IEC TS 62862-1-2:2017

Solar thermal electric plants - Part 1-2: General - Creation of annual solar radiation data set for solar thermal electric (STE) plant simulation

IEC TS 62862-1-2:2017(E) defines the procedures for the creation of annual solar radiation data sets (ASR) for solar thermal electricity (STE) plant simulation. This document defines procedures needed for the ASR construction as well as its components and parameters. The scope of application of this document refers to the needs associated with solar thermal power plant projects and mainly related to the simulation of an annual period with a solar radiation sum close to a normal annual value (from among an estimation of all possible annual values).

General Information

• Status: Published
• Publication Date: 28-Nov-2017
• ICS: 27.160 - Solar energy engineering
• Technical Committee: TC 117 - Solar thermal electric plants
• Drafting Committee: PT 62862-1-2 - TC 117/PT 62862-1-2
• Current Stage: PPUB - Publication issued
• Start Date: 29-Nov-2017
• Completion Date: 22-Nov-2017

Overview

IEC TS 62862-1-2:2017 provides a standardized methodology for creating an Annual Solar Radiation (ASR) data set for use in solar thermal electric (STE) plant simulation. The Technical Specification defines the elements, components and procedures needed to construct an ASR - a functional equivalent of a Typical Meteorological Year (TMY) - that represents a single year with solar radiation and related meteorological variables close to the long‑term normal for a project location.

Key topics and requirements

• Scope and purpose: ASR generation for STE plant engineering and annual production simulation (not intended for extreme-event analysis).
• Elements of an ASR: geographic and time identification (location, time reference, time frequency), required variables (mandatory solar radiation measures and associated meteorological parameters), and data format.
• Procedures for ASR generation:
  • Measurement campaign guidance, including station setup, recommended variables and metadata.
  • Quality control methods and routines (checking physically possible values, detecting outliers, coherence between radiation variables).
  • Validation and gap filling to handle missing or inconsistent records.
  • Study of representative long‑term value using one or multiple data sources to establish normal annual solar radiation.
  • Generation of representative series (procedures based on measurements or estimates) to assemble a year (commonly 8,760 hourly records) representative of long‑term conditions.
• Reporting requirements: documentation of methods, data sources, quality checks and assumptions.
• Informative annexes: measurement station recommendations, station equivalence, and detailed quality‑control procedures.
• References include related resource methodologies (e.g., historical TMY development) and standards such as ISO 9488 for radiation terminology.

Applications and who uses it

• STE plant designers and simulation engineers use ASR data sets to model annual electricity output, thermal storage performance and plant controls.
• Resource assessment consultants and project developers rely on standardized ASR datasets for bankable energy yield estimates and feasibility studies.
• Researchers and policy makers use ASR-based simulations for techno‑economic studies and grid integration analysis.
• Software vendors for solar simulation tools implement ASR formats and quality procedures to ensure consistent inputs.

Related standards

• Part of the IEC 62862 series on Solar Thermal Electric Plants.
• Cross‑references terminology in ISO 9488 (solar radiation, irradiance/irradiation).

Keywords: IEC TS 62862-1-2:2017, annual solar radiation data set, ASR, STE plant simulation, typical meteorological year, solar resource, measurement campaign, quality control, data gap filling.

Standards Content (Sample)

IEC TS 62862-1-2 ®
Edition 1.0 2017-11
TECHNICAL
SPECIFICATION
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Solar thermal electric plants –
Part 1-2: General – Creation of annual solar radiation data set for solar thermal
electric (STE) plant simulation
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IEC TS 62862-1-2 ®
Edition 1.0 2017-11
TECHNICAL
SPECIFICATION
colour
inside
Solar thermal electric plants –

