Any feedback on Solar A/C systems?

[ErVikingo]

Solar Cooling by Sedna Aire USA

Your feedback is appreciated!

[TimT]

I don't know anything about that system...

but I am sure some posters with chips on their shoulder and 17K+ post will tell you how wrong you can be LOL

[MarKoBrow]

Technically it seems sound.

[ErVikingo]

I was hoping you would chime in as this is up your alley.

Additional feedback is appreciated.

[speedracing944]

it is bull. they are "super heating" the fluid after it is heated from the air from your home to increase the delta T for better heat rejection at ambient conditions.

All they are doing is adding addition unnecessary heat energy only to remove it. WTF.

Speedy

[turbo6bar]

I don't understand their proposal either. Why would you want to super heat the refrigerant? At what point is this "solar heat" removed from the system? Looks stupid.

[MarKoBrow]

Originally Posted by speedracing944

it is bull. they are "super heating" the fluid after it is heated from the air from your home to increase the delta T for better heat rejection at ambient conditions.

All they are doing is adding addition unnecessary heat energy only to remove it. WTF.

Speedy

Originally Posted by turbo6bar

I don't understand their proposal either. Why would you want to super heat the refrigerant? At what point is this "solar heat" removed from the system? Looks stupid.

I am assuming that you two are HVAC types? If you remember while studying HVAC technology there are two types of Air Conditioning / Refrigeration and Heat pumps. The one we are most familiar with is the Vapor Compression type. In our homes it usually consists of a compressor/ condenser outside while the evaporator is inside. The other is a Absorption type of Air conditioning / refrigeration. Absorptive refrigeration uses a source of heat to provide the energy needed to drive the cooling process. From what I am reading on the site provided by the poster is a "hybrid" using what seems to be the best of both systems. By taking advantage of r410 refrigerant which has characteristics very close to Lithium Bromide they have been able to take advantage of Absorption chilling when the sun is out hence the 36 SEER rating and when temperature is lower Vapor Compression is used hence the 16 SEER rating. I am looking forward to speaking with someone at this company about this product on Monday.

[sammyg2]

Careful guys, if you post facts someone without a clue will accuse you of bursting their fantasy bubble.

So go ahead and spend a whole bunch of money that you may never get back.
Go ahead and blow that money even though putting it in T bills will provide you with many times the return on your investment.

[MarKoBrow]

Originally Posted by sammyg2

Careful guys, if you post facts someone without a clue will accuse you of bursting their fantasy bubble.

So go ahead and spend a whole bunch of money that you may never get back.
Go ahead and blow that money even though putting it in T bills will provide you with many times the return on your investment.

Sammy, what does this mean or are you being contrary again? Please explain.

[billybek]

The interesting thing about absorption is that the refrigerant (typically water) is absorbed by the lithium bromide. The heat is the energy that makes the system run instead of electricity.
RV refrigerators are similar but a bit of a different process.
The evaporator in an absorber is the same, heat boils the refrigerant in the evaporator and the vapor travels to the absorber section. The absorbent absorbs (duh!) the water and is moved (pumped) to a concentrator where the refrigerant (H20) is split out of the absorbent by heating the dilute solution. The strong solution is returned to the absorber section, the refrigerant vapor is cooled in a condenser then the liquid refrigerant is re introduced to the evaporator.
This seems to be a different slant on things, but home absorption units (typically gas fired to provide the heat) do exist.
It would be neat (for me anyway!) to see a more detailed description of the refrigerant cycle.

[turbo6bar]

Well, ya learn something every day. I looked up absorption chillers and finally have a clue about what's going on. How many tubes would you need to make a significant impact? I've seen efficient vacuum solar tubes quoted at 2000 btu per day. You'd need a helluva lot of tubes to make a dent in even a 2 ton system. Or is there something I'm missing?

[billybek]

Originally Posted by turbo6bar

Well, ya learn something every day. I looked up absorption chillers and finally have a clue about what's going on. How many tubes would you need to make a significant impact? I've seen efficient vacuum solar tubes quoted at 2000 btu per day. You'd need a helluva lot of tubes to make a dent in even a 2 ton system. Or is there something I'm missing?

