H2Tech - Q1 2021 - 31

INFRASTRUCTURE AND DISTRIBUTION
ondary standards could help reduce the
cost and time needed for verification.
Also present in this project are non-flow
activities such as the development of H2
fuel reference materials, guidance for the
implementation of analyzers and sensors
at H2 refueling stations, standardization of
the sampling methodology at H2 refueling
stations and the development of a harmonized protocol for fuel cell stack testing.
Flow measurement challenges for
hydrogen-based heating. H2 is also be-

ing considered for use as an alternative to
natural gas in domestic applications such
as gas boilers, cookers and fires. This can
either be in the form of H2 or blends of H2
with natural gas. H2 has the obvious advantage of producing only water vapor as
a combustion product.
Provided that the hydrogen used is
either green or blue H2, no CO2 will be
released into the atmosphere. The use of
H2 blended with natural gas does not have
this advantage but will still result in a decrease in CO2 emissions compared to using only natural gas.
Despite the advantage of an H2-only
fuel, the use of H2 and natural gas blends
should not be dismissed. In the UK, the
use of the blended gas has been investigated by the HyDeploy project, with results
showing that up to 20 mol% H2 can be
blended into natural gas and used without
any modifications to the appliances. This
may provide a suitable interim solution until appliances are modified for use with H2.
Regardless of whether H2 or blends
of H2 with natural gas are used, the accuracy requirements set out for domestic gas
flowmeters must be met to ensure the accurate billing of consumers. In Europe, the
requirements for domestic gas meters are

stipulated in the Measuring Instruments
Directive (MID), which is European Directive 2004/22/EC. This directive was
established to develop a single market for
measuring instruments throughout the EU.
Flowmeters used for domestic gas metering must demonstrate conformance to
the MID, which can be achieved in three
different ways:
* Conforming with a harmonized
standard for the measuring
instrument that has been
published in the Official Journal
of the European Union
* Conforming with parts of
normative documents that have
been listed in the Official Journal
of the European Union
* Conforming directly against
the essential requirements
described in the MID.
The most common domestic gas flowmeter used in the UK is the diaphragmtype meter. The device consists of a
housing containing four chambers, two
of which are enclosed by bellows that expand and contract as they are charged and
exhausted, respectively. Flow into and out
of the chambers is accomplished by means
of slide valves. The volume of gas passed
through the meter is obtained through a
linkage arrangement, connecting the diaphragm to a mechanical readout system
that records the number of displacements.
Diaphragm meters demonstrate conformity to the MID through the harmonized standard for diaphragm domestic gas
meters: BS EN 1359:2017. This standard
requires that diaphragm gas meters must
conform to the Class 1.5 within the MID.
In terms of flowmeter accuracy, this essentially means that the MPE is ±1.5% on initial testing, with allowances up to ±3% for

30 bar

PRV

Compressor
Electrolyzer Lowpressure
storage

Configuration 1
meter location

Pressure
ramp
High-pressure Flowmeter controller
buffer tanks
900 bar section

200 bar
200 bar
200 bar

Institute for Standards and Technology
(NIST) being the first. Four more have
been developed through the EMPIR Joint
Research project ( JRP), Metrology for
Hydrogen Vehicles (MetroHyVe) and by
several national metrology institutes and
designated institutes: METAS, Justervesenet, CESAME-EXADEBIT and VSL.
Korea Research Institute of Standard and
Science (KRISS) has also developed a
field test standard for use in South Korea.
TÜV SÜD National Engineering Laboratory is planning to build two field test
standards, one for dispensers filling lightduty vehicles and the other for heavy-duty road transport vehicles.
The MetroHyVe project partners,
which include TÜV SÜD National Engineering Laboratory, have completed a test
program to assess the potential sources of
error from the flowmeter. Effects of pressure and temperature were investigated,
along with the potential to use alternative
fluids to calibrate the flowmeters prior to
installation. Since Coriolis mass flowmeters are based on mass flow measurement,
the use of alternative fluids, such as air, nitrogen and water, would allow calibrations
to be undertaken at significantly lower
pressures and ambient temperatures while
still achieving the same mass flowrate.
Some positive results were seen in these
trials; the flowmeters tested performed well
over a range of constant temperatures and
pressures representative of those found in
a refueling station. Also, alternative fluids
were shown to be suitable for the calibration of flowmeters, removing the need to
calibrate using H2 in challenging operating
conditions and reducing the cost of calibration. Another positive result was that pressures of up to 850 bar had an insignificant
influence on flowmeter performance.
The JRP MetroHvVe II, launched in
September 2020, aims to further develop a
metrological traceable framework for testing H2 dispensing meters. One task of this
project is to develop primary standards for
heavy-duty H2 vehicles, which have a refill
of approximately 30 kg-40 kg compared
with 4 kg-6 kg for passenger vehicles. Additionally, the project will look at the development of secondary standards that are
traceable to the primary standards developed in the initial MetroHyVe project for
verification of H2 refueling stations.
As it is costly to build primary standards and time-consuming to undertake
the verification process using them, sec-

Configuration 2
-40°C meter location
precooler

Flowmeter

Discharge
valve

Cutoff
valve

Vent to
atmosphere

Hose and
nozzle

FCV

Fuel dispenser
20-700 bar

H2 MCP

FIG. 1. Schematic diagram of an example of a hydrogen dispenser. Photo courtesy of TUV SUD Ltd.
H2Tech | Q1 2021 31

H2Tech - Q1 2021

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