Sealed vacuum tube solar heater, any experience?

[4JawChuck]

I have found this mfg really close to me and the concept seems ideal especially in my Canadian climate where air temps don't get above 20C for much of the day until June or so, doe anyone have experience with this system or similar? The price certainly looks reasonable, $400 for each panel and a much smaller footprint too!

http://www.wsetech.com/poolheaters.php

Comparison photo of Enersol style and WSE47 panel.

 

[JasonLion]

Vacuum tube solar heaters are usually significantly less efficient for pool heating than the usual solar mats designed for swimming pools. Vacuum tube solar is best when air temperatures are very low and you want to bring the water up to a much higher temperature than it starts at. Pool solar is normally used when the air temperature is reasonable and only a very small increase in temperature is required.

 

[4JawChuck]

I did some research on the two types trying to find a comparison of heat input over time and found the glass tube is rated at 32 500 btu's per 10 hr day (actual) and the Enersol style rubber mats are rated at 40 000 btu's per 10 hour day for the 10 ft length. Seeing as they take less room the glass tubes sure seem to be a higher efficiency. The only downside seems to be the fact they can't be used for heat rejection like a mat style can at night. Where I live heat rejection is not an issue but air temperature being below pool temp is a big one, particularly when these mat style heaters won't be doing much heating for much of our season due to the delta V problem. When run under pressure the glass tube equals the mat style in efficiency so all I need to do is run a separate pump system to keep them pressurized

I think this is an ideal product for the Canadian/Northern environment considering how much longer it could extend your season and how much quicker it would warm up your pool even on cool days in the summer, its 18C here right now but yesterday it was 28C. Since they are so close in price and modular (looks like durable construction too) I think I am going to buy these instead of the mats that are prevalent here, my neighbor across the street has 14 Enersol mats and says they don't do much until July and hence don't use the pool until then...I want to swim now!

I have never seen this style anywhere around here before so it must be new, I like the idea of being able to heat my sunroom for free with radiant floor heating in a closed cycle system for free in the winter. Making that room 4 season as opposed to 3 would be a bonus! If anyone has these glass style solar heaters I would sure appreciate you letting me know how the company was to deal with and what your experience with the product was, send me a PM if you don't want to post...having a first hand experience before I buy would be appreciated.

 

[chem geek]

You might be interested in Solar Panel Technology Comparisons. Though evaucated tube solar collectors are good for domestic hot water applications which have a lower water volume and a greater temperature differential, they are not usually as good or as cost effective as glazed panel collectors for heating swimming pools which are high volume and lower temperature differential and certainly not as cost effective as flat black mat (unglazed) panels, though these unglazed panels aren't good in cold windy climates.

Given that even the inexpensive black flat mat panels of decent quality absorb 80% of the sun's energy over the panel area, the numbers you are getting quoted for BTUs can't be right (just look at the space between the evacuated tubes even if the collector area were 100% absorbing). They are probably quoting the energy per tube "collector area", not per physical area the entire panel takes including the air and glass gaps between the tubes which are substantial (you need to look at the "gross area base efficiency"). Many of these companies try to cheat in their specs in this way and you need to compare carefully. I talk about relative efficiencies for the best panels of each type in this post in that same thread noted above.

As for the WSE47, based on this link their panel is 56.5" wide and 1.5 meters (59 inches) long (for the tubes) though including the header it's 64" long. This is 2.33 square meters and they claim a peak output of 2200 BTU/hr which is around 645 Watts (they say 586 Watts, but that's not right). Peak sunlight is around 1000 Watts per square meter so the base efficiency of these panels is 645/2.33/1000 = 28% which is downright awful so their peak output claim had better be in Canada only on a not so sunny day. Their claim of "One WSE47 is equivalent to a 4ft by 10 ft or 2ft by 20 ft unglazed collector on a sunny hot day with equivalent price." is clearly bogus since the unglazed collectors have efficiencies of around 80% on a sunny warm day and 4'x10' is 3.7 square meters. Since the manufacturer is really close to you, why don't you question them about these claims.

If you want a good panel for the pool for colder climates, consider a flat glazed panel. It'll use an intermediate fluid (that won't freeze) and heat exchanger, but will have high efficiency on sunny days for faster heating and should be about half the price of the evacuated tube panels for the same area though the price of the WSE47 is pretty decent.

Richard

 

[4JawChuck]

Thanks for the input Richard.

The quoted outputs are for Saskatchewan and are actual values as tested by the mfg at their location. The values are low because of the low sun angle here up north, the output values are actual numbers for a single collector as constructed...not an estimate. I am seriously thinking of going with this system due to the ability to use the system to more than just heat my pool, heating my sunroom and more is a really attractive proposition for me. The fact that they work even at -40C is attractive especially since it would sit on top of my flat roof garage and I could heat that space with a radiant ceiling radiator. Heating a double garage here in Winter would cost 100's of dollars per month, free heat for me to work in there would be a bonus. Opening the pool in March or April means I could extend the season by a few months not to mention add a degree of freeze protection if there is a cold snap for the pump etc. The price being only slightly higher is really attractive considering it comes with a mount already.

I know these types of systems have little application South of the border but up here air temperatures at night and even on the odd day means those flat panel rubber collectors aren't working a good percentage of the time, the cooling aspect isn't even a factor...no one here needs to cool their pools! In the height of summer I likely could divert the system to heat my home water tank so the energy savings multiply with its diversity.

