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IEC TS 61836:2007 — Solar Photovoltaic Energy Systems: Terms and Symbols
Comprehensive Terminology and Graphical Symbols for PV Engineering
Key Insight
IEC TS 61836:2007 provides a standardized vocabulary of over 500 terms and graphical symbols used in solar photovoltaic energy systems, ensuring unambiguous communication across the global PV industry from cell research to power plant engineering.
IEC TS 61836:2007 provides a standardized vocabulary of over 500 terms and graphical symbols used in solar photovoltaic energy systems, ensuring unambiguous communication across the global PV industry from cell research to power plant engineering.
1. Scope and Importance of IEC TS 61836
IEC TS 61836:2007 is a technical specification that establishes a unified terminology and set of graphical symbols for the solar photovoltaic energy industry. As the PV sector has grown into a multi-terawatt global industry, the need for consistent terminology has become critical for international trade, system design, installation contracts, and regulatory frameworks. The standard covers terms related to photovoltaic cells, modules, arrays, balance-of-system components, system performance metrics, and testing methodologies. It also defines graphical symbols for schematic diagrams of PV systems, ensuring that electrical engineers worldwide can interpret PV system designs without ambiguity. The standard is organized into thematic sections covering device physics, cell technologies, module construction, system configurations, and performance characterization.
Scope Limitation
IEC TS 61836 is a terminology standard and does not provide performance requirements, test methods, or design specifications. Those are covered by other standards in the IEC 60904 series (PV device measurement) and IEC 61215/61730 (module qualification and safety).
IEC TS 61836 is a terminology standard and does not provide performance requirements, test methods, or design specifications. Those are covered by other standards in the IEC 60904 series (PV device measurement) and IEC 61215/61730 (module qualification and safety).
2. Key Terminology Categories
The standard categorizes PV terminology into several major groups, each corresponding to a specific aspect of photovoltaic technology. Understanding these term categories is essential for engineers working across the PV value chain, from materials research to system installation.
| Category | Number of Terms | Examples | Application Area |
|---|---|---|---|
| Fundamental photovoltaic terms | ~80 | Photovoltaic effect, band gap, minority carrier lifetime, quantum efficiency | Cell physics and material science |
| Cell and module technology | ~120 | Monocrystalline, multicrystalline, thin-film, bifacial cell, passivated emitter | Manufacturing technology |
| System components | ~100 | Inverter, maximum power point tracker, combiner box, string monitoring | BOS component specification |
| System configurations | ~60 | Grid-tied system, off-grid system, microgrid, building-integrated PV (BIPV) | System design and architecture |
| Performance parameters | ~80 | STC rating, NOCT, performance ratio, capacity factor, degradation rate | Performance evaluation and warranties |
| Testing and measurement | ~70 | I-V curve, spectral mismatch factor, flash test, electroluminescence imaging | Quality assurance and testing |
2.1 Critical Performance Terminology
Among the most important definitions in the standard are those related to PV device performance measurement. The standard defines Standard Test Conditions (STC) as irradiance of 1000 W/m², cell temperature of 25 °C, and spectral distribution corresponding to AM 1.5. The Nominal Operating Cell Temperature (NOCT) is defined for modules mounted in open-rack configuration at 800 W/m² irradiance, 20 °C ambient temperature, and 1 m/s wind speed. Understanding the distinction between STC and NOCT ratings is crucial for accurate energy yield prediction. The standard also defines key performance metrics such as maximum power (Pmax), fill factor (FF), efficiency (eta), and the temperature coefficients of current, voltage, and power.
Engineering Best Practice
When specifying PV modules for a project, always reference the temperature coefficient of Pmax (gamma, in %/°C). Modules with lower absolute gamma values (e.g., -0.30 %/°C vs. -0.45 %/°C) can deliver 3-5 % more annual energy yield in hot climates — a difference that often exceeds the module price premium.
When specifying PV modules for a project, always reference the temperature coefficient of Pmax (gamma, in %/°C). Modules with lower absolute gamma values (e.g., -0.30 %/°C vs. -0.45 %/°C) can deliver 3-5 % more annual energy yield in hot climates — a difference that often exceeds the module price premium.
