9. Grid+Stor (Gas+H2)

Question 1

Repurposing natural gas infrastructure (for hydrogen): What needs to be considered? (4)

Answer 1

Regarding Pipes:
Preventing hydrogen embrittlement (for example through Protective internal coating or inhibitor gas)

Regarding compressor and metering station:

Hydrogen has different compressibility than natural gas
-> therefore replacement of Compressors necessary

Hydrogen is a smaller molecule than natural gas
-> therefore seals and gaskets need to be replaced

Motor will be fulled by electricity
-> therefore the motor needs to be replaced

(…)1

Question 2

Can for the future hydrogen grid the same infrastructure components be used?

Answer 2

The repurposing is preferable whenever possible (only 20-30% of the cost for the construction of a new pipeline)
-> some changes to existing infrastructure components need to take place (for example compressors)

Question 3

Switch from Town gas to natural gas (1960s and 1970s):

Before natural gas was commonly used, “Town gas” or “Coal gas” was produced locally at many cities from coal.

Town gas was a mixture of several gases which differed from town to town. (roughly 50% H2, 20% CH4, 15% N2, 10% CO)

Most german cities switched from town gas to natural gas in the 1960s and 1970s. (West-Berlin not before 1990s due to independency reasons)

Answer 3

…

Question 4

Switching from ??-Gas to ??-Gas (2020s)

Answer 4

L-Gas to H-Gas

Question 5

L-Gas has a different composition than H-Gas and a higher heating value.

true/false?

Answer 5

FALSE

-> lower heating value than H-Gas

Question 6

Which country is the main supplier for L-Gas?

Answer 6

The Netherlands
-> announced to reduce their natural gas production and will stop supplying Germany from 2029 on.

Question 7

See Map slide 6

Answer 7

…

Question 8

A fuel gas is passed through a pipe to the gas appliance by ?(1)?

The lighter a gas is (i.e. the lower its density in kg/m^3), the ?(2)? the gas can be moved at the same pressure.

However the density of the fuel gas doesn’t simultaneously increase the calorific value by the same rate.

Thus, when exchanging one gas with another the volume flow will change, but not at the same rate to create the same heat flow at the combustion.

As a result the ?(3)? was introduced because a value was needed that considers both the ?(4)? and the ?(5)?

Answer 8

(1) pressure differential

(2) faster

(3) Wobbe index

(4) calorific value

(5) density

Question 9

A fuel is passed through a pipe to the gas appliance by pressure differential.

true/false?

Answer 9

true

Question 10

The heavier a gas is (i.e. the higher its density in kg/m^3), the faster the gas can be moved at the same pressure.

true/false?

Answer 10

FALSE!

The LIGHTER a gas is (i.e. the LOWER its density in kg/m^3), the faster the gas can be moved at the same pressure.

Question 11

1) Why was the Wobbe index introduced?

2) What does the Wobbe index represent?

3) What is the Wobbe index useful for?

Answer 11

1) value was needed that considers both the calorific value and the density.

2) a characteristic value for the interchangeability of gases with regard to heat load

3) Defining the quality of fuel gases (e.g. natural gas, biogas) which differ from each other due to their composition

Question 12

Formula(s) of Wobbe index? (W_S an W_i)

Answer 12

W_s = H_s / Wurzel(d)

W_i = H_i / Wurzel(d)

Mit zuvor: d = roh_fuelgas / roh_air

H_s: Upper calorific value of the fuel gas [J/m^3 or kWh/m^3)

H_i: H_s: Lower calorific value of the fuel gas [J/m^3 or kWh/m^3)

d: Relative density

Question 13

Exmaple of different heat flows, resulting from different gas properties.

Example of same heat flows, resulting from gases with the same Wobbe index.

see slides 8+9

Answer 13

…

Question 14

If the Wobbe indices of both fuel gases are the same, they will result in the ?(1)? heat load on the burner at the same ?(2)? and when ?(3)? are used.

Answer 14

(1) same

(2) burner pressure

(3) identical burner nozzles

Question 15

With the same Wobbe index, the output of the burner is ??

Answer 15

constant (despite the different calorific values of the gases!!)

Question 16

With the same Wobbe index, the output of the burner is constant despite the different calorific values of the gases.

Therefore what is possible?

Answer 16

An exchange of the gas types without changing the burner nozzle

Question 17

The ?? is a characteristic value for the interchangeability of gases with regard to heat load.

Answer 17

Wobbe index

Question 18

Wobbe index:

A distinction is made between ?(1)? and ?(2)? Wobbe indices

Answer 18

(1) upper (W_s)

(2) lower (W_i)

Question 19

The Wobbe index is useful for defining the quality of fuel gases (e.g. natural gas, biogas) which differ from each other due to their composition.

true/false

Answer 19

true

Question 20

Calculate the density of dry air under standard conditions:

R_S (Dry air) = 287,1 J/kgK (specific gas constant)

p0 = 101.325 Pa

T0 = 0°C

Answer 20

siehe Rechenweg ex.

pn = 1,293 kg/m^3

Question 21

Calculate the Wobbe index of various gases…

(see exer)

Answer 21

….

Question 22

Using the natural gas grid for blends of hydrogen and natural gas is often suggested as a ?? solution

Answer 22

transitional

Question 23

Name 2 advantages and 2 disadvantages of blending hydrogen with natural gas! (over methanation)

Answer 23

Advantages:

Minimal investment needed (transport and storage infrastructure in place)

No dedicated hydrogen storage required

(Minimal additional energy losses (no additional processes)

(Substantial existing storage and transport capacity in countries with highly developed natural gas infrastructure)

Disadvantages:

H2/Natural gas ratio is technically limited to 17-25vol.% in some parts of the distribution grid, and not above ~5vol.% in the transport grid

The H2 blending limit is uncertain and very system specific (limited by grid integrity, safety, energy transport, capacity and the specifications of end-use applications)

(Compliance with strict blending limits in a pipeline with large daily fluctuation in gas demand may require the costly adaptation of the real-time hydrogen-injection rate)

(Legislation for HENG remains sparse)

Question 24

Repurposing of Pipelines

Name 5 main elements of the natural gas network!