Part 1-2: General – Creation of annual solar radiation data set for solar thermal

electric (STE) plant simulation

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.160 ISBN 978-2-8322-4978-9

– 2 – IEC TS 62862-1-2:2017 © IEC 2017
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 8
4 Elements forming the ASR data set . 9
4.1 Geographic and time identification . 9
4.1.1 Geographic identification . 9
4.1.2 Time reference . 10
4.1.3 Time frequency . 10
4.2 Variables . 10
4.2.1 General . 10
4.2.2 Mandatory variable . 10
4.2.3 Other variables . 10
4.3 Format . 11
5 Procedures and methodology for ASR generation . 11
5.1 General . 11
5.2 Measurement campaign . 12
5.2.1 General . 12
5.2.2 Quality control . 12
5.2.3 Validation and gap filling . 12
5.3 Study of the representative long-term value . 13
5.3.1 General . 13
5.3.2 One source . 13
5.3.3 Several sources . 15
5.4 Generation of the representative series. 17
5.4.1 General . 17
5.4.2 Procedure based on estimates . 17
5.4.3 Procedure based on measurement campaign . 17
6 Report . 18
Annex A (informative) Expression and relationships between formats of types of time . 20
Annex B (informative) General recommendations for measurement stations . 22
Annex C (informative) Equivalence of measurement station locations . 23
Annex D (informative) Quality control of measured data . 24
D.1 General . 24
D.2 Procedure 1: checking for physically possible values . 24
D.3 Procedure 2: checking for extremely rare values . 25
D.4 Procedure 3: checking for coherence of radiation variables . 25
Bibliography . 26

Figure 1 – Sections of ASR generation procedure . 12

Table 1 – Direct solar irradiance place label values . 11
Table 2 – Table format for the estimation of a representative long-term value based on
one data source . 14

Table 3 – Table format for estimating the representative long-term value from several
different data sources . 16
Table D.1 – Quality control procedure 1 – Physically possible values . 24
Table D.2 – Quality control procedure 2 – Extremely rare values . 25
Table D.3 – Quality control procedure 3 – Coherence of variables . 25

– 4 – IEC TS 62862-1-2:2017 © IEC 2017
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SOLAR THERMAL ELECTRIC PLANTS –

Part 1-2: General – Creation of annual solar radiation data set
for solar thermal electric (STE) plant simulation

FOREWORD
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The main task of IEC technical committees is to prepare International Standards. In
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Specification when
• the required support cannot be obtained for the publication of an International Standard,
despite repeated efforts, or
• the subject is still under technical development or where, for any other reason, there is the
future but no immediate possibility of an agreement on an International Standard.
Technical Specifications are subject to review within three years of publication to decide
whether they can be transformed into International Standards.
IEC TS 62862-1-2, which is a Technical Specification, has been prepared by IEC technical
committee 117: Solar thermal electric plants.

