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The Innovative Technology of Hydraulic Compression and Boosting for Filling the Vehicles and Storage Systems with Natural Gas and Biomethane

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The article describes the technology of the “hydraulic piston”, as well as the studies that confirm the viability of this technology, implemented in various devices, designed to compress natural gas (CNG) and biomethane (bio-CNG), to accumulate CNG and bio-CNG, to deliver bio-CNG from the production site to the point of its injection into the natural gas network or to the vehicle fuelling stations to fill the Natural Gas Vehicles (NGV). The article presents prototypes of personal fuelling devices and mobile fuelling systems developed by Hygen Ltd. (Hygen), thereby showing the potential of the technology to contribute in the deployment of alternative fuel infrastructure and into the global GHG emissions reduction, mainly in the transport sector.
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Environmental and Climate Technologies
2020, vol. 24, no. 3, pp. 8093
https://doi.org/10.2478/rtuect-2020-0087
https://content.sciendo.com
80
©2020 Aleks ey Safronov, Julia Guzeye va, Jev geniy Be gens, A nsis Mezulis.
This is an open access article licensed under the Creative Commons Attribution License (http ://creativecommons.org/
license s/by/4.0), in the man ner agre ed wit h Sciendo.
The Innovative Technology of Hydraulic
Compression and Boosting for Filling the Vehicles
and Storage Systems with Natural Gas and
Biomethane
Aleksey SAFRONOV1, Julia GUZEYEVA2*, Jevgeniy BEGENS3, Ansis MEZULIS4
1–3Hygen Ltd, Matisa iela 103A-3, Riga, LV-1009, Latvia
4Laboratory of Materials for Energy Harvesting and Storage, ISSP UL, Latvia
Abstract The article describes the technology of the hydraulic piston, as well as the studies
that confirm the viability of this technology, implemented in various devices, designed to
compress natural gas (CNG) and biomethane (bio-CNG), to accumulate CNG and bio-CNG,
to deliver bio-CNG from the production site to the point of its injection into the natural gas
network or to the vehicle fuelling stations to fill the Natural Gas Vehicles (NGV). The article
presents prototypes of personal fuelling devices and mobile fuelling systems developed by
Hygen Ltd. (Hygen), thereby showing the potential of the technology to contribute in the
deployment of alternative fuel infrastructure and into the global GHG emissions reduction,
mainly in the transport sector.
Keywords: Alternative fuel; compressed biomethane (bio-CNG); compressor;
decarbonisation; gas storage; greenhouse gas (GHG); renewable gas
Nomenclature
bio-CNG Compressed biomethane
bcm Billion cubic metres
CF Cascade fuelling
CNG Compressed natural gas
EU European Union
EV Electric vehicles
GHG Greenhouse gas
ICEV Internal combustion engine vehicles
NGV Natural gas vehicle
PF Parallel fuelling
TRL Technology Readiness Level
VFA Vehicle Fuelling Appliance
* Corresponding author.
E-mail address: julia@hygengroup.com
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1. INTRODUCTION
Accelerating the decarbonisation process, biomethane (renewable gas) can be easily used
to fuel the vehicles and to reduce their carbon footprint. Natural gas infrastructure and
vehicles are fully compatible with renewable gas, without extra costs. Through renewable gas
from municipal waste or Power-to-Gas production pathways, close-to-zero greenhouse gas
emissions are achieved. In a recent study from Centre on Regulation in Europe (CERRE) a
production potential of 124 bcm/year renewable gas at EU level has been estimated [1].
Implementation of electric vehicles (EVs), especially in highly polluted city centres plays
a great role in decarbonisation as well as in noise levels reduction in the urban areas [2].
However, the study of International Energy Agency (IEA) states that in the countries, where
electricity production is based mostly on fossil fuels, Well-to-Wheel emissions for EVs are
associated even with more GHG emissions than internal combustion engine vehicles
ICEV [3].
Natural (also renewable) gas technology is ready to provide a fast and strong contribution
to the challenge of decarbonisation. In 2018, several countries devoted considerable shares
of renewable gas to transport, namely Iceland (100 %), Sweden (90 %), the Netherlands
(55 %), Finland (50 %) and Switzerland (25 %), making carbon neutrality in transport already
a reality [4].
