Thermosyphon solar

TonyS

Has anyone here installed these units in a colder climate?  Opinions and facts please. I am considering offering these units, they have a very low cost and no controls. Just concerned about long periods of no sun in freezing weather. Any clever anti freezing methods?  

Charlie from wmass

I would say it depends on how far north.

At least every other year we get a week of -20 F here in Berkshire county, Massachusetts, 100 degrees over -20 is 80 Still better than 42 for ground water temps. I will be checking on this post for my own knowledge.

Kevin_in_Denver_2

Thermosiphons and freezing climates

This design does have huge potential.  Murphy's law governs.



New construction methods (conditioned attics) make these worth considering:

http://greenbuildingindenver.blogspot.com/2009/02/passive-solar-dhw.html



"Freeze tolerant" PEX is one idea.   Very large supply and return pipes are another.

"Superinsulated" supply and return pipes is a third.



I wouldn't even try it with an unconditioned attic.



These are super ugly.  Don't let anyone talk you into putting it on the front of the house.

TonyS

Heres an idea for freezing and stagnation

Just trying to put a few options together, what do you think? New B&G circ only uses 10 watts, at that low consumption you could lose the freeze stat and run it 24/7.

Kevin_in_Denver_2

constant circulation for freeze protection

You have to analyze your failure modes.   This design would freeze up when you have a cold snap and a power or pump failure.  Hence my suggestion of freeze tolerant pipe.  Worst case is that the system is out of comission for a week or so until it thaws out.



NOTE:  The high temp/stagnation problems have been already solved in the ingenious collector design.  The collector is a heat pipe with an organic heat transfer fluid that completely vaporizes at high temps.  As a vapor, it stops transferring heat.   Whenever the tank temperature exceeds the condensation temp. of the fluid, heat transfer stops.  So you don't need the overtemp stat or a heat  dump of any sort.



I love it, go for it.  Just limit your first installations to "understanding" clients, friends and family.

hot_rod

679 lbs

for the small one, 1052 for the 80- gallon when filled. Better make sure the roof can handle that. More and more jurisdictions are requiring load calc for solar installs.



53 or 80 gallons of water outside in the winter doesn't sound that efficient to me?? What are the losses in 0 degree outdoor conditions?



If you have to add freeze stats and other electrical components, why not a closed loop glycol or drainback?



They are pushing this system in So. California and parts of Arizona. Very low installed cost, under $4500.00 is the target.



These are very common in warm areas of Europe and most of Israel. They build them as throw aways like we do tank water heaters. You get maybe 7- 10 years and replace the whole thing.



hr

TonyS

On the up side

These things are priced along the lines of a 6 year powervent gas water

heater of comparable size. and they have the same warranty. That alone

is a huge plus in bringing solar to the masses. Even if you had to

drain it in the winter, you still get free hot water all summer spring

and fall. Even if we have to go back and replace it every 10 years,..

thats what we do now with standard gas and electric water heaters. Im

going to order one and put it in the front yard and do some testing.

Kevin_in_Denver_2

Keep us posted

From their online information, it's unclear what's going to happen at stagnation.

TonyS

I have done some research

I started at Alibaba, the big Chinese market house. They have many manufacturers of these units in several configurations. The one from Sunmaxx has double wall vac tubes that fill with water and glycol mix as you fill the tank others use heat pipes inside the vac tubes and sealed wells on the tank. Both types are available with coils inside the tank or the tank just fills with the domestic water(warm areas only). The Sunmaxx type has a small expantion tank on the top and the domestic water flows through the coil inside the tank. I suppose if stagnation takes place the tank just boils and exits the expansion tank. It appears it is an open system on the tank side(but not sure). They may seem a little ugly but I guess beauty is in the eye of the beholder. I could see these on rooftops of city homes by the thousands, contrary to these systems that cost thousands of dollars for the well to do. Lets face it, these upscale systems we see are not going to even dent the real problem. I will keep you posted.

michael_34

Hey Tony

Do you sell SunMaxx?

