Centre of excellence
for low carbon and fuel cell technologies
Cenex
Holywell Park
Loughborough University
Ashby Road
Leicestershire
LE11 3TU
telephone 01509 635 750
facsimile 01509 635 751
Cenex Stornoway Hydrogen Vehicle Trial
Project Partners:
Cenex
Comhairle nan Eilean Siar (Western Isles Council)
Revolve Technologies
Royal Mail
Name
Position
Prepared
Steve Carroll and
Technical Specialist
Peter Speers
Authorised
Chris Walsh
Head of Technical Support
and Consultancy
Signature
Stornoway Hydrogen Vehicle Trial
Contents
1
Executive Summary ........................................................................................................................ 4
2
Introduction ................................................................................................................................... 6
3
Trial objectives ............................................................................................................................... 7
3.1
Vehicle and fuelling performance ........................................................................................... 7
3.2
The role of islands in the early hydrogen economy ................................................................ 7
4
Project partners ............................................................................................................................. 8
5
Methodology .................................................................................................................................. 9
6
5.1
The vehicle............................................................................................................................... 9
5.2
Vehicle certification............................................................................................................... 10
5.3
Vehicle route and duty .......................................................................................................... 11
5.4
Hydrogen fuel supply and dispensing ................................................................................... 11
5.5
Data acquisition ..................................................................................................................... 13
Trial results and discussion .......................................................................................................... 13
6.1
Initial refuelling station tests and refuelling protocol .......................................................... 13
6.1.1
Vehicle leak detection strategy and fast-fuelling .......................................................... 14
6.1.2
Vehicle refuelling at very low on-vehicle storage pressure ........................................... 15
6.1.3
Final refuelling and driving strategy .............................................................................. 15
6.2
Vehicle routes and duty cycles .............................................................................................. 15
6.3
Hydrogen refuelling data ...................................................................................................... 17
6.4
Vehicle distance travelled and fuel consumption data ......................................................... 17
6.5
Vehicle and fuelling station availability................................................................................. 18
6.6
System efficiency analysis ..................................................................................................... 19
6.7
Emission analysis ................................................................................................................... 20
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6.8
7
Usability ................................................................................................................................. 21
Trial outcomes and next steps ..................................................................................................... 21
7.1
Publicity and dissemination .................................................................................................. 21
7.2
Hydrogen vehicle certification .............................................................................................. 21
7.3
Vehicle improvement ............................................................................................................ 22
7.4
Future Revolve trial activity .................................................................................................. 22
7.5
Future activities in the Outer Hebrides ................................................................................. 22
8
Abbreviations ............................................................................................................................... 22
9
Acknowledgements...................................................................................................................... 23
10 References ................................................................................................................................... 23
11 Enquiries....................................................................................................................................... 25
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1 Executive Summary
This report details the trial of a hydrogen powered light goods vehicle conducted in Stornoway, Outer
Hebrides, Scotland in July-August 2010. The trial involved the use of a demonstration Ford Transit converted
by Revolve Technologies to a bi-fuel petrol/hydrogen internal combustion engine (HICE) vehicle operated by
Royal Mail on two delivery routes out of its Stornoway delivery office over a six week period. Hydrogen fuel
was provided by Comhairle nan Eilean Siar (Western Isles Council) via its H2seed facility. H2seed generates
renewable hydrogen by feeding electricity generated by a biogas engine to an electrolyser. The trial sought
to examine the reliability, ease of fuelling and usability of the vehicle and fuelling regime, and the suitability
of the HICE vehicle in fleet operation.
Islands offer an ideal bounded model of the operation of a future hydrogen economy. Stornoway is the
largest town and administrative centre of the Western Isles, an island chain off the west coast of Scotland,
and the Western Isles Council is seeking to exploit the region’s natural resources, particularly wind and
marine energy, to avoid dependence on imported fuels and energy, and as a driver of economic
regeneration.
In order to operate a hydrogen vehicle on UK roads during the trial a Vehicle Special Order (VSO) was
obtained from the UK Department for Transport. In order to obtain the VSO for the trial Revolve certified
the vehicle’s compliance with regulation 2007/46/EC (EU framework for type approval of motor vehicles and
trailers) and UNECE GRPE 2004/3 (Draft United Nations Economic Commission for Europe Working Party on
Pollution and Energy Uniform Provisions concerning the approval of (a) Specific components of motor
vehicles using compressed gaseous hydrogen (b) Vehicles with regard to the installation of specific
components for the use of compressed gaseous hydrogen).
As the trial involved the first use of the Stornoway facility to refuel vehicles, pre-trial work was needed to
commission the station and establish a suitable vehicle refuelling regime. This led to two recommendations
for operation during the trial: firstly, due to limitations identified with the hydrogen leak detection strategy
employed by the vehicle, the hydrogen tank was only filled to around two-thirds of its rated capacity of
4.5kg; and secondly, the vehicle was fuelled with hydrogen at the end of its daily duty and the hydrogen fuel
left to equilibrate overnight before operation. Both of these steps were necessary to avoid a false triggering
of the vehicle’s major leak alarm.
The trial period monitored by Cenex involved 19 trips (17 rural, two urban) either completely or partially
fuelled by hydrogen for a total of 723 miles. The refuelling station was not available for four working days
during this period due to issues with the dispensing system. Efficiency of hydrogen use on the rural route
was around 19miles/kgH2, giving an extrapolated hydrogen-only range (based on a full tank of 4.5kg H2) of
85miles. By contrast, the hydrogen consumption on the urban route was 12miles/kgH2, giving an
extrapolated range of 55miles.