The amount of Well-to-Wheel GHG emissions from various automotive fuels, recalculated
to CO2 equivalent, is given in Fig. 1.
Fig. 1. Well-to-Wheel GHG emissions in CO2 g/km [5].
The diagram shows that CO2 emissions are close to zero (5 g/km) only in case, when
electricity is produced from the wind (or from similar renewable sources). EU-mix electricity
application for transport provides CO2 reduction comparing to the petrol only as 75 g/km,
however bio-CNG shows the same low level of emissions, as E-mobility using wind energy
for electricity production. Also, the diagram on Fig. 1 shows that the biogas when blended
24 %
–39 %
–97 %
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with the natural gas, plays a significant role in CO2 reduction: adding of 20 % biogas to the
natural gas gives 39 % of CO2 reduction, comparing to petrol.
The Directive of the European Parliament and of the Council on the deployment of
alternative fuel infrastructure (DAFI) defines the alternative fuels. One of them is the natural
gas, including biomethane the upgraded biogas. DAFI sets out minimum requirements for
the building-up of alternative fuels infrastructure, including refuelling points to be
implemented by means of Member States' national policy frameworks [6].
The European Biogas Association (EBA), the Natural & bio Gas Vehicle Association
(NGVA Europe) and the European Automobile Manufacturers’ Association (ACEA) on
January 21, 2020 called on EU policy makers to accelerate the deployment of infrastructure
to deliver natural gas and renewable gas/biomethane across the European Union [7]. The
revised Renewable Energy Directive (RED II), increases the overall EU renewable energy
consumption target by 2030 from 27 % to 32 %. RED II sets a minimum transport fuel share
of 14 %, which must be produced from renewable energy sources to 2030 [8].
The renewable gas produced today is fully in line with the strictest sustainability criteria
established through European legislation. By 2030, the gas mobility market has a growth
potential 10 times higher than today, reaching a fleet of 13 million units. In parallel, the
production of renewable gas will increase drastically: for 2030, a conservative estimation
demonstrates a production potential of close to 45 bcm/year, largely overcoming the entire
demand for gas fuel of about 30 bcm/year, which corresponds to a 13-million-unit fleet. This
would significantly contribute to the European decarbonisation path: 30 % renewable gas will
provide a GHG emissions reduction of more than 45 % compared to conventional fuels on a
Well-to-Wheel basis [4].
1.1. Biomethane
Biogas typically contains 5575 % methane and has an energy value of 5.0–7.5 kWh/m3
(energy value of a pure methane is 9.97 kWh/m3) [9]. In order to use biogas as biomethane
fuel, it must be purified to an appropriate quality as defined by national directives. Numerous
biomethane purification technologies from biogas are developed, allowing to achieve up to
99 % purification. [10]
Biomethane production delivers CO2 neutral production. It particularly suits on-farm use
by agricultural vehicles as farmers already possess the raw materials and the space to produce
the biogas and upgrade it up to biomethane. This enables agri-business to be fuel sufficient.
In addition, biomethane can be injected into the gas grid to power communities, creating a
truly virtuous cycle.
1.2. Currently Available Technologies of NGVs Fuelling
Existing technologies allow biogas compression and dispensing by widely presented on the
market mechanical CNG compressors, e.g., COLTRI [11] or FuelMaker [12]. They can be
installed on biomethane production site and perform light duty and agricultural vehicle
fuelling by time-fill, requiring 5–8 hours, depending on the productivity of compressor and
volume of the vehicle’s fuel tank. Existing vehicle fuelling solutions employ reciprocating
compressor technology and due to that are less reliable. These compressors use an electric
motor to rotate a crankshaft, which is tied to several metal pistons that pump to compress the
gas. This technology requires pistons and piston rings, crankshaft and bearings, cylinders and
valves. Since all these components generate friction and heat during operation, the
compressor and related components require regular maintenance and a complete compressor
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overhaul at specified service intervals, which is costly. And, even with a regular servicing,
unexpected component failure is often experienced [13]. In many cases, the combined
maintenance costs end up being higher than the cost of the equipment itself. Since most of
the components in reciprocating compressor solutions are specifically designed and
manufactured, these tend to cost more and often have longer lead times for replacement parts.
