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IEC TS 62862-1-1: Solar Thermal Electric Plants — Terminology and Classification
Standardized vocabulary and classification framework for concentrating solar power (CSP) systems
Concentrating Solar Power (CSP) represents a unique value proposition among renewable energy technologies: it combines large-scale power generation with inherent thermal energy storage capability, enabling dispatchable renewable electricity independent of instantaneous solar availability. IEC TS 62862-1-1, published in 2018 as part of the multi-part IEC 62862 series, establishes the standardised terminology and classification framework essential for unambiguous communication in the CSP industry.
IEC 62862 is a comprehensive series developed by TC 117 (Solar Thermal Electric Plants). Part 1-1 provides the foundational vocabulary, while subsequent parts address specific technologies, component testing, and plant performance evaluation.
Scope and Classification of CSP Technologies
The standard classifies solar thermal electric plants into four primary technology families:
- Parabolic trough collectors (PTC) — line-focusing with synthetic oil HTF, 350–400 °C, over 80% of installed global capacity
- Linear Fresnel collectors (LFC) — line-focusing with flat mirrors, 250–350 °C, direct steam generation
- Power tower / central receiver (CRS) — point-focusing with heliostats, 500–600+ °C, highest conversion efficiency
- Dish-Stirling systems — point-focusing dish with Stirling engine, 10–50 kWe per unit, highest optical efficiency
A common source of confusion is the conflation of “solar multiple” (SM) with “thermal energy storage hours.” Solar multiple is the ratio of solar field thermal power to power block design input; TES capacity is measured in equivalent full-load hours.
Key Terminology and Definitions
IEC TS 62862-1-1 defines over 200 terms covering the entire CSP plant. Some critical definitions include:
| Term | Definition | Unit |
|---|---|---|
| Solar field | Array of solar collectors converting radiation into thermal energy in the HTF | — |
| Solar multiple (SM) | Ratio of solar field thermal power to power block thermal input at design | — |
| Design-point DNI | Direct normal irradiance at design condition, typically 700–950 W/m² | W/m² |
| Peak optical efficiency | Maximum ratio of absorbed to incident solar power at normal incidence | % |
| TES capacity | Quantity of thermal energy storable and dischargeable at rated conditions | MWhth |
| Capacity factor | Ratio of actual annual energy to theoretical maximum output | % |
| Levelised cost of electricity (LCOE) | Ratio of total lifecycle cost to total lifetime electricity generation | USD/kWh |
Thermal Energy Storage Classification
The standard classifies storage by medium (sensible, latent, thermochemical), configuration (direct/indirect, single/dual-tank), and operational role (buffer, daily cycling, inter-seasonal). For molten-salt systems, round-trip efficiency is typically 93–97 %.
Round-trip efficiency that ignores freeze protection parasitics may overstate true performance by 10 % or more, significantly affecting LCOE calculations.
Engineering Design Insights
Standardised CSP terminology through IEC 62862 enables accurate comparison of plant designs across technologies and locations. The defined “net capacity factor” accounts for all parasitic loads including HTF pumping, heat tracing, and cooling fans, providing a meaningful performance baseline for EPC contracts.
Frequently Asked Questions
Q1: What is the difference between “solar multiple” and “capacity factor”?
A: Solar multiple is a design ratio; capacity factor is an annual performance metric.
A: Solar multiple is a design ratio; capacity factor is an annual performance metric.
Q2: Which CSP technology has the highest operating temperature?
A: Central receiver (power tower) systems achieve 500–600 °C with molten salt, up to 1 000 °C with air receivers.
A: Central receiver (power tower) systems achieve 500–600 °C with molten salt, up to 1 000 °C with air receivers.
Q3: How does the standard handle hybrid CSP/PV plants?
A: IEC 62862 provides terminology for “solar share” and “dispatchability factor” for hybrid configurations.
A: IEC 62862 provides terminology for “solar share” and “dispatchability factor” for hybrid configurations.
Q4: What is the typical round-trip efficiency of molten-salt thermal storage?
A: 93 % to 97 % for well-insulated two-tank systems, including thermal losses but excluding parasitic loads.
A: 93 % to 97 % for well-insulated two-tank systems, including thermal losses but excluding parasitic loads.