TonyS

Yes

I do

TonyS

Here is a good link

http://www.alibaba.com/showroom/thermosiphon_solar_tank.html

TonyS

Here is a picture

oF flat panel thermosyphon units in israel.

Charlie from wmass

I am guessing here,,,,

But I think Israel gets a bit more sun and stays a bit warmer than western Massachusetts. I say good luck to those who can use a simple technology for green energy. I want to know what works where I am though. Whats new in solar for heating living space?

TonyS

I dont know how warm

it is there. but it must still get cold enough to require a solar panel. I lived with my crazy X#2 in Vera Cruz for a year. Our home only had a black plastic tank on the roof and the water was hot enough to burn your skin off.

Mark Eatherton

Freeze breaks....

I had a customer who once had a roof mounted "Bread Box" heater. Essentially a 40 gallon tank, painted flat black, inside a triple glazed super insulated box. Worked like a champ in the summer, but froze and broke almost annually. The tank was OK, but the 3/4" copper supply and return lines, which were insulated with 6" thick foam insulation, would freeze and break. Her insurance company finally quit paying for the damage and told her to remove or disable the system or lose her coverage for water damage.



We yanked it off the roof at her request.



I wouldn't mind using one of these for my Summer cabin. Makes great sense. Just don't forget to drain it out (which I do every fall anyway...)



Reminds me of the drain down collectors of yore. To a fault, almost every one I saw had had some freeze issues at one point of time or another, and some of them were under glass, which on a 2-1/2 story building, in the middle of the winter was a TOUGH repair to form.



We finally adopted the term "FREEZE down" as opposed to drain down. Too many things to go wrong, and too many moving parts.



Proceed with caution...



ME

Slimpickins

Drain downs

Ahhh yes,  I remember the SunSpool Drain Down Valve's. 

michael_34

Tony

In all due respect...

No more sales pitches please.

Michael

TonyS

Michael, your way off base

I dont sales pitch anything, especially to these guys. I was refering to sunmaxx because that is the brochure that I had and posted. I am a one man show, not that I havent put a few apprentices through the school. If I do two boilers a month, Im good to go. Most of my customers are or become personal freinds. Will I install some Sunmaxx units this year? Maybe. Depends how many mini- splits I sell. Everything  I sell is installed in my own home or shop, Prestige 110, Climatemaster w/w/ geothermal,Navien tankless, SunMax 40 tube drainback system, GE water equipment, Samsung minis. This equipment is whats remaining. The pile of junk after 20 years after building this place is much larger, I wont mention those units. In larger shops when something fails, they send out a tech and eat a few bucks. If I get a callback, its more than a few dollars, its my time.. that we all have way to little of. Time I could be spending with my Wife or family. I wont let anyone steal that from me.  Trust me , youll never here me sing the hip hip hooray song for any manufacturer, or collect points to go on a vacation. If I mention a brand here it has nothing to do with pushing that brand.  

michael_34

Tony

Sorry, but that is the way it came across. I did not take it for enthusiasm.

You have my apologize.

Michael

Kevin_in_Denver_2

Freezedown systems

In the winter, those systems wasted way too much water as well.  On a cold partly cloudy day, they might drain down a couple times an hour, probably draining as much water as they heated.



HOWEVER, tricky design problems CAN be solved through technology, and thorough testing can eliminate field failures.  In other words, a reliable draindown valve could yet be manufactured if it were the best way to heat water with solar.



Here's your analogy :   Steam boilers in 1900 were exploding and killing people by the thousands.  But the technology and benefits were so compelling that instead of abandoning that design, engineers eliminated the failure modes one by one until the death rate is now almost zero.

Mark Eatherton

Technology is the root of the problem in the first place...

You are depending on a $100 valve, or a $10 sensor, or a $120 controller to protect thousands of dollars of investment on the roof. Remember, if it is electrical or mechanical, it IS subject to failure, and usually when you least expect it.



Personally, I don't think the potential loss of equipment is worth the risk compared to the increase in efficiency.



