LONGi Hi-MO X10 Scientist LR8-66HVD 640–665W — N-type HPBC 2.0 Module at up to 24.62% Efficiency

The LONGi Hi-MO X10 Scientist LR8-66HVD is a 640–665W N-type module built on HPBC 2.0 back-contact cells with a busbar-free 0BB front, reaching 24.62% module efficiency in the 665W version — currently the top tier of what is commercially available. This is the panel our engineering team specifies when a Phuket villa or hotel roof simply does not have the square metres for a lower-efficiency module. See how it fits into a complete design on our services page, compare it against other modules under equipment, or get a first estimate of the system size you need with the calculator.

What exactly is the LR8-66HVD, and how does back-contact differ from an ordinary panel?

On a conventional panel, silver fingers and busbars run across the front of every cell to collect current, and every one of those lines shades the silicon underneath it. HPBC 2.0 moves all the electrical contacts to the back of the cell and removes the front busbars entirely — that is what 0BB means. More of the light that lands on the glass actually gets converted, which is how LONGi reaches 24.62% module efficiency on a panel that still measures a standard 2382 × 1134 × 30 mm. In practical terms: the same roof area gives you more kilowatts. The module is a glass-glass build using 2.0+2.0 mm semi-tempered glass front and back, with a 75±5% bifaciality factor, so the rear face contributes real output when the panel is elevated or sits above a light-coloured surface. The trade-off is mass: 33.5 kg per module, which your roof structure has to carry. The specification that matters most in a tropical climate is the Pmax temperature coefficient of -0.260 %/°C — lower than the Hi-MO X6 Max and Hi-MO 7 families, meaning less output is lost on a hot afternoon. If you are still deciding between technologies and budgets, our page on solar cost in Phuket explains where the money actually goes, and hybrid with battery backup covers what changes if you also want protection from outages.

Highlights from the datasheet

• Nothing shading the cell face: with all contacts on the rear and no front busbars, the module presents a uniform black surface that captures light across its full area — the direct route to 24.62% efficiency at 665W, and to needing fewer modules for the same array size.
• Temperature coefficient of -0.260 %/°C: the label rating is measured at 25°C, a temperature a Phuket rooftop passes early in the morning. Each degree above that costs only 0.260% of output — better than LONGi's own HPDC and HPBC+ families, and that small margin compounds into real kWh every single day.
• 75±5% bifaciality: the rear face produces roughly three-quarters of the front when it receives reflected light. That is worth paying for on elevated rooftop racking, light concrete decks or ground mounts — but flush-mounted on tile it earns very little, and we will tell you which case you are in before you order.
• Long, slow-degrading warranty: 15 years on the product itself, plus a 30-year linear power warranty — no more than 1% loss in year one, then 0.35% per year, so year 30 must still deliver 88.85% of nameplate output.
• 5400 Pa front / 2400 Pa rear mechanical load: hail-tested with 25 mm ice balls at 23 m/s and rated for operation from -40°C to +85°C, which comfortably brackets Andaman monsoon conditions provided the mounting clamps follow the manufacturer's installation zones.
• DC1500V system rating: IP68 junction box with 3 bypass diodes, Protection Class II, IEC Class C fire rating, and a maximum series fuse of 35A — the figure that determines how many strings can share one protective device.
• The numbers that drive the design: the 665W version delivers Vmp 41.28 V / Imp 16.11 A and Voc 50.02 V / Isc 16.78 A at STC. That current level is well above older-generation panels, so DC cable, connectors and inverter MPPT channels must be rated for it — a detail cheap installations routinely get wrong.

Key specifications (LR8-66HVD 640~665M)

Note: every figure above comes straight from the LONGi Green Energy Technology Co., Ltd. (隆基绿能科技股份有限公司) datasheet. Actual system design (strings per MPPT, cable sizing, breakers) must be calculated for each site.

Why this model suits Phuket

• Heat, all year: Phuket modules almost never operate near the 25°C STC reference condition, which makes the -0.260 %/°C coefficient more relevant to your electricity bill than the headline wattage.
• Roof space is the real constraint: pool villas and hotels typically offer several small roof planes plus a plant-cluttered flat deck. At 24.62% efficiency, you fit meaningfully more capacity into whatever usable area exists.
• Monsoon wind and rain load: the glass-glass construction rated at 5400 Pa front and 2400 Pa rear, together with the IP68 junction box, is built for the wind and standing-water conditions the west coast sees each year.
• Partial shade is normal here: LONGi states that the soft-breakdown design of HPBC 2.0 reduces shading-related power loss and hotspot heating. On Phuket roofs shaded morning and evening by coconut palms, water tanks and extract stacks, that behaviour matters more than a spec sheet suggests.

Who it suits

• Hotels and resorts: properties maximising daytime bill reduction from a fixed roof area, with concrete or steel structures that carry a 33.5 kg glass-glass module without reinforcement.
• Rental pool villas: where air conditioning, pool pumps and water heating run precisely when the array produces most, and the owner wants an asset backed by a 30-year power warranty.
• Homes with small roof planes: houses with only a few square metres of well-oriented pitch that still need enough kW to move the monthly bill.
• Restaurants and commercial buildings: daytime-load businesses that consume nearly everything they generate, and whose flat roofs already carry partly shading plant equipment.
• Ground-mounted and elevated arrays: installations over light-coloured concrete or gravel that can actually collect on the 75±5% rear-side gain.

Summary

The LONGi Hi-MO X10 Scientist LR8-66HVD 640–665W is the module to choose when your limiting factor is available roof area rather than module count — 24.62% peak efficiency, a -0.260 %/°C temperature coefficient and a 30-year power warranty. The honest trade-off is the 33.5 kg glass-glass weight per module, which is why we survey your roof structure before finalising any layout. Start with the calculator for a rough system size, review what a full installation includes under services, and then contact our team for a site visit and a design matched to how your property actually uses power.

See other models from this brand on the LONGi overview, or browse all the equipment we install.

Download the datasheet (PDF) — full manufacturer specification sheet