Answer 24

Storages (UGS - Underground Gas Storage -systems)

Compressor stations

Transmission network

Distribution network

Gasdruckregel- und Messanlage

Question 25

Repurposing of Pipelines Beschrifte slide 17!

Answer 25

...

Question 26

Describe hydrogen embrittlement!

Answer 26

Due to its small size, hydrogen diffuses through the metal and creates cracks which lead to material failure over time. Depends on the material (some steel types are more at risk than others, plastic pipes are not affected)

Question 27

Plastic pipes are not affected by hydrogen embrittlement. true/false

Answer 27

true

Question 28

Hydrogen embrittlement needs to be considered when constructing new or repurposing existing pipelines for hydrogen. true/false?

Answer 28

true

Question 29

Hydrogen embrittlement Hydrogen from the plating process (Beschichtungsprozess) creates pressure and causes ?(1)?. Hydrogen molecules ?(2)? through metal and create ?(3)? inside the cavities.

Answer 29

(1) cracking (2) diffuse (3) pressure (see slide18)

Question 30

What can be done to prevent pipes from hydrogen embrittlement? Name 4 options

Answer 30

Protective internal coating Pipe-in-pipe Inhibitor gas Increased maintenance (lifetime of pipeline about 25% lower)

Question 31

Protective coating on the inside of the pipeline. No experience with existing pipelines, only done during construction until now. What method to prevent pipes from hydrogen embrittlement?

Answer 31

Protective internal coating

Question 32

Installation of a thin plastic pipeline within the existing pipeline. The outer pipeline provides stability, the inner pipeline protection. What method to prevent pipes from hydrogen embrittlement?

Answer 32

Pipe-in-pipe

Question 33

Adding small percentages of another gas (inhibitor gas) (e.g. 2% CO or 0.015% O2) which reduces ??.

Answer 33

hydrogen embrittlement

Question 34

What changes need to be done at compressor and metering stations when switching from natural gas grid to hydrogen? (Name three causes for action and what needs to be done therefore)

Answer 34

Hydrogen has different compressibility than natural gas -> compressor needs to be replaced Hydrogen is a smaller molecule than natural gas -> seals and gaskets need to be replaced Motor will be fueled by electricity instead of natural gas -> motor needs to be replaced

Question 35

Most natural gas compressor stations are driven by natural gas. Why will hydrogen compressor stations not be powered by hydrogen?

Answer 35

Adesso.de: "Compressor, regulating and pressure-reducing station contain many mechanical components and seals that can be prone to leakage or material failure." ???

Question 36

Repurposing natural gas pipelines for hydrogen only costs ?? % of the construction of new pipelines.

Answer 36

20-30%

Question 37

Repurposing pipelines for hydrogen is preferable whenever possible. true/false?

Answer 37

true (only 20-30% of the costs for constructing new pipelines)

Question 38

Repurposing pipelines for hydrogen is preferable whenever possible. But in what cases could it be necessary to build a new pipeline for hydrogen?

Answer 38

When new connections are needed for which no natural gas pipeline exists. When a natural gas pipeline is still needed for the transport of natural gas.

Question 39

How could there still be cost savings when a new hydrogen pipeline needs to be build because the existing natural gas pipeline can't be repurposed because the pipeline is still needed for the transport of natural gas?

Answer 39

Through building the new pipeline in parallel to the existing one because no new corridor is needed.

Question 40

Perspective of a gas distribution network operator. What impact will the development of the natural gas and hydrogen demand have on the network and the customers? What economical/technological/organisational aspects needs to be considered? (4)

Answer 40

Shrinking number of natural gas customers and demand -> Maintaining the same network length with fewer customers leads to rising network tariffs which leads to even fewer customers Part of the distribution network will be needed to supply hydrogen to industry Large parts of the distribution networks might become obsolete (as connections to households will not be needed for hydrogen (or would be very expensive)) A possible shutdown of infrastructure needs to be communicated well in advance to prevent problems for industrial and household customers

Question 41

1) Name 3 types of underground gas storages (UGS)! 2) Which of them is well suitable for hydrogen? (and which probably not)

Answer 41

1) Storage in Depleted (Gas) Fields Storage in Depleted Aquifers Salt cavern storages 2) Well suitable: Salt cavern storages Probably not suitable: the other two

Question 42

Problems regarding the storage of hydrogen in deplented gas fields or aquifers? (3)

Answer 42

Risk of ground instability, as hydrogen attacks some types of rock Risk of bacterial methanation (loss of hydrogen) Contamination of stored hydrogen

Question 43

Why are salt cavern storages well suitable for hydrogen? (3)

Answer 43

Hydrogen does not react with salt rock already tested for several years only little contamination of stored hydrogen

Question 44

Repurposing and construction of salt caverns for hydrogen. What is needed? (1)

Answer 44

New compressor stations are needed (but cavern only needs to be emptied)

Question 45

Where in Germany is the potential for storing hydrogen in salt caverns large and therefore likely in the future?

Answer 45

in the North (even though the consumers are more in the south)

Question 46

Similar to natural gas now, ?? might have the largest hydrogen storage capacities in the EU in the future.

Answer 46

Germany