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INTRODUCING VEHICULAR LNG IN THE NETHERLANDS Sergi Forns

Engineering Manager

Ros Roca Indox CryoEnergy

ABSTRACT

On 2010 the first LNG fuelling station in The Netherlands was opened. This opening means the start of LNG spreading

in vehicular solutions in this country. But it has been a relatively long project which started three years before together

with Daimler-Mercedes, LNG Europe, VOS Logistics and Van Gansewinkel.

There have been several steps in the process, but some points have been key in this project: Technical requirements for

the LNG Tank, which demanded a new design, Homologation of the LNG Tank in The Netherlands according to Lloyd’s

requirements, Certification of the Fuelling Station as far as there is no specific regulation yet, the LNG supply chain to

the Station and solving the specific experiences in this station, technical and human.

The problems, alternatives and solutions in each case are explained in this paper, providing a clear view about the

launching of vehicular LNG in The Netherlands.

1. INTRODUCTION

Introducing a new fuel in a new country is always challenging. Normally there are no

specific regulations and there is a certain reluctance from authorities or notified bodies to

accept/certify new technologies. There is no infrastructure and no customers neither that

justify the infrastructure. To break this circle to introduce LNG there are two main

options: a) Using an existing regasification plant to complete it with a dispenser, so the

largest investments (civil works and cryogenic tank) are already covered or shared or b)

Cooperating with a captive fleet in order to get a minimum critical mass to invest on a

reasonable infrastructure of one Fuelling Station.

In The Netherlands the are no regasification plants, so first option was not easy (an

additional end user (industrial) would have been required). Second option requires a

captive fleet demanding LNG vehicles and LNG supply. This was the case in The

Netherlands.

The LNG station can be owned either by the end user or by an LNG supplier. When there

is -or it is planned to be - more than one fleet fueling in the station, station will be

normally owned by the LNG supplier.

ENDUSER

NG Vehicle

LNG Tank

LNG Station

LNG Supply

Regulations

Fig. 1. Main Characters introducing a new fuel in a country

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Organization chart for a project like this is shown on Fig.1.

The end user requests an LNG vehicle to get a cheaper and more environmentally-friend

fuel with a reasonable range (in comparison at least with CNG). The end user also requests

a fueling station.

The vehicle supplier is normally an OEM with a vehicle model already running on CNG.

This OEM needs to substitute the CNG bottles by LNG cryogenic tanks.

The supplier of LNG tanks has to adapt the design to the specific requirements of the

OEM, mainly pressure and dimensions, and has to get the approval of the authorities.

Regarding the fueling station it is required to identify the owner which will decide the

investment to be done in the station. This is a key issue as far as consumption and storage

have to be very well balanced and some systems are offered to compensate some

deviations in this balance: CNG dispensing and/or boil-off preventive or handling systems.

Also redundancy will be a matter of decision.

And the station requires an LNG supply coordinated with the station manager, so the

station tank never run out of LNG and LNG deployment is close to a complete tanker,

otherwise transport costs rise.

Additionally to all these relations, there are the authorities, which sometimes delegate on

notified bodies, that require fulfillment of regulations and have to create new requirements

for the new fuel/technologies. And this affects to the LNG tank and to the LNG station, as

far as the NG truck is supposed to be already approved.

Main actors in this project are listed in table 1.

PROJECT LNG AT OSS

END USERS VOS LOGISTICS / VAN GANSEWINKEL

VEHICLE MODEL ECONIC NGT

VEHICLE SUPPLIER MERCEDES

TANK SUPPLIER ROSROCA INDOX CRYOENERGY (RRIC)

FUELING STATION OWNER LNG EUROPE

FUELING STATION SUPPLIER ROSROCA INDOX CRYOENERGY (RRIC)

LNG SUPPLIER LNG EUROPE

TANK HOMOLOGATION RDW (+LLOYD’S REGISTER)

TRUCK GAS INSTALLATION HOMOLOGATION

RDW (+KIWA GASTEC)

STATION HOMOLOGATION MUNICIPALITY OF OSS (+Bureau Veritas)

Table 1. Companies involved in the project “LNG at Oss”

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2. TANK REQUIREMENTS

Mercedes NGT Econic vehicle requires a gas supply pressure to the engine of 18 bar at

full load. This is because of the way the engine manages the load. This is normal as far as

this engine was designed to run on CNG. But LNG tanks in the market were not designed

for pressures over 17.2 bar. This means that converting NGT Econic with CNG into LNG

required an specific design of the tank.

