Solar at Last

After literally years (I bought the major components in May of 2015!), we finally have an operational solar hot water heating system. Let’s start in the basement utility room.

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The collection part of the system

Here is the 800L (211 gallons) solar hot water storage tank. I choose this size on the highly scientific principle that it was the largest one that would fit under the 7½’ ceiling. The grey box on the wall is solar pump/controller. When the rooftop panel temp is higher than the storage tank temp (and the tank is less than 145 160 °F [Updated June 1st 2017 after system fine-tuning]) it starts pumping. The insulated pipe coming out the top of the box goes to the rooftop panels where the heat is collected and comes down though the right-hand pipe, through a heat exchange coil in the tank, then back up to the box. The red thing is an expansion tank. This system is a closed loop that has a 50/50 water/propylene-glycol mix (good down to minus 39 degrees).

solar-heat-controls

The heat distribution part of the system

On the opposite wall we have the underfloor heating pump and controls. The green box on the right is the control module. When a thermostat calls for heat in any of the 3 zones, it sends a signal to the appropriate thermal actuator (the small white cylinders atop the manifold in the center of the picture. Once the actuators are open (visually you can see a blue ring at the top) the controller starts the circulator pump (on the left — it is a delta-T variable speed pump that reacts to individual zones opening and closing to maintain a constant temperature differential between the inlet and outlet). This part of the system is a open loop — it uses the water directly from the big storage tank (which also provides pre-heated water into our small electric DHW heater.

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The collector frames

Last week I completed the assembly of the three rooftop solar panel frames. Each of the three frames will hold 30 evacuated/vacuum collector tubes. Together the three frames are about 23 feet long. At the top of each frame is a manifold — this is the only part that has water running in it, to capture the heat from the tubes.

Installation begins

Monday, the contractors arrived, two guys with two ladders. The frames are unwieldy but fairly light. After some discussion we decided to take off the relative heavy manifolds and take them up separately. Here is the first frame getting fastened to the roof; rather than put any holes in our shiny new standing roof I choose specialized clamps.[/caption]

Here is the second frame being carried up the two ladders. I am working the safety rope from underneath.

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Day one done

By the close of the first day’s installation, the contractors had completed the plumbing hookup to the frames; meanwhile I got the hookups done in the utility room. I pressurized the system with 30 psi of air and left it overnight to test for leaks. It failed the test. When the contractors got here at 8am on the day two, I put them to installing the column and posts for the ramp railing (see a few pictures down), while I hooked up the submersible pump to flush the solar system and pinpoint leaks. I had two in the utility room — both cheap-ass fittings I got at the Capon Valley Market yesterday since I ended up short. I managed to crank one down enough to stop it, and for then other I had found the proper fitting and got that in. Meanwhile, since water was dripping off of the roof the contractors went up and tightened the leaking compression fittings up there.

Leaks fixed, they started in on putting aluminum tape over the rooftop foam pipe insulation to protect it from the sun, while I drained the flush water from the system and re-pressurized it with a 50% polypropylene glycol mixture. I turned on the pump controller, and we started installing the 90 heat tubes. I was on the upper veranda unpacking the tubes from the shipping boxes, smearing thermal paste on the copper condenser tips, handing each tube up to guy one who was on the ladder, who then handed them to guy two to insert in the frames. Six of the tubes were broken, but the manufacturer was pretty generous by sending 30 spare tubes (but just the tubes, I had to remove the sealed copper tube inserts and aluminum heat-collection fins from the broken tubes).

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The finished product from the front (south side)

solar-rooftop-backside

And from the back (north side). To the right you can see the newly-installed posts; the shorter two are original to the house, they were part of a handrail on the front porch. I’ve been saving them for lo these 18 years — glad to have finally found a use for them!

The system seems to be working fine, the 211-gallon solar water storage tank went from 59 degrees 96 by the end of the day. Was still at 93 this morning. (I ultimately want to get the tank to 145 160 °F [Updated June 1st 2017 after system fine-tuning].) This morning I turned on the underfloor heat in the addition, we’ll see how it does getting the room from 65 to 68. Also interested in whether the rooftop unit can glean heat on a cloudy day.

It feels very good to have this project done! (Well, except for some more pipe insulation in the utility room.)

And, as a bonus, I discovered that my Moto phone had made a highlight reel (complete with cheesy music!) of the photos and videos I took yesterday late afternoon. It was a gorgeous day to review the completed project from the vantage point of the pasture and spring run. And our livestock guardian dog Satie enjoyed it as well.

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