Wood to Solar transition

[SteveJ]

Here is a link to a comparison of flat plate and evacuated tubes used all year in a freezing climate:

http://www.solarh2ot.com/images/Performance%20-%20Flat%20Plate%20vs%20Vacuum%20Tube.pdf

 

[wdc1160]

Steve, If you read that close, they are testing with the evac tubes cover with snow. That maybe real world test, but in central indiana it doesn't represent what is normal. Especially if you put the evac tubes at 70 degrees raise. I am not sure those give graphs give me a good representation of what I can expect here in IN. Anthony's expereince only underscores that. He has stories were he simply create too much heat in some cases. Your thoughts?

 

[BrownianHeatingTech]

Steve, If you read that close, they are testing with the evac tubes cover with snow. That maybe real world test, but in central indiana it doesn't represent what is normal. Especially if you put the evac tubes at 70 degrees raise. I am not sure those give graphs give me a good representation of what I can expect here in IN. Anthony's expereince only underscores that. He has stories were he simply create too much heat in some cases. Your thoughts?

Exactly. If you keep them clean, they work great. If you don't keep them clean... well, the reason that flat plate collectors stay clean is because they are wasting heat to melt the snow. I'd rather just run a foam-edged roof rake over them to knock the snow off. And, like you said, the angle will help to reduce that. As will using a frame to keep them elevated from the roof more.

Joe

 

[antknee2]

Anthony. The primary thing this controlller lacks is logging. Take it from a computer scientist, they made logs for a reason. We don't want to hover over our equipment all day long.

I am so interested in the outcome of this antony I would send you a controller. I just havne't found one that is user friendly. I have been working with a similar controller to Nofossil's. But, for people who don't want to learn the finer points of php and linux, its not likely a good fit. I wanted to contribute to the board by donating a setup script of a controller like nofos. And, I still think I will, but I haven't found the time yet.

I will have more time to wrestle with an answer to the question after april 15.


I really have spent most of my controller time on my controller. Maybe someone can find a simplier controller that has logging. PS If you'll notice from nofo's logs we can see most aspects of his energy use. He happens to put his data in graph from which helps analysis, but I think even a txt file would help enormously. We could turn the txt into a graph easily enough. I am getting off topic.

Resol controllers have always worked well for me, and offer data logging (with an external data logger that is attached to the controller).

They are re-sold by a number of companies. I happen to use Caleffi as a supplier, because I buy most of my other solar piping and controls from them...
http://www.caleffi.us/en_US/caleffi/Details/News/files/257_Series.pdf

That file doesn't show the data logger, but if you look for the Resol data logger on the web, I'm sure you can find it...

Joe

Bill & Joe thank you very much for your input and links . I am starting to realize that without any data logging I have no clue what happens during the day especially with the solar energy produced . Like today , perfect clear day I figured the tanks temps would be around 170-180 . Not today 140 F , but pool temp up 4 degrees , if the return water temperature to the solar system rises to 190 F it triggers pool heater zone to kick in . All other zones are set very low . Go figure ??

 

[wdc1160]

Anthony, from your observations I know those things are going to make you pool boil this summer. I don't know how big your pool is, but raising even 15K gallons(small pool) 4 degrees is alot of heat. You can do the math. I think the newest era solar evac tubes must be just ridiculous. I am more intersted in real world winter doability.

As an example if you system inthe winter could do 50000 btu on a clear day in winter - half of purported daily output. That may be able heat my house even at 30F during winter- an almost certainly heat my house at 40. If I turn down certain zones it could even fare better. Now all I have to do is learn how to eliminate cloud cover??

 

[Bob Rohr]

Crunch the numbers carefully when comparing evac tubes to flat panel collectors. Yes they may be easier to install, and they may provide a bit higher temperatures.

The temps are the big thing. Capturing energy isn't meaningful, if the absolute temperature is too low to put it to use. Efficiency numbers that don't take that into consideration aren't helpful.

By their own admission the evac tube manufacturers projected a 10 year realistic life span. Newer models with better seals are looking for 15 years. Quiz the manufacture about the warranty with any panel or tube.