From an strictly technical point of view there is no restriction for reaching more than 18

bar. RRIC, under requirement of Mercedes, designed a 24 bar tank. The design has to be

more robust to withstand the higher pressure and valves have to be according to this

pressure. But there is no major issue.

However, the tanks are one part of the system. The other part relays on the fueling station,

which will have to refill the tank leaving the LNG tmperature corresponding to the

equilibrium temperature at 18 bar of presure, so around -111ºC. But in this scenario there

is a thermodynamical behaviour which affects the performance related to boil-off. There

tanks are cryogenic, so one of their functions is to prevent heat transfer to the LNG. But

this definition is not totally true. The real target is to prevent pressure increase inside the

tank, which would lead into safety valves opening. And this small wording difference is

pointed out because when operating at higher equilibrium temperature-pressure the

influence of a certain amount of heat into the LNG has a more significant effect to

pressure raise.

In Fig.2 it is shown the typical LNG Temperature-Pressure equilibrium curve.

0

5

10

15

20

25

30

35

40

45

50

-150 -130 -110 -90 -70

Temperature [ºC]

Pre

ssur

e [b

ar]

0

1

2

3

4

5

6

7

8

9

10

C [k

J/kg

K]

Equilibrium Curve Cp

PL

PH

Fig. 2. Temperature-Pressure Equilibrium curve and Specific Heat

In this curve it is shown the effect of an increase of temperature on the pressure either at

low (-136ºC and 6 bar: LEC) and at high (-111ºC and 18 bar: HEC) equilibrium

conditions. It is also shown the specific heat as a function of the temperature.

At LEC, 1ºC increase means an increase of 0,31 bar. At HEC 1ºC increase means an

increase of 0,66 bar.

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However, same heat transfer does not mean same increase of temperature in both cases.

Specific heat at LEC is 3,77 kJ/kg K and at HEC is 4,51 kJ/kg K. This means that the

effect of 1kJ is as follows:

1 kJ on 1 kg of LNG at

136ºC and 6 bar (LEC) →

0,08 bar

increase

1 kJ on 1 kg of LNG at

111ºC and 18 bar (HEC) →

0,15 bar

increase

Therefore, the effect of 1 kJ of heat into the tank is 1,8 times higher at HEC in comparison

to LEC.

Additionally, tanks with working pressure at 6 bar nornally have safety valves setting at

17.2 bar, while tanks with working pressure at 18 bar have safety valves at 24 bar. The

consequence of this situation is shown in Fig. 3.

0

5

10

15

20

25

30

35

40

45

50

-150 -130 -110 -90 -70

Temperature [ºC]

Pre

ssur

e [b

ar]

0

1

2

3

4

5

6

7

8

9

10

C [k

J/kg

K]

Equilibrium Curve Cp

PL

Fig.3. Pressure increase from working pressure to maximum working pressure

The allowed pressure increase is significantly higher for LEC. Considering a mean

specific heat of 4 kJ/kg K for LEC and 4,8 kJ/kg K for HEC, to raise the pressure of 1 kg

of LNG from working conditions up to safety valves setting conditions (maximum

working pressure) it is required following energy:

LEC: Pressure Raise from

-136ºC and 6 bar to

-113ºC and 17 bar

→ 96 kJ

HEC: Pressure Raise from -

111ºC and 18 bar to

-103ºC and 24 bar

→ 38 kJ

Therefore, the required heat to increase pressure from working conditions up to safety

valves setting condition (maximum working pressure) at LEC is 2,5 times the required

heat for HEC.

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This means that tanks (same design) will perform better at low rather than high

temperature in terms of insulation.

Anyway, this is true when vehicles are left parked. When vehicles are running the gas

phase is consumed through the economizer so pressure is always around working pressure.

Obviously if heat has entered into the tank the liquid will be boiling and once the vehicle

is stopped, pressure will start increasing. This effect will be more significant for HEC

tanks, but this only means that the vehicles should be parked for less days and/or tanks

require a better insulation.