The text of this Technical Specification is based on the following documents:
Enquiry draft Report on voting
117/67/DTS 117/77/RVDTS
Full information on the voting for the approval of this Technical Specification can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 62862 series, published under the general title Solar thermal
electric plants, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC website under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• transformed into an International standard,
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
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– 6 – IEC TS 62862-1-2:2017 © IEC 2017
INTRODUCTION
During the various stages of planning, design and start-up of a solar thermal electricity (STE)
plant, engineering and economic studies often require the simulation of plant power
production, and an analysis of the response of its various components and systems. All these
simulation studies use precise, organized and standardized information of the solar resource
and other meteorological variables.
As a one-year period includes the most important meteorological cycle, the response of a
power plant is simulated for a complete year, and attempts to achieve results that can be
extrapolated to the long term. The need therefore arises for a complete year of data for the
meteorological variables that influence plant operation and provide a response to solar
thermal power plant simulation studies. This standard year of data, which is known as the
typical meteorological year (TMY), serves for both annual plant electricity production studies
and engineering studies associated with a solar thermal power plant project, except for
studies on extreme events.
The meteorological information for a specific place, especially knowledge of the solar
resource, is always subject to uncertainty. Furthermore, this information comes from quite
different sources and its availability is very irregular. Therefore, in order to generate a typical
meteorological year, a standard, characteristic methodology is used which ensures its
operability in the framework of solar thermal power plant projects, and offers adequate
support for decision-making in this type of project.
This functional typical meteorological year as defined by this document is hereinafter called
the annual solar radiation (ASR) data set.
Precise knowledge of the solar resource available is important for the design and
development of any system that intends to make use of the energy from the sun. The large
non-determining component of solar radiation and the need to simulate the response of a
solar system in the long term have led to the development of a methodology for generating a
reference year that includes information on diurnal and seasonal variations in the
meteorological variables involved as well as their long-term averages.
The typical meteorological year that has made this name best known was developed at
Sandia National Laboratories [4], and employed part of the SOLMET/ERSATZ (1951-1976)
database [5] made up of 248 stations of which 26 provide solar radiation measurements and
the rest estimated data, for the US and adjacent territories. This TMY was built up from the
concatenation of typical months to form a year with 8 760 hourly records. Each month was
selected by evaluating nine variables: the mean, maximum and minimum temperature and
dew point temperature, maximum and mean wind speed and global horizontal radiation. A
weighted sum of the Filkenstein-Schafer statistic [5] [6] was used, resulting in the selection of
five months. The final choice of the typical month considered the long-term persistence of
climate patterns.
Although various authors have proposed slight variations in the Sandia methodology, in
essence it remains practically unaltered in the generation known as TMY2 and TMY3 [5] [7].
TMY version 2 employs data from the National Solar Radiation Database (NSRDB) from 1961
to 1990, with 93 % of the data estimated by models and 7 % from data measured for
239 locations. The records include measurements of associated meteorological variables
___________
In this document, the term solar radiation is used as a generic reference to the "radiation emitted by the Sun"
(as is defined in ISO 9488:1999, 3.13), and irradiance and irradiation are used as the physical magnitudes
defined in ISO 9488:1999, 3.4 and 3.5 respectively]. On the other hand, these references notwithstanding, in
2 2
this document, it has been agreed to express irradiance in W/m and irradiation in Wh/m .

such as temperature, humidity, cloud cover and visibility. The solar radiation measurement is
present at 52 NSRDB stations, but the measurement period is short.
The TMY version 3 was produced using hourly solar radiation data and meteorological data
from 1 454 stations, from NSRDB database time series (1961-1990) and its update, consisting
of NSRDB station time series (1 %) and a dataset estimated using the State University of
New York (SUNY) model based on geostationary operational environmental satellite (GOES)
images for an eight-year recording period (1998-2005).
Finally, it should be mentioned that there are other methodological proposals that differ
somewhat more from the National Renewable Energy Laboratory (NREL) TMYs, involving
other variables, with a variety of statistics and even proposing the collection of typical
meteorological data for only a few days a month instead of a whole year.
As the data necessary for generating the TMYs mentioned above are not available in the
locations of most STE plant projects, a procedure is defined for the creation of an annual
solar radiation data set for the plant simulation that standardizes the procedures currently
used for this.
In this document, a set of procedures are presented. Only the minimal requirements of these
procedures are described even when there may be additional considerations that will be more
than welcome during the application of the procedures, but there may be times that they will
not be available and the inclusion in this document will block the option of following it.
It is important that all the proposed methodologies use a measurement campaign with well-
defined quality characteristics during a whole year and at least containing direct solar
irradiance (G ) measurements in the expected location.
b
Two options are proposed to generate the annual solar radiation data set depending on the
data availability. One only uses measurements of G but in addition uses high quality G
b b
estimations during more than 10 years. This methodology is very similar to the classic TMY
but with a preliminary assessment of coherence with the local measurements. In this
methodology, the ASR could be formed by the estimations selected in the process, by G
b
measurements or by simultaneous measurements of GHI and G .
b
The other option uses G measurements as well as global horizontal irradiance (GHI); and
b
uses a methodology for GHI long-term estimation based on additional sources of information
(aimed low quality GHI estimations). In this second methodology, the ASR will always be
formed by simultaneous measurements of GHI and G .
b
Recent works, such as the creation of multiple annual solar radiation (MASR) data sets for the
simulation of a STE plant, are out of the scope of this document even when their use could be
better than the use of a unique annual data set of data for the prefeasibility assessment of a
STE plant project. At the moment of the elaboration of this document, there is not a
consensus or a relation of procedures for MASR creation.
MASR creation as well as annual solar radiation data sets referred to an annual percentile
(commonly the 10th percentile 10 of the estimated annual values distribution) could be
covered in future projects.
This document is related to works developed in the context of the International Energy Agency
SolarPACES and Solar Heating and Cooling agreements as a liaison organization of experts
in solar radiation for energy applications. Coordination with subcommittee 1 of ISO technical
committee 180 is also considered.

