OK..... here is a detailed technical discussion.
Technical Review of Solakool Air Conditioning System
Summary
Put simply, the Solakool Air Conditioning system as put forward at*
www.solakool.com.au*cannot possibly work in the manner described and the claims made for it such as “With Solakool’s patented technology, compressor run time is reduced by up to 80%” are preposterous.
The product is either an outright scam, seeking to defraud those who wish to reduce their environmental impact and/or save energy (most likely), or it is the product of someone with gross misunderstandings of how the refrigeration cycle works (unlikely).*
It may be possible that the “solar panel” actually delivers a small increase in cycle efficiency by providing additional cooling capacity to the condenser, thereby reducing the energy used by the condenser fan. However, this is in total contradiction of how the system is claimed to work and the benefit delivered would be nothing like the 80% reduction in energy use claimed.
OK firstly I am not an air conditioning expert. I do work on them regularly on aircraft and had training on air conditioning systems during my trade training to become a Licensed aircraft maintenance engineer. I am also open to learning and the fact that you may indeed be correct. I have no affiliation or interests in any of this stuff.
Some of your claims about Solarkool are, let’s say quite strong. No skin off my nose. I'm just trying to get closer to the truth.
In Australia, as in most developed countries, ps I am Australian, they have the ACCC to protect consumers from fraudulent business claims. If there are customer complaints about products this can be pursued quite vigorously. A quick search didn’t bring anything up that I could see. Do you know something I don’t? Australians in my experience aren’t shy to complain about something they feel misled about.
I agree that the explanation is somewhat vague. This could be them protecting their technology or it could be them preying on the markets desire to be green by exaggerating or flat out bullsh..g. It wouldn’t be the first time.
Why it cannot function as described
Let’s take a look at the explanation posted under “How it Works” on the Solakool website:
I’ll start by giving a brief explanation of the gas compression refrigeration cycle. Starting with the cooling element, , cooling takes place the evaporator (5) as heat from the air that is being cooled boils off the refrigerant liquid in the evaporator. The liquid is at a low pressure and at that pressure, it boils (changes to gas phase, or vaporises) at a very low temperature – typically -10⁰C to 0⁰C.*
As the liquid vaporises, it takes up a much larger volume and thereby pressurises the vessel containing it, which would stop further vaporisation if the gas was not removed to maintain a low pressure in the evaporator.*
The first function of the compressor is to remove the gas from the evaporator so that cooling can continue – Point 1.*
As the compressor runs, the compression of the gas generates heat, known as the heat of compression. After leaving the compressor, the gas is hot – typically 75⁰C to 100⁰C. In order for it to condense back to a liquid it must be cooled. The function of the condenser is to transfer the heat to the air being heated (outside air) causing the refrigerant to condense to liquid. Because the liquid has a much lower volume than the gas, this lowers the pressure in the condenser, allowing gas to continue to flow from the compressor.*
If the liquid was not cooled, the pressure in the condenser would quickly rise to the point that is was equal to the discharge pressure of the compressor and no further gas would flow – Point 2.
To complete the cycle, the cooled liquid (typically at 40⁰C to 50⁰C) passes through a restriction (4) into the much lower pressure evaporator vessel.*
Yes I agree with your explanation above. This is my understanding of the operation of a vapor cycle system.
Now note where the Solakool “Solar Panel” is located. At the part of the cycle where cooling is required to condense the refrigerant back to liquid, they claim to be adding heat from the sun. Furthermore, they claim that this heat raises the pressure of the gas, which it would – right at the part of the cycle where the primary goal is to reduce the pressure of the gas to allow more refrigerant to flow to facilitate cooling (Point 2).*
The explanation claims that by adding heat from the solar panel, the heating increases pressure to reduce the duty on the compressor "by up to 80%".
Yes agree that this number is unlikely. Sales pitches are never conservative when they are talking about their products attributes. Remember in the thread title it ends in a ?
I didn’t take this as a research paper from a highly respected scientist. These are usually discredited at some stage later too. Cant believe everything we read eh.
This claim is ludicrous on 2 counts:
1.The increase in pressure would not do the work of the compressor – it would actually make the job of the compressor harder by increasing the discharge pressure and by adding more heat to the system that would have to then be rejected by the condenser.*
You may be correct but my understanding is that the compressor discharge has a reed valve. Or maybe they have added one it there wasn’t one initially. Again they are not too big or specific on details. Least the ones I work on do.