Production of one kg of hydrogen at the H2seed facility required an estimated input of 71kWh of electricity
for the electrolysis step and 97kWh for compression and dispensing; the overall system efficiency was 23%.
The relative inefficiency of the production process was due to the large proportion of energy (58%) devoted
to the compression step, which highlighted a known issue with compressing the hydrogen from the relatively
low output pressure from the electrolyser (12bar maximum) to the high pressure storage (420bar maximum)
of the refuelling station.
Assuming electricity for electrolysis and compression and dispensing was delivered by combustion of the
biogas produced from anaerobic digestion (AD) at the Stornoway facility gave CO2e emissions of 155 and
239g/km from hydrogen-only operation on the rural and urban routes respectively. The CO2e emissions
from this production route are due to fugitive methane emissions from the AD plant and biogas engine. The
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Stornoway Hydrogen Vehicle Trial
introduction of other renewable electricity sources such as wind in the system would reduce system CO2e
emissions in operation to zero.
Driver feedback revealed that the HICE substituted ably for the conventional vehicles that typically operate
the delivery routes. The main negative feedback on the vehicle was its perceived lack of power in hydrogen
mode when compared to petrol mode and to conventionally-fuelled vans, an issue that manifested itself
most clearly on the hillier section of the rural delivery route.
The trial proved that hydrogen fuelled vehicles are able to substitute for conventional light good vehicles
with little compromise in duty cycle or performance in return to base delivery applications in rural and urban
settings. The trial also revealed perhaps predictable issues with the trialling of early demonstrator vehicles
in relatively remote locations, primarily due to the distance between the maintenance personnel and the
vehicles/refuelling equipment. These issues could be solved in future deployments by the local presence of
trained personnel.
Feedback from the work has helped Revolve to continue to evolve and improve the vehicles. The third
generation HICE is currently involved in the trial with ITM Power of an integrated portable hydrogen fuelling
system in public and private sector fleets across the UK. The Western Isles Council is assembling a case for
support for the future deployment of two fuel cell passenger vehicles into its fleet to utilise the hydrogen
fuelling facility at Stornoway. Funding is also being sought to deploy a stationary fuel cell at H2seed to fully
utilise the hydrogen production capacity of the facility.
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2
Introduction
Hydrogen is an energy vector. When generated from zero carbon energy sources, hydrogen and fuel cell
technologies provide long-term options for decarbonising road transport, and for the storage and provision
of zero carbon electricity. At present, there are relatively few hydrogen vehicles in use – it has been
estimated that cumulative worldwide shipments of fuel cell vehicles from 1997-2009 were of the order of
1,000 units (Fuel Cell Today, 2009).
Recent developments give confidence that hydrogen and fuel cell vehicles, initially in volumes of hundreds,
will begin to appear in the EU from 2015 onwards. These developments include the signing in September
2009 of the memorandum of understanding (MoU) for the H2 Mobility consortium, a public-private
partnership for the deployment of a national fuelling infrastructure in Germany (AP, 2010). Also, in
November 2010 the Hydrogen Coalition (‘McKinsey’ study) was released, providing scenarios and an
evidence base for the deployment of hydrogen vehicles and infrastructure in Europe from 2015
(Zeroemissionvehicles, 2010).
In order to build real-world experience in anticipation of the eventual roll-out of hydrogen vehicles a number
of trials are taking place worldwide of fuel cell passenger cars and buses (for examples, see FCH JU, 2011 and
JHFC, 2011). There is limited trial activity with hydrogen-fuelled commercial vehicles, despite the fact that it
is widely acknowledged that ‘return-to-base’ commercial fleets offer potentially the most promising market
for the early adoption of alternatively-fuelled vehicles (for a discussion of low carbon vehicle technologies
and vehicle trials, see Cenex, 2010).
Hydrogen vehicle technologies remain immature and are not market proven. Recently the Automotive
Council’s low carbon commercial vehicle and off-highway roadmap examined the applicability of current and
emerging technologies including hydrogen to the decarbonisation of the non-passenger vehicle fleet. By
segmenting vehicles according to their use, the report identified electric vehicles as most appropriate for
light duty cycles and hydrogen fuel cell vehicles as having potential use for medium duty cycle applications.
Both technologies however are reliant on breakthroughs in energy storage before they can achieve massmarket acceptance. The study concluded that internal combustion engine (ICE) vehicles fuelled by
sustainable gaseous or liquid fuels will remain most appropriate for heavy duty cycles (Automotive Council,
2011, Figure 1). One such sustainable gaseous fuel for use in an ICE is hydrogen, where HICE vehicles have
an advantage of over fuel cell vehicles is that they do not require as high a purity of hydrogen as is currently
needed for operation of proton exchange membrane fuel cells. They are also currently significantly less
expensive than fuel cell vehicles, although this differential is likely to diminish as production of fuel cell
vehicles increases.
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Figure 1. Low carbon commercial vehicle and off-highway roadmap (Automotive Council, 2011)
3 Trial objectives
3.1 Vehicle and fuelling performance
The report details the monitoring of a trial of a HICE light goods vehicle as part of an existing vehicle fleet in
Stornoway for a six week period in July-August 2010. The aim was to examine the reliability, ease of fuelling
and usability of the vehicle in real-world fleet use.
