1 · Cold return inlet
Introduces cooler loop water to the manifold/header.
Evacuated Tube Collector learning centre
ETC: efficient vacuum insulation for everyday hot water.
An ETC uses concentric borosilicate glass tubes. A vacuum between the layers suppresses convection and conduction losses while a selective coating converts sunlight into heat.
Conceptual educational cutaway—not a construction or manufacturer drawing.2 · Heated outlet
Carries absorbed solar heat toward storage.
3 · Insulated manifold/header
Collects heat from tube necks or condensers while limiting standby loss.
4 · Heat pipe option
A sealed copper heat pipe transfers heat to its condenser in the manifold.
5 · Tube seal/support ring
Supports the glass neck and reduces water, dust and abrasion at the opening.
6 · Outer glass tube
Transparent borosilicate envelope admits solar radiation and encloses the vacuum gap.
7 · Selective inner absorber
The coated inner tube absorbs radiation; the surrounding vacuum suppresses heat loss.
8 · Support frame and rail
Holds manifold and tube ends at the approved inclination and spacing.
Passive circulation
Thermosiphon: hot water rises, cold water returns.
The tank must be above the collector. Density difference drives flow without a circulation pump; large or poorly arranged piping can stop the loop through air locks and excessive resistance.
☀
HOTCOLD
COLLECTOR
↑ heated water
↓ cool return
- 1Sunlight heats the absorber or coated vacuum tube.
- 2Heat transfers into water in the collector circuit.
- 3Warmer, lower-density water rises toward the tank top.
- 4Cooler, denser water leaves the tank bottom and returns to the collector.
- 5Stratification stores the hottest water near the upper draw-off.
- 6Opening a tap draws hot water while cold make-up enters low through a diffuser.
Advantages
Why choose ETC?
- Vacuum insulation reduces heat loss in cold or windy conditions.
- Compact collector area and modular tube replacement.
- Good low-temperature solar capture with properly maintained vacuum tubes.
- Simple thermosiphon packages suit many domestic applications.
Limitations
What must be engineered?
- Glass tubes are vulnerable to impact, hail and thermal shock.
- Direct wet tubes can accumulate scale in hard water.
- Stagnation can create very high temperatures when demand is low.
- Lost vacuum, poor seals or unsafe refill can reduce life and output.
Complete setup
Accessories and what each one does.
Actual quantity, pressure class, pipe material and safety devices follow capacity, water quality, building pressure and the approved product data sheet.
Vacuum-tube bank
Absorbs solar radiation with low heat loss; tube number follows model and capacity.
Insulated manifold or tank header
Receives heat from wet tubes or heat-pipe condensers and limits standby loss.
Tube seals and end cups
Support glass safely, maintain alignment and reduce leakage or abrasion.
Cold-water diffuser
Introduces make-up water gently at the lower tank zone to protect stratification.
Temperature-pressure safety valve
Provides an engineered relief path; its discharge must terminate safely.
Magnesium anode (where fitted)
Sacrificially protects exposed steel and must be inspected as a consumable part.
Backup thermostat/heater provision
Optional project-specific backup with dedicated protection—not assumed on every system.
Flushing and scale-control points
Support sediment removal and material-compatible descaling in hard water.
Installation sequence
Survey to safe handover.
Demand, roof, shade, structure and water test
Select capacity, direct/indirect loop and tank material
Fix supports, orientation, tilt and maintenance clearance
Mount collector/tubes and tank without stressing connections
Install insulated piping, valves, vents, drains and controls
Flush, fill slowly, remove air, leak/pressure test
Verify flow direction, safety relief and temperature rise
Record settings, train user and issue maintenance plan