A solar concentrator can be built from three kinds of salvage: mirror glass cut into tiles and glued onto a bowl, polished aluminium sheet bent over a curved frame, or a satellite TV dish covered with either. Glass mirror reflects about 95% of sunlight and well-polished aluminium 80-90%, so mirror glass gives the most heat, while sheet metal is the easiest to shape into a trough.
Part of Concentrated Solar Power
Salvage reflectors are mirrors and curved bodies recovered from ruined buildings and vehicles and rebuilt as solar concentrators.
Pick The Reflective Material First
The material limits both the reflectance and the shape you can make:
| Material | Reflectance (parent page) | Shape it can take |
|---|---|---|
| Glass mirror | about 95% | Small flat tiles; cut with a glass cutter |
| Polished aluminium | 80-90% | Bends into a trough; scratches easily |
| Mylar film | reflective; wrinkles badly | Stretched over a frame; short-lived |
Every 5 percentage points of reflectance is 50 W of lost power per square metre of mirror at 1,000 W/m². A tiled glass dish of 1.77 m² at 95% reflects 1,680 W; the same area at 80% reflects 1,420 W, 260 W less.
The shape follows the metal. A flat sheet bends easily in one direction, which makes a trough (Polished Sheet Metal). It cannot bend into a bowl without wrinkling, so a dish needs either a ready-made bowl (Satellite Dish Conversion) or many small flat tiles that approximate the curve (Mirror Tile Parabola).
Where The Pieces Come From
Mirrors and curved reflectors are found in cars, bathrooms and shops (Glass, Mirrors, Lights & Reflectors); lifting glass out whole is covered in Glass Salvage & Handling. Satellite dishes sit on abandoned buildings. Aluminium sheet comes from signs, roofing and printing plates.
What You Need
- Reflective material — mirrors, aluminium sheet or a dish
- Adhesive that survives heat and sun (Mirror Tile Parabola)
- Gloves, eye protection, a glass cutter
- A frame or mount strong enough to hold the reflector against wind
- A test target — a card on a stick
- A cover — an opaque sheet or tarp
Method: Choose A Route
Step 1: Count what you have. A large dish plus mirrors points to a tiled dish. Aluminium sheet and timber points to a trough.
Step 2: Build the support and the mount first, because the reflector will need to move.
Step 3: Fit the reflective surface; test the focus with a card, never your hand.
Step 4: Make the cover before first use, so the reflector can be shaded the moment you step away.
Common Mistakes
- Starting with the reflective surface. An unfinished concentrator lying in the sun is already dangerous.
- Cheap adhesive. Common silicone degrades in sun; the parent page calls for high-temperature RTV silicone or epoxy rated for 200°C or more.
- Skipping the wind plan. A dish or trough catches wind like a sail.
Safety
A reflector under construction is already a hazard
Even a half-covered mirror bowl focuses sunlight enough to burn skin, ignite tinder and damage eyes permanently and painlessly. Keep a cover within reach from the first tile, never look at the focus or at the reflection of the sun in the mirror, and wear gloves and eye protection when cutting glass. Tempered glass shatters when cut.
What’s Next
- Learn next: Satellite Dish Conversion — the fastest route to a dish
- Combine with: Accuracy & Focus Testing — checking what you have built