Encapsulating a solar panel means sealing the cells between a glass front and a backing sheet in a clear material that keeps water out, holds the cells in place and stays solid at the temperatures a panel reaches in the sun, which can pass 60°C. Clear silicone is the carrier’s first choice; beeswax melts at 62 to 64°C and shellac softens at 65°C, so neither suits, and any moisture that reaches the cells corrodes the connections within months.
Part of Solar Panel Construction
The layers of a weatherproof solar panel, the choice of clear sealant, and how to frame and test it.
A Panel Is A Sandwich That Must Stay Dry For Years
From the sun outward the layers are: glass, clear encapsulant, cells with their ribbons, more encapsulant, a backing sheet, and a frame with sealed edges, with a junction box where the wires leave. The glass admits light and protects against hail and debris; the encapsulant couples the glass to the cells, holds them in place and excludes water; the backing and frame give strength. The carrier’s warning is blunt: any moisture that reaches the cells corrodes the connections and degrades performance within months, so the seal must be complete and durable.
The Sealant Has To Survive Heat
A dark surface in the sun can pass 60°C easily (Solar Energy Fundamentals), and cells run hotter than the air around them. So the sealant has to stay solid at least that warm. The corpus gives:
- Beeswax: melts at 62–64°C (Beeswax), too close to panel temperature.
- Shellac: softens at 65°C and melts at 75–80°C (Shellac), marginal.
- Pine resin and pitch: these can be remelted and soften in heat (Pine Resin, Tar and Pitch). The carrier names pine resin as an alternative; no corpus figure says how it performs in a hot panel, and general knowledge, not from the other articles, is that resin darkens with sunlight and heat, which would cut the light reaching the cells.
- Clear silicone: the carrier’s first choice; it is an industrial product, so the usable supply is salvaged tubes, which age.
Because the corpus gives no tested figure for a village sealant in a panel, test one: make a small trial laminate of two glass pieces with the sealant between, put it in a black box in full sun with a thermometer, and look after a week for flow, clouding or yellowing.
What You Need
- Cells in strings with tabbing and bypass diodes — Tabbing Wire and Bus Bars, Bypass Diodes
- A glass cover — Glass Cover Preparation
- A clear sealant — silicone or a tested alternative
- A backing sheet — thin plywood, sheet metal or a second glass pane (carrier)
- A frame — aluminium angle or hardwood strips (carrier)
- A junction box with cable gland — Junction Boxes
Method: Build The Sandwich
Step 1: Lay the glass face-down on a clean flat surface and clean it.
Step 2: Apply a layer of sealant over the glass and lay the cell strings face-down onto it, pressing out air.
Step 3: Cover the backs with more sealant, leaving no air pockets.
Step 4: Add the backing sheet (Sealing and Backing).
Step 5: Frame the edges with aluminium angle or hardwood and seal every edge.
Step 6: Fit the junction box and strain-relieve the cable.
Step 7: Test the output in sun and the insulation to the frame before putting the panel outside.
Worked Example: Size Of A 36-Cell Panel
Assume square cells 8 cm × 8 cm (an assumed size; 62.5 cm² cells match the carrier’s 0.5 A at 4% efficiency) laid 4 across and 9 along with 3 mm gaps. Width = 4 × 80 + 3 × 3 = 329 mm. Length = 9 × 80 + 8 × 3 = 744 mm. With a 25 mm border on each side the panel is 379 × 794 mm, an area of 0.379 × 0.794 = 0.301 m². The cells cover 36 × 64 = 2,304 cm² = 0.23 m², a packing fraction of 0.23 ÷ 0.301 = 76%. At the corpus’s 1,000 W/m² and 4% efficiency, 0.23 × 1,000 × 0.04 = 9.2 W, which matches the carrier’s 18 V × 0.5 A = 9 W. The check shows the carrier’s panel figures are consistent with cells of that size.
Common Mistakes
- A sealant that softens in the sun — cells shift and ribbons tear
- Air bubbles over the cells — they shade the cell and trap moisture
- A rigid frame bonded hard to glass without a gap — thermal expansion breaks something
- Skipping the insulation test — a panel with water inside looks fine for a week
Safety
Wet cells make a live frame, and glass cuts
A panel is live in any light, and if moisture gets in, current can leak to a metal frame, so test the frame for voltage before touching. Work with the string covered or disconnected, and treat it as live regardless. Solvent and sealant fumes need ventilation; broken glass cuts and tempered glass bursts into small cubes (Glass Recovery).
What’s Next
- Learn next: Glass Cover Preparation — choosing and preparing the front glass
- Combine with: Sealing and Backing — closing the back and edges