Thursday, January 13, 2011

Solar Sundays Part IX- Finishing up

We purchased Palram's twinwall polycarbonate panels from Farmtek to glaze the collectors. Since it is now the dead of winter, I brought them all inside to warm up before applying the gaskets. I sealed the top edge openings with Tyvek tape, and the bottom edge with a vapor-permeable tape supplied by Farmtek. Next, the perimeter was lined with adhesive-backed gasket strips. Back outside, I put the glazing panels up and covered the seams with cedar trim you can see, it has been a snowy winter so far. The finished solar array: The 'closet' at the far left end of the array houses the supply & return plumbing and wiring before it goes underground: The hot fluid exits the solar array at the top and connects to the 1" pex line below. The tee fitting at the top left leads to a schraeder valve for purging air from the high point of the system. The two valved tees midway down the closet are for a summer bypass loop- this is yet to be completed, but will likely lead to a heat exchanger in an outdoor shower system I'd like to build. The return water enters the array bottom right. Since I separated the 9-panel array into two 'banks', there are two separate supply lines. The two stubbed lines in the middle are for a spring/fall diverting loop which will dump excess heat into our garden beds to preheat the soil- this will be connected later. The diversion is controlled by the 3-way diverter valve at the first tee.
Inside the barn, I installed addition plumbing and controls to tie the solar system in to the existing hydronic system. My dad said it looks like "an organized Rube Goldberg project" and I can't really argue with that. I have managed to fit a 3-zone hydronic system, boiler and the solar hot water controls in about 4 square feet of floorspace...not bad. And it is actually quite simple- The solar heated fluid enters the barn through a pump (the pump is activated by a snap switch inside the first solar collector via a single-zone relay). The pump will send the hot fluid through the in-slab hydronic loops (2- 300 ft lengths of 7/8" pex tubing embedded in the concrete floor) then back to the collectors. Should the slab get too warm (say, spring and fall when not much heat is required), a thermocouple in the slab will signal an aquastat to switch a pair of 3-way diverter valves, thus bypassing the slab and sending the hot fluid to the diversion loop instead. The first diverter valve is located middle left in the photo below and the other in the closet at the collector array. Finally, the two stubbed lines at the top left are to send the hot fluid through a yet-to-be-installed DHW preheat tank. The photo below was taken as I charged the system with glycol, so the temp hoses and bucket-o-glycol are shown as well. Again, there are a lot of dangling wires since the controls for the diversion system are not yet connected, but you get the idea.Here is a shot from inside the utility room (actually just a 2 foot deep closet). The existing hydronic system is on the facing wall, and the solar branch controls are on the left wall.
SOOOO, I'm ready to flip the switch- all we need now is some sun!

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