# looking for some direction on solar collectors for dhw



## 2.beans (Oct 6, 2008)

im sure there already a post but input would be nice thanks


----------



## rhetoric (Oct 7, 2008)

dhw?


----------



## myzamboni (Oct 7, 2008)

rhetoric said:
			
		

> dhw?



domestic hot water


----------



## DaveM195352 (Oct 7, 2008)

tons of material to read on-line  - google solar hot water, etc
the best site I have found is:
builditsolar.com
good luck and keep us posted

Dave from Maine


----------



## daveswoodhauler (Oct 9, 2008)

Another good site is:
http://www.wind-sun.com/ForumVB/
You can probaly use the search function and find what your need


----------



## 2.beans (Oct 10, 2008)

i spoke to a solar salesman and he recommend the stiebel eltron flat plate solar collector. pexsupply sells them for 850$ delivered . anybody running these maybe? i think i really want to try some panels instead of messing with my wood boiler during the shoulder months.


----------



## steam man (Oct 10, 2008)

I am just now finishing up installing my system. I installed it myself-120 evacuated tube for DHW first and space heating to come. Only 60 tubes are in for now. The tubes I got from here-www.siliconsolar.com. I worked out the design criteria myself. It was not a simple installation for one man. I have been making some heat for about 2 days. I'll post some pictures later today.

Mike


----------



## peakbagger (Oct 10, 2008)

I dont know where you are in NH but there is a solar co-op in the Plymouth area that does bulk buys of Apricus evacuated tube collectors and has weekend installs. Their website is http://www.plymouthenergy.org/. They have several installs coming up and each install, has an open house. 

I have flat plate collectors with a DC pumping system run by a 40 watt solar panel. It is very good at generating lots of warm water but not so good in the winter at generating hot enough water. The evacuated tube collectors are less efficient but are better at making hot water year round. Bascially a flat plate system will generate water no more than 80 F warmer than outdoor temp, versus evacuated tube can go 200F over the outside temp. So if you want smaller volumes of  hot water year round directly off a solar panel go evacuated tube, if you use larger amounts of hot water and have a efficient means of stepping up the temp, go flat plate.

Some trade offs for evacuated tubes are 

More fragile, (consider that the tubes are basically thick fluorescent tubes laying out flat on your roof). 

You need to find a way to dump the heat in summer as the fluid will boil and pressurize. Alternately you need to come up with a way of covering the panels when you dont need the heat.

You want to make sure your pumping system is robust as overheated stagnant fluid in the tube header will breakdown quickly. 

As for DC pumping with a PV panel, it sounds neat and runs during a power outage, but it adds $400 to the system cost (note, most of the kits that are sold with DC pumping use a 20 watt panel which is insufficent to run a system in NH). I would install a 110 AC Taco cartridge circulator with a differential controller.   The DC systems usually sell themselves as no need for controls "when the sun is out the pump runs", that is not fully true, it will work but you will lost some heat in the mornings and evenings when the tank temp is higher than the collector temp, yet the pump runs. There is a DC controller built by a guy in Maine (artec?) that works well to get around this issue.

And lastly, make sure that you have mutiple check valves in the system and inspect their operation on a annual basis. Most of the failed systems from years past were taken out of service due to reverse thermosyphoning on a real cold night. If the check valve fails open, the system will send all the heat to the collectors on the roof and freeze the potable water side of the heat exchanger (usually bursting it). 

Drop me a PM if you have more questions


----------



## steam man (Oct 10, 2008)

Quote-Some trade offs for evacuated tubes are 

More fragile, (consider that the tubes are basically thick fluorescent tubes laying out flat on your roof). 

You need to find a way to dump the heat in summer as the fluid will boil and pressurize. Alternately you need to come up with a way of covering the panels when you dont need the heat.

You want to make sure your pumping system is robust as overheated stagnant fluid in the tube header will breakdown quickly. 



I have a few comments on the above points. The evacuated tubes seem to be very robust. I man-handled them while installing and if the didn't break then I can't see them breaking from anything. Keep in mind flat plate panels having glazings that can break if enough force hits them. Certified evacuated tubes pass a test simulated to heavy hail hitting them. Losing the vacuum seal will be a greater concern. However, one tube loss does not shut down the whole system.