3. Graphical Symbols and Engineering Applications
The standard defines a comprehensive set of graphical symbols for use in PV system schematic diagrams. These symbols enable clear communication of system architecture, from single-line diagrams to detailed wiring schematics. Proper use of standardized symbols is essential for engineering documentation, permit applications, and as-built records.
| Symbol | Description | IEC 61836 Reference | Typical Application |
|---|---|---|---|
| Single PV cell | Basic photovoltaic cell symbol with arrow indicating light incidence | Symbol 06-01-01 | Cell-level schematic or equivalent circuit |
| PV module | Module symbol with multiple cell symbols enclosed | Symbol 06-01-02 | Module-level diagrams and layout plans |
| PV array | Array symbol combining multiple modules with series/parallel notation | Symbol 06-01-03 | System single-line diagrams |
| Inverter | DC/AC converter with standard power conversion symbol | Symbol 06-02-01 | Power conversion section of schematics |
| Combiner box | Junction box with multiple string inputs and protection devices | Symbol 06-02-04 | String combiner in array field layouts |
| Bidirectional meter | Net energy meter with bidirectional arrow notation | Symbol 06-03-02 | Grid interconnection point diagrams |
3.1 System Configuration Terminology
The standard provides precise definitions for different PV system configurations. A grid-tied system is defined as a PV system that operates in parallel with the utility grid and may feed energy into the grid. An off-grid system (standalone system) operates independently of the utility grid and typically includes energy storage. A hybrid system combines PV with other generation sources such as diesel generators or wind turbines. Building-integrated PV (BIPV) refers to PV modules that serve as both power generators and building envelope components. Understanding these definitions is critical for specifying appropriate system designs and for regulatory compliance with interconnection standards and building codes.
2.3 PV Module Technology Terminology
The standard provides specific terminology for the major PV cell technology categories. Monocrystalline silicon cells are defined as cells fabricated from a single crystal silicon ingot, typically using the Czochralski method. Multicrystalline (polycrystalline) cells use cast silicon with multiple crystal grains. Thin-film technologies include amorphous silicon (a-Si), cadmium telluride (CdTe), and copper indium gallium selenide (CIGS). The standard also defines emerging technologies such as heterojunction (HJT) cells combining crystalline and amorphous layers, and back-contact cells where both electrodes are on the rear surface. Each technology definition includes the characteristic device structure, typical efficiency ranges, and distinguishing performance features.
Common Misunderstanding
A frequent source of confusion is the distinction between “rated power” and “nameplate power.” IEC TS 61836 defines rated power as the maximum power output under STC as measured by a calibrated testing laboratory, while nameplate power is the value marked on the module label. These values should agree within measurement tolerances (±3 % per IEC 60904), but nameplate values may be subject to positive sorting tolerance (e.g., “0 to +5 W”) that should not be confused with actual performance.
A frequent source of confusion is the distinction between “rated power” and “nameplate power.” IEC TS 61836 defines rated power as the maximum power output under STC as measured by a calibrated testing laboratory, while nameplate power is the value marked on the module label. These values should agree within measurement tolerances (±3 % per IEC 60904), but nameplate values may be subject to positive sorting tolerance (e.g., “0 to +5 W”) that should not be confused with actual performance.
4. Frequently Asked Questions
Q1: Why is IEC TS 61836 important if it does not provide performance requirements?
Standardized terminology is foundational to every other PV standard. Without a common vocabulary, performance specifications, warranty terms, and test reports would be open to misinterpretation. For example, the term “module efficiency” can refer to aperture area, total area, or cell area efficiency — the standard explicitly defines each variant to prevent ambiguity in commercial transactions.
Q2: How does IEC TS 61836 relate to IEC 60904 and IEC 61215?
IEC TS 61836 provides the terminology and symbols used in all other PV standards. IEC 60904 covers measurement principles and procedures, while IEC 61215 specifies module design qualification and type approval. All three use the common terminology established in IEC TS 61836 to ensure consistent interpretation of test methods and results.
Q3: Are the graphical symbols in IEC TS 61836 compatible with general electrical symbol standards?
Yes. The PV-specific graphical symbols defined in IEC TS 61836 follow the conventions of IEC 60617 (graphical symbols for diagrams) and IEC 61082 (preparation of documents used in electrotechnology). This ensures that PV system diagrams can be integrated into larger electrical system documentation without symbol conflicts.
Q4: Has the standard been updated to cover newer technologies like PERC, TOPCon, and HJT?
IEC TS 61836:2007 was published before the widespread commercialization of PERC (passivated emitter and rear cell), TOPCon (tunnel oxide passivated contact), and HJT (heterojunction) technologies. Engineers working with these technologies should refer to the latest industry terminology documents and the most recent revisions or amendments to the standard for updated definitions.
