IOT123 - SOLAR TRACKER DOME

There are many DIY designs for solar tracker chargers, but most of them are not weather-proof. This is a big problem because most of the time, being in sunlight, means being in the weather. This instructable steps you through the process of building a dome for those solar trackers.

I will concentrate on using locally sourced products, but the method can be applied to what you have available.

Step 1: Materials and Tools

1. Plastic Pot Plant Base (290mm)
2. Clear Plastic Salad Bowl with lip (285mm)
3. 0.5mm HIPS (High Impact Polystyrene)
4. 75mm x 10mm Expansion Joint Filler
5. 4G x 6mm stainless self-tapping pan head screws (~20 off)
6. Small cable ties (~2mm wide)
7. Plastic Primer (clear)
8. UV Paint (clear)
9. Drill and ~2.2mm drill bit
10. Phillips head screw driver
11. Sharp straight pick

Step 2: Screwing the HIPS to the Base

This provides a durable collar to keep the circular membranes in shape.

Before cutting or drilling anything do a dry run and modify the dimensions to suit. Even if you source the exact class of items I have, minor manufacturing variations will impact on lengths and hole placements. The rest of the instructions assume you will do this pre-fit first.

1. Cut the HIPS to the dimensions shown.
2. Use the straight pick to create "pilot" impressions, then drill the holes with a ~2.2mm drill bit.
3. Loop the HIPS strip into a circle and fasten the 2 middle end holes together with screw from the outside to inside (temporarily).
4. Place loop over inverted plastic pot base.
5. Align bottom edge of loop and bottom edge of base.
6. Use the pick to create pilot holes in the base, where the lower holes are in the HIPS.
7. Fasten the HIPS to the base through the 8 lower holes.
8. Remove the 2 screws from the middle end holes fastened in step #2.

Step 3: Adding the Outer Expansion Joint Filler

This provides a membrane to keep water out of the dome and a seal for the bowl to sit on.

The tear-off joint on the foam should be pointed up.

Again do a pre-fit prior to cutting anything and alter as needed.

1. Cut the Expansion Joint Filler as shown above.
2. Create a loop with the cut piece, butting not overlapping this time.
3. Insert inside the HIPS with the joint opposite the HIPS joint, sliding down the wall as you go.
4. At the bottom, carefully compress the foam so it goes to the angled recess.
5. Makes sure the foam is roughly level with the HIPS and in shape.
6. Screw the 2 middle end screws (removed last step), this time through the HIPS into the foam.

Step 4: Adding the Inner Expansion Joint Filler

This provides an inner membrane to seal where the bowl sits on the walls.

The tear-off joint on the foam should be pointed down.

Again do a pre-fit prior to cutting anything and alter as needed.

1. Cut the Expansion Joint Filler as shown above.
2. Create a loop with the cut piece, butting not overlapping this time.
3. Insert inside the previous foam ring with the joint offset from the other 2 joints.
4. Force the foam down to the base.

Step 5: Adding the Dome Lid

The following step will be completed after you have installed the solar tracker.

1. Place the inverted bowl on top of the outer foam ring, with the inner foam ring inserting into the bowl.
2. Ensure the HIPS ring is aligned concentric with the bowl.
3. Mark on the lip of the bowl where the 4 top holes align, marking the HIPS joint hole for identification later.
4. Remove the bowl and place on a solid flat surcace on the inverted lip.
5. Drill the 4 holes with the ~2.2mm drill bit.
6. Replace the bowl, aligning the 2 joint holes marked in step #3.
7. Place cable ties through the HIPS to the outside of the foam into the holes in the lid.
8. All four may need to be threaded prior to tightening the cable ties.

Step 6: Painting the Dome

After the solar tracker is installed and the dome fastened, the dome may be painted to protect mainly from UV degradation. If the least maintenance in the field is a goal, this should be done. If regular maintenance field trips are expected, replacing the dome (bowl) periodically may be considered.

1. Follow all the usual precautions.
2. Apply clear plastic primer as directed.
3. Apply clear UV (resistance) paint as directed.

Step 7: Next Steps

1. Depending on your climate/humidity several holes may need to be drilled into the base for air flow.
2. The whole dome will need to be fixed in the field. A sturdy bracket can be fastened to the underside of the base, fixing to it through the base with flange washers on the topside.
3. All the usual calculations and proof-of-concepts will be needed on the current draw, battery capacity and solar collectors prior to relying on it in the field.
4. Check out the Instructable for a Solar Tracking Rig.