In addition, reciprocating compressors may cause unwanted vibration, and resonance in the
pipelines [14].
To deliver biomethane from the production site to the customer or to the point of injection
into the gas grid the mobile storage systems are applied. The existing on the market mobile
storage systems allow to avoid the development of the costly new pipelines, however they
require mother station on the biomethane production site and daughter compressing stations
on the vehicle fuelling site, that adds the costs to such a project. Besides that, the existing
mobile storage systems, based on free gas flow dischargement principle (both buffer and
cascade), does not allow complete discharge of the storage system, - the “parasitic” volume
of gas will always present in the storage cylinders [15].
1.3. Main Challenges for Biomethane Application in Transport Fuelling Sector
The technical problems of widening biomethane application to be resolved are:
storage cylinders filling to high pressure in efficient way;
bio-CNG delivery to the destination (injection point to the grid or fuelling station);
development of an efficient fuelling appliance for on-farm application;
complete gas storage cylinders dischargement.
The complete dischargement of the gas storage cylinders is a quite challenging task,
because the fuelling from the gas storage systems, when being performed by a free flow of
gas ends when the pressures are equalized between the gas storage cylinders and the target
fuel tank. Simultaneous discharge of multiply storage cylinders is named “parallel fuelling”
(PF). Another option is a serial discharge of multiply storage cylinders, named “cascade
fuelling” (CF).
Comparing PF vs CF, the major benefit of CF is that this method refuels the target tank to
higher pressure. Fig. 2 displays numerical simulation of filling of a 130 L target tank with
initial natural gas pressure of 5 bars from the storage of four cylinders, 22 L each, being filled
with compressed to 200 bar natural gas, by both PF and CF methods.
Fig. 2. Numerical simulation of complete cascade fuelling (CF) and parallel fuelling (PF).
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From Fig. 2 it is seen that CF reaches 109 bars in the target tank, comparing to 90 bars of
the PF. The third cascade fuelling step out of four almost reaches the ending pressure of PF.
Nevertheless, the possible achievement of the multiple cascades of reasonable number is far
from required pressure, close to 200 bars, in a target tank. Besides that, the cascade principle
has a significant disadvantage multiple cylinders require complicated piping and valve
triggering circuits. The only reasonable way to discharge the storage volume close to entirely
is to employ a kind of boosting, i.e., to apply a pushing force.
2. METHODS AND METHODOLOGY
Latvian engineer Aleksey Safronov has invented and patented in 2008 a new method for
hydraulic compression of gaseous fuels (Hydraulic piston) and a device for implementation
thereof (the international application number: PCT/LV2008/000007, dated September 9,
2008) [16]. Hygen has developed the Technology of hydraulic piston and implemented it in
various compressed natural gas vehicle fuelling systems intended for gas compression,
accumulation and discharge (extortion). Unlike conventional and world-wide available
mechanical multistage compressors, the technology of hydraulic piston uses a method of gas
compression by means of a working fluid, which is pushed by a sufficiently powerful
hydraulic pump. The technology of hydraulic compression allows to solve all problems
mentioned in section Main Challenges for Biomethane Application in Transport Fuelling
Sector, with minimal costs, since devices made on the basis of hydraulic piston technology
use mass-produced components widely available on the market. By solving economic
problems of gas compression and delivery the technology opens the door for wider application
of bio-gas on transport. This contributes to solving the environmental problems associated
with the effects of greenhouse gases from transportation that cause climate change, and the
social problems associated with the impact of noise and harmful emissions on human health.
2.1. Method of the Hydraulic Piston Compression
Hydraulic gas compression has many significant advantages over a mechanical, where the
latter is characterised by a high noise level, high temperature, rapid wear of moving parts.
The technology of hydraulic piston can be explained with a help of Fig. 3:
Fig. 2. Hydraulic piston compressor and storage.
