Flat solar thermal panels or evacuated tube?

[Peter69_56]

[QUOTE=MikeSolar;58301]The real differences start with the intended uses for the system. If you need low temp output such as DHW chances are you will get just as much heat output, per m2 gross area, even where I am in Toronto in the winter with a flat panel as a tube (note I didn't say aperture area). You need to get quite cold ambient for the tube to overtake the flat panel and many people add one or two extra tube collectors to get an even better winter performance. The problem with this is it is grossly oversized in the summer and WILL lead to a shorter lifespan and no economy because it sits at stagnation for much of the summer. Tubes need replacing, periodically because nature abhors a vacuum and they have a tendency to lose it. I have changes way more tubes than care to count and it is not, as yet, a long term solution. QUOTE]

I can only comment on what I have compared to a few friends who have flat panels. Mine outperforms them all year around. We have done comparisons and they are less than happy with what they have. This is Melbourne Australia so not as cold as Toronto I would expect.

My tubes are guarenteed for 15 years so I see no issues there. I have not had mine at stagnation more than 4 days in the whole year so I don't see an issue there either. My info is based on real data and not assumptions. We live close and have similar family size so similar water usage, similar weather, similar tank size etc etc. The difference being evacuated tube vs flat panel.

I dont represent any solar hot water supplier/installer I am just an end user. Mike, do you supply/sell solar and if so which type/brand.

[russ]

Peter - You are basing your evaluation on personal observations and comparisons made with friends.

Unless you have a proper set of instruments (insolation, temperature and flow) and a data collection format plus you personally do the data collection from both your systems and your friends system it is of interest but has no real meaning. Data take at random periods with guesses in between to smooth things out has no meaning. Data shared over a beer has even less.

Data collected by SRCC and used in their evaluations is done in a proper scientific manner - it has meaning.

Russ

[MikeSolar]

[QUOTE=Peter69_56;58318]

The real differences start with the intended uses for the system. If you need low temp output such as DHW chances are you will get just as much heat output, per m2 gross area, even where I am in Toronto in the winter with a flat panel as a tube (note I didn't say aperture area). You need to get quite cold ambient for the tube to overtake the flat panel and many people add one or two extra tube collectors to get an even better winter performance. The problem with this is it is grossly oversized in the summer and WILL lead to a shorter lifespan and no economy because it sits at stagnation for much of the summer. Tubes need replacing, periodically because nature abhors a vacuum and they have a tendency to lose it. I have changes way more tubes than care to count and it is not, as yet, a long term solution. QUOTE]

I can only comment on what I have compared to a few friends who have flat panels. Mine outperforms them all year around. We have done comparisons and they are less than happy with what they have. This is Melbourne Australia so not as cold as Toronto I would expect.

My tubes are guarenteed for 15 years so I see no issues there. I have not had mine at stagnation more than 4 days in the whole year so I don't see an issue there either. My info is based on real data and not assumptions. We live close and have similar family size so similar water usage, similar weather, similar tank size etc etc. The difference being evacuated tube vs flat panel.

I dont represent any solar hot water supplier/installer I am just an end user. Mike, do you supply/sell solar and if so which type/brand.

I've got 20+ years in this business and I have imported containers of chinese tube collectors. I was the Canadian distributor of a highly regarded German tube product and I have come full circle which means I mostly install flat collectors again.

We are just in the middle of a study of 100 systems and so far we are finding wide discrepancies between similar systems, just because of how a pipe is placed, for example, or the amount of water consumed and at what times so anecdotal evidence doesn't work that well in solar. We have sensors, dataloggers and calibrated flow meters on everything.

My data comes from that experience and that of the IEA and ESTIF report in their studies as well as my own repairs of different types of systems. Simply put, a flat panel is under less stress than a vacuum tube, long term and runs at a lower potential max temp which means that every component in the system will also have less long term stress on it and it will last longer.

If gas or electricity was $1/kwh, it might not matter so much but with paybacks of 12 - 15 years (and in some places more), it is false economy to install the device that needs repairs after 5 years.

[Jbergess]

[QUOTE=MikeSolar;58321]

I've got 20+ years in this business and I have imported containers of chinese tube collectors. I was the Canadian distributor of a highly regarded German tube product and I have come full circle which means I mostly install flat collectors again.

We are just in the middle of a study of 100 systems and so far we are finding wide discrepancies between similar systems, just because of how a pipe is placed, for example, or the amount of water consumed and at what times so anecdotal evidence doesn't work that well in solar. We have sensors, dataloggers and calibrated flow meters on everything.