Correctly sizing the system will minimize overheating. Proper design parameters and high quality heat transfer fluid must be used that is meant for evacuated tube temperatures.

The temperature load should dictate what to use. Roughly, lower temp systems can utilize flat plate while higher temp's required should use evacuated tubes. 

Its just after 10am and my tubes have been on for almost two hours making heat in northern Maine.

Mike


----------



## 2.beans (Oct 11, 2008)

steam man what size storage tank do you use and what have you been able to get your tank temp up to?


----------



## steam man (Oct 11, 2008)

2.beans said:
			
		

> steam man what size storage tank do you use and what have you been able to get your tank temp up to?



I've had it up to 110 deg or so today and yesterday. However, I still have pipes to insulate, some tweaking of control parameters, etc. We have already done laundry and showers so it is a little hard to tell. I want to try and use the heated water at the lowest temp during the day since solar collection is much more efficient at those temps. The heat calculator on the controller says I have made about 5kw every hour today minus .15 KW-hr for the pump operation. That's about 17,000 btu/hr. average. I still  have to verify some parameters so it is hard to say. The 120 gallon solar preheat tank is hot though. I actually turned off my 40 gallon indirect it feeds into. YEAH
I only have 60 out of 120 tubes in for right now and possibly will go to 180 tubes. I want to be sure I don't over do it. I will have a large tank for radiant heat collection going in. I do have my pool that can take the excess heat. But this is the off season for that, of course. I'll go take some pictures and see about getting them on here.

Mike


----------



## steam man (Oct 11, 2008)

My tank just hit 120 deg at 2:00 PM. Collector temp is 133 deg. 

Below is my installation.


----------



## steam man (Oct 11, 2008)

Made a mistake. I hope this works.


----------



## steam man (Oct 11, 2008)

steam man said:
			
		

> My tank just hit 120 deg at 2:00 PM. Collector temp is 133 deg.
> 
> Below is my installation.



4:00 PM tank is 128 deg. Collector about 138 deg

Mike


----------



## 2.beans (Oct 11, 2008)

could you let me know what you lose in temp in the overnight. looks good


----------



## steam man (Oct 11, 2008)

We'll be using some hot water tonight. Ideally, you should use it when it gets hot and have the tank relatively cool by sun up the next day for more efficient heat collection. Even using hot water during during the day when the tank gets hot should help collect more energy. Its like I tell my wife-living with solar requires a little timing change in our lifestyles. No big problem.

Mike


----------



## steam man (Oct 12, 2008)

3:00 AM tank was 125 def F. Filled large whirlpool and temp went to 110 deg. 8:00 tank was about 98 deg. What I have an issue with is that having the tank sensor on the outside of the tank under the insulation probably gives it a slow response time, especially since it is a stone-lined tank. If I could fabricate an exceptionally long thermowell  I could get the sensor inside the tank.

Mike


----------



## 2.beans (Oct 13, 2008)

what are you doing up at 3AM? ive built some long thremowells but its easyer to show in a picture than trying to describe it. ill try to post a picture this week of the thermo well.if your temp sensor is on the outside i bet your inside temps are higher. im wondering what i would need to heat up 1000 gallons for useable hot water. i can shut off one tank so id only have 500 gallons though, which may be easyer. keep up the posts, thanks


----------



## steam man (Oct 13, 2008)

2.beans said:
			
		

> what are you doing up at 3AM? ive built some long thremowells but its easyer to show in a picture than trying to describe it. ill try to post a picture this week of the thermo well.if your temp sensor is on the outside i bet your inside temps are higher. im wondering what i would need to heat up 1000 gallons for useable hot water. i can shut off one tank so id only have 500 gallons though, which may be easyer. keep up the posts, thanks



Had to take the Pups out for their thing. Actually, I have to get on an early flight today. 

Tank made it to about 126 deg. I did notice the outside "skin " temp was 4 deg hotter than the the temp coming directly out of the exchanger for a little while. That shut down the circ so I do have a temp response issue. I have a 3/4" pipe plug at the top of the tank if I could put an extended thermowell down through there. What have you got in mind?

Mike


----------



## Hansson (Oct 13, 2008)

steam man said:
			
		

> You need to find a way to dump the heat in summer as the fluid will boil and pressurize. Alternately you need to come up with a way of covering the panels when you dont need the heat.
> 
> 
> Mike



I know that people here are building systems so the can reach stagnation.