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Cylinders 1 and 2 are paired to form a hydraulic compressor. The amount of the working
liquid (red fill in Fig. 3) slightly exceeds the volume on one compressing cylinder. The
working liquid is transmission oil that has been chosen to avoid any chemical reaction with
the gas, as well as to have minimal gas diffusivity. One of the compressing cylinders is filled
with low pressure gas, the other one with hydraulic liquid. By rotating the hydraulic pump
and triggering the valves, the working liquid is alternately pumped from one of the
compressing cylinders to another and back. Supplying the liquid to the cylinder, which is
filled with gas, results in gas compression and forcing out into the storage cylinder. At the
same time, decrease of liquid level in another compressing cylinder allows a new portion of
low-pressure gas to be supplied into this cylinder. Such alternative pumping of hydraulic
liquid results in gradual pressure growth in the storage cylinder 3 up to 200 bars (at 15 °C),
preparing the device for fuelling a vehicle. The main technological problem was to prevent
the penetration of the working liquid from the compressing cylinder into the gas line. This
problem was solved by invention of the multi-valve, which is placed in the neck of the
compressing cylinder and provides a safe shut-off, when the working liquid reaches the top
of the compressing cylinder. The multi-valve is a part of the Hygen patent [16].
2.2. Method of Hydraulic Piston Boosting
In order to empty the storage cylinder 3 of gas far behind the free flow principle, the
boosting mode is implemented. The principle of boosting is displayed in Fig. 4.
Fig. 3. Hydraulic piston operating in a boosting mode.
At connecting the storage tank to the vehicle’s filling nozzle, the fuelling occurs by free
flow until pressure equilibrium is achieved. After the free flow stage, the remained high-
pressure gas from the storage cylinder (light blue arrow) is supplied to the compressing
cylinder for boosting, where it is further compressed (by acting the hydraulic piston) and
forced out directly into the vehicle’s fuel tank (dark blue arrow). Boosting cycles repeat
alternately in the compression cylinders. The number of boosting cycles to achieve 200 bars
pressure in the vehicles fuel tank depends on the volume and initial pressure of the tank. In case
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of a light duty vehicle with a standard fuel tank, 13 boosting cycles will be enough to fill the
vehicle completely.
3. RESULTS
The hydraulic piston technology was tested in the framework of Plan of Latvia Development
2020, in a research project KC1.2.1.1/18/A/008 lead by Mechanical Engineering Competence
Centre and by Hygen proven team of high-level specialists from engineering, hydraulics,
electronics and physics. The tests were performed on a Hygen testing bench.
The aim of the project was to test the behaviour of hydraulic piston at different inlet
pressures and to study the technology at higher inlet pressures and flow rates, i.e., at boosting
stage conditions. All tests have been performed with the aim to develop economically
efficient smart vehicle fuelling appliance, capable to provide vehicle fuelling up to 200 bar
pressure. Performed tests simulated different vehicle tank volumes, different inlet pressures
and different emergency situations. The boosting mode was tested on the testing bench with
two pairs of compressing cylinders and four storage cylinders. Electricity consumption, as
well as gas quality after its contact with hydraulic piston were measured.
3.1. Gas Inlet Pressure Tests
The compression mode has been tested at various gas inlet pressures in a wide range. The
hydraulic pump with productivity of 8.6 L/min, driven by 4 kW electric motor was applied.
During each test a 100 L storage cylinder was filled with natural gas up to 200 bars. Gas flow
rate has been calculated at three gas inlet pressure steps, Table 1.
TABLE 1. HYDRAULIC PUMPING RATE AT THREE GAS IN LET PRESSURE STEPS
No. Gas inlet
pressure, bar Flow rate, m3/h Pumping rate to inlet
pressure, m3/h·bar
1 3 1.14 0.38
2 6 2.3 0.38
3 16 5.17 0.32
Results of Table 1 testifies that flow rate, related to gas inlet pressure, starts slightly reduce
after 6 bars, and the reduction is less than 20 % up to 16 bars. Such characteristics is eligible
for a proper compression of gas at inlet pressures in impressive 17 mbar 16 bar range.
3.2. Boosting Stage Tests
If the volume of the target tank is smaller than that storage capacity of the testing bench,
fuelling up to 200 bars is rather simple and fast. For example, to fill a volume of 240 L the
compressor operated in a boosting mode for about 13 min, and the total electrical
consumption of the device during this period is 1.12 kWh. The gas temperature in the tank
first decreases until –8 °C due to the gas expansion and then increases to 35 °C at the end of
the filling (ambient temperature at 8 °C). Fig. 5. displays fuelling the target tank of 240 L at
85 bars from the storage capacity of 400 L at 200 bars.
