IEC TS 62796:2013
(Main)Energy efficiency in electroheating installations
Energy efficiency in electroheating installations
IEC/TS 62693:2013(E) is applicable to industrial electroheating installations using electric energy as input, alone or in combination with other kinds of energy. However, external combustible fuel energy input is not dealt with, and all considerations begin at the electric only mains frequency source to which the installation is connected. Any external voltage transformation from the supply network to the plant into a special voltage which is fed into the installation is not dealt with in this Technical Specification, since it is not considered a responsibility of the manufacturer of the installation.
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IEC/TS 62796
®
Edition 1.0 2013-05
TECHNICAL
SPECIFICATION
Energy efficiency in electroheating installations
IEC/TS 62796:2013(E)
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IEC/TS 62796
®
Edition 1.0 2013-05
TECHNICAL
SPECIFICATION
Energy efficiency in electroheating installations
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
Q
ICS 25.180.10 ISBN 978-2-83220-855-7
Warning! Make sure that you obtained this publication from an authorized distributor.
® Registered trademark of the International Electrotechnical Commission
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CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope and object . 6
2 Normative references . 6
3 Terms and definitions . 6
3.1 General concepts . 7
3.2 Equipment, operations and workloads . 7
4 General aspects of energy efficiency measurements in electroheating . 9
4.1 General . 9
4.2 Instrumentation . 9
4.3 Ambient conditions and initial temperature of the workload . 9
4.4 Non-ambient pressures . 10
4.5 Chemical reactions . 10
4.6 Cooling and heat leakage to ambient . 10
5 Workload categories and requirements . 10
5.1 General . 10
5.2 Use of workloads for comparative tests . 11
5.3 Use of normal workloads for enthalpy determination . 11
5.4 Use of dummy workloads for enthalpy determinations . 11
5.5 Use of performance test workloads . 11
6 Measurement of electric power and ancillary energy factors . 12
6.1 Measurement of cold start-up energy consumption and time . 12
6.2 Measurement of hot standby power . 12
6.3 Measurement of pressurising and depressurising energy consumption . 12
6.4 Measurement of holding power . 12
7 Measurement of efficiencies . 13
7.1 General . 13
7.2 Measurement of electric-only conversion efficiency . 13
7.3 Measurement of electroheating energy consumption and efficiency . 13
8 Energy recovery . 13
8.1 General . 13
8.2 Temperature and pressure of the fluid . 14
8.3 Hot fluid heat capacity performance factor . 14
8.4 Calculations of thermal recovery in the process . 14
8.5 Determination of external energy recoverability . 14
8.6 Calculation of the endoreversible thermal efficiency for a heat engine
(exergy) . 15
9 Aspects of management of operation flexibility (smart grid connectivity) . 15
9.1 Load management and smart grid . 15
9.2 Applicability to electroheating installations . 15
9.3 Tune down times . 15
9.4 Shut-down and start-up capability evaluations . 16
Bibliography . 17
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TS 62796 © IEC:2013(E) – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ENERGY EFFICIENCY IN ELECTROHEATING INSTALLATIONS
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
The main task of IEC technical committees is to prepare International Standards. In
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• 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 62796, which is a technical specification, has been prepared by IEC technical
committee 27: Industrial electroheating and electromagnetic processing.
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The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
27/882/DTS 27/903/RVC
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 publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site 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.
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TS 62796 © IEC:2013(E) – 5 –
INTRODUCTION
This Technical Specification (TS) was prepared by a working group of IEC TC 27, whose
overall intent was to develop guidelines for the classification of industrial electroheating
systems, which allow for the determination of the performance/efficiency of a given system
and a comparison with other systems of that class.
The initial technical considerations suggested that TC 27 should at first limit its focus on
determination of energy consumption for a defined output of processed workload. The next
step should then be consideration of performance characteristics influencing the energy
efficiency, such as metallurgical or thermal processing particulars. However, during the
course of the work, it turned out that comparisons of performance can best be made by
specifying different workloads for different kinds of comparisons.