To evaluate the performance of the vehicle and hydrogen fuel in the trial, a number of metrics were
considered. These were performance (fuel consumption), reliability, emissions and usability. The trial aimed
to quantify CO2 savings by performing a well-to-wheel analysis on the fuel used. This analysis quantifies the
greenhouse gas (GHG) emissions during the extraction, processing, delivery, dispensing and combustion of
the fuel.
3.2 The role of islands in the early hydrogen economy
Addressing the question of what can be achieved at an island, city or regional level given the scale of
investments and timescales involved in introducing hydrogen and fuel cells (H2FCs) into the national energy
mix, Hodgson et al. (2008) differentiate between:



Islands which act as a bounded model of how a future hydrogen economy could operate. Examples in
H2FCs include Iceland and Hawaii
Large cities which seek environmental and economic benefit, and potentially self-sufficiency, through
the deployment of disruptive energy technologies. Examples in H2FCs include London and San Francisco
Networks of smaller cities, which act as showcases and test beds for the introduction of H2FC
technologies. Examples include cities involved in multi-partner demonstration projects under the
European Fuel Cell and Hydrogen Joint Undertaking (FCH JU)
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Stornoway Hydrogen Vehicle Trial

Regional clusters which promote economic development linked to the particular strengths of an area,
such as the British Midlands
Stornoway is the largest town and administrative centre of the Western Isles, an island chain off the west
coast of Scotland (Figure 2).
Figure 2. Stornoway and the Western Isles (Google Maps)
Clearly, the Stornoway trial fits into the island typography described above. The Western Isles Council is also
seeking to exploit the region’s natural resources, particularly wind and marine energy, to avoid dependence
on imported fuels and energy, and as a driver of economic regeneration (http://www.cne-siar.gov.uk). The
trial therefore examined the suitability of renewable hydrogen produced by electrolysis for fleet fuelling
applications.
4 Project partners
The hydrogen vehicle and fuelling infrastructure trial was a collaborative project. Each organisation and
their role in the project is summarised below.
Cenex (www.cenex.co.uk) is the UK’s first Centre of Excellence for Low Carbon and Fuel Cell Technologies.
Cenex is at the forefront of UK ultra-low carbon vehicle trial activities, overseeing and reporting on projects
in biomethane, electric and hydrogen fuelled vehicles – for more details see www.cenex.co.uk/projects.
Cenex loaned the hydrogen vehicle to the project, as well as providing technical and financial assistance and
undertook the project evaluation.
Revolve Technologies (formerly Roush Technologies Limited UK, www.revolve.co.uk) is an UK-based
automotive engineering design consultancy. Revolve converted the Ford Transit vehicle used in the trial to
operate in bi-fuel compressed hydrogen/petrol mode using funding provided by Cenex. Revolve also
provided technical assistance during the trial.
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Figure 3. Revolve Technologies bi-fuel hydrogen/petrol Ford Transit
Comhairle nan Eilean Siar’s H2seed Project (http://www.cne-siar.gov.uk/renewable/h2seed.asp) is
delivered by Comhairle nan Eilean Siar (CnES, Western Isles Council) in conjunction with Highlands and
Islands Enterprise, Lews Castle College, The Stornoway Trust, PURE Energy Centre LTD and NTDA Energia.
The project aims to address the whole value chain of hydrogen technologies: renewable hydrogen
production from electrolysis, hydrogen storage, hydrogen filling station and hydrogen use in both stationary
and transport applications. H2seed provided the hydrogen and hydrogen refuelling facility for the project.
Royal Mail (www.royalmailgroup.com) operated the vehicles on two delivery routes from its Stornoway
depot.
5 Methodology
The following section describes the trial methodology in more detail.
5.1 The vehicle
The characteristics of the converted petrol-hydrogen bi-fuelled Ford Transit supplied by Revolve as a
technology demonstrator to Cenex in 2009 are summarised in Table 1.
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Parameter
Model year
Fuel
Fuel capacity
Engine
Engine Cylinders
Engine Power
Supercharger
Vehicle range (unladen)
Value
2009
Petrol/compressed hydrogen (350bar)
Petrol: 80litre.
Hydrogen: 4.5kg at 350bar in three underslung tanks (2x74litre, 1x39litre)
2.3 litres spark ignited
4
104kW (petrol); 75kW (estimated, hydrogen)
Belt-driven with intercooler. Provides additional combustion air at up to
0.8bar pressure in hydrogen mode only
Urban – 82 miles; highway 135 miles (estimated)
Table 1. Hydrogen ICE vehicle characteristics
The driver changes the vehicle between hydrogen and petrol modes using a switch mounted on the vehicle
dashboard. For this demonstrator vehicle, the switch must be operated when the vehicle is stationary.
Hydrogen and petrol fuelling is carried out using separate fill valves/fill ports located under the fuel filler
flap. The hydrogen tank configuration is shown below in Figure 4.
Figure 4. Hydrogen ICE vehicle hydrogen tank configuration
5.2 Vehicle certification
At the time of the trial, hydrogen vehicles were not certified to carry loads on UK public UK roads. In order
to operate the vehicle in Stornoway a test and trials Vehicle Special Order (VSO) was obtained from the UK
VCA under Section 44 of the Road Traffic Act 1988 (http://www.vca.gov.uk/vca/vehicle-specialorders/vehicle-special-orders.asp). VSOs are issued for periods of up to five years to vehicles that do not
meet the construction and use regulations (C&U Regs), provided reasons for non-compliance can be justified
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Stornoway Hydrogen Vehicle Trial
and suitable information is presented to the VCA to ensure that appropriate care has been taken to address
safety issues and requirements.