I have try to find some info in English 
http://www.aee-intec.at/0uploads/dateien48.pdf


----------



## steam man (Oct 13, 2008)

Hansson said:
			
		

> steam man said:
> 
> 
> 
> ...



I am going to read the article with some interest. I am an engineer so I have looked at every detail of the design criteria for trying to do just that. Survive stagnation. Every component subject to those temperatures would have to be rated for it. The biggest obstacle I have found is the heat transfer fluid. Any "safe" propylene glycol product is probably not going to work. Other heat transfer fluids have toxicity problems, usually above 400 deg F not to mention flammabilty issues. Most importantly, finding a fluid that has the heat carrying capacity is also an issue. Ones I have looked  had less than half the heat carrying capacity of water. There's also material capatibilty problems. Hopefully I will get that problem worked out. I do have heat dump capacity but there is always a weak link such as having one pump. I was thinking if the tubes could be low there could be a gravity dump zone above them. I'll read the article. If you get any more info on this subject I would appreciate you posting it.

Mike


----------



## Hansson (Oct 13, 2008)

I found a lot of info but not in English :-(
You can try to find something here
http://www.du.se/Templates/InfoPage____4176.aspx?epslanguage=EN


----------



## steam man (Oct 13, 2008)

Thanks Hansson. I'll check it out.

Mike


----------



## steam man (Oct 24, 2008)

Here's an update on my solar dhw heating. I have plans to connect the tubes to some radiant floor tubing as a dump but haven't got around to it yet. So......I figured with the shorter days I could just install most of the tubes and use my 160 g of storage without much trouble. I got 103 out of the 120 tubes installed. Seeing the tank temp approach 140-150, I ran the dishwasher, and then two loads of laundry. The tank temp didn't drop much but the collector temp dropped and started cycling the pump. This told me that the cold water in the bottom of the tank was affecting the glycol temp but the tank skin temp has a slow response. That was reading up to 149 deg. I fabricated an extended thermowell that reached from the top down to the bottom 1/4 of the tank. That temp now read 167 deg F-an 18 deg difference. That shut the pump down since I had the high temp limit set at 160. It was late in the day so the sun was going down. Introducing cold water into the tank also gave a much quicker tank temp response. Looks like I'll have to get the floor tubes going.

Anyone know what the max temp a dhw tank should store water at? I don't see anything stated right off hand.

Mike


----------



## Westernmainer (Dec 10, 2008)

[This question is for Mike?


How is your system working now with the recent cold weather?

We are looking at systems for our house in Maine




'v


----------



## steam man (Dec 12, 2008)

Westernmainer said:
			
		

> [This question is for Mike?
> 
> 
> How is your system working now with the recent cold weather?
> ...



Sorry about the delay. I haven't been home in about 5 weeks to really keep track of my system. I have to depend on my wife to give me the numbers when I call. I will have a web based data logger set up next month to get accurate numbers. November was a crappy month for sun where I live though the tubes almost always make some heat. The tubes seem to be more dependent on having some solar radiation rather than what the outside temperature is. Hopefully I will get some numbers to post eventually. I did just receive an oil fill up today (the last about the time I started the system) and the drop in oil useage seemed significant. Though I don't expect much heat gain this time of year I think with solar you have to think over a longer time frame. My yearly savings is what I am thinking about. I did see my tubes making heat covered in some frost. That was weird.

Mike


----------



## Techstuf (Dec 20, 2008)

By jove....I think I've got it!  A scaled down, pedal powered version of this:


http://www.youtube.com/watch?v=yh_-DUKQ4Uw

http://www.youtube.com/watch?v=V0M2GnQluJk

You want to wash some dishes?  5 minutes on the stationary bike!

A bath?  10 minutes!

Etc....etc....  You get in shape and have nearly on demand hot water no matter the weather.  

Call it the "Cavitation Station".

Or, if you're really lazy, let the wind make your hot water.