I visited with a bunch of solar contractors in Denver this weekend. One told me of a 100 tube array installed 5 years ago that has had 25 tubes failures, lost vacuum. A very un happy customer.

Which manufacturers say that?

"Work is underway to further improve their lifetimes. in the near future the standard lifetime of glass tubes will be 15 years says Zhi Xian Shen of Bao Guang" Granted these are Chinese tube manufactures speaking, but many of the evac tubes sold in the US are from China. Sunda, Oventrop, Apricus, Eos, etc.

Thermomax tubes have a 10-year warranty, and are likely to last at least twice that, if not longer.

Actually, the last shipment I got was dropped and speared with a forklift by the freight company. Of 30 tubes, one was damaged. It had the condenser end sheared right off it. Still had vacuum integrity (and still does, sitting in the corner of my shop, a couple months later).

I believe there is a place for the evac tubes, under the right conditions, just be sure to do the numbers by the data available at the SRCC. To say they are better under all conditions???

I would hope no one would say that...

Joe, spend some time walking the trade show halls and you will hear some pretty wild claims regarding performance of evac tubes. I had one big name manufacturer tell me recently that their performance numbers are based on 800 btu/hr./ft. sq. That's a bold statement.

Joe

 

[Bob Rohr]

Master, Awesome link, here is another helpful link that I found on that same page

http://www.caleffi.us/en_US/caleffi/Details/Magazines/pdf/idronics_3_us.pdf

A solar webinar will be presented May 1 also, sponsored by Caleffi, and presented by well know hydronic and solar guru John sigenthaler. A bargin at 49 bucks if solar is in your plan.

hr

http://www.caleffi.us/caleffi/en_US...s~news_detail_0000391/type/newshome/index.sdo

 

[Bob Rohr]

Steve, If you read that close, they are testing with the evac tubes cover with snow. That maybe real world test, but in central indiana it doesn't represent what is normal. Especially if you put the evac tubes at 70 degrees raise. I am not sure those give graphs give me a good representation of what I can expect here in IN. Anthony's expereince only underscores that. He has stories were he simply create too much heat in some cases. Your thoughts?

Exactly. If you keep them clean, they work great. If you don't keep them clean... well, the reason that flat plate collectors stay clean is because they are wasting heat to melt the snow. I'd rather just run a foam-edged roof rake over them to knock the snow off. And, like you said, the angle will help to reduce that. As will using a frame to keep them elevated from the roof more.

Joe

Is it realistic to expect the homeowner to "rake" off their solar collector after snowfalls? Just make sure they don't snag the clips that hold they onto the rack

hr

 

[wdc1160]

I guess, it depends on where the solar panel is located. But, I don't have snowfall like many of you do. Although It does get cold and windy, I am located in a place where snow fall is a minor nuisance. I don't know where the testing took place. I just know the average winter day in Lafayette doesn't include any snow. When it does, it usually melts quickly due to ambient temps.

My hurdle is my local government rapes me on Nat gas prices. So on a btu per dollar basis, people in Chicago pay much less than I do. They are working on a way to tax the sun, but so far have become unsuccessful.

Although you point is valid, the test doesn't hold true to my locality.

 

[steam man]

I haven't been on for a while since I am traveling and currently in Puerto Rico for a short stay. I have 9 older flat plate collectors that have yet to be installed (and may not) but just purchased a 120 evacuated tube system. I am waiting on a re-roofing this spring. I am considering doing a hybrid setup to actually study the differences over time between the two systems or just adding another 60 tubes to get where I would like to be. I am running out of roof space. I've looked at the resol controller and thought of using the setup for an east-west panel system for a flat plate/evacuated tube system with data logging. I've read the research on the winter verses the summer performance and it intrigues me. The ease of installation of the evacuated tubes sort of swings me to that side. Not only that but I plan to add the tubes to utilize the heat as I build the system I want in stages. The heating calculations tell me that I would need add quite a few more tubes for pool heating. I think I am about 40-50% on space heating with the 120 tubes but there are no guarantees with anything. I am also looking at data logging but haven't decided on any one setup yet. I do have an interesting concept design for the solar and wood boiler heating combination. When I get it fully drawn out I will let you guys "rip" it apart. LOL.