Measurements of efficiencies are split into two main categories: electrical-only and of the
electroheating in normal operation. The latter has a relationship to other performance aspects
which are also dealt with.
Testing requires specification limits on workload and three kinds are defined:
– normal workloads – i.e. such within the specifications provided by the manufacturer;
– dummy workloads – artificial items specially designed to very efficiently absorb the
available output power without being processed or modified as the normal workload, and
by that promoting the accuracy of enthalpy increase measurements;
– performance test workloads – artificial or partially artificial workloads specially designed
for discrimination of processing results.
The TS provides general methods for determination of the efficiency of electroheating
systems and is intended to assist in creating a consistent terminology and structure in various
TC 27 test standards dealing with specific equipment types. The TS material is to be covered
1
.
by the future third edition of IEC 60398 [3]
___________
1
Numbers in square brackets refer to the Bibliography.
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ENERGY EFFICIENCY IN ELECTROHEATING INSTALLATIONS
1 Scope and object
This Technical Specification is applicable to industrial electroheating installations using
electric energy as input, alone or in combination with other kinds of energy. However, external
combustible fuel energy input is not dealt with, and all considerations begin at the electric
only mains frequency source to which the installation is connected. Any external voltage
transformation from the supply network to the plant into a special voltage which is fed into the
installation is not dealt with in this Technical Specification, since it is not considered a
responsibility of the manufacturer of the installation.
The object of this Technical Specification is to provide methods for determination of the
efficiency of a given system as well as enabling comparisons with other equipment using the
same principle for processing of the workload.
For satisfactory comparisons to be possible, differences in end product quality and influences
of environmental factors on heat recovery are included.
Heat recovery aspects are dealt with but limited to the temperature changes, the specific heat
capacity characteristics, and the physical properties of the usually fluidic substance obtained
from the installation and employed for energy recovery use. Conversion into mechanical
energy is dealt with.
Adaptation to the needs of operation and performance management as might be necessary
for the implementation or application of smart grid technologies, is addressed but no test
methods are given.
A guideline is provided for the development of the detailed electroheating efficiency tests for
the particular test method standards. The different principles of electroheating for processing
a workload, and types of equipment, are given in Clause 1 of IEC 60519-1:2010.
If energy from combustible gases or liquids is used in addition to electric energy, the
measurement and calculation of the energy efficiency contribution of combustion in the
installation are made according to the relevant ISO standards. These may deal with the
electric energy input in other ways than in this Technical Specification.
NOTE The relevant standards in the ISO 13579 series are listed in the Bibliography [4 – 7].
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60519-1:2010, Safety in electroheating installations – Part 1: General requirements
3 Terms and definitions
For the purposes of this document, terms and definitions given in IEC 60519-1:2010 and the
following apply.
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TS 62796 © IEC:2013(E) – 7 –
NOTE General definitions are given in IEC 60050, International Electrotechnical Vocabulary [1]. Terms relating to
industrial electroheat are defined in IEC 60050-841.
3.1 General concepts
3.1.1
enthalpy increase
sum of energy added through heating of an object and the mechanical work of expansion of it
done in pushing against the ambient (atmospheric) pressure
Note 1 to entry: The energy of the mechanical work of expansion is stored in the surroundings and can be
recovered if the system collapses back to its initial state.
3.1.2
exergy
maximum fraction of energy in a system including a medium at an initial temperature T which
1
can be converted into useful work during a process at the end of which the system
temperature is T
0
Note 1 to entry: This is the theoretical quantity related to the endoreversible thermal efficiency of a heat engine.
3.1.3
heat engine
system that performs the conversion of thermal energy into mechanical work by bringing a
working medium from a high temperature state to a lower temperature state
Note 1 to entry: In the context of this document, the mechanical work is either used directly with an external
generator to create electricity, or with a second external heat engine operating in the heating mode for increasing
the temperature of a part of the hot medium, for further use.