12,000 BTU per ton of refrigeration.
Depending where you are a small 1000 sq ft bungalow needs 2-3 tons to cool it.

[nota]

we had a propane powered ice box on a houseboat

all it needed was a small flame to boil the working fluid [ammonia ]
it would make ice but was not super cold or quick to cool

so yes adding heat can make cold
and with no real moving parts too

[Hugh R]

Looks like a propane refrigerator to me. The problem with them is they are slow and not good at recovering a heat loss very rapidly. When camping with my propane frig in my camper, you don't want to put anything hot in it. It takes forever to recover.

[MarKoBrow]

The first time I ever saw a propane powered fridge was in the Amish community in Lancaster ( they are not very fond of electricity) Absorption chillers are used where large amounts of waste heat is present also. The one that sticks in my head was a the AC in a local supermarket was powered by the condenser heat from the freezers, they were essentially getting an AC free ride.

The major difference between this set-up and a typical propane fridge is what they are calling a solar compressor on what appears to be lowside which would speed the recovery up considerably

[sammyg2]

Originally Posted by MarKoBrow

Sammy, what does this mean or are you being contrary again? Please explain.

second post in this thread.



As with a propane fridge, heat can be used as a pumping force. In other words it can replace the compressor which theoretically could save energy.
But propane refrigerators are very inefficient and weak. They are only reasonable where there isn't enough electricity to run a compressor.

BTW here's how refrigeration or air conditioning works:

You take a chemical that has the correct boiling and freezing points, hopefully pretty close together.
It also has to have a fairly strong phase change absorption.

You pressure it up with a compressor, and cool it with a heat exchanger until it turns into a liquid at near ambient temperature. Cooling coils and a fan are typical for this step. Condenser.

Then you run the cooled liquid through an orifice and allow the pressure to drop significantly. The transition from liquid to a gas, along with the rapid expansion of that gas, makes it get cold.
It then flows through an evaporator where warm air from the house blows through the evaporator and gives off some of it's heat. The air get cooler and the gas inside the tubes gets warmer. Then the compressor grabs it and the cycle is repeated.

Now to this system: similar to a propane fridge, they use the solar heating to heat the gas and cause the pressure to increase (boyles law) and then cool it down in a condenser, so the solar heating would take the place of the compressor.

Onliest problem is, that would be incredibly inefficient. It would have to be at least 10 times the size of a conventional system, would have to cost 10 times as much as a conventional system, and the payback would be several decades if ever.

A better system would have tubes buried deep in the ground, and pump heat exchanging fluid through the tubes to give off heat into the ground, and then pump it through the house to cool it down.
that would be as efficient or more than that solar heating scam, but the initial cost would still be fairly high. Much more than a conventional system and the maintenance and upkeep would be much more too.

Hey, install an underground heat pump system and put in an acre or two of solar panels to run the pump!

[MarKoBrow]

Sammy, Do you greet anything you don't understand with such criticism ? The original poster asked a question based on the website that he posted. Based on the information from that website the seller might have a viable product. Looking at the images and illustrations provided by the manufacture it doesn't seem like it would be 10 times larger or at this point not even ten times the cost. At this point more details are needed before it gets dismissed as a scam cause it has the word solar in it. I am well aware how refrigeration AC and Heat pumps work and I am sure others on this forum can figure it out.

[red-beard]

Can you explain how the 410 refrigerant works in an absorption mode in this application? I don't see a separation of components in the cycle, which is essential to absoption systems.

[billybek]

Originally Posted by red-beard

Can you explain how the 410 refrigerant works in an absorption mode in this application? I don't see a separation of components in the cycle, which is essential to absoption systems.

That, I believe is the question!
More details are needed and the web site is pretty sketchy on the drawings and how it works.

[idontknow]

Originally Posted by billybek

12,000 BTU per ton of refrigeration.
Depending where you are a small 1000 sq ft bungalow needs 2-3 tons to cool it.

12000 BTUs per hour but the solar tubes were rated 2000 btus per day. It's going to take a LOT of solar tubes to make a dent in the power bill.