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Fig. 4. Boosting stage of fuelling a target tank.
As the volume of the target tank is smaller, 400 L storage capacity is enough to fill the
target tank up to nominal 200 bars. It takes 5 hydraulic boosting cycles and about 760 s of
time, Fig. 5.
3.3. Temperature Tests Results
The tests proved that during both compression and boosting cycles the downstream
temperature of the gas does not reach the safety threshold of any type of a standard fuel tank.
Two different cooling systems were tested: liquid and air. Both of them showed good
results. Temperature of the gas supplied to the target tank after compression and after boosting
modes did not exceed 60 °C. The air-cooling system was chosen for application in the
prototype due to its simplicity comparing to the liquid cooling system.
3.4. Gas Analysis
With the liquid piston compression and boosting the gas fuel is in molecular contact with
the working liquid, periodically up to 200 bars pressure. It is necessary to ascertain, are not
the liquid molecules captured by gas, thereby making the gas fuel polluted.
Gas analysis was performed as follows: the natural gas sample has been taken at the outlet
of the Hygen testing bench on a 1 L 40 bars pressure cylinder. Additionally, natural gas at the
outlet of the network has been sampled in order to evaluate the composition modification
after a contact with working fluid under 200 bar pressure. The analysis has been performed
using Thermal-Desorber/Gas-Chromatography/Mass Spectrometry (TD/GC/MS) and
micro-Gas Chromatography (µGC/MS). The results of these gas analysis are presented in
Table 2.
If the general differences regarding the Aliphatic hydrocarbons are not significant between
the two samples, one can notice that the heavy aliphatic hydrocarbons C14-C16 is rather high
(0.9 mg/cm3). This might originate from the working liquid of the compressor that could
volatize into the gas fuel.
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TABLE 2. RESULTS OF GAS ANALYSIS
Permanent gases C Number Reference HYGEN
CH4 % 92.64 89.92
CO2 % 0.8 1.79
N2 % 1.43 1.22
COV mg/m3 C Number Reference HYGEN
Total Aliphatic Hydrocarbons mg/m3 79 539 111 200
Ethane C2 53 831 69 170
Propane C3 11 498 24 023
Isobutane C4 6825 7520
Butane C4 3132 6112
Aliphatic hydrocarbons >C6C8 C6C7 2158 1626
Aliphatic hydrocarbons >C5C6 C5 2005 2717
Aliphatic hydrocarbons >C8C10 C8C9 85 24.5
Acetylene C2 3.8 4.4
Aliphatic hydrocarbons >C10C12 C10C11 0.82 1.26
Aliphatic hydrocarbons >C12C14 C12C13 0.07 0.09
Aliphatic hydrocarbons >C14C16 C14C15 < 0.06 0.9
Alcohol mg/m3 C Number Reference HYGEN
1-Butanol (n-Butanol) mg/m3 < 0.06 2.9
Ester mg/m3 C Number Reference HYGEN
2-Propenoic acid, 2-methyl-, butyl ester < 0.06 0.07
Mercaptan /Sulfure mg/m3 C Number Reference HYGEN
Hydrogen disulphide (H2S) < 1.5 < 1.5
Silane/ Siloxane mg/m3 C Number Reference HYGEN
Cyclotetrasiloxane, octamethyl- (D4) < 0.06 0.09
Total COV (without H2S) mg/m3 79 605 111 250
The presence of siloxane was observed at the outlet of Hygen testing bench with a non-
significant value closed to the detection limit. One of the reasons of this observation could be
a pollution of the Gas Chromatography column. Measured 0.09 mg/m3 is however compliant
with the limit of EN 16723-2 [17], which set the limit of silica compound at 0.3 mg Si/m3.
The overall gas composition at the outlet of Hygen testing bench is satisfactory for the use
in a gas engine of an NGV. The marginal differences in term of permanent gas and
hydrocarbons does not seems to originate from the compressor but rather on the fluctuating
composition of natural gas coming from the network.