I am planning on utilizing a PLC controller to monitor the pool and it is not that hard to add a solar collector into the system and monitor and control it too. As I mentioned in a previous post this type of automation is not that common (up here at least) unless its a government facility with cubic dollars at their disposal, it seems to be more common in Europe where the cost savings are attractive for large installations. The flat plate sealed collectors I have reviewed seem to be suited primarily for domestic hot water heating with low flow rates and 3/4" NPT connections and pressurized only operation, tube collectors can operate in both modes with an associated loss in efficiency when run open high volume flow.

The closest competitor would be this company in the US whose panels cost $900 USD each but contain 50 collecting tubes as compared to 20 tubes for the WSE47, seems that they are just starting out as they make no claims as to efficiency or output but I doubt their tubes work any better than these ones. The three warranty is kind of worrying and I can tell you the shipping up here would make them a no go...doubling that price is what it would take to get them here usually.

http://www.siliconsolar.com/50-tube-project-collector-p-501178.html

My neighbor across from my backyard has 14 10' Enersol Kits installed on his roof and they are still not swimming yet but he is heating everday, it was only 2 weeks ago that it became cost effective to even turn the pump on to the collectors during the day as the air temps made them not worthwhile to run. This is a serious limitation of this type of collector for Canada. I haven't checked his pool water temperature yet but I am guessing its around 15C if its still to cold to swim.

BTW Here is an air temp graph and sunhours estimate based on historical data for my area.

As you can see air temps being over 20C only begins to be prevalent in June which makes our summers three months long at best.

 

[chem geek]

I wasn't suggesting that you use the flat black plastic mat panels since those are not good with cold air temperatures and certainly not freezing temperatures. I was suggesting that you also consider flat glazed (i.e. enclosed in glass) panels such as those from Heliodyne or other similar manufacturers. You are right that these won't work as well in well-below-freezing temperatures with cloudy sky conditions (though even the evacuated tubes are low efficiency in that situation), but you should read this article about how the evacuated tubes are almost "too good" in freezing temps since their glass doesn't warm up enough to prevent frost which then prevents sunlight from getting through the tubes.

Nevertheless, the price of the tubes you are looking at is very competitive -- just compare with a glazed flat panel so you make sure you've looked at all reasonable alternatives. You are right that if you wanted to use the same panels switched over to heat domestic hot water (i.e. 120ºF or hotter), not just for the pool, then the evacuated tubes would be better.

 

[4JawChuck]

Thanks again Richard, I really appreciate your input. I have been looking at the flat glazed collectors as per your suggestion and their efficiency is attractive especially for the hot water heating and radiant flooring application.

The only part that concerns me is flat panels seem to be geared primarily towards closed pressurized systems with heat exchangers (or stratification tanks) for pool applications, the all copper construction would appear to rule them out for direct heating not to mention the low flow plumbing connections. Tubes appear to be compatible with either application with a simple valving setup and charging with liquid coolant for the winter to utilize it for radiant heating, the two methods seem to offer close to identical efficiencies when you consider the losses from a heat exchanger when using an enclosed system and flat panels.

I need to sit down with a spreadsheet and do a cost comparison between the two systems to see which one save me the most money overall when compared over an entire year when installed as dual use. Lots of things to factor in like complexity and durability plus operating costs when running dual pumps for part of the day, having free heat in the winter for the sunroom and garage are really just icing to me...warm pool water for the lowest up front installed cost would be the overiding factor for me which is where tubes seem to excel.

The document regarding tubes in comparison to flat collectors is interesting, who would have thought that the tubes would collect frost but it makes perfect sense. There is a time period here where frost would be a problem but our deep winter temps are much much colder than 0C and frost sublimes at our temps so it wouldn't be an issue except during the fall and spring. Obviously there is no magic bullet for all applications just like everything in life. If you were really going to get serious a dual system running both types of collectors would be the ideal if a pool is part of the equation.

 

[ChiknNutz]

Anything further on this? Although we're not in Canada, we're not far from it (a couple hrs south of the Canadian border or about 40 miles north of Seattle). We have similar enough weather that I am following this with interest in something similar. So, the typical mats are of little value here, at least to expand the swimming season? We typically see winter temps of right around freezing, but have seen it dip into the teens for a few weeks, so that has to be taken into account. I also like the idea of being able to divert some to a hot water heater, though that is not the primary motivation. Anyway, hoping to hear more on this...

 

[4JawChuck]

I have set aside money for this tube heater project but I want to visit the mfg before I commit to buy. The Canadian Government has a program available to assist people in upgrading to solar but to get the grant you have to purchase and have it installed by a "certified" solar contractor...but guess what...none of them carry this brand of tube heater.

Soooo....to avoid the BS I am going to visit the factory to see the equipment, it is so inexpensive I am hesitant to put down my hard earned dollars sight unseen. Who knows I may just become a local distributor and installer myself and use my home to prove the tech if I like the company and its owner. This will likely happen this fall when I am settled in the new place and I decide on an electronic managment scheme to control the water temps in the pool and figure out whats the best way to integrate it into my garage heating and sunroom requirements, trying to stay away from heat exchangers at the present time although it may be the best scenario for a dual use system.

So many projects, so little time.

 

[solarboy]

I've just spent a bit of time fitting these systems for underfloor radiant heating and hot water heating. This industry is white hot at the moment. We had tons of problems. The glycol used in the primary circuit "creeps" meaning it finds leaks at any weak point. The systems are extremely stressed and complicated and I would only ever use one for domestic hot water. It is true that the evac tubes work better in northerly climates but I think the system is just too complicated. And unless you have a HUGE collector area it just won't be of any help. If you're seriously considering a cheap source of heat for your northern pool I would look into ground loop systems using a heat pump.