In order to obtain the VSO for the trial Revolve Technologies certified the vehicle’s compliance with
regulation 2007/46/EC (EU framework for type approval of motor vehicles and trailers) and UNECE GRPE
2004/3 (Draft United Nations Economic Commission for Europe Working Party on Pollution and Energy
Uniform Provisions concerning the approval of (a) Specific components of motor vehicles using compressed
gaseous hydrogen (b) Vehicles with regard to the installation of specific components for the use of
compressed gaseous hydrogen).
5.3 Vehicle route and duty
Royal Mail operated the HICE vehicle on two delivery routes from its Stornoway Delivery Office. The routes
are summarised below:


Rural route: Stornoway-Shawbost. Round trip approximately 130 km
Urban route: around Stornoway.
5.4 Hydrogen fuel supply and dispensing
The hydrogen fuel was supplied by the H2seed hydrogen facility located adjacent to CnES’s Integrated Waste
Management Facility (IWMF) at the Creed Enterprise Park on the outskirts of Stornoway. The hydrogen
production system of H2seed is depicted in Figure 5; its components and the rationale behind its design are
described in more detail below.
Figure 5. Hydrogen generation and dispensing at the H2seed facility
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1. Biogas is produced at CnES’s adjacent Integrated Waste Management Facility (IWMF) from the
anaerobic digestion of municipal organic waste. The rate of production is variable, dependent on
the composition of the organic waste fed into the anaerobic digester.
2. The biogas is fed to a gas engine (output 240 kWe) producing electricity and heat which are partially
re-used to supply the IWMF’s energy demands. Excess electricity is exported to the electricity
distribution network. The variable biogas production rate results in the gas engine operating in a
batch mode. During the trial, the biogas engine was operating for between six and ten hours per
day.
3. When the biogas engine is operating, the H2seed facility uses the excess electricity to power an
alkaline electrolyser to generate hydrogen. The electrolyser, supplied by Pure Energy Centre, had a
rated capacity of 5.33Nm3/hr or 0.46kg/hr at Standard Temperature and Pressure. During the trial
the typical daily hydrogen production was around 40Nm3 or 3.4kg H2 per day.
4. The hydrogen passes from the electrolyser directly to the low pressure (LP) buffer storage at up to
12bar prior to transfer to the high pressure (HP) storage at up to 420bar. The storage and hydrogen
compression system was supplied by Air Products.


5.
The LP buffer storage consists of two Air Products Maxipack units providing a nominal storage
volume of 4,512 litres. At 15°C and 12bar the LP storage holds approximately 4.5kg of hydrogen.
However, the transient (or usable) capacity of the LP storage depends on the operating set
points of the hydrogen compression system. With an upper set point of 12bar and lower set
point of 9bar the transient capacity is 1.1kg, which dictates the quantity of hydrogen that can be
transferred from the LP buffer storage to the HP storage prior to replenishing the buffer.
The HP storage consists of a total of fifteen composite cylinders providing a total nominal
volume of 1,230 litres. The Air Products S100 fuelling station unit has three integral composite
cylinders which is augmented by an Air Products HP pack consisting of a further twelve cylinders.
At 15°C and 420bar the HP storage holds approximately 34.1kg of hydrogen.
The AP S100 refuelling unit dispenses the stored hydrogen achieving pressures of up to 350bar in
the receiving vessels.
Figure 6 shows the vehicle at the Stornoway refuelling facility during the trial.
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Figure 6. Hydrogen vehicle refuelling at the H2seed facility
5.5 Data acquisition
To evaluate the performance, reliability and usability of the vehicle duty and refuelling regime the following
were monitored as part of the trial:




Hydrogen consumption
Vehicle availability and refuelling station availability
Tailpipe and well-to-wheel emissions
Driver feedback
In addition, the vehicles were fitted with a Racelogic VBox II telemetry system which facilitated second-bysecond monitoring of vehicle speed, position and elevation. The outcomes of these measurements will be
discussed further as the results are displayed in the following sections.
6 Trial results and discussion
6.1 Initial refuelling station tests and refuelling protocol
The trial marked the first use of the Stornoway hydrogen vehicle refuelling facility. It also marked the first
occasion that the trial vehicle could be refuelled from empty to 350bar in a continuous refuelling operation –
hereafter this process is referred to as fast-fuelling. Previous refuelling events were a two stage process.
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During initial trial refuelling of the vehicle two issues emerged:


Vehicle leak alarm activation following fast-fuelling
Difficulties in refuelling the vehicle if the pressure in the hydrogen tank was allowed to drop below
10bar.
These problems are discussed further below.
6.1.1 Vehicle leak detection strategy and fast-fuelling
Initial efforts to refuel the vehicle to its full capacity of 4.5kg at 350bar resulted in the vehicle’s major leak
alarm being trigged, which disabled the vehicle from further operation and required Revolve’s engineers to
travel to Stornoway to reset the vehicle’s control systems. In order to investigate the cause of the alarm,
Cenex monitored the temperature and pressure of the on-vehicle storage vessel every 10 seconds during
and after a 3.8 minute fill from empty to 350bar; the results are shown in Figure 7:
Figure 7. Hydrogen tank pressure and temperature variation following 350bar vehicle refuelling
The figure shows an initial relatively sharp decrease in pressure from the maximum value of 350bar and then
a much more gradual decrease over time. The maximum observed rate of pressure decrease was
12bar/minute, which is below the 21.1bar/minute level which triggers the major leak alarm. However, the
10 second resolution of the temperature and pressure recording might not have captured transient steeper
decreases in pressure in the very early stages after fuelling.