In this case, for the Mercedes Econic, the tanks were using perlite as insulation layer. Then

the design was modified from the typical cylindrical shape into the squared shape, as the

insulation level for perlite is a function of layer thickness, with the target of increasing

insulation capability.

Fig. 4 3D Model of a Cryogenic Tank for Trucks

Considering the original distance between inner and outer tank, the squared design offers

an increased insulation section and a better adjustment to the available space in the truck

(height and width are not exactly equal). In total, insulation performance is about 200%

better with squared shape instead of rounded shape (see fig.5).

Fig. 5 Comparison between standard rounded tank and squared tank

This design tends to compensate, then, the more difficult conditions that means working

with “hot” LNG.

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3. TANK HOMOLOGATION

The homologation process was under the scope of RDW, but lead by Lloyd’s Register for

the tank as a component and Kiwa Gastec for the new gas installation in the vehicle.

The requirements for the tank include:

- production inspection stages

- material & components certificates (R110)

- quality checks

- tests procedures

mainly based on TPED, ADR, EN-1251-2 and common requirements.

Additionally Lloyd’s Register required/discussed the following issues:

- FEA on tank & supports considering:

o Longitudinal: 6.6 G

o Transversal: 5 G

- Lateral impact: potential leakage

- Insulation behaviour when loosing vaccum (accident)

- Documentation: P&ID, Equipment list, Hazop or DFMEA, Declaration of Conformity

according to TPED for additional components (vaporator, pressure measurement

devices, valves, pressure relief valves) User’s Manual and the Test & Inspection Plan.

The FEA considering the acceleration requirements are to be solved considering the

complet system, so the tank together with the brakets.

In the specific design for the ECONIC the brakets are welded to the outer tank, so the

whole system is bolt clamped to the chasis. The two main critical points are the connection

of the inner tank to the outer tank (specially under longitudinal acc.) and the welded area

between the brackets and the outer tank. A picture from the FEA is shown in fig. 6.

Fig. 6. Tank and Brackets FEA under acceleration conditions

Lateral impact was simulated in terms of acceleration, but the question arised regarding a

direct impact into the outer tank. This is an important issue as a major leak after a road

accident could lead into a very dangerous situation.

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There might be several ways to improve the performance in the situation of a direct

impact. For this project it was analyzed the behaviour of the perlite under direct impact

conditions. The perlite acts like a liquid, so distributing the impact to the rest of the perlite

increasing the inner pressure, and protecting inner tank from the direct impact.

The different performance due to the action of the perlite is shown in fig.7. The tank with

Perlite is transferring a distributed load to the inner tank. The tank without Perlite is

collapsing from outer tank into inner tank.

Perlite is not the only solution, as there might be different reinforcement solutions to

protect inner tank from an impact.

a)

b)

Fig. 7. Behaviour of a tank under direct impact located in the center of the tank. a) with

perlite b) without perlite

To minimize safety risks this aspect should be taken into account when designing a

cryogenic tank for vehicles.

In the event of an accident a second effect to be considered is the vacuum loose. As far as,

in general, cryogenic tanks for vehicles use a vacuum chamber in addition to the specific

insulation material (multilayer or perlite), it is significant to consider the performance of

the insulation system once vacuum is lost, because it is exactly under these conditions

(accident) when it is more important to keep a reasonable insulation, otherwise tank may

start venting, which could be dangerous.

The analysis of heat transfer of the two main insulation systems, multilayer and perlite, is

shown in fig. 8. Both of them perform depending on the vacuum level. At high vacuum

level multilayer offers theoretically an slightly better insulation, as far as there is no

conductivity, no convection (no air) and almost no radiation (rejected by the multilayer).

With Perlite there is no convection and no radiation, but there is still the conduction of the

perlite, which, although it is very limited, can not be removed.

At low vacuum level the performance of both of them is converging as far as the

convection is very significant with the multilayer, not with perlite as the air is blocked

between the small perlite particles. Anyway, Perlite performance will also enworsen as air

has a certain conductivity, higher than vacuum.

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But at no vacuum, multilayer is a poor insulation (Q = 240 W/m2) while perlite still keeps

a reasonable insulation level (Q = 63 W/m2). Multilayer offers around 4 times more heat

transfer than perlite.