My data comes from that experience and that of the IEA and ESTIF report in their studies as well as my own repairs of different types of systems. Simply put, a flat panel is under less stress than a vacuum tube, long term and runs at a lower potential max temp which means that every component in the system will also have less long term stress on it and it will last longer.

If gas or electricity was $1/kwh, it might not matter so much but with paybacks of 12 - 15 years (and in some places more), it is false economy to install the device that needs repairs after 5 years.

Hey Mike (and Good Morning),

I work for, and represent an American manufacture of evacuated tubes and flat Plates. I agree with Mike, if you are installing a system that breaks down in 5 years and needs to be repaired, it's not worth it. However, a solar collector - flat plate or e-tube alike - that breaks in 5 years is simply a bad design. We have both plates and e-tubes installed all over North America that have been in operation for 8-10+ years. Tubes and flat plates alike should last 15-20 years without the need for repairs on the system.

However, Mike does have an excellent point. Flat plates are not going to be operating at the same level of temperatures as a flat plate. Manifold temperatures in one of our 30-tube collectors can reach (during dry stagnation) temperatures exceeding 350F. You are dealing with a collector that produces higher temperatures, and it can cause strain on the various components of the system, depending on how the system is installed. If the controls are setup properly (proper flow rates, sensors, etc) then no component in the system should come into contact with temperatures exceeding 140F or so.

As far as payback and cost, 12-15 year payback is pretty steep, but it can be the case in an area where you have low fuel costs. Keep in mind, though, that much of the cost of a system being installed is not the collector. It's everything else. The difference between a flat plate and an e-tube collector is usually around $300. Flat plates, however, do tend to cost less. We sell complete package kits starting at $2700 with flat plates. In areas with low fuel costs, it can be a longer payback.

However, payback really is no longer an issue. To give an example - we offer a financing program through our dealers, so that homeowners can make payments and not pay out-of-pocket. If you spend $5,000, for example, on a DHW system that saves you $50/month in energy, your payments would be around $25 ~ $30 a month, netting you an immediate savings. Furthermore, you are now insulated from rising energy costs, while helping the planet. With these kinds of numbers - and a 10 year warranty, which is the industry standard for most American manufactures - it's caused a lot of people to turn to solar regardless of a payback of 5 years or 12 years.

[Peter69_56]

Peter - You are basing your evaluation on personal observations and comparisons made with friends.

Unless you have a proper set of instruments (insolation, temperature and flow) and a data collection format plus you personally do the data collection from both your systems and your friends system it is of interest but has no real meaning. Data take at random periods with guesses in between to smooth things out has no meaning. Data shared over a beer has even less.

Data collected by SRCC and used in their evaluations is done in a proper scientific manner - it has meaning.

Russ

Russ,

I agree that unless you do it scientifically your results are not truely accurate, however because the results I have are not done faithfully this way, does not "as you say have NO MEANING". They may be less valid, but they are an indicator. The more often you compare results the better the indicator. In the case of scientific checks, even more accurate again. So for you to say our comparisons (which we do on a very regular basis as we take daily readings on tank inlet and outlet temperatures etc) have no meaning is rubbish. yes they are less valid than the scientific ones but they do have some meaning and over time give a fair indicator.

What I do find interesting is that many of the people who push a certain type of product. One might assume that they therefore have vested interest in pushing their case (biased). I have no vested interest in pushing any product except an efficient and effective one. I do NOT sell anything and have no bias as to which to use other than it being efficient and effective. I am simply an end user.

If you put up a post here, perhaps you should divulge your interest first so we are all clear as to where you are coming from. That you sell or import doesnt mean that you WILL be biased, but it lets the reader have all the information to make a quality judgement on your discussion.

Lets all have a bit of honesty here. We have found people doing similar things here in Australia pushing certain products on forums on the pretext of being "interested and informed" when in fact they sell them.

Honest gives credability. I appreciate that Mike Solar has stated where he comes from and now I can read and take on board his discussion in that light. I appreciate his thoughts and comment. He has an impressive background.

I am an end user and and do not have a technical background in Solar HWS. I do however have 35 years in power generation and steam/water energy so do have a good understanding of therodynamics. That doesnt make me an expert in solar and nor do I suggest I am. I am an interested person. I enjoy soaking up the information. I do however detest people with hidden agendas hiding behind an name on a forum. Lets all be up front and honest and then allow others to grow in this industry as well with help from everyones comments given in good faith. Its good that the last few posts state background and if they sell one type or both and the reasoning behind their discussion.