Localised temperature and pressure increases inside on-vehicle storage vessels during fast gaseous fuelling
are a well-understood and studied phenomenon (e.g., Hirotani et al., 2007). It was clear that the leak
detection strategy used by the Revolve vehicle during the trial meant that it would not be possible to fill the
vehicle to its maximum capacity. Following further investigation it was decided to stop vehicle fuelling when
the tank pressure recorded by the refuelling station reached 200bar which replicated the refuelling strategy
used in previous trials of the Revolve vehicle conducted by Cenex in Birmingham and Loughborough. In
order to further eliminate issues of localised gas heating when fuelling, the vehicle was filled with hydrogen
at the H2seed facility at the end of its daily operation. The vehicle was then left overnight to stabilise the
hydrogen tank temperature and pressure and started on hydrogen the next day.
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6.1.2 Vehicle refuelling at very low on-vehicle storage pressure
The Revolve Transit used during the trial had a warning light on the dashboard which illuminated when
pressure in the vehicle hydrogen tanks had dropped such that the remaining range on hydrogen was less
than 10 miles. Once this warning light was illuminated the vehicle’s operator was expected to switch to
petrol operation.
However, in one instance the hydrogen level in the vehicle dropped below 10bar. This revealed a safety
feature of the Air Products S100 fuelling unit. The fuelling sequence is terminated prior to commencing
refuelling if a low on-vehicle pressure is detected during initial safety checks. In practice, a small amount of
hydrogen is transferred to the vehicle during the safety checks. Thus after multiple aborted fuelling
sequences the on-vehicle pressure eventually exceeded the minimum pressure and the fuelling sequence
continued to completion. The S100 manual suggests a minimum pressure of 20bar was necessary although
in practice a pressure of 10bar was sufficient for the fuelling sequence to proceed.
6.1.3 Final refuelling and driving strategy
As a result of the investigations discussed above the vehicle operators were issued with the following
instructions for vehicle operation/refuelling which were continued throughout the trial and the vans were
put into service on 22th July 2010:
1. Fill out the Hydrogen Trip Record sheet and start the delivery round with the van set to operate on
Hydrogen.
2. If the H2 Low warning light illuminates during the delivery round then complete the trip record in the
Hydrogen Trip Record sheet and switch the van to operate on petrol.
3. On completion of the round report to the Hydrogen filling station and switch the van onto petrol
operation mode (if it isn’t already on Petrol Mode).
4. When the van has been refuelled, complete the Fuel Used record sheet.
5. Start van and drive back to Royal Mail yard on Petrol.
6.2 Vehicle routes and duty cycles
Figure 8 displays the rural and urban delivery routes used during the HICE trial:
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Figure 8. Google Maps view of the rural (green) and urban (red) delivery routes (view produced using GPSVisualiser.com)
Figure 9 below plots the speed and altitude profiles of the rural and urban delivery routes of the trial:
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Stornoway Hydrogen Vehicle Trial
Figure 9. Comparison of speed and altitude for rural and urban delivery routes
Figure 9 reveals that the rural delivery route is characterised by much higher maximum
(106km/h) and average speed (47km/h) compared to the urban route (58km/h and 23km/h
respectively). The altitude traces also show that the rural route is characterised by larger
changes in elevation.
6.3 Hydrogen refuelling data
Table 2 summarises the hydrogen refuelling data obtained during the trial for 20 fuelling events:
Parameter
Average hydrogen fill
Average refuelling time
Value
3kg
3 minutes 30 seconds
Table 2. Hydrogen fuelling data
The vehicle fuelling time compares favourably to that observed with other gaseous alternative fuels such as
compressed natural gas (Cenex, 2009).
6.4 Vehicle distance travelled and fuel consumption data
Table 3 presents the vehicle distance travelled and fuel consumption data obtained when running on
hydrogen during the trial:
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Parameter
Rural route
Number of trips
17
Estimated hydrogen-only range (miles, based on full tank of
85
4.5kg hydrogen @ 350bar)
Average trip distance (miles)
44
Average hydrogen consumption (bar/mile)
4.1
Trial distance fuelled by hydrogen (miles)
Urban route
2
55
13
6.3
723
Table 3. Trial distance travelled and fuel consumption data
Although there were fewer trips on the urban delivery route than the rural the data suggests that the fuel
economy of the rural operation was significantly greater than that of the urban route. Figure 10 offers a
graphical summary of the vehicle’s performance during the trial:
Figure 10. Summary of hydrogen vehicle performance during the trial
Fuel efficiency and range observed for the HICE during the trial are low compared to the stated range of the
vehicles presented in Table 1 (which gave a highway range of 135 miles and urban range of 82 miles)
indicating that the Royal Mail’s operations and duty cycle in Stornoway are particularly demanding. This may
in part reflect the weight loading of the vehicle for its Royal Mail duties during the trial, but it is also likely to
reflect the difference between real-world range and that obtained from testing using standard drive cycles in
laboratory conditions.