My understanding is that the compressor wouldn’t be operating, ie cycled off, when these temps and pressures were high. Ie the sun is heating the panels.
2.If the compressor is not running, the gas is not extracted from the evaporator and cooling quickly ceases (Point 1.)
Yes agreed, if there is no gas flowing through the system to create a pressure drop across the capillary tube at the start of the evaporator there will be no expansion, and as you correctly say no cooling. But I think there would be a flow through the system with heat being applied to the refrigerant before the condenser. The old caravan propane or kerosene small absorption chillers worked like this.
Your explanation is not so convincing as you have put your understanding or interpretation there of, of the operation of this stuff but no facts or credible corroborating evidence. I for example have many opinions and no doubt most them are wrong.
80% reduction in compressor run time would also reduce effective cooling by around 80%.
OK again you may be correct. My perhaps misguided thinking is that there should be a flow without the compressor turning past the compressor valves. It can only go in one direction due the valves. The motive force for the flow I would think would be the expansion of the refrigerant being heated before the condenser. So I think it should be forced into the condenser,
Then as you say the gas cools and condenses into liquid. Being cooled through the condenser will reduce the pressure. So should there not be a flow from the high pressure before the condenser to the low pressure decreasing as it goes through the condenser? Basically a thermosyphon.
So what is actually happening?
I’m not saying that this air conditioner doesn’t work – clearly it does actually produce cooling;
OK, I was starting to wrongly get the impression you thought it didn’t work using words like scam, ludicrous etc. it sounds like you’re passionate about all this.
it is just that the claims made regarding the “Solar Panel” are bogus.*
‘Bogus’, subtle choice of words, seeing your telling me you think it works. Claims exaggerated, I have very little doubts. It is marketing hype let’s face it.
The first clue is here: “The result is that the condenser coil fills with refrigerant that has changed phase completely into liquid instead of aerated fluid as in regular air conditioners.”
Yes, again I’m not sure exactly how it is done. Maybe that is a deliberate tactic or oversimplified or just not articulated well. I don’t think this is evidence of it conclusively working or not working.
If the refrigerant had been heated by the “Solar Panel”, it would be driven further into the gaseous phase and would take longer to dissipate the heat and condense to liquid in the condenser. But this statement claims the opposite.*
Again I don’t know but I would have thought that a hotter ambient air would I agree take longer to dissipate the heat because of a smaller temp difference (delta T) between ambient and the refrigerant. But a hotter refrigerant is the opposite. Yes I agree that a hotter charge will be ‘more gaseous’. But if the compressor is cycled off it is not adding to the heat it is simply replacing the heat the compressor would have generated.
This could only happen if the “Solar Panel” is dissipating heat, acting as an additional condenser.*
Maybe it is, a bigger (effective) condenser capacity doesn’t sound like a ‘smoking gun’ to me.
Now consider that, as anyone who owns a solar hot water heater knows, it takes several hours of full sunshine to raise the temperature of a tank of hot water to around 75⁰C.
Yes, sure 75C will take some time. So will the required cooling load. I guess in the pre 75C times is what a compressor is for.
You seem very sure of your interpretation of this. You could be correct.
One of my nagging doubts is that it must work to at least some degree, being they haven’t been run out of town yet. I’m definitely not sure that’s why I’m putting this out there. The more I learn the more questions I have. I am here to learn. I certainly don’t believe all of these guys claims.
Yet this “Solar Panel” is receiving refrigerant above typically above 75⁰C; it seems highly unlikely (so you don’t know. You seem confident enough to comment strongly) that any significant additional heat would be added.
I assume the cooling loads are less too during these periods.
Furthermore, in other than full sunshine, it would definitely act as a cooler to the hot gas.*
Confirmation of the hypothesis that the “Solar Panel” is acting as an extra cooling stage comes from the “Case Studies” section of the website:
I’m not sure if you’re saying this is proof it doesn’t work. It sounds like how you described how condensers work and I agree with. Maybe it can/ does work either ways depending on the ambient temperature. I don’t know. You sound quite sure it cant. How do you explain that it does?