3.1.4
energy recoverability
usefulness of a hot substance obtained in or from a process for providing energy back into the
process or to an external purpose
Note 1 to entry: The usefulness depends on the temperature and ease of handling of the hot substance, and on
the temperature of the recipient.
Note 2 to entry: Transformation into mechanical energy by heat engines is a separate item.
Note 3 to entry: Transformation into chemical energy is not included.
Note 4 to entry: Any heat of combustion of the substance is excluded.
3.2 Equipment, operations and workloads
3.2.1
ambient conditions
environmental conditions
characteristics of the environment which may affect performance of a device or system
EXAMPLE Pressure, temperature, humidity, radiation, vibration.
3.2.2
equipment capacity
measure of the production rate capability of equipment in normal operation
EXAMPLE Flow, mass or volume.
Note 1 to entry: The equipment capacity does not refer to the volume of the working space.
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3.2.3
equipment class
group within a type of equipment, using the same principle for processing of the workload and
the size of this as well as the equipment capacity
Note 1 to entry: An example of type is equipment for induction heating, and a class example is such equipment
for metal wire heating in a specified capacity interval, using medium frequency.
3.2.4
efficiency,
ratio of the usable enthalpy increase in the workload to the electric energy supplied to it at the
location of the equipment, during a cycle of batch operation or stationary operation during a
suitable time period for measurements
[SOURCE: IEC 60050-841:2004, 841-22-70, modified – Enthalpy increase in the workload is
specified instead of useful energy, and measurement time limits have been added.]
3.2.5
performance,
degree to which the intended functions, including energy or power consumption and output as
well as the result of the treatment of the workload are accomplished
3.2.6
end product quality
degree to which a set of inherent characteristics of a processed workload fulfils requirements
3.2.7
power factor
under periodic conditions, ratio of the absolute value of the active power P to the apparent
power S
Note 1 to entry: This is applied to the supply network under normal operation.
[SOURCE: IEC/TS 62257-12-1:2007 [2], 3.4, modified – Note 1 to entry has been added.]
3.2.8
cold start-up
process by which the equipment is energised into hot standby operation from the cold state,
including all other start-up operations which enable the equipment to run under normal
operation
Note 1 to entry: This mode of operation applies to cases where there is a significant energy consumption needed
for obtaining a state of the equipment allowing the actual processing of the workload, see 6.1.
3.2.9
holding power
electric power consumption during which the workload is kept in the treatment chamber at a
specified temperature
Note 1 to entry: The temperature is typically maintained during a time intended to equalize the workload
temperature.
Note 2 to entry: This mode of operation is not applicable for certain types of electroheating equipment.
3.2.10
hot standby operation
mode of operation of the installation occurring immediately after normal operation
Note 1 to entry: This mode of operation of the equipment is with its hot state remaining, without workload, and
with the means of operation ready for prompt normal operation.
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TS 62796 © IEC:2013(E) – 9 –
3.2.11
normal operation
range of output settings with the normal workload in allowable working conditions of the
equipment, as specified in the manufacturer’s documentation
3.2.12
normal workload
object being processed at nominal output power, as specified in the manufacturer’s
documentation
Note 1 to entry: The workload is called charge in some electroheating contexts.
Note 2 to entry: The workload includes any container, holder or other device necessary for the processing and
which is directly or indirectly subjected to the output power. The processed object/material as such is also called
load.
3.2.13
dummy workload
artificial item with known thermal properties, designed for accurate enthalpy increase
measurements by absorbing the available output power
3.2.14
performance test workload
artificial or partially artificial workload designed for discrimination of processing results
Note 1 to entry: Examples of such results are relative slag content, relative or absolute areas or volumes of
unsatisfactorily processed material.
4 General aspects of energy efficiency measurements in electroheating
4.1 General
Clause 4 deals with the instrumentation and some general non-electric factors connected with
energy efficiency measurements. Clause 5 deals with the requirements for comparative
testing, Clause 6 with measurements of electric power and ancillary energy factors, and
Clause 7 with the measurements of efficiencies.