TS


----------



## Rickard (Jan 7, 2009)

Hi Steam man

I am very interested in your setup. I am looking to put in a Sunmax system this spring. I am thinking of going with a 125 tube system for heat and hot water with a wood boiler for back-up. I am hoping to get temperatures at least to 140F from the tubes. I have two 500 gallon propane tanks for storage where one can be valved off if necessary. It is exciting to hear that you are getting temperatures above that range at this time of year. I am looking to do a drainback system instead of a glycol system. Since it is designed around the wood boiler I would be happy to see the storage aproaching 200F if that were possible.

What do you think of Sunmaxx? What made you decide on that company?

thanks

Dean


----------



## steam man (Jan 7, 2009)

Just got home yesterday from being gone a few months. So far since October, my system (with 105 tubes installed out of 120-hoping to get to 180) has averaged 11,650 btus/hr when running. That's the kicker-November was without sun. However, yesterday when temps were in the teens the tubes were cranking out heat because there was clear sun. Its run about 230 hours total. I am checking out a data logger system to be installed shortly. Certainly in NJ you should get more heat than northern ME. I am on my way to getting storage and the radiant tubes going. Seems like still a lot of work. You'll have a lot of variables to consider when installing with a wood boiler. I sent you a PM with my ph#. Give me call anytime-I am a slow typist.

Mike


----------



## velvetfoot (Jan 7, 2009)

Are the tube collectors less sensitive to a southerly orientation?
I'd like to dabble with solar, but the house roof is facing 45* to the east of south (southeast, I guess.)
Thanks.


----------



## steam man (Jan 7, 2009)

velvetfoot said:
			
		

> Are the tube collectors less sensitive to a southerly orientation?
> I'd like to dabble with solar, but the house roof is facing 45* to the east of south (southeast, I guess.)
> Thanks.



Collectors should face true with a + or - margin of 10 degrees without a penalty. Use a compass to find magnetic south and then correct for magnetic declination (or variation). Go to http://www.ngdc.noaa.gov/geomagmodels/struts/calcDeclination. That would be true south. If you don't get within 10 degrees you would have to add more collector area to make up the difference. Tubes can receive radiation at wider angles than flat plate collectors depending on the manufacturer. 

Mike


----------



## velvetfoot (Jan 8, 2009)

Thanks for the link.  I'm not so sure solar is in the cards for me.


----------



## karl (Jan 13, 2009)

How many BTUs an hour do those tubes produce for a given delta?


----------



## steam man (Jan 15, 2009)

karl said:
			
		

> How many BTUs an hour do those tubes produce for a given delta?



I am not really sure. I seem to get a pretty consistent 10-12 deg rise right now across 1 collector or 30 tubes at a flow rate of 1.6 gpm. I split my system to make a "reverse-return flow" to balance the flow with a parallel-series scheme. The actual flow rate is twice that or 3.2 gpm. I am waiting for some info on a data collection system before I install it so I don't have detailed data.  I have 105 tubes installed (15 more to go) heating a 120 gal tank. I seem to get about 11,600 btu/hour average. I have had no problem heating it over 150 deg (if not using much hot water) with single digit temps outside as long as the sun shines. I am kind of pressed to get a heat dump zone ready, probably the tubes in my basement floor at first. I have some other variables to consider. I'll know more as time goes on.

Mike


----------



## karl (Jan 18, 2009)

11,600 btus/hr?   Are you sure that's correct?

That's pretty low isn't it?  Sunmaxx 20 tube system is rated at 4684btu/hr.  You have 5 times as many tubes.  That would be 23,420 btu/hr/  I realize thats under ideal conditions but I would think you would do bettter than half that much.


----------



## steam man (Jan 18, 2009)

The 11,600  btu/hr seems pretty consistent based on what my flowmeter registers and what the energy meter calculates. Assuming my flowmeter is right, I think I am slightly under half output from what the tubes are rated for. But keep in mind we are just off the lowest insolation level of the year. I think they are probably about where they should be on the seasonal curve. You piqued my curiousity and I will double check to be sure sure. I do know that at before daylight the collector sensor reads -12 deg F. By 9:30 its over a 100 easily and cranking heat. I have up to 160 gallons to heat and typically by 1:30PM I usually have to use some hot water since the tank could be 160 deg. That is probably not heating from 55 deg as the water may still be warm from the night before. Keep in mind I am in northern Maine with low but clear sun. Its only going to increase from here. I have to get that heat dump zone going pretty soon. I will have a data logger soon enough and will be able to post some graphs. 