“At least 4 hours of daylight per day (direct sunlight not required, only daylight)”
And this gem:
“The SolaKool system operates for up to 15 hours over night after only 4 hours exposure to daylight.”
I guess this comes down to storage volume and collector area and efficiency. I don’t know so cant comment.
How well does a solar hot water system operate on “daylight” – rather than “direct sunlight” ?
Yes agreed, not particularly good choice of words.
Well as anybody that has ever used a solar hot water system knows, the answer is that it does not heat at all – your water goes cold as more heat is radiated off than absorbed in.*
True, but it is not as if the heat from the system will be radiated away as the controller has stopped the flow through the panels at this point. So obviously we don’t get solar heating at night or cloudy days. That’s when the booster system kicks in. Heating some of the time is better than none of the time like non solar systems.
Now, as final confirmation, examine the photos of recent installations. Note the size of the panels – they are tiny. Also note that they are located to avoid full exposure to the sun.
So how well does it work?*
Here are the claims from the website:
“Depending on normal operating conditions savings of up to 80% may be achieved over a conventional system.”
“Based on standard operating conditions, the carbon footprint may be reduced by up to 80% compared to a conventional system.”*
These claims – if true would be verified by the Energy Star appraisal process and would dramatically exceed “conventional systems” in their performance. Astoundingly, they are foolish enough to publish the actual Energy Star ratings: Yes I never said their
marketing guys are technically conversant.
3.5 stars – that’s middle of the road performance and way below the 5 star efficiency systems that are readily available and deliver significantly higher energy efficiency!*
(See:*
http://www.canstarblue.com.au/applia...conditioners/*)
Yes not good. But I also know there are many holes in the Energy star ratings/ SEERs etc.
I am not sure of the facts about this, which is why I am answering the question. I have very little doubts there’s a lot of marketing hype in here.
In addition to all this there are multiple
references to "Carbon Credits" Yes agreed this is playing on Joe publics desire to feel environmentally responsible. Advertising drivel. as if they have some monetary value – which at present they do not – and certainly wouldn't be available for a bogus product like this anyway. It's just further evidence that this is a scam to defraud those that actually care about their carbon emissions.
I have to say I appreciate your effort in spending time on this but you haven’t really added much more than some supposition and some emotive words. To me your arguments, like Solarkool, are a little light on conclusive facts. Neither you or Solarkool have convinced me either way.
My thinking on this stuff is that there is something to it, the big question is how much to determine if it is to some extent practically usable?
In answer to the comment re propane ammonia fridges.
Yes they are another example of ‘Thermal’ driven chillers. Very old and established technology. However not quite the same as this is a vapor cycle system. Similar in a number of ways but the actual cooling is derived by absorbing and evaporating water in and out of ammonia. Vapor cycles work on expansion and vaporizing of a refrigerant.
I’m also not understanding the comment about “An extreme amount of
insulation would be required to get the thermal load down to a few hundred watts for people and some low power
appliances (LED lights and low powerelectronics).”
Insulation? I’m not sure where this comes into the discussion. Or ” size of the solar collector either direct
electric conversion via solar panels for a compressor or ammonia cycle”.
I’m not sure how we got to panel size or ammonia cycle (I’m aware of absorption chillers)? Did I miss something?
Also, I’m not very smart but I cant understand what is meant by “There's no reason to expend the refrigerant”.
“a Compressor doesn’t circulate, it compresses”
I’m not sure what you’re trying to say here. I would say it does both. But term it’s function however you like. It is just a mechanical displacement device, usually with valves. The valves are going to ensure that the flow will only ‘circulate’ in one direction. And yes if there is a restriction, (which there will be in any system) then I guess it will ‘compress’. As I understand it a restriction to flow causes an increase in pressure, ie compression. But I am willing to hear and learn from your explanation.
Yes agreed the main cooling function of the a vapor cycle system happens at the ‘Thermal expansion valve’.
However there is also a pressure drop across the condenser when it cools the charge (which is supposedly a condensers function). Heating increases pressure, and cooling decreases pressure when I went to school, might have been 4th grade.
I think the truth is that this obviously works to some extent. I have heard a lot of ‘hypothesizing’ but very few of us have a chance to find out the facts on it.
I’m not trying to convince anyone.
All good stuff.