I just blew a safety valve on a large marine boiler coming into port today. It wasn't one of my finer moments. %X#%^&*

 

[steam man]

I just saw the picture of the panels with the snow cover. I can have 3 ft of snow on my roof easily. I plan on raising the feet up somewhat higher off the roof and maximizing the angle for snow shedding and winter heating. The wind load is something I will take into consideration. I have also looked at somehow adjusting the angle of the panels for different seasons but the risk of panel damage and complexity for a large array along with the cost leads me to believe it would be easier just to add extra panel area for summer use with a larger tilt angle for winter. Certainly I should have the summer covered.

 

[Bob Rohr]

One nice thing about evac tubes is you can easily remove some to adjust summer output. I built some racks on the ceiling of my shop to store "off season" tubes.

Solar contractors with snow country experience tell me at least a 45 pitch to help with snow slide. Another suggested some of those windshield waxes to help the snow slide off the tubes.

I've seen pictures of evac tubes in a vertical position also. The U of Maryland Decathlon home had an Apricus array mounted vertically. Although the winning home had flat panels

I'm still researching longevity issues with evac tubes. I have talked with longtime solar installers in Colorado, New Mexico, and North Carolina recently, trying to get a feel for tube reliability. I'm still researching, but all three tell me tube replacement is a real consideration.

You can get more absorber plate per square foot on the roof with panels when you consider the space between the tubes, the vacuum space, and the header.

The Apricus website shows tubes on pole mounted tracking racks if you really want to maximize the solar window

hr

 

[antknee2]

Anthony, from your observations I know those things are going to make you pool boil this summer. I don't know how big your pool is, but raising even 15K gallons(small pool) 4 degrees is alot of heat. You can do the math. I think the newest era solar evac tubes must be just ridiculous. I am more intersted in real world winter doability.

As an example if you system inthe winter could do 50000 btu on a clear day in winter - half of purported daily output. That may be able heat my house even at 30F during winter- an almost certainly heat my house at 40. If I turn down certain zones it could even fare better. Now all I have to do is learn how to eliminate cloud cover??

The pool is only 14 x 8' x 4' deep very well insulates and always covered with 2'' styro foam panels , they float on the water . The pool is indoors . Bill you have a good point about overheating the pool if the water is over 83 degrees that would make my workout allot harder . Cool water is the way to go .

 

[Nofossil]

If you don't heat with wood, I guess it might make sense to look at really expensive high-performance solar collectors that can heat your DHW in the midst of winter.

On this forum, though, I'd assume anyone with enough ambition to do solar is already heating DHW with wood during the winter. In that case, a much less expensive and exotic solar system can easily provide DHW during the summer months.

I just built my last fire, and starting in about two days, I expect to get very nearly 100% of my DHW from my el cheapo solar panels.

 

[antknee2]

Supplementing with solar as a boost to you thermal storage system is a definite wild card when it comes to predicting what your energy requirement for the day in the winter . I will admit on the very clear days when you see the solar system keeping up and then some with you heating requirements , it will bring a smile to your face and save some wood .

 

[Nofossil]

Supplementing with solar as a boost to you thermal storage system is a definite wild card when it comes to predicting what your energy requirement for the day in the winter . I will admit on the very clear days when you see the solar system keeping up and then some with you heating requirements , it will bring a smile to your face and save some wood .

We have plenty of southern facing glass. If it's calm, sunny, and over 20 degrees we don't need any heat during the day. Nighttime is another story, but I don't think even the best solar collectors do much with moonlight ;-)

My solar panels put out something in the order of 100,000 BTU/day in early summer. If I could protect them from heat loss to the environment, they still wouldn't do more than a third of that on the best winter days, when I don't need heat anyway. Mostly when I need heat it's cloudy and/or dark. 30,000 BTU is less than 1/2 hour of boiler operation. I did a back-of-the-envelope calculation and decided that even an ambitious solar system would save me only a fraction of a cord of wood per year. I put the money in a gasifier instead, and my next investment is a radiant zone.