3.5. Products Developed on the Basis of Hydraulic Piston Technology
Hygen has implemented the hydraulic piston technology in three products: GasDroid,
HYGEN+ and GasLiner.
3.5.1. GasDroid
GasDroid, (Fig. 6) is developed to TRL 8, i.e., the device is complete and qualified.
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Fig. 6. VFA GasDroid.
GasDroid is a certified vehicle fuelling appliance (VFA) intended to fuel light duty vehicles
with CNG and/or bio-CNG by self-flow of gas from GasDroid internal storage to the vehicle’s
fuel tank. GasDroid is equipped with two compression cylinders 33 L each and four storage
cylinders 21 L each. GasDroid is capable to supply a vehicle with a portion of fuel providing
120150 km of the daily run. The specifications of GasDroid are detailed in Table 3.
TABLE 3. SPECIFICATIONS OF GASDRO ID
Compression flow rate 1.2 m3/h
Gas outlet pressure 200 bars
Storage capacity 84 water litres
Fuelling time 4 min
Electrical power 0.5 kW max 6 A
Power supply line 220 V
Gas inlet pressure 1725 mbar or 3 bars
Dimensions L x W x H (cm) 90 × 50 × 1765 cm
Weight (with working liquid) 390 kg
GasDroid can be installed on the biogas/biomethane production site to be operated as
follows.
1. Preparation for the fuelling or high pressure gaining: biomethane is compressed within
compressing cylinders and accumulated in the storage cylinders. Compression mode can
last up to 3 hours, depending on the pressure of the biomethane on the outlet of the upgrade
plant (usually 10 bar) and on the pressure left in the GasDroid internal storage after the
previous fuelling.
2. Vehicle fuelling: compressed biomethane flows freely from the internal storage cylinders
of GasDroid to the vehicle’s fuel tank. Fuelling process lasts 4 minutes to equalize pressure
between the storage and the target tank (approximately 80110 bars, depending on the size
of the target tank), thus supplying the vehicle with a daily portion of fuel for 100150 km
of run.
3.5.2. HYGEN+
HYGEN+, (Fig. 7) is an Alpha prototype of VFA, which is supplied with the boosting
feature.
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Fig. 7. VFA HYGEN+ for commercial vehicle fuelling, with a boosting feature, manufactured by Hygen.
It has integrated four compression cylinders 33 L each and four storage cylinders 95 L each.
The whole system is optimized for complete fuelling of vehicles having fuel tank capacity up
to 300 L, up to 200 bars in 1520 minutes, depending on the remaining pressure in the
vehicle’s fuel tank before fuelling. The specifications of HYGEN+ are detailed in Table 4.
TABLE 4. SPECIFICATIONS OF HYGEN+
Compression flow rate 4.4 m3/h
Gas outlet pressure 200 bars
Storage capacity 380 water litres
Fuelling time up to 25 min for 60 m3 at 200 bars
Electrical power (2 pumps) 4 kW max 7.9 A
Power supply line 380 V (three phase)
Gas inlet pressure 1725 mbar or 3 bars and above
Dimensions L × W × H (cm) 120 × 100 × 170 cm
Weight (empty) 1500 kg
HYGEN+ can be installed at biomethane production site and serve for vehicle working as
follows.
Preparation for the fuelling or high-pressure gaining that lasts for 4–6 hours, depending on
the pressure of biomethane after purification (approximately 10 bars) and initial pressure in
the storage after the previous fuelling. Biomethane will be compressed within compression
cylinders and accumulated in the storage cylinders.
Vehicle fuelling proceeds in two stages:
Stage 1: Free flow of gas from the internal storage cylinders of HYGEN+ to the vehicle’s
fuel tank, that lasts for ca. 4 minutes to equilibrate pressure between the storage and the target
tank (70120 bars, depending on the size of the target tank);
Stage 2: Boosting remained medium high pressure gas from the storage (70120 bars) is
supplied to the inlet of the compression cylinders alternately for additional compression and
pushed to the target tank, until 200 bars pressure in the target tank is achieved (it can take up
to 6 compressing cycles to fill the target tank of 240 L).