0,10

1,00

10,00

100,00

1000,00

0,1 1,0 10,0 100,0 1.000,0 10.000,0 100.000,0 1.000.000,0

Vacuum (micrHg)

Q (W

/m2)

Perlita CRS-W

Fig.8. Multilayer and Perlite insulation vs vacuum level

Therefore, the insulation system has to be considered specifically for the vehicular

application. And this includes a proper balance between performance at high vacuum and

performance at no vacuum.

However, insulation has no much to do when LNG is introduced already “hot” into the

tank during refilling. If the temperature is higher than the equilibrium temperature for 24

bar, LNG will continuosly tend to vaporize over safety valves setting pressure. LNG

temperature depends on the way the station is managed, the balance between storage and

consumption, the amount of trucks, etc. This is discussed on following point.

4. STATION APPROVAL AND EXPERIENCE

There is no dutch regulation for LNG fueling stations and there is neither an ISO standard

yet, but EN13645 was taken as a reference, including some more requirements/agreements

by the local municipality of Oss, also assisted by the Fire Department.

This requirements and agreements included the risk analysis, type, size and location of fire

extinguishers, pressure test on the complete facility and approval of the loading procedure.

The notified body Bureau Veritas checked and certified that all these requirements were

fulfilled.

There was a discussion related to the venting of the station. In the EN13645 there is no

requirement for the venting line. However, it was proposed to introduce an air mixer or a

burner to either eliminate the explosion risk (by obtaining a mixture below explosion

limit) and/or reducing CH4 emissions to the atmosphere.

However, venting an LNG plant should be exceptional, and safety valves should open only

in rare situations.

Anyway, it is true that an LNG fueling station is more demanding than a Regasification

plant or a CNG fueling station (even when this CNG is provided from LNG).

The two standard situations for venting CH4 in an LNG fueling station are:

- Truck venting before refilling

- Station venting due to pressure raise

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Truck Venting before refilling

When there is a single tank per truck fueling can be done with a top filling concept. So

inlet pressure has to be high enough to start filling, but then gas phase collapses due to

cold liquid entering into the tank. However, when the pressure inside the tank is too high,

it is required to vent the tank before starting filling.

In the past this venting used to be directly to the atmosphere by means of a manual valve

in the tank.

Currently it is standard to have a second hose and nozzle which vents back to the station.

This venting is only necessary when the truck has been stopped for some days.

However, this top filling effect is only effective for one tank. When the truck is carrying

two tanks, collapsing the gas phase in the first tank does not force the pressure go down on

the second tank. And as far as both tanks are connected, pressure is not dropping.

The option is to have a permanent vent line connection during fueling, connected back to

the storage tank. Then the pumping system is just working against the flowing looses in

the system integrated by pipelines, hoses, nozzles and tanks.

Therefore, when the fueling station pretends to refill trucks with two tanks, two hoses

(fueling and gas return) are required.

The looses in the line will be higher with two tanks rather than with one tank, specially

when refilling the second tank.

At the fueling station at Oss flow, at constant pump speed, is changing during the load (see

fig.9).

Input Flow

Vent Flow

First tank filled up

Second tank filled up

Stop filling

Fig.9. Input and Vent (output) Flow during truck filling (two tanks)

This flow evolution permits to evaluate the loading situation. There is a fast filling of the

first tank, but when first tank is filled up the flow drops dramatically. This is due to the

diameter connecting the two tanks, which is limited by the rounting in the chasis of the

vehicle.

When the second tank is also filled up vent flow raises as liquid is flowing outside the

tanks to the vent line. Then filling is stopped.

The calculation of loaded mass must count the input mass and remove the output mass.

With this configuration no gas is sent to the atmosphere. However, this return gas is sent

to the storage tank, which means that there is heat going into the stored LNG.

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Station venting due to Pressure raise

Considering that the station offers a vapour return connection, pressure raise in the storage

tank is the possible option to vent under normal conditions.

In an LNG regasification plant the only chance for increasing LNG pressure is because of

heat transfer through the walls of the storage tank. However, in an LNG station this effect

is minor in comparison with the heat provided by station cooldown (before each truck

filling) and heat provided by gas returned from the truck.