But that is just my humble opinion.



ME

Kevin_in_Denver_2

Risk/Benefit ratio

Mark,



Everyone in the industry agrees with you about draindown systems. I don't think you can even buy a draindown valve anywhere. Like you, no one thinks the risk/benefit ratio is justified.



Back to TonyS system, which has much more potential for success. He's proposing a (low-loss) recirculation system that inherently has fewer failure modes. In fact, if he puts in a constant recirculation pump, then there are only two failure modes: 1. Power failure during freezing conditions. 2. Pump failure under freezing conditions.



The possibility of #2 could be reduced by installing redundant pumps. The probability of #1 could be reduced by having battery backup. Both failure modes are eliminated ed by eliminating any non-freeze tolerant pipe that is exposed to low temperatures.



One more reason I like Tony's strategy: I used to receive customer feedback on SDHW systems. High on the list of annoyances was a quirk of two tank systems. Two tank systems were by far the most common, because the customer's existing gas-fired tank was usually retained as the backup heat source, piped in series with the solar preheat tank.



The problem was and is that even though the solar preheat tank might be 180F, they found that their backup tank kept firing to make up for standby losses during periods of no load (like 9am to 5pm and overnight ).



One solution to that problem is to have a tiny recirculation pump that transfers heat from the solar tank to the backup tank when appropriate. In Tony's system, you'd have to make sure that you never heat the solar tank on the roof with fossil fuel, but this little pump could perform both functions of freeze protection and making up standby losses.

hot_rod

the beauty of ICS

integrated collector storage systems is they don't require pumps or electricity to operate. This and the low cost is why they are so common in many warm climate and low income area.



I'm still wondering about using fossil fueled energy to keep them from freezing, and the need of a pump to accomplish that? Seems more energy could be used to keep them safe than they harvest on many winter days. It would be interesting to data log that energy consumption.



I wonder still that a pure water drainback isn't the most efficient in cold climates. They fail safe, always. They have freeze protection power on or power off. And they have high solar radiation, low load protection.



I have a Grundfos Alpha on my 128 square foot drainback system. It runs on a 27 W power consumption. Waiting for the Grundfos ECM drainback pumps to make it to this market.



hr

hot_rod

DP

TonyS

Things went wrong today

Besides having this lousy head cold for the last 4 days, I decided to go in the yard and play catch with the dog. I looked at my panels on the roof and thought..well at least my solar system is making me some money today. Then I noticed an icicle  growing between my panels. At first I thought I just didn't tighten the union enough when I installed the system over a year ago..not so lucky! I went inside and checked the control and it showed full power to the pump and everything looked OK so I went to the second floor to check the drainback tank and didn't hear any percolating, then I noticed on the sight glass that it was completely full. I thought that was strange because I don't even have an external feed to the closed drainback loop, then my heart sank!! The internal copper exchanger inside the stainless tank got a hole. I should say the non replaceable copper exchanger! First thing I checked was the calcite in the neutralizer and it was low. The acid water had eaten the soft copper coil in the tank.  I guess  one way to fix this would be to use an external plate exchanger tied into the drainback loop on one side and a low wattage pump to the domestic tank on the other side. I'm using a Tekmar 257 control and it has the ability to cycle another pump. Any other ideas? A word of advice... if you have kids that recently turned into teenagers and have a calcite neutralizer on the well water, expect to double your calcite consumption and check it more often! Happy New Years everyone!!

Kevin_in_Denver_2

How Old?

Tony,



Sorry to hear about this.   I hope a little Silfoss will repair the panels.

How  many years has this drainback tank been operating?



Re: Sunmaxx ,   I just spoke with Chris at Silicon Solar Sunmaxx, and he said your recirculation idea could be done.   He was recommending very short supply lines (good idea).  I asked if they had an engineered control scheme for the recirculation, and they didn't.

Kevin_in_Denver_2

Sunmaxx

Tony,



How are you getting your hands on Sunmaxx product?

My email is kevdickson (at) gmail (dot) com