[russ]

Comments within the text in bold.

Russ,What I do find interesting is that many of the people who push a certain type of product. One might assume that they therefore have vested interest in pushing their case (biased). You seem to be very worried over this point. None of your business and if you followed the forum you would realize it but I have never sold anything solar and never plan to. I am a retired mechanical engineer - a lifetime of designing, building and operating state of the art iron ore reduction plants. The typical project I have run costs in the 40 million dollar range.

If you put up a post here, perhaps you should divulge your interest first so we are all clear as to where you are coming from. That you sell or import doesnt mean that you WILL be biased, but it lets the reader have all the information to make a quality judgement on your discussion. Like I mentioned previously, if you bothered to read the forum before complaining you would have seen that the attachments of the main posters & moderators has is well known.

Lets all have a bit of honesty here. We have found people doing similar things here in Australia pushing certain products on forums on the pretext of being "interested and informed" when in fact they sell them Cut the bull and stop trying to act like the consumer watchdog.

[Peter69_56]

Russ, I never accused you of being anything. I simply talked about how you said my observations were not worth anything and you dismissed them out of hand. Surely I am allowed to have my opinion on that. I have reread what I wrote to you and it was a general comment about being up front about ones comments (not a shot at you personally). I did not question your validity at all about your skill, knowledge or experience, so I am somewhat suprised at your reaction to my comments. You are obviously pissed off that I question your statement about my observations. You have your opinions and I have mine and obviously they differ. Are we not allowed to have differing opinions here?

With your second comment I suppose its fair enough, I havent read everything like you have, however seeing you are a moderator I would expect you know most everything about this forum, I however am just a simple reader and read what I can when I can. I saw this post and it took my interest and so I followed it. That I am not up to 100% speed on everything on this forum, I apologise and will try and do better before I open my mouth and put my foot in it.

I find your third comment offensive. I am not in any way a consumer watchdog but am sick of seeing forums where people espouse their opinion only to find out after questioning that they in fact sell the product and are shamelessly promoting it. I am not saying it is shamelessly happening here but I think its fair to ask the question given some people have fairly strong opinions about some products.

Correct me if I am wrong, but arent these forums set up on the basis of information for others less informed, and contributers are not supposed to promote their products as such (I stand corrected if you allow this here). Its supposed to be about people with the passion for solar, not a shopping mart. As a simple reader and occassional contributer, I have no real idea who is who in the zoo unless they state it, thus my statment about saying what you sell if you do. If people have nothing to hide such as Mike Solar then they have nothing to fear by stating such. I give him credit, he openly has talked about his products and given he has dealt with both would have a good feel for both.

I feel I have been attacked by you to say "pull your head in and question nothing, you are but a simple mindless reader". I ask questions to further my understanding and knowledge, nothing more. I dont have anything to push, I have no political banner, I ask questions and make comment if I think it will help or better my or someones understanding. If I have offended someone and can clearly see it I would apologise.

I could go on about democracy and freedom of speech etc but I wont waste my time or yours or anyone elses by dribbling on. If you wish me not to contribute anymore simply ask me to leave and I will.

If I have offended anyone else by my comment or questions here please tell me here and I will address them or apologise.

[russ]

No one here is selling to anyone on the site. A few of the fellows including one moderator are in the industry but among the regulars I have never seen anyone try to push their product. Any member that tries to sell is warned and repeat offenders are quickly banned. We are far more concerned about the point than you seem to imagine.

Mike Solar, LucMan, Naptown and SunKing for starters are all in the business but very open and honest about what they do in business and all three may have preferences but they never let that come in the way of what is best.

My opinion of personal observations, whether at home or in industry, you have heard. Unless data is systematically collected with proper equipment and timings observations are of interest but no real value. They may point one in the direction to do more checking.

What I am saying is that our histories and preferences are seen daily to those that read the posts. Just because our opinions don't agree with yours everything seems to have come into question.

Forget the democratic line - I see that point all the time on the net - nothing democratic or about free speech in forums.

Enough - Welcome to Solar Panel Talk.

[Peter69_56]

No one here is selling to anyone on the site. A few of the fellows including one moderator are in the industry but among the regulars I have never seen anyone try to push their product. Any member that tries to sell is warned and repeat offenders are quickly banned. We are far more concerned about the point than you seem to imagine.