Before starting a truck filling it is required to cool down the station, mainly the pump.

When filling one truck after the other this process is not required as the system is already

cold.

To cool down the pump there is a simple connection to the top of the tank so liquid flows

from the bottom of the tank through the pump and then back to the top of the tank. But

during this process the liquid is being heated up and gasifying. Then, as far as gas phase

mass is increasing with almost same gas phase volume, pressure is raising. Also after

refilling the liquid trapped in the pipelines is gasifying if no more truck fillings are

required. And this gas is sent back to the storage tank.

On the other hand, during refilling liquid is being transferred to the truck so available

volume for gas phase is increasing, so pressure is decreasing according to this parameter.

Therefore, pressure raise inside the storage tank is a balance which considers amount of

kilograms transferred to the vehicle per each station cooling down.

In Fig.10 it is shown the pressure evolution in the storage tank, which is at 90% storage

level. There is a single truck filling at 6:30, which implies cooling down the station: 5 bar

pressure raise. The truck is filled up with 90 kg (pressure drop). After the truck filling

vaporization of trapped liquid increases pressure during 2 hours up to 2,5 bar regarding

original pressure.

At 16:15 another truck filling is starting. The Station cooldown raises pressure 5 bar. The

first truck refills 62 kg. Before station starts warming up a second truck is refilled with 70

kg. And again a third truck is refilled before station warming up with 85 kg. So 270 kg in

total. After this 3 truck fillings pressure is roughly 0,5-1 bar lower than pressure before

cooldown.

The experience at Oss shows that refilling less than 200 kg for each station cooldown

increases pressure significantly. Obviously when storage tank level is high (i.e. 90%) the

effect on pressure is more significant than when tank level is low (i.e. 10%).

In these pressure variations there is a transient effect related to gas pressure increase or

decrease which is related to mass and volume, not with real temperature changes that

affects equilibrium conditions, and it is detected immediately. And there is a real heating

effect of LNG which can be felt at mid-term.

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Truck filling

CoolDown

P↑↑↑↑P

Fig.10. Storage Tank Pressure evolution (red line) and Pump Cooling Temperature (grey

line) for 1 truck fillings and 3 truck fillings

This real heating effect increases LNG temperature. This is shown in fig.11 where it can

be seen that after 15 cooldown processes the LNG temperature can reach -116ºC, with an

equilibrium pressure of 15 bar. This situation is the maximum acceptable from a

reasonable point of view, as far as the trucks have to be refilled at 18 bar.

-145

-140

-135

-130

-125

-120

-115

-110

-105

-100

0 2 4 6 8 10 12 14 16 18

Number of Cooldowns

LNG

Tem

pera

ture

[ºC

]

0

2

4

6

8

10

12

14

16

18P

ress

ure

[bar

]

Temperature Pressure

Fig. 11. LNG Temperature and related equilibrium pressure according to Number of

Cooldowns

In table 2 it is shown the result of the calculation of number of refillings per truck. For the

station of Oss it is 15,75 refillings. This means that as far as less than 15 cooldowns are

required to avoid a heating problem in the station, the four running trucks should refill at

the same time, so only one cooldown process is required for all of them. In case this is not

possible, pressure will raise faster and storage tank will require an early refill to collapse

gas phase pressure and cooldown the remaining LNG.

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Tank size 30 m3LNG Density 0,42 Tn/m3Maximum tank level 85 %Mínimum tank level 5 %Mass to be consumed 10.080 kgVehicles 4 unitsMass per vehicle 2.520 kg/vehicleMass per filling/vehicle 160 kg/filling a vehicleAmount of refillings per vehicle 15,75 refillings/vehicle

Table 2. Calculation of amount of refillings per vehicle required for one full LNG storage

tank

This clearly shows that this situation is the limit acceptable situation and any scenario with

more vehicles improves the global performance and any scenario below this becomes

critical. Normally a pilot project is started with “few units”, “lower requirements” in terms

of performance, etc. For LNG stations it is easier to handle as much units as possible. The

big threat to LNG stations is “heating” the LNG. And “few units” create this problem.

This issue could be improved with partial discharges on the storage tank, but this is

possible when there are several fueling stations spread in the country.