4.2 Instrumentation
Electric instruments shall be of class 2 or better. Other instrumentation shall allow
measurement inaccuracies of maximally 2 %, with the exception of measurements of
quantities having only a small influence on the overall power/energy data, and for workload
enthalpy increase.
It may be unavoidable to accept inaccuracies exceeding 2 % of the enthalpy increase under
conditions addressed in 4.4 and 4.5, as well as for large solid workloads. Specifications on
instrumentation and accuracy requirements on those quantities shall be stated in the test
method standard for the particular type of equipment.
4.3 Ambient conditions and initial temperature of the workload
Ambient conditions, in particular the temperature, will influence the energy efficiency, and
even more so the need for integrated or ancillary cooling or preheating equipment. The
energy recoverability is also affected.
Installations of the same type and class may thus be different depending on the specified
ambient conditions, in particular with regard to the limits of specified ambient temperature at
nominal power operation. Also the initial temperature of the workload is important in many
cases and its variations shall be considered. Satisfactory comparison of installations requires
specification and report of these variations and of the ambient conditions throughout the tests.
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Construction differences with regard to cooling and heat recovery between installations or
equipment to be compared shall be stated in the calculations and test report.
The ambient conditions are of importance for the use in external recovery of energy, since a
lower ambient temperature provides an improved efficiency of heat engines. This is dealt with
in Clause 8.
4.4 Non-ambient pressures
4.4.1 The energy of compression or liquefaction of gaseous fuels – and of other gases
including oxygen, other oxidants and passive gases such as inert gases – shall not be
included in the used and lost energy calculations of the equipment if the compression has
taken place external to the equipment.
4.4.2 The energy of compression or decompression of steam, air or any other gas in the
process chamber, including vacuuming, integral to the process, shall be included in the used
and lost energy calculations of the equipment.
4.5 Chemical reactions
The exothermic or endothermic chemical energy involving any reactive gases in the
processing of the workload shall be either included or not included, as stated in the test
method standard for the particular type of equipment.
4.6 Cooling and heat leakage to ambient
4.6.1 The cycle of batch operation for the measurement shall begin after hot standby
operation.
4.6.2 The cooling action by any excess reactive and/or inert gases in the processing of the
workload shall be included in the calculation of used and lost energy of the installation.
4.6.3 Any cooling of the processed workload to ambient or for further treatment shall not
be included in the calculations of used and lost energy of the installation, unless a significant
part of this heat is transferred back into the process. Such recycling of heat shall be reported
separately, to allow comparisons with other equipment in the same class but without this
feature.
5 Workload categories and requirements
5.1 General
Satisfactory comparisons under normal operation are typically possible only within the same
equipment class. A likely condition is then that the manufacturer’s specifications allow for
some deviations in workloads and settings so that comparative tests can be made with
workloads being identical with respect to the process. If that is not the case, comparisons may
be deprecated but equipment with a very narrow equipment capacity interval is by that
declared to have a performance disadvantage.
With many processes, the end result will not be directly related to an overall enthalpy
increase of an actual workload. There are three basic cases, described in the following and
using one of the following:
– a normal workload,
– a dummy workload or
– a performance test workload.
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TS 62796 © IEC:2013(E) – 11 –
The reliance on the manufacturer’s specifications is motivated by safety and by the principle
that the equipment shall be allowed to do its best. The manufacturer is therefore referred to in
the definitions of normal operation and normal workload. Since the specifications of the
dummy workload and performance test workload are typically not by the manufacturer, safety
precautions shall be observed by the party or parties carrying out the tests.
5.2 Use of workloads for comparative tests
For comparative tests, the workloads shall be equal and chosen within the manufacturer’s
specification limits for normal operation. The same workload category and amount shall be
used throughout. This includes any container, holder or other device which is directly or
indirectly subjected to the output power and then removed from the equipmen
...
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