Renewable Energy
Copper–aluminium transitions for solar, wind, BESS and EV charging systems — free of galvanic corrosion, lasting 15+ years.
The problem you need to solve
In renewable energy systems, copper and aluminium always meet — and that is precisely where failure starts. On solar module frames, the Al frame contacts the Cu earth conductor and within a few years an oxide layer builds at the joint. In DC combiner boxes, the contact resistance between Al fuse terminals and Cu busbars doubles in 3–5 years; the connector heats up and the warranty disappears. In BESS cabinets, the weld between Li-ion cell Al positive tabs and the Cu module busbar cracks under thermal cycling, increasing internal resistance by 40% after 300 cycles. In wind turbine nacelles and tower earthing, the Al/Cu transition can arc or corrode under lightning discharge. In DC fast chargers, the thermal cycle breaks the copper oxide layer, the joint loosens.
How CUPAL solves it
CUPAL is a diffusion-bonded copper-aluminium bimetal — not an alloy, not a fastener, but a single inseparable base material. Each side connects to its own metal: the copper side to the copper conductor, the aluminium side to the aluminium busbar or frame. The source of galvanic corrosion — the electrochemical potential difference between the two metals in open contact — simply disappears. The joint passes the surge current required in IEC 62305 lightning protection systems, the IEC 61400-24 LPL I lightning protection level, the busbar current density loading per IEC 61439, and the IEC 61215 PV module –40 → +85 °C thermal cycle test with unchanged contact. No grease, no spring washers, no annual re-torque needed — once installed, the joint is maintenance-free for the full design life of the system.
Measurable performance
Where it's used
Six specific applications from solar, wind, BESS and EV charging sectors.
Solar module frame to earth conductor
The problem you need to solve. The aluminium module frame contacts the Cu earth conductor (min. 6 mm² PE per IEC 60364-7-712) directly. In wet, saline coastal installations the galvanic cell oxidises the joint over 10–15 years — taking down the equipotential bonding with it.
How CUPAL solves it. CUPAL washer in the frame-lug bolted joint: Al side to the frame, Cu side to the earth cable. The bolt clamping force breaks through the Al oxide, the contact closes through each metal's own surface, and the PE bond lasts the system lifetime.
DC combiner box and string inverter DC input
The problem you need to solve. 8–32 PV strings combine onto a common Cu DC busbar through Al fuse terminals. The PV day cycle (–10 → +70 °C) causes thermal slip between the different-expansion metals, fretting corrosion starts, and contact resistance rises 50% in 3–5 years.
How CUPAL solves it. CUPAL transition shunt between terminal and busbar. One piece, M6/M8 bolted, copper side to the Cu busbar, aluminium side to the fuse seat. Per IEC 61439 1.2 A/mm² Cu capacity — no oversizing needed.
BESS cell holder and module busbar
The problem you need to solve. Li-ion cell Al positive and Cu negative tabs connect to the Cu module busbar by ultrasonic/laser welding. Brittle CuAl₂ intermetallic phase forms at the Cu-Al interface; welding cycle cracks cause 40% internal resistance increase after 300–500 cycles.
How CUPAL solves it. Pre-bonded CUPAL shim (Al side to the cell tab, Cu side to the busbar) with mechanical connection or low-temperature soldering. The intermetallic phase is avoided; the diffusion bond interface holds stably beyond 5000 cycles.
Wind turbine nacelle and tower earthing
The problem you need to solve. The generator Cu winding connects to an Al converter busbar; the pitch and yaw Al systems connect to the tower Cu earth network. At lightning discharge (LPL I: ≥200 kA, 10/350 µs), the Al/Cu joints see arcing, heating and erosive corrosion — accelerated by salt spray offshore.
How CUPAL solves it. CUPAL bonding plate (6–8 mm) at the transition points with M8–M12 bolted connection. Passes the IEC 61400-24 Annex E surge test in implementable geometry; Cu side can be soldered to the earth network, Al side bonded further to the tower structure.
PV park collector busbar system
The problem you need to solve. In medium and large PV parks, Al collector busbars connecting string converters meet central Cu collection points inside outdoor cabinets. Per IEC 61439 busbar systems, contact resistance must not increase more than 20% over 10 years of operation.
How CUPAL solves it. Custom-cut CUPAL busbar transitions (from sheet, 3–10 mm) bolted between the Cu busbar and the Al busbar. Busbar cross-sections unchanged, Cu 1.2 A/mm² current density maintainable — no need for 33% larger Al cross-section.
DC fast charger and grid connection
The problem you need to solve. Inside 50–350 kW DC chargers, Al DC switches, contactor housings and Cu power terminals require extra connectors. At 500 A, 0.5 mΩ contact resistance means 125 W heat dissipation per charge — fretting loosens the joint in 5 years.
How CUPAL solves it. CUPAL shunt (50×30×5 mm, customised) at 600 A continuous, 1200 A 10 s surge loading. One part, one bolted connection — replaces the old multi-step lug-cap-grease assembly.
Compared to alternatives
10-year operating cost and installation complexity of four common Cu/Al transition solutions.
| Solution | Initial contact resistance | Maintenance | Lead time | 10-year TCO / joint |
|---|---|---|---|---|
| Insulating washer + Cu lug + paste | 0.5–2 mΩ | New paste every 2 years | 1–2 weeks | €20–30 (labour) |
| Special bimetal lug (imported) | <0.1 mΩ | None | 6–12 weeks | €35–50 |
| Pure copper transition (oversized) | <0.05 mΩ | None | 4–6 weeks | €12–20 |
| CUPAL custom cut (EU) | <0.05 mΩ | None | 2–4 weeks | €3–5 |
Common questions from installers and engineers
Recommended CUPAL products
Applicable standards for this field
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