Throughout the construction phase of our work, we've been exceedingly lucky in remaining somewhat trouble-free when it came to our systems. Interestingly enough, most of the glitches have, in one way or another, involved water. If you own a home, you probably understand how water issues can be quite frustrating to solve. In our case, we've have some leaks from our water storage tanks (not ususual considering the fact that we bought them used) and we have sprung a couple of leaks in the pex tubes under our floors (always related to screwing the boards back down). But these issues have been long resolved and are in fact quite minor compared with what we faced this past week.
Tom was working one morning at the building and somehow had the intuition that something might not be right with the heating system, and decided to get online and look at the numbers for the solar panels. He discovered that although the panels themselves read 195F degrees, the water coming out of them read 64F degrees. Clearly something was wrong. Joe got onto the roof and discovered that in fact they were leaking water. Two of the panels appeared damaged.
Panels with evidence of water damage
We were, of course, puzzled by the problem. The panels had been up and running for a number of months now without a glitch. Joe put in calls to the manufacturer and to others at the Green Garage who might give us some insight. Tom also developed a page on our wiki (appropriately called Frozen Solar Panel Incident) with questions and possible scenarios.
The manufacturer suggested, not surprisingly and perhaps quite appropriately, that we replace the damaged panels with new ones. We decided, instead, to attempt to repair the damaged panels. So the next day a team got on the roof, found 3 damaged panels (instead of 2), took them down and disassembled them. They called in a representative from Expert Mechanical (who has worked with us to set up this system) and he brazed (repaired) the holes and cracks in the copper tubing.
Brazing the holes and cracks in the panels
The panels were reassembled and returned to the roof. All three panels were repaired in three hours. At this point we saw that they ran and drained properly. No issues. The cause was a mystery.
Laurie and Joe scoping the tanks
The answer didn't come until a couple of days later. Tom had asked Laurie Catey and the Sustainability Labs crew to take this on during their regular Friday session. The group spent most of Friday afternoon talking through possible scenarios, and finally got up on top of the tanks to conduct some hands-on investigation. Joe had begun to suspect a problem with water levels in the tanks, and so Laurie decided to send a small scope with camera down into the tanks to see if this was the case. Sure enough, she found the source of the problem. We think the problem was they didn't drain fully because the end of the solar panel return line was in the water. The design called for it to be above the water line to let air in the return line allowing it to drain. The probe found that the return pipe was only 0.5 - 1.0 inch above the water line. Given that we regularly lose some water (tiny tank leak) and we lost water during the panel leak, it is highly probable that in the near past that pipe was submerged in the water. With the return line in the water, the water on the solar panel supply side drained down only to the point where the suction (vacuum) from above was as strong and the weight of the returning water (the head). This caused the panels to drain to about 2 feet from the bottom of the panel...which is where the panel tubing fractures occurred. As Joe said, the problem is as if you put your finger on the top of the straw and then lifted it out of your drink ... all the water stays in the straw...the vacuum holds it up. Lift your finger and air comes in and the water falls out.
So Joe has cut the drain pipe, making it shorter, so this should not occur again. When we got the panels running again, the temperature of the 5,000 gallons of water in the tanks rose 7 degrees in one day!
The reason I'm reporting on this in such detail is not that you will ever need this specific knowledge - I doubt most of you have this sort of heating system in your homes. There is a larger issue, and it has to do with transparency and openness in solving problems. Often when systems go wrong, mechanical or otherwise, organizations tend to become inward-focused. Knowledge of the problem is not offered to the public or the larger working community until a solution has been found. In our case, we immediately put word out to an extended network and communicated the issue on our site and social networking. In the end, it was a combination of responses and skill-sets that provided the solution.
Sustainability work can be messy, and things will not always go according to plan. Some of the things we are doing are, to say the least, unusual, and so the learning curve is steep. When we committed to a continuous commissioning of this building, I think we understood that we were developing a problem-solving methodology that was also going to be non-traditional. The real beauty of this is that it's working!
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