Again, my choices are based on my situation. Others may arrive at different conclusions. It would be interesting to put together a budget guideline / spreadsheet providing some sort of roadmap about what investments have the best return: If this is your situation and you have X to spend, this is a likely best approach. For instance, insulation is probably the best investment up to a certain level, then better windows, and so on. Wood stoves, conventional boilers, gasification boilers, solar DHW, solar heating, PV, and other goodies fall in at different points along the continuum.

 

[Bob Rohr]

good points NoFo. A solar array that would supply even a small portion of a winter heating load will turn into an overheating machine in the summer. How much would one spend to purchase a 6-8 month system. A 4X8 panel may only provide 20K per DAY

It may be that a PV system with it's year around energy use potential, and buy back, net metering from the power company, may be a better investment for some.

hr

 

[BrownianHeatingTech]

Is it realistic to expect the homeowner to "rake" off their solar collector after snowfalls?

Yes. Most folks around here own roof rakes, and rake their roof anyway, so why not rake the panel while they're at it?

I have also looked at somehow adjusting the angle of the panels for different seasons but the risk of panel damage and complexity for a large array along with the cost leads me to believe it would be easier just to add extra panel area for summer use with a larger tilt angle for winter. Certainly I should have the summer covered.

If you look at the pictures of how the frames work, back on the first page of the thread, it's pretty easy to just un-bolt the brace and re-bolt it at a different angle (provided that you design your braces slightly different from the ones shown in that picture, so the angle-iron doesn't interfere with the panel.

Another suggested some of those windshield waxes to help the snow slide off the tubes.

I like that idea, although it would probably want to be done after installation, to avoid dropping tubes while handling them...

I'm still researching longevity issues with evac tubes. I have talked with longtime solar installers in Colorado, New Mexico, and North Carolina recently, trying to get a feel for tube reliability. I'm still researching, but all three tell me tube replacement is a real consideration.

What brand tubes are they using? I've never heard of a failed Thermomax tube (except the one that the freight company broke). I had (at the time) two suppliers for the tubes, and they were both scratching their heads on how to get me a single tube, because they had literally never had to ship out a replacement tube before. One had to replace a whole box of ten tubes that got rolled-over by a truck, but never any for repair use. I ran into a similar problem when I first started carrying these things, and I wanted a single tube to use as a demonstration model for home shows and the like.

I always tell my customers that, if a tube ever breaks due to natural causes (except not something like a tree falling on the house, which would break anything, flat-plate or evacuated), I'll replace it free of charge. I don't expect to ever need to honor that warranty.

Joe

 

[BrownianHeatingTech]

I did a back-of-the-envelope calculation and decided that even an ambitious solar system would save me only a fraction of a cord of wood per year.

Personally, on a residential scale, I don't think solar (when purchased retail and installed by a contractor) will actually have a reasonable return on investment. If you do it yourself, as you did, then it can.

I sell the stuff, but I don't tell my customers that it will pay for itself. The ones who have done solar have done it because they like the idea of solar and the convenience of using little or no fuel during the summer. At current technology costs and fuel costs, solar is something that you do because you want solar, not because you think that it will save you massive amounts of money. If it does return on the investment and saves you something, that's a bonus.

There's nothing wrong with doing something for those purposes. Look at central air. It's not likely to save you money - quite the opposite. But a lot of people still have it for the convenience and just because they want it.

Joe

 

[Bob Rohr]

Is it realistic to expect the homeowner to "rake" off their solar collector after snowfalls?

Yes. Most folks around here own roof rakes, and rake their roof anyway, so why not rake the panel while they're at it?

I have also looked at somehow adjusting the angle of the panels for different seasons but the risk of panel damage and complexity for a large array along with the cost leads me to believe it would be easier just to add extra panel area for summer use with a larger tilt angle for winter. Certainly I should have the summer covered.

