Solar Fans


This step in the solar kiln construction process will probably be much simpler for most of you than the following process. The empty, city lot where I keep my equipment and do all of the milling does not have electricity. I have very limited space at my house for a kiln and moving the lumber back and forth would be added, unnecessary work. Having electricity run at the log lot would be an added, ongoing expense that I just couldn't justify. The obvious answer for me was to run solar powered fans.

Hours of internet searches turned up the same solar attic fans that it seems everyone is selling. Unfortunately, these are priced in the $300 to $400 range. They are typically rated for 800 cfm and run off a 10w panel. Luckily I found an alternative at Home Depot. The GAF Masterflow solar gable fan includes a 10w panel and is rated for 500 cfm (not that I believe any of these manufacturers' ratings) and cost $179. If the flow ratings are correct, then the price per cfm isn't much different between the fans. However, I felt having more fans would more evenly distribute the air flow through the lumber stack. I bought three.

This is the box to look for on the shelf Here's what you get - the fan, motor, & housing; some basic brackets for the fan; 10w solar panel & mounting bracket and about 8 ft of wiring 10w panel and adjustable mounting bracket
The included fan mounting brackets are simple angles that are bolted through predrilled holes in the fan housing. But when they are installed, the brackets extend past the face of the fan housing. To minimize any air gaps, I wanted the fan housing to extend just beyond the face of the fan deck plywood or at least flush with it. The brackets as supplied could mount to the back of the fan deck but that would leave a substantial gap between the fan housing and fan deck. Because of the bracket bolt head and the close fit between the fan housing and the fan deck, it wasn't possible to screw the brackets to the front of the fan deck. To fix this minor issue, I simply drilled new holes for the brackets further back on the fan housing so the brackets could be screwed directly to the back of the fan deck while some of the fan housing fit through the fan deck opening.
Here is the mounting bracket installed in the supplied bolt holes.  Note how far the mounting bracket extends past the face of the housing This shows both the stock bracket location along with the newly created bracket location A view of the mounting brackets from the rear of the fan deck
A view of a fan mounted with the housing sticking through the fan deck plywood

The supplied brackets for the photovoltaic created another set of minor problems. The brackets were intended to lift the panels up off an already sloping roof. My plan was to install the panels to the vertical surfaces at the front of the solar kiln. There just wasn't enough "lift" to get the panels out to approximately 45° to optimize solar capture. Two separate modifications were made. One to make the brackets functional and one just because I wanted to.

The first modification was to remove the mounting brackets, drill a couple new holes in the pv panel frame and remount the panel to the brackets after rotating them 90°. The only reason I turned the panels sideways was to reduce how far they stuck out from the front of the kiln, since the panels are rectangular not square. Yeah, I know, it's a goofy reason to add more work, but I like it better this way.

The second modification was to make some new, longer connector bars that span the distance between the panel itself and the mounting bracket on the front wall of the kiln. Using some spare aluminum I had laying around, I carefully and slowly cut out strips on the table saw (man, I hate cutting aluminum on the table saw), drilled some end holes, rounded the corners, and cleaned up the edges on my edge sander. The longer brackets allow mounting the pv panels at an angle equivalent to the kiln roof line. I experimented some by making a couple additional bars of varying lengths. The thought was, I may use the longer bars in the summer to get more adjustment in the panels so they lay almost horizontal and capture more sun. Likewise, the shorter bars will allow the panels to adjust to almost vertical since the sun lies lower in the winter sky.

Mounting the pv panels to the kiln wall was a simple matter of nailing some left over treated 3/4" plywood strips to the studs, then screwing the pv panel mounting brackets to the plywood strips. The mounting location on the front kiln wall should allow rain to run from the roof directly onto the pv panels while keeping the wires and attachments under the panels dry. At one point I had considered mounting the panel to the higher portion of the roof, but it occurred to me that there was no good reason for that. Mounting the panels to the front of the kiln made it very easy to install and it makes it easy to access the panels for cleaning.

The original pv panel mounting bracket The original connector bars and the bracket that attaches to the back of the panel The connector bars and bracket were riveted together.  Here are the separate pieces after drilling out the rivets
The original connector bar on the far left and three longer variations that were made The mid-length bar gets the panel out to about 45 degrees when mounted to a vertical surface Another view of the new connector bar in use
Plywood nailer strips attach to the front wall studs while the pv panel mounting bracket is screwed to the nailer strip All three pv panels installed All three pv panels and all three fans installed
The wiring included with the fans are "plug and play". The pv panels are prewired with an eight foot length of wire and a connector. These connectors mate to a connector prewired to the fan motor. Luckily, there was just enough length in the wire to reach from the front of the kiln to the fan motors..... barely. The panel connector and wire was fished under the polycarbonate and over the wiggle foam to get into the kiln. I then ran each wire on the underside of the closest rafter, up and over the fan deck, and then attached to the fan motor connector. As soon as the single connection was made, the fans started spinning.
Wire running under the polycarbonate and over the wiggle foam Backside view of the fans and the fan motor connectors Another backside view of the fans
Here you can see the fans are running and the routing of the wires on the bottom of the rafters Another view of running fans and wire routing
 
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