Vacuum tube solar collectors

[mlappin]

So what are peoples experience with em?

Worth the added cost over a flat panel collector?

I’ve been looking into them pretty heavily, would like to install some my self, then if happy offer em to my customers.

 

[jebatty]

Evacuated tube hot water solar collectors can work very well ... and can be a nightmare. Disregarding the cost, really important are the design, the control system, and an ability to use all the hot water the system may produce. The system with which I have experienced is a 300 tube array which was to meet the need for DHW for a large campus environmental learning center, including kitchen facilities, with an annual average of about 10,000 visitors, day and overnight. Even though professionally designed, with participation of a rep from the maker of the tubes, and professionally installed, the system suffered from repeated failures. Following a major redesign, adding additional equipment, and reprogramming the controller, the system has performed well. The redesign was a last effort in an attempt to make the system work before deciding to scrap the system entirely.

Search this forum with the key words "evacuated tube" and member "jebatty" for detail on my experience.

 

[peakbagger]

Run away !

Despite there always being a "new improved design every year" the tubes tend to fail frequently after a few seasons. Companies will honor the warranties for a few years and then go out of business or make the replacement process . Dealers get caught in between with upset customers when they cant get replacements. In snow areas, the snow tends to cover them over and take longer to clear off. Its too bad as the potential benefits are great but the durability isnt there.

When a tube fails its usually is not obvious. The system performance usually degrades slowly and most people dont realize it. A thermal scanner will identify bad tubes. I have heard of several installations that were under performing, when scanned 1/3 to /12 of the tubes had failed.

The upfront capital cost effectively makes SHW a loser compared to installing grid tied PV and a Heat pump hot water heater. If you want a flat plate system, keep an eye on used units. Flat plates are pretty simple and many will last a long time if properly installed and maintained. Usually the controls and heat exchangers fail long before the collectors do. I see good flat plates on craigslist for sale all the time as roofers usually convince home owners to take them down when re-reroofing. They are fairly easy to test if you a have bucket of fittings to seal up the collector inlet and outlet. All you need to do is charge them up with air with a pressure gauge and then see if they leak down. If the system wasnt maintained the antifreeze can go acidic and eat the collectors from the inside out. The leak test will pick that up. If they leak walk away. There is also a very critical check valve in many systems, if it fails the system can reverse thermosyphon on a cold night and freeze the fresh water side of the heat exchanger.

I have a flat plate system that has run for 15 years, I run straight off the panels for around 7 months a year in NH and then switch over to preheating my incoming water when the temps drop.

 

[mlappin]

Sounds disappointing at best. I suppose actually finding a brand thats manufactured domestically is either near impossible or cost prohibitive?

My plan was to ground mount em right behind my G200 and use it for thermal storage during the summer.

I’m kinda weird about stuff being mounted on my roof, no matter how well done, its still a potential leak in the future. With most or all gas appliances being forced draft and thru the wall anymore, when we roofed the house the chimney came off and I made DirecTV ground mount the satellite dish as I wasn’t having any holes in a new roof.

 

[georgepds]

You might consider solar pv alone. Here are the reasons:

http://www.greenbuildingadvisor.com/blogs/dept/musings/solar-thermal-really-really-dead

Solar Thermal Is Really, Really Dead
A new analysis shows how much cheaper it is to heat water with PV modules than with solar thermal collectors



"Solar thermal buffs make the argument that solar hot water systems are simple, elegant, affordable, and delightful. I sympathize with their emotional attachment to these systems, and I wish them all the luck in the world. However, most people I know who have installed solar thermal equipment have a tale or two involving maintenance headaches. (If you are a hobbyist, these technical glitches are sometimes exciting to solve. If you are an average homeowner, however, these glitches are just ordinary headaches.) Owners of PV systems are much less likely to have as many stories of maintenance problems."

Read more: http://www.greenbuildingadvisor.com...olar-thermal-really-really-dead#ixzz4vQdc07b0
Follow us: @gbadvisor on Twitter | GreenBuildingAdvisor on Facebook

 

[peakbagger]

I cant dispute the prior post. I have flat panels and they work but I cant in good faith recommend them to someone given the alternatives.