– 8 – IEC TS 62862-1-2:2017 © IEC 2017
SOLAR THERMAL ELECTRIC PLANTS –

Part 1-2: General – Creation of annual solar radiation data set
for solar thermal electric (STE) plant simulation

1 Scope
This part of IEC 62862 defines the procedures for the creation of annual solar radiation data
sets (ASR) for solar thermal electricity (STE) plant simulation.
In addition to the definition of procedures needed for the ASR construction, its components
and parameters will be also described.
The scope of application of this document refers to the needs associated with solar thermal
power plant projects and mainly related to the simulation of an annual period with a solar
radiation sum close to a normal annual value (from among an estimation of all possible annual
values).
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
ISO 9488:1999, Solar energy – Vocabulary
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
annual solar radiation data set
ASR
complete standardized set of solar irradiance data, which may be accompanied by other
meteorological variables considered of interest, and which attempts to establish a reference
for radiometric evolution in a specific place during the year
Note 1 to entry: This data set shall have a solar radiation sum close to a normal annual value (among an
estimation of all possible annual values).
3.2
direct measurement
value of a certain variable found with a measurement instrument on the surface at the specific
site
Note 1 to entry: Direct measurement data shall be considered to be any statistic derived from values of the same
variable that meet the above definition for a given period of time. For example, those found by the arithmetic mean
of values recorded by the corresponding measurement instrument (sensor and data acquisition system) for a given
period of time are direct measurements.
3.3
indirect measurement
value of one variable found by combining direct measurements of other variables
EXAMPLE The measurement of direct solar irradiance with a pyrheliometer directed at the sun is a direct
measurement process. On the other hand, its determination from the direct measurement of global solar irradiance
and diffuse solar irradiance is an indirect measurement involving two previous direct measurements.
Note 1 to entry: Finding direct solar irradiance from a numerical model, for example, a regression equation, may
not be considered either direct or indirect measurement.
3.4
derived data
data found from a statistical function that relates to a set of simultaneous data for different
variables at the same place
EXAMPLE Data found from regression models, such as some models for calculating direct solar irradiance from
global horizontal irradiance, are derived data.
3.5
synthetic data
interpolated data of the same variable recorded in another
space and/or time frequency
EXAMPLE All data found from spatial or temporal interpolation are synthetic data.
3.6
satellite data
data found from information collected by a measurement instrument on board a satellite
Note 1 to entry: This document distinguishes between high and low quality satellite data. High quality satellite
data refers to satellite data with a temporal resolution of one hour or less, and a maximum spatial resolution of
20 km [8]. ASR data sets could be formed by high quality satellite data.
3.7
meteorological model data
NWP
data found from models that include a numerical solution of differential equations defining the
behaviour of the atmosphere based on given initial conditions
Note 1 to entry: This document distinguishes between high and low quality data from meteorological models. High
quality data from a meteorological model refers to data from a meteorological model with a temporal resolution of
one hour or less, and a maximum spatial resolution of 20 km [8]. ASR data sets could be formed by high quality
data from meteorological models.
4 Elements forming the ASR data set
4.1 Geographic and time identification
4.1.1 Geographic identification
The WGS 84 world geodetic system standard is taken as the reference ellipsoid to define the
geographical location on lambertian coordinates.
The geographic identification of the place to which the data set refers to is determined by:
• the geodetic latitude and longitude coordinates;
• the elevation above mean sea level.