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3.5.3. GasLiner
For various off-grid situations Hygen proposes a cost-effective and convenient solution a
mobile bio-CNG system named GasLiner. Currently an Alpha prototype of GasLiner is
developed. It is capable to:
compress the gas (biomethane) by itself, i.e., without usage of a mother station;
accumulate compressed to 250 bars gas in its storage cylinders;
deliver gas (biomethane) to the selling/distribution points;
fuel simultaneously any number of vehicles (being connected in parallel) with CNG
(bio CNG) in 1.5 hours without using a daughter station.
Avoiding employing the mother and daughter stations in the virtual pipeline system,
GasLiner allows a significant reduction of the whole virtual pipeline costs for all kind of
gaseous fuels. GasLiner has a modular structure that allows to form a system of any capacity.
Developed GasLiner module with dimensions (L × W × H) 162 × 240 × 271 cm is shown in
Fig. 8. Eight modules can be placed on a standard platform, carrying up to 8000 m3 of
CNG/bio-CNG) on board.
Fig. 8. GasLiner modules in mobile and stationary application.
As measured, off-grid fuelling process reached very high 98 % efficiency with a flow rate
of biomethane of 80 Nm3/min. Besides that, GasLiner module can also be used as the
stationary fuelling off-grid station, to be supplied with bio-CNG by GasLiner mobile trailer
and providing vehicles fast fuelling with CNG/bio-CNG.
4. CONCLUSION
To accelerate the decarbonisation of the planet, the biomethane, as a motor fuel, has a
promising potential. The greatest challenge for that is to create an efficient fuelling
infrastructure. Hygen has developed an innovative technology of hydraulic piston, allowing
to produce a wide spectrum of vehicle fuelling appliances for bio-CNG fuel. The further
development of this technology shall be focused on creation of flexible solutions, applicable
at biogas/biomethane, production sites, for bio-CNG compression, transportation and fast
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discharging to the NGVs or injection into the gas grid in a cost effective and convenient way.
The technology has a great potential and needs to be explored and developed further for
application with hydrogen. As stated by European Commission in 2020, hydrogen is predicted
to be the fuel of the future [18], [19]. Hydraulic compression allows to achieve higher
compression ratios required for hydrogen, solving the existing problems arising from
employment of reciprocating compressors [20], as well as benefits the idea of combustion
hydrogen enriched CNG in sparkle ignition engines of NGVs [21]. Potentially the technology
of hydraulic piston allows to develop the emerging hydrogen market in two ways: enabling
gas grid decarbonisation through hydrogen blending with natural gas and as a new
compression solution for hydrogen as vehicle fuel.
ACKNOWLEDGEMENT
The research leading to these results has been supported by the European Regional Development Fund project Competence
Centre of Mechanical Engineering, contract No.1.2.1.1/18/A/008 signed between Competence Centre of Mechanical
Engineering and Central Finance and Contracting Agency, Research No. 3.1. “Additional research and integration of the
technology of hydraulic piston, aiming to develop and demonstrate economically efficient compressed natural gas smart
commercial vehicle fuelling appliance”. Our special gratitude to Gaspard Bouteau, PhD, Research Engineer, who conducted
the research work in Engie Lab CRIGEN. Co-authorship of Laboratory of Materials for Energy Harvesting and Storage, ISSP
UL has been supported by the Ministry of Economics of the Republic of Latvia, project LAGAS No VPP-EM-INFRA-2018/1-
0003. We are thankful to Alina Safronova, the master student of Riga Technical University, faculty of Power and Electrical
Engineering for help in finding data and formatting this work.
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... To increase the utilization of compressor and reservoir tanks, CNG fast filling stations operates in a buffer or cascade storage system and the reservoir tanks are arranged to increase the pressure [43,44]. Figure 1 shows a schematic diagram of a cascade CNG fast filling system. ...
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Moraga J. L., Mulder M., Perey P. Future markets for renewable gases and hydrogen: what would be the optimal regulatory provisions? Brussels: Centre on Regulation in Europe, 2019.
Directive 2014/94/EU of the European Parliament and of the Council of 22 October 2014 on the deployment of alternative fuels infrastructure
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European Parliament and the Council. Directive (EU) 2018/2001 of the European Parliament and of the Council of 11 December 2018 on the promotion of the use of energy from renewable sources. Official Journal of European Union 2018: L 328/82.