As discussed in Section 2 HICE vehicles fuelled by renewable hydrogen have been identified by the UK
Automotive Council as offering a future low carbon solution when operating on heavy duty cycles. Electric
vehicles are deemed more appropriate for light duty cycles, and hybrid vehicles for medium duties. Royal
Mail has been trialling ten Ashwoods hybrid vehicles at its Premier Park depot in London since November
2010 as part of the UK Low Carbon Vehicle Procurement Programme. Results from the 18-month trial will
help show whether hybrid vehicles offer a more appropriate low carbon solution to the Royal Mail’s needs,
at least in an urban environment.
6.5 Vehicle and fuelling station availability
This report addresses 19 days of vehicle operation during the period that the vehicle was at Stornoway.
Initially, the trial proceeded smoothly using the protocol of running to hydrogen exhaustion, returning to the
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refuelling station on petrol, refuelling with hydrogen and returning to base on petrol ready for the next day’s
hydrogen operation documented in Section 6.1. However, refuelling was prevented on a total of four days
due to two separate fault conditions reported by the S100 fuelling unit. On each occasion the fault condition
prevented initiation of the fuelling sequence despite there being sufficient hydrogen available in the HP
storage.
The hydrogen vehicle was out of service for two days during the trial due to a suspected low supercharger oil
level. However, this was due to a failure to adhere to documented servicing procedures so this event has
been omitted from the trial availability figures. A further day was lost due to a local public holiday resulting
in no staff cover at the H2seed Facility.
The first generation HICE employed during the trial was supplied to Cenex as a demonstrator vehicle and was
based in Loughborough. Issues that emerged during previous trials of the vehicle at Birmingham and
Loughborough were resolved by a combination of Cenex and Revolve personnel working together on-site
and at Revolve’s headquarters in Essex. Deployment to Stornoway introduced additional difficulties of
distance, time and expense in resolving issues. This manifested itself principally in the work needed to
investigate issues arising from fast-fuelling and the vehicle leak detection strategy during the commissioning
of the vehicles and the refuelling station. Resetting the vehicle major leak alarm involved deployment of a
Revolve engineer to Stornoway to reset control systems within the vehicle. Clearly, such factors must be
considered when trialling immature vehicles in relatively remote locations.
6.6 System efficiency analysis
Consideration of the energy inputs at each stage of the hydrogen production and dispensing system shown
in Figure 5 allows the efficiency of hydrogen production at the H2seed facility to be calculated. The energy
required to produce and dispense 1kg by electrolysis in the H2seed facility is represented below in Figure
111:
Figure 11. System energy efficiency of hydrogen production at Stornoway during the trial
The overall system efficiency is relatively low at 23%. The estimated efficiency of the electrolyser at 55% is
lower than the figure of around 80% quoted for large scale electrolysers (UKHFCA, 2011). Also Figure 11
shows that the majority (58%) of the input energy is expended on compression and dispensing of the gas.
This dominance of the energy requirements of compression and distribution in the production of hydrogen
by electrolysis contrasts with those of the energy and GHG balance pathways outlined in the standard
‘Concawe’ emissions reference document Well-to-Wheels analysis of future automotive fuels and
powertrains in the European context (JRC, 2008). As an example, in its electricity to compressed hydrogen
pathway KOEL/CH1 the on-site electrolysis stage requires three times more energy input than the
compression step.
1
39.4kWh is the energy content of 1kg of hydrogen at Higher Heating Value (HHV, NIST, 2003).
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The system efficiency of 23% is based on the energy content of 1kg of hydrogen at higher heating value
(HHV) – i.e., it also reflects the energy required to condense the water product to liquid after combustion. A
number of combustion studies, including the JRC document cited above, utilise the lower heating value (LHV)
of a fuel, which does not include condensation of the water product. The system efficiency drops below 20%
based on the energy content of 1kg hydrogen at LHV (33.3kWh).
The principle reason for the inefficiency of the compression steps is the low output pressure (12bar) of the
electrolyser. The compressor was specified on the basis of a 30bar electrolyser. A design fault in the original
electrolyser resulted in a modified specification to the lower pressure system. The reduced input pressure
effectively halved the achievable transfer rate, doubling the energy requirements of the compression step.
Appropriate sizing of the compression step to improve its efficiency would be crucial if the H2seed hydrogen
production facility is ever scaled up to meet demands beyond those of the trial.
6.7 Emission analysis
Emissions from a road transport fuel are considered on a well-to-wheel basis, which quantifies the energy
usage and associated emissions from fuel production to combustion. Well-to-wheel (WTW) emissions can
be broken down into two parts, well-to-tank (WTT) and tank-to-wheel (TTW) emissions. Well-to-tank
emissions comprise the greenhouse gases emitted during fuel production, extraction, processing,
transportation and dispensing. Tank-to-wheel emissions are more commonly known as tailpipe emissions,
and can be broken down into greenhouse gas and air quality emissions.
One of the principal advantages of hydrogen fuelled vehicles is the fact that they have zero tailpipe carbon
emissions as complete combustion of hydrogen fuel with oxygen yields water as the only product2.
Therefore the ensuing discussion focuses on the WTT CO2 emissions associated with production of the
hydrogen fuel at the H2seed facility.