– 10 – IEC TS 62862-1-2:2017 © IEC 2017
4.1.2 Time reference
For each individual data point in the ASR, two timestamps should be given. One timestamp
should indicate the time of the value within the ASR (functional date). The other timestamp
corresponds to the time to which the original data value belongs (original date). The time in
the ASR cannot be completely defined without stating the year. In order to avoid errors and
ambiguities, the year of the ASR data set should be set to 2015. This way, the solar position
can be calculated in the same way by all users and it is clear that the ASR is no leap year.
The record date shall follow the time reference established in this document, that is, they shall
correspond to the UTC referencing system (see Annex A).
4.1.3 Time frequency
ASR data set frequency has to be hourly or higher (higher frequency corresponds to a shorter
time period). The value corresponding to the time period (one hour, ten minutes, five minutes,
etc.) may come from a high sampling frequency, which has to be an exact divider of one hour.
The corresponding record is assigned an average, maximum, minimum, or instantaneous
value for that period, depending on the variable observed. In the case of direct solar
irradiance, ASR shall at least be the average.
4.2 Variables
4.2.1 General
The ASR data set shall contain the number of records corresponding to a whole year at the
frequency of direct solar irradiance and in all available variables. There shall be records
corresponding to twelve different months from January to December, not necessarily
consecutive nor do they have to be from the same year.
4.2.2 Mandatory variable
-2
, expressed in integer numbers. In this document,
The unit for direct solar irradiance is Wm
direct solar irradiance is understood as the value of the magnitude as defined in ISO 9488,
i.e. direct solar irradiance is the radiant flux received on a flat surface from a small solid angle
centered on the solar disk, and the area of this surface, which is perpendicular to the axis of
the solid angle.
The detailed definitions of direct solar irradiance given in IEC TS 62862-1-1 should be taken
into account.
In the framework of this document, we refer to a small solid angle that corresponds to
the recommendations for new pyrheliometers from the WMO [20].
The recommended nomenclature for direct solar irradiance is G (ISO 9488), although other
b
nomenclatures commonly used for this variable are: DNI (from Direct Normal Irradiance), B
(from the term beam radiation) and I [9].
b
4.2.3 Other variables
The direct solar irradiance series may be accompanied by other variables, such as:
• global horizontal irradiance;
• diffuse horizontal irradiance;
• ambient temperature;
___________
Under preparation. Stage at the time of publication: IEC BPUB 62862-1-1:2017.

• relative humidity;
• wind speed;
• wind direction;
• atmospheric pressure.
These variables have to be reported for the same period of time and shall be in the same time
frequency (frequency as described in 4.1.3) as the direct solar irradiance and be physically
and dynamically coherent with it. That is, if ten-minute direct solar irradiance is supplied, the
rest of the meteorological variables shall also be ten-minute, and at the same time have to be
coherent with it in absolute values (physically) as well as its sequence (dynamically).
Ambient temperature, relative humidity and atmospheric pressure measurement have to be
measured with instruments not exposed to sudden changes in temperature and from vibration
and dust. Ambient temperature and relative humidity values should correspond to a height of
between 1,2 m and 2,0 m above ground level as defined in [20].
Wind surface measurements, such as wind speed and wind direction, will be referenced "at a
standard height of 10 m above open flat ground" for the exposure of wind instruments as
defined in Chapter 5, Part I, of [20].
4.3 Format
The annual series should be formatted according to IEC TS 62862-1-3.
A label showing where data are from is a parameter which gives information on the origin or
type of data of the minimum variable (direct solar irradiance) and should be included in the
data set. Depending on the origin, values would be from 2 to 7 (corresponding to definitions
3.2 to 3.7), reserving 1 for "unknown". Possible label values are summarized in Table 1. Two
label columns should be provided for each record, one associated with the original date
("label_orig") and the other associated with the functional date ("label_func").
Any data on the label associated with the functional date that are not for the annual instant to
which it corresponds (where the original date and the functional date are not identical –
except for the year) are considered synthetic, whatever the origin they are from.
Table 1 – Direct solar irradiance place label values
Data from Label
Direct measurement data 1
Indirect measurement data 2
Derived (modelled) data 3
Synthetic data 4
Satellite data 5
Meteorological model data
(NWP)
5 Procedures and methodology for ASR generation
5.1 General
The ASR generation procedure is divided into three sections (see Figure 1):
• measurement campaign;
•
...