem I have with a system where refrigerant is piped through solar collectors is that they are most often tested at 10-15 bar and certified for 8-10 bar. I know of many vacuum tube systems where I wouldn't trust those pressures, Viessmann, Kingspan (thermomax) and most chinese made collector headers. There are others I would trust Paradigma (Ritter Solar) for example.

Superheat values????