Human factor

A potential problem when starting this kind of projects is the capabilities and attitude of

the people that will have to deal with this new technology.

On one side there is the maintenance of the station and tanks. It is required a service with

fast reaction, with mechanical, electrical and software knowledge. And with experience on

LNG or, at least, with NG and cryogenics. This requires a company based in the country.

In this project the field service is currently provided by Tekoma with the support of

Cryonorm Projects as LNG experts and with the service by phone and internet from RRIC.

Up to now the team based in The Netherlands is earning autonomy through training

programs and experiences.

On the other side there is the coordination between Mercedes dealers and RRIC to

identify, in case of a truck malfunction, the origin of the problem: engine or LNG supply.

There is a cooperation between the two companies through training sessions to instruct the

mechanics and technicians from Mercedes in The Netherlands to handle the LNG vehicles,

in terms of safety and in terms of detecting potential problems.

And last but not least, the End User is a key actor on this kind of project. VOS Logistics

and Van Gansewinkel selected ideal drivers and encouraged them to use LNG. Refilling in

an LNG station may seem to be more delicate than refilling diesel, but additionally the

first plant in a country may arise some new problems. And the end users are required to

warn about these problems, to handle them, to communicate with the supplier to help to

quickly identify the root cause of any problem, and to make recommendations to improve

the handling of the system.

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One example is the performance of the Nozzle. The installed nozzle was the standard

nozzle used in the LNG refilling stations in Spain by RRIC, and it was performing well

enough. However, in The Netherlands the climatic conditions are different, specially the

humidity. And the result has been ice blocking the nozzle after each refilling. In some

ocasions it has been required to use a water hose to remove the ice and unblock the nozzle.

It is not a safety issue but it was a clear complain from the drivers. JC Carter offered a

nozzle with an Ice-breaker patented solution. RRIC together with JC Carter organized

testing the nozzle. The results were absolutely satisfactory for all users and engineers.

Then RRIC and JC Carter started the homologation process in Europe that was completed

on 11th February 2011. In short time JC Carter nozzles will substitute the old nozzles.

a)

b)

Fig. 12. LNG Nozzles. a) Original nozzle. b) JC Carter Nozzle, with better performance

The performance of an LNG fueling station depends significantly on the requirements of

the customer, the conditions of the project (i.e. amount of trucks), the care to fulfill the

needs of the manager of the plant and the care to fulfill the requirements of the end users

of the plant. The safety of an LNG fueling station depends on the quality and on the

experience of the supplier company in terms of risk analysis and on the proper supervision

of the authorities.

5. LNG LOGISTICS

The official opening of the station in Oss was in September 2010, although trials had been

performed during previous months. However, LNG is not yet available to be distributed by

road tankers in The Netherlands from a nearby LNG Terminal. Therefore, for this project

LNG has been brought from Barcelona LNG Terminal.

This solution means an extra operative cost to the project. However, this is an acceptable

interim measure to launch LNG while the new TLF (Truck Loading Facility) in Zeebrugge

was not yet ready. This TLF is planned to be operative during this first quarter 2011.

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6. CONCLUSIONS

There are several conclusions from this experience:

- LNG tanks for trucks have to be designed considering it is a vehicular application.

- Working with perlite insulation on the truck tanks is not always offering a better

performance than multilayer at high vacuum level, but it is a robust and safer

solution in case of road accident (direct impact) to minimize the risk of leakage

and to prevent venting in the event of vacuum loose.

- Balance between storage and consumption is key for a good performance of an

LNG fueling station. Against common sense, the more vehicles using the station,

the better performance.

- Technology on LNG is, in general, reasonably mature. But there are still some

improvements to be done, specially when changing countries/conditions. JC Carter

nozzle is a good example of better technology that improved the standard

performance in Europe.

- To bring one project like this into a success it is required the coordination, hard

work and tolerance of many companies and people that believe/invest, and

goverments, authorities and notified bodies that trust that this is the way to the

future and help to make it safer without blocking it.

We would like to specially thank Mercedes, LNG Europe, VOS Logistics and Van

Gansewinkel for their faith in LNG and in this project.

Joop, Koos, Jack, Hans, Ad and Sam: Thank you!