The technical specification (employer’s requirements) is where bankability is won or lost. This guide walks through the anatomy of a rigorous solar-plant specification — from module IEC certification and inverter grid-code compliance to transformer protection, cabling, testing and warranties — and the standards a defensible specification should reference.
Why the specification is a bankability document
Certification alone proves very little about how equipment will perform in the field, which is why a rigorous specification — not a marketing datasheet — is what protects an owner. The technical specification sets enforceable benchmarks and warranties, and gives the owner and its lenders the basis to reject non-compliant equipment. Independent technical review of the major components against the specification is standard bankable practice.
Plant concept and design basis
A good specification starts by fixing the design basis: the DC engineering (array sizing, DC/AC ratio, stringing), the AC engineering, the substation and grid-substation design, and the climatic conditions the plant must withstand. Everything downstream — component ratings, protection settings, testing — flows from these inputs, so they must be site-specific and explicit.
Solar modules
The module clauses should require the full IEC certification suite — IEC 61215 (design qualification), IEC 61730 (safety), IEC 61701 (salt mist), IEC 62716 (ammonia corrosion), IEC 61853 (performance and energy rating), IEC TS 62804 (PID), IEC TS 63342 (LETID), IEC 62790 (junction boxes) and IEC 62941 (manufacturing quality) — and set technical benchmarks for nominal power and efficiency, bifaciality, positive power tolerance, temperature coefficients, fill factor and module sorting.
Warranties deserve close reading: benchmark against a 25–30-year design life and a power warranty in the region of 90% at ten years and 80% at twenty-five, and confirm whether the warranty is written against nominal power or against minimum (nominal minus tolerance) power — the difference matters over the asset’s life.
Inverters
Inverters carry the plant’s power-quality and grid-code obligations, so the specification should call up IEC 62109 (safety), the anti-islanding standards (IEC 62116 / IEEE 1547 / UL 1741), IEEE 519 (harmonics) and explicit fault-ride-through compliance, alongside efficiency and field-experience benchmarks, testing and warranty terms. Because inverters are typically replaced every five to ten years despite headline reliability figures, the specification should also address serviceability and spares.
Transformers, cabling and monitoring
Inverter-duty and power transformers should be specified for design, construction, oil and windings, with a full protection scope — Buchholz relay, pressure-relief device, oil and winding temperature protection and nitrogen-injection fire protection — and routine, type, site and functional testing. DC and AC cabling, connectors, string-monitoring boxes and the SCADA/monitoring system complete the electrical specification, tying back to the O&M monitoring requirements.
Structures, quality assurance and testing
Mounting structures and trackers need structural design requirements plus tracker availability and stow behaviour. The specification should then set out the quality-assurance regime — a quality assurance plan, pre-dispatch inspection and factory acceptance testing, and site acceptance — so quality is verified before and after equipment reaches site. It should also constrain the module-cleaning method so operations remain warranty- and IEC-61215-compliant.