If you look at the pictures of how the frames work, back on the first page of the thread, it's pretty easy to just un-bolt the brace and re-bolt it at a different angle (provided that you design your braces slightly different from the ones shown in that picture, so the angle-iron doesn't interfere with the panel.

Another suggested some of those windshield waxes to help the snow slide off the tubes.

I like that idea, although it would probably want to be done after installation, to avoid dropping tubes while handling them...

I'm still researching longevity issues with evac tubes. I have talked with longtime solar installers in Colorado, New Mexico, and North Carolina recently, trying to get a feel for tube reliability. I'm still researching, but all three tell me tube replacement is a real consideration.

What brand tubes are they using? I've never heard of a failed Thermomax tube (except the one that the freight company broke). I had (at the time) two suppliers for the tubes, and they were both scratching their heads on how to get me a single tube, because they had literally never had to ship out a replacement tube before. One had to replace a whole box of ten tubes that got rolled-over by a truck, but never any for repair use. I ran into a similar problem when I first started carrying these things, and I wanted a single tube to use as a demonstration model for home shows and the like.

I always tell my customers that, if a tube ever breaks due to natural causes (except not something like a tree falling on the house, which would break anything, flat-plate or evacuated), I'll replace it free of charge. I don't expect to ever need to honor that warranty.

Joe, at the next RPA get together just start asking the members that specialize in solar for their experience with tubes. I'm sure they will share brand, % of failures, location and pictures if you would like. I'm not here to flame manufacturers in a public forum. The data is real, and it's out there. Or ask the people that make evac tubes, they should give an honest answer, they have the numbers as they send out the replacements. If not the installers doing the replacements will

Kudos for you for taking care of any warranty issue for your customer, regardless of the cause, that's the best policy you can offer.

hr

Joe

 

[BrownianHeatingTech]

Joe, at the next RPA get together just start asking the members that specialize in solar for their experience with tubes. I'm sure they will share brand, % of failures, location and pictures if you would like. I'm not here to flame manufacturers in a public forum. The data is real, and it's out there. Or ask the people that make evac tubes, they should give an honest answer, they have the numbers as they send out the replacements. If not the installers doing the replacements will

Drop me an email with the info, if you don't mind. It's good to know what issues may exist, if someone asks my opinion on Brand X. I know some are such low quality that they actually ship spare tubes with the panels. Others are such high quality that (as I mentioned), they don't even know how to go about ordering a replacement tube.

Kudos for you for taking care of any warranty issue for your customer, regardless of the cause, that's the best policy you can offer.

My favorite kind of warranty is the one I don't expect to ever need to actually honor (not that I wouldn't, but I like warranting products that I expect to be highly reliable).

Joe

 

[Bob Rohr]

As more and more of my customer starting asking about solar I set out to find out what products are out there and which have good track records. It doesn't take long to figure out the product info and reputation "spiel" you get from the sales and marketing folks differs somewhat, often greatly from the info I recievied from the installers"in the field"

Furthermore as you discover how the sales and marketing personal move from company to company their stories change dramatically. Suddenly the previous brand they worked for had nothing but problems Seems the company they currently work for is the one and only trouble free product Do you have the same experience? Really doesn't matter what the product is trucks, boilers, solar collectors, etc. It's a common tale.

So I decided to start polling contractors I know with 20 years or more of hands on solar experience. The more service experience they have, with solar, the better the data. It's reallly the service contractors that get exposed to more of the problem systems. Many times the original installers are long gone by the time the problems occur.

I noticed you are an RPA member and I know a dozen or more RPA members with many years of solar installation and repair experience. Same with the gang at heatinghelp.com. 200 of us gathered in Denver last weekend to talk hydronics and solar. It was a great place to meet face to face and get first hand experience from hands on folks.

I'm not looking to discredit one type or brand, just looking for real world experience. You have the power of the keyboard to do this research, call on your peers, this is why we form and join associations. Share the knowledge. Knowledge is power and it buys you less headaches, many times.

