patrick stadelmann, empa 17. september 2019 · 2019. 9. 18. · metrology for hydrogen vehicles...
TRANSCRIPT
Metrology for Hydrogen Vehicles
Patrick Stadelmann, Empa
17. September 2019
Outline
1. Introduction
2. Testing device to determine accuracy of meters and dispensers
3. Test campaign of hydrogen filling stations in operation
4. Preliminary conclusions and recommendations
Outline
1. Introduction
2. Testing device to determine accuracy of meters and dispensers
3. Test campaign of hydrogen filling stations in operation
4. Preliminary conclusions and recommendations
Background on hydrogen flow metering
Hydrogen supplied can vary up to 875
bar in pressure and between -40°C to
ambient temperature during refuelling
Unknown mass of
hydrogen is lost
during venting
Flow meters in the
refuelling station
must be accurate to
1% (OIML R 139-1)
Refuelling stations
cannot cost their
customers with
required accuracies
Background on hydrogen flow metering
• Up to now the sale of H2 without certified flow meter is tolerated by the authorities
(demonstration projects, limited group of users)
o By entering the commercial phase with extension of the HRS network, uncalibrated sales of
H2 cannot be tolerated anymore
• Until beginning of 2018, no certified reference testing device in Europe to
determine the global accuracy → of meters and dispenser
Hydrogen accuracy classes
• Revision of the OIML R139 standard for gaseous dispenser
o New version approved and published in Oct 2018
o Accuracy classes have been largely discussed and revised:
→ Class 2 & Class 4 have been created for hydrogen service
→ In principle Class 2 is accepted for future stations, whereas Class 4 is tolerated for existing stations
Note: Class 4 seems to be tolerated in France for a limited period only
Outline
1. Introduction
2. Testing device to determine accuracy of meters and dispensers
3. Test campaign of hydrogen filling stations in operation
4. Preliminary conclusions and recommendations
Hydrogen field test standard
• Testing device designed and manufactured by Air Liquide and Metas
Air Liquide reference testing device Metas reference testing device
Design of METAS testing device
Composite tanks
Housing (ESD plastic)
Hydraulic system
High precision scale
Design of METAS testing device
• Main characteristics
o High precision scale: resolution 0.05g, Ex-certified
o Composite tank of 2x36L (i.e. 3.0 kg of H2 at 700 bar, 15°C)
o Mobile test bench to be moved on each HRS
o Housing (ESD plastic) as protection against wind:
o Stable measurements, even with wind conditions
o Several nozzles to flood the housing with inert gas to limit
possible ice build up
o Improved depressurization system:
o Depressurization time (from 700 to 20 bar): 1h30 to 1h45
o Possibility to lift the frame from the scale for transport
o Valve panel to inert tank with N2 for transport
Outline
1. Introduction
2. Testing device to determine accuracy of meters and dispensers
3. Test campaign of hydrogen filling stations in operation
4. Preliminary conclusions and recommendations
Specific constraints
• Installation on site:
o Trailer must not move for the whole test campaign
o HRS must remain accessible for car fueling
o Preparation work ahead on HRS layouts
o Safety issues must be taken into account (safety
perimeter)
• Needs / Data recording
o Electrical power for the scale
o Nitrogen bundle/bottles
o Data expected from the HRS
Tests performed
• Accuracy tests
o Series of tests:
o 1 full fillings 20-700 bar Automatic stop
o 1 partial fillings 20-350 bar Manual stop
o 1 partial fillings 350-700 bar Automatic stop
o 4 MMQ fillings (1kg) with different starting pressure (450bar – 20bar – 180bar – 350bar) – Manual stop
o This series of tests is performed 4 times
Note: filling time is quick (around 3 min), but
depressurization time is very long:
→ 1h45 + time to prepare cylinder for the
next filling (de-freezing)
Tests performed
Remark:
The tests performed in this test
campaign are more exhaustive than the
ones required by OIML R139, but also
more severe…
Specificities of HRS tested
Remark:
The CFM is located in the container, far from the dispenser
Test results
Measured accuracies
Discussions
• Influence of distance between CFM and dispenser
Advantages: stable working conditions of the CFM (low
variation of pressure and temperature)
Disadvantages: far from the transfer point (errors induced due
to the CFM location)
Discussions
• Influence of distance between CFM and dispenser
o Situation at beginning of a fuelingMass of H2 (pressure P1):
not counted but given to the customer
→ Depends on end pressure of previous filling
(independent of the customer)
Discussions
• Influence of distance between CFM and dispenser
o Situation at end of a fuelingMass of H2 (pressure P2):
counted but not in the customer tank
→ Depends on end pressure given by SAE J2601
protocol (automatic stop) OR manual stop decided
by the customer OR abnormal stop (fueling error)
Vented quantity: counted, but not
in the customer tank
Discussions
• Influence of distance between CFM and dispensero If P1 ~ P2: the customer pays exactly the quantity delivered in his tank ● Full fillings 200-700 bar
o Initial mass of H2 is replaced by the same quantity at end of fueling ● MMQ (1kg) 450-700 bar
m_delivered ~ m_invoiced
o If P1 > P2: the customer get more hydrogen than the quantity invoiced ● Partial fillings 20-350 bar
o Initial mass of H2 is replaced by a lower quantity at end of fueling ▲ MMQ (1kg) 20-180 bar
m_delivered > m_invoiced (negative error)
o If P1 < P2: the customer get less hydrogen than the quantity invoiced ● Partial fillings 350-700 bar
o Initial mass of H2 is replaced by a higher quantity at end of fueling ★ MMQ (1kg) 180-350 bar
m_delivered < m_invoiced (positive error) MMQ (1kg) 350-580 bar
Discussions
Measured accuracies
Outline
1. Introduction
2. Testing device to determine accuracy of meters and dispensers
3. Test campaign of hydrogen filling stations in operation
4. Preliminary conclusions and recommendations
Conclusions
• Good reliability of the testing device in real conditions
• Influence of the measuring system configuration (distance between the CFM and
the nozzle):
o The greater the pressure difference in the pipe at the beginning and end of the refueling
process, the bigger the error
• Recommendations:
o Reduce as much as possible the volume between CFM and the nozzle
o Knowing the precise volumes, errors can be calculated and corrected
Next steps
• Conclusions to be completed with upcoming results
• Deep analysis of all measurements (fueling data,
environmental conditions etc.)
• Deliverable (D1) – «Good practice guide describing
calibration and validation of flow meters used at HRSs for
quantifying hydrogen dispensed into vehicles»
→ For further details, refer to https://www.metrohyve.eu
Thank you for your Attention!
Empa – Swiss Federal Laboratories for
Materials Science and Technology
@Empa_CH