The H2seed facility’s control system ensures that the electrolyser is only operated when the biogas engine is
running. The operation of the compression system and other auxiliary power requirements were not so
restricted, and could draw power from the local grid during periods when the biogas engine was not
operating. However, the biogas engine (rated capacity 305kWe, current operating capacity 240kWe) more
than satisfies the combined instantaneous heat and power requirements of the IMWF and H2seed facility,
exporting excess electricity to the local grid. On average the engine generates around 640,000 kW of heat
and 590,000 kW of electricity annually (ENER-G, 2010). For the purpose of this report it is assumed that the
power requirements of the H2seed Facility are supplied by the biogas engine. GHG emissions from
production of the biogas are therefore the most important factor in this analysis as discussed below.
Biogas produced from the anaerobic digestion of organic waste offers an attractive low carbon source of
energy (e.g., see Cenex, 2009a). While emissions from biogas production from this route are often
considered zero or even negative, small amounts of methane emissions, a more potent GHG than CO 2, are
associated with the biogas plant and gas engine. Concawe pathway OWEL1a electricity from municipal
waste (local power plant) estimates these emissions at 7.7gCO2e (CO2 equivalent GHGs) per MJ electricity
used (equal to 27.7gCO2e per kWh). Based on this number, and the energy inputs to the production of
2
Testing of the hydrogen ICE vehicle at Millbrook Proving Ground showed trace emissions of hydrocarbons and carbon
monoxide and dioxide in the exhaust. This was attributed to residual petrol in the exhaust system, or trace amounts of
oil in the combustion chamber. The emission analysis also revealed high levels of NOx, which were reduced to below
Euro IV levels by improvements in the engine calibration in the next generation of the vehicle, and to Euro VI standard
in the current version.
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hydrogen shown in Figure 11, the GHG emissions associated with the production and use of hydrogen on the
rural and urban duty cycles of the trial are presented in Table 4 below:
Electrolysis
(kgCO2e/kgH2)
Rural
Urban
1.99
1.99
Compression
dispensing
(kgCO2e/kgH2)
2.69
2.69
and Kilometres travelled gCO2e/km
per kgH2
30.2
19.6
155
239
Table 4. CO2e emissions for hydrogen production and use on rural and urban routes during the trial
By comparison, if the compression and dispensing steps were powered using non-renewable grid electricity
which was not offset by the electricity produced from biogas, emissions on the rural route would rise to
almost 2,000gCO2e/km based on a UK grid average figure of 617.07gCO2e/kWh (Defra, 2010) demonstrating
the importance of the local renewable electricity to this system. The introduction of other renewable
electricity sources such as wind into the system would reduce the CO2e emissions in operation to zero.
Although caution should be exercised as the urban analysis is based on a relatively small number of trips, the
relative efficiency of hydrogen use by the HICE in rural and urban applications has a significant effect on the
emissions associated with each duty cycle.
6.8 Usability
The vehicles were operated at normal loads and on the same delivery routes used by the Royal Mail’s vehicle
before the trial with no effect on delivery times.
Although no feedback questionnaire was issued to vehicle operators during the trial, informal feedback on
performance aspects of the hydrogen vehicle and the refuelling system were mainly positive.
Negative feedback on the vehicle highlighted that it was underpowered for certain parts of the Royal Mail
duty cycle in Stornoway. This manifested itself particularly during relatively hilly periods of the rural route
where operators reported having to shift down to first gear in order to crest hills normally tackled in third or
fourth gear in a conventionally-fuelled vehicle.
7 Trial outcomes and next steps
7.1 Publicity and dissemination
The trial attracted significant national press attention (e.g., Guardian, 2010) and offered positive publicity for
the environmental work of Comhairle nan Eilean Siar and Royal Mail, as well as promoting UK low carbon
capabilities offered by Revolve Technologies and Cenex.
7.2 Hydrogen vehicle certification
Certifying the vehicle’s compliance with EU and UNECE regulation proved the practicality of obtaining a VSO
and furthered the case for UK support to the addition of H2 vehicle type approval to EU regulations.
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7.3 Vehicle improvement
Feedback from the trial, together with laboratory test work conducted by Cenex in 2010, has supported
Revolve’s evolution of the HICE transit from a demonstration vehicle. The process of vehicle modification
towards a market-ready offering following the building of the first demonstrator vehicle for Cenex in 2009
and the trial in 2010 is summarised in Figure 12. Increased power output during hydrogen operation,
modification of the leak detection strategy and the ability to switch the fuel system from hydrogen to petrol
while driving mark significant improvements over the demonstrator HICE vehicle employed for the trial.
Figure 12. Evolution of the Revolve Hydrogen ICE
7.4 Future Revolve trial activity
In 2011 Revolve and ITM Power initiated the HOST (Hydrogen On-Site Trials), which deploy ITM’s
Transportable electrolyser HFuel high pressure refuelling unit plus two third-generation Revolve HICE transit
vehicles with private and commercial fleets for a one-week period. These trials offer a further step towards
market introduction and to the wider adoption of hydrogen vehicles by commercial fleets (ITM, 2011).
7.5 Future activities in the Outer Hebrides
Based on the outcomes of the trial, Comhairle nan Eilean Siar is assembling a case for support for the future
deployment of two fuel cell passenger vehicles into its fleet to utilise the hydrogen fuelling facility at
Stornoway. Funding is also being sought to deploy a stationary fuel cell at H2seed to fully utilise the
hydrogen production capacity of the facility.