Mike Solar, LucMan, Naptown and SunKing for starters are all in the business but very open and honest about what they do in business and all three may have preferences but they never let that come in the way of what is best.

My opinion of personal observations, whether at home or in industry, you have heard. Unless data is systematically collected with proper equipment and timings observations are of interest but no real value. They may point one in the direction to do more checking.

What I am saying is that our histories and preferences are seen daily to those that read the posts. Just because our opinions don't agree with yours everything seems to have come into question.

Forget the democratic line - I see that point all the time on the net - nothing democratic or about free speech in forums.

Enough - Welcome to Solar Panel Talk.

Russ I am sorry we got off to a bad start. I am glad you run the forum as you state and thats all I was concerned about. I question everything but not to be offensive its just me validating me and what I know. That other people already know doesnt mean I do, and same for others who follow me, some of us are somewaht ignorant and are just seeking knowledge, but are concerned to sort the wheat from the charf.

I agree with your assesment of Mike Solar (but dont know of the others you speak of), and I agree he is open and up front and I think thats (as I would say in Aussie language"Bloody Great"). I welcome guys like him (and girls too I am not sexist).

I guess I have been burnt a little by forums in australia where people there have shamelessly pushed their product and its only after some serious detective work that one sees the real truth in their so called "opinions" I guess that has tained me somewhat and I apologise to all here for that. I will try and leave the past behind and get on with what we all love here and thats SOLAR.

I am passionate about it and love knowing everything about it. I promote it as much as possible. Any solar is better than non!

I have solar Hot water and Solar PV. In 12 months I have saved $800 on gas usage for hot water and $2500 on electricity. Yes in Auz energy is expensive and increasing daily. I read my energy imports and exports daily and calculate the energy used and saved daily. I have invested $15,000 in solar and am so pleased I have. I have over capacity for solar hot water but am mindful of cooking it in summer so cover some panels to derate it when there is significant solar capacity, this gives me better returns in spring, autumn and winter. Have also boosted roof insulation, in particular with the central heating duct work which was poorly insulated at best and the highest user of gas. Also insulated hot water pipes which are normally not insulated here and just grey plastic pipes in the roof.

Any home I own from now on will be fully solar.

[russ]

Funny part is that the site is sponsored by Solar Town. Their only request is that they be a suggested supplier in the event we name any names.

Quite fair on Solar Town's part I think.

Russ

[Peter69_56]

Solar Town

Funny part is that the site is sponsored by Solar Town. Their only request is that they be a suggested supplier in the event we name any names.

Quite fair on Solar Town's part I think.

Russ

I agree, if they sponser the whole forum, then they are entitled to get mentioned as a supplier if people are going to discuss where to get stock. If we couldnt agree to do that we would probably not be talking now.

[jtellerelsberg]

Tubes aren't that new on the scene

Flat solar panels are less expensive to install. The tube type solar heat panels have no history. Flat solar panels have been around over 20 years.

It's true that evacuated tubes are a more recent technology with less of a track record, but they aren't that new. They've been around since the 1970s, so plenty of time for people to have figured out their pros and cons. Flat panels have been around since early in the 1900s, so have lots more history, but anyhow...

[cssolar]

I think flat plate and vacuum tube collectors and solar water heaters are both good.

And both have good and bad points.

But I think the most important thing is that, Solar water heating works and is worth while. ( here in Spain anyway )

I do feel it is a shame that in most country's its so little used, the other day I was up at Alicante castle looking down over the roof tops, I only saw 2 solar collectors , on the thousands of roofs I could see.
The sun was strong and I couldn't help thinking , what a shame so much free energy not being used.

Cheers Tony

[russ]

100% agreed Tony! Same for solar air heating.

[jtellerelsberg]

The evidence in Ithaca, NY

Evacuated tubes are better, but if you live in a snowy area, then flat panel maybe better. The evacuated tubes do not melt off the snow as good as the flat panel does.

Bob Nape, a solar installer in Ithaca NY, decided that the theoretical arguments were't satisfying and put up side-by-side systems. You can see the ongoing data comparisons and historical behavior at http://goo.gl/EMMM9. Here's a link to the previous 12 months of data of thermal output from the systems: http://goo.gl/2ZfX1. It shows the flat panel system producing slightly more BTUs in every month. The difference is rather small.

Will you get the same results? Maybe, maybe not -- depends on the particulars of your system and the particulars of your climate. Given that I'm in a similar climate (in mid-Vermont), this is convincing evidence that I should go with a flat panel system and plow my savings into other energy saving or generating efforts.