Mike


----------



## karl (Jan 18, 2009)

I got to thinking about my last post and I hope I didn't offend you.  If I did, I'm sorry.

I am curious about a solar hot water system for my house.  I'm a guy and I live alone, so DMH isn't a big deal to me.  

I'm interested  in using solar to heat my house.  I live in West Virginia.  Day time highs during the winter are usually in the low 40s.  I'm trying to decide if evacuated tubes or flat panels would be better for me.  I can fabricate flat panels to save money.  I'm guessing I would need 90-100 degree water for a radiant system.


----------



## steam man (Jan 18, 2009)

I don't know why you think your post was anyway offensive. No problem. -It got me thinking. I am still collecting performance data. I will probably be expanding to 180 tubes at some point but I have to get the heating part going and I have a pool to heat for the summer. The collector performance in WV would probably be a fair amount higher than northern Maine. Day time highs here may hit low teens. I like good solid numbers to work from. The 11,600 btu/hr is an average since the middle of October. November/first half of December was a real sunless time around here so I think that put the average down. I don't have a peak heat production on a per/hr or per/day but I will be looking at that. If your living alone your hot water demand would be pretty low. I went with evacuated tubes since I plan on using under floor radiant at some point. That generally needs 140 deg water or so. At lower collection temps flat plates may work just fine or even better. A btu is a btu at 90 or 140 deg. BTW-my dad's family was all from WV.

Mike


----------



## Blevesque (Jan 22, 2009)

Just wanted to pop my head in here and tell you my story. In november I installed a 30 tube collector for my uncle in the sugerloaf area of maine. The collector is made by EOS which is a maine based company. We did his a little differant the the normal, he has a Tarm Solo 40 with a 1000 gal. pressurized storage tank with a DHW coil built into it. He wanted me to tie the solar into his existing 1000 storage tank, I was reluctant at first but figured what the heck we can try it and if it doesn't work we already have the 60 gal. superstor that I pipe in. He have been getting very good temperatures from the collectors, but it's been tough to really know what it can do. The reason I say that is because he always builds a fire when the tank gets down to 150-160 he starts a fire usally in the mornings. So by the time the sun comes out his tank is up to 180-190. We have the it set up so the water has to be 185 in order to turn the pump on. Well yesterday he decided not to build a fire in the morning an see what it does. He called me last night and said I'm not going to believe this. 7:00am the tank was at 151 @ 4:00 the tank was @ 162 he gained 11 degrees in the tank yesterday and the high temp at the collector was 232 deg. So these things do work. Brian


----------



## 2.beans (Jan 23, 2009)

any way we could get some pictures? i have a similar setup without solar yet.


----------



## Blevesque (Jan 26, 2009)

Hi 2.beans, I just wanted to correct something from my original post. The 232 degrees was because the glycol slushed up and was not pumping well, it was -44 that morning he says the operating temps are usually 175-185 from the collector. His setup is pretty neat because he can rotate the collector to get the most heat from them between the seasons. Brian


----------



## 2.beans (Jan 26, 2009)

i like it, did you build the whole thing?


----------



## Blevesque (Jan 27, 2009)

He designed and built the whole thing by himself and had a buddy of his set it with his cherry picker. You really have to see this thing in person to really appreciate it. All I did was pipe it up and install the controls. I forgot my camera today, I'll try to remember tomorrow.


----------



## 2.beans (Jan 28, 2009)

could you take some pics on how the heat exchanger is built? i want to start gathering parts to build in the spring.


----------



## Blevesque (Feb 9, 2009)

Sorry it took so long 2.Beans, here are the inside pics showing the flat plate heat exchanger. Let me know you have any questions.


----------



## 2.beans (Feb 9, 2009)

nice work. whats the black box? a was also interested in the build of the solar collector. did he use copper pipe or plastic?


----------



## Blevesque (Feb 10, 2009)

Hi 2.Beans, the black box is the pump station and the controller goes mount in the front. Sorry to confuse you, he didn't build the collector, he just built the rotating stand that it is mounted to. The collector is made by EOS and is vacuum tube. Brian


----------



## WoodMann (Feb 10, 2009)

HEy Mike- looking at your solar installation, looks good. Is that an open or closed system? And did you make your own heat exchanger if it's a closed system...........


----------