8 Abbreviations
BIS
CnES
Department for Business, Innovation and Skills
Comhairle nan Eilean Siar (Western Isles Council)
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CO2e
FCH JU
GHG
H2FC
HHV
HICE
HP
ICE
CO2 equivalent greenhouse gas emissions
Fuel Cell and Hydrogen Joint Undertaking
greenhouse gas
hydrogen and fuel cell
higher heating value
hydrogen internal combustion engine
high pressure
internal combustion engine
IWMF
Integrated Waste Management Facility
kW
kWe
kWh
LHV
LP
TTW
VSO
WTT
WTW
kilowatt
kilowatt (electrical)
kilowatt hour
lower heating value
low pressure
tank-to-wheel emissions
Vehicle Special Order
well-to-tank emissions
well-to-wheel emissions
9 Acknowledgements
Cenex would like to thank the following for their help and support during the project:
Ruairi MacIver, Project Manager (Renewable Energy), Comhairle nan Eilean Siar (Western Isles Council).
Stephen Pegrum, Principal Design Engineer, Revolve Technologies Limited.
10 References
Automotive Council (2011) Low carbon commercial vehicle and off-highway roadmap, Automotive Council,
May 2011. Available from http://www.automotivecouncil.co.uk/wp-content/uploads/2011/04/COM-OHRoadmap-BIS.pdf (accessed 9 August 2011).
Cenex (2009) Camden Biomethane Trial, Steve Carroll,
http://www.cenex.co.uk/resources (accessed 6 September 2011).
November
2009.
Available
from
Cenex (2009a) Cenex Biomethane Toolkit, June 2009. Available from http://www.cenex.co.uk/resources
(accessed 12 September 2011).
Cenex (2010) Fleet carbon reduction guidance, Cenex, September 2010.
http://www.cenex.co.uk/consultancy/fleet-carbon-reduction (accessed 9 August 2011).
Available
from
Defra (2010) 2010 Guidelines to Defra/DECC’s GHG Conversion Factors for Company Reporting, Department
for
Environment,
Food
and
Rural
Affairs,
October
2010.
Available
from
http://archive.defra.gov.uk/environment/business/reporting/conversion-factors.htm
(accessed
12
September 2011).
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Stornoway Hydrogen Vehicle Trial
ENER-G
(2010)
Optimised
biogas
utilisation,
October
2010.
Available
from
http://www.energ.co.uk/resources/files/265_Energy%20from%20digester%20gas%20Oct%202010.pdf
(accessed 12 September 2011).
FCH JU (2011) Transport and Refuelling Infrastructure Projects, Fuel Cell and Hydrogen Joint Undertaking.
Available
from
http://www.fchju.eu/Projects%20by%20application%20area/Transport%20and%20refuelling%20infrastructure (accessed 6
September 2011).
Fuel Cell Today (2009) 2009 Light Duty Vehicle Survey, Lisa Callaghan Jerram, May 2009. Available from
http://www.fuelcelltoday.com/media/pdf/surveys/2009-Light-Duty-Vehicle-Free.pdf (accessed 9 August
2011).
Guardian (2010) Royal Mail goes Green in Hebrides, Severin Carrell, 7 September 2010. Available from
http://www.guardian.co.uk/uk/2010/sep/07/royal-mail-green-hebrides-hydrogen (accessed 9 September
2011).
Hirotani, R., Terada, T., Tamura, Y., Mitsuishi, H. and Watanabe, S. (2007) ‘Thermal Behavior in Hydrogen
Storage Tank for Fuel Cell Vehicle on Fast Filling’ in SAE Proceedings, SAE World Congress 2007, Detroit, USA.
Hodgson, M, Marvin, S. and Hewitson, A. (2008) ‘Constructing a typology of H2 in cities and regions: an
international review’, International Journal of Hydrogen Energy, vol 33(6), March 2008, pp1619-1629.
ITM (2011) Hydrogen On-site Trials.
(accessed 9 September 2011).
Available from http://www.itm-power.com/page/49/HOST.html
JHFC (2010), WG2: Fuel Cell Vehicles WG, Japanese Hydrogen and Fuel Cell Demonstration Project. Available
from http://www.jhfc.jp/data/seminor/fy2010/pdf/day1_E_10.pdf (accessed 6 September 2011).
JRC (2008) Well-to-Wheels analysis of future automotive fuels and powertrains in the European context.
WELL-TO-TANK Report Version 3.0. Appendix 2: Description and detailed energy and GHG balance of
individual pathways, November 2008.
Available from http://ies.jrc.ec.europa.eu/jec-researchcollaboration/downloads-jec.html (accessed 9 September 2011).
LowCVP (2010) Light Goods Vehicle – CO2 Emissions Study, AEA Technology, February 2010. Available from
http://www.lowcvp.org.uk/assets/reports/Van%20CO2%20Final%20Report.pdf (accessed 12 September
2011).
NIST (2003) Standard Reference Database Number 69, National Institute of Standards and Technology,
March 2003 Release, Gaithersberg, Md.
UKHFCA (2011) Did you know …, UK Hydrogen and Fuel Cell Association.
http://www.ukhfca.co.uk/did-you-know/ (accessed 9 September 2011).
Cenex
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11 Enquiries
Cenex
Chris Walsh, Head of Technical Support and Consultancy +44 (0) 1509 635 750.
Comhairle nan Eilean Siar (Western Isles Council)
Ruairi MacIver, Project Manager (Renewable Energy) +44 (0) 1851 822665 ext. 274.
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