When I hear lines like we don't know how to ship... because we never have had a failure, that make me wonder. Doesn't it you?

hr

 

[BrownianHeatingTech]

Furthermore as you discover how the sales and marketing personal move from company to company their stories change dramatically. Suddenly the previous brand they worked for had nothing but problems Seems the company they currently work for is the one and only trouble free product Do you have the same experience? Really doesn't matter what the product is trucks, boilers, solar collectors, etc. It's a common tale.

Indeed. That's one of the ways I've found to sort the professionals from the less-than-professional.

For example, I recently was talking to one of my suppliers about some material for a particular job. They said, "well, I can sell you this, but [name of competing supply house] stocks [other brand], which will work better and be less money for you in this application." This isn't the first time that they've done that for me.

I noticed you are an RPA member and I know a dozen or more RPA members with many years of solar installation and repair experience. Same with the gang at heatinghelp.com. 200 of us gathered in Denver last weekend to talk hydronics and solar. It was a great place to meet face to face and get first hand experience from hands on folks.

Sounds like a good time. I haven't managed to travel anywhere out of the general area in many years. If I did, I'd have to visit some family members as a higher priority than conventions, though.

I'm not looking to discredit one type or brand, just looking for real world experience. You have the power of the keyboard to do this research, call on your peers, this is why we form and join associations. Share the knowledge. Knowledge is power and it buys you less headaches, many times.

Yeah... that's why I asked your opinion on the matter.

When I hear lines like we don't know how to ship... because we never have had a failure, that make me wonder. Doesn't it you?

Not in this case. The response was the same from two completely separate companies (the first of which was the supplier mentioned above), and there actually isn't even a part number for a single tube in the manufacturer's catalog (or, at least, was not at that time - I haven't checked recently).

Joe

 

[Bob Rohr]

Here is how I handle evac tube shipping. This tube has traveled with me to numerous seminars, in my check on airline baggage!
I put one wrap of plastic bubble wrap around it. This demo tube was shipped to me in the manufacturers box encased in foam blocks, as was the 8 tube array I installed on my shop.

With the info I have gathered to date, and the personal hands on experience I have, I feel comfortable in saying the flat panels have a much better longevity track record. Consider also there are many more panel installatons than tubes in this country.

If the question is installation ease, yes, tubes do have an edge there. Performance difference for my designs is pretty much a wash. Return on investment IF both can go 20 years without a replacement, hands down the flat panels.

Not all contractors are as generous as you with the 10 year no charge labor and parts replacement. In the case I mentioned above with 25 tubes replaced in 5 years, even with a miniuum truck/ labor SOMEBODY has to pay for that. Even with a free tube, there are costs to be absorbed. Even a generous contractor, at some point has to question that business decision.

Just my 2 cents. I'm off to install a tube system as we speak :0

hr

 

[BrownianHeatingTech]

Here is how I handle evac tube shipping. This tube has traveled with me to numerous seminars, in my check on airline baggage!
I put one wrap of plastic bubble wrap around it. This demo tube was shipped to me in the manufacturers box encased in foam blocks, as was the 8 tube array I installed on my shop.

Little different from an actual, full-length tube

With the info I have gathered to date, and the personal hands on experience I have, I feel comfortable in saying the flat panels have a much better longevity track record. Consider also there are many more panel installatons than tubes in this country.

There are a lot of non-functional panels around here. Seems that snow and ice plus flat glass equals... cracked panel. I know of one individual who has literally replaced the glass after every winter. The panel has been up for 15 years, and has had to have the glass replaced each of 15 springs.

Breaking a quality evacuated tube is very difficult. It's strong glass, in the best possible shape for strength (other than a sphere, which would not be practical).

Not all contractors are as generous as you with the 10 year no charge labor and parts replacement. In the case I mentioned above with 25 tubes replaced in 5 years, even with a miniuum truck/ labor SOMEBODY has to pay for that. Even with a free tube, there are costs to be absorbed. Even a generous contractor, at some point has to question that business decision.

Which is why it's important to choose quality products, which you won't actually have to warranty, because they won't fail.

Joe