People like to know how much and what they are paying for, and the way it is measured is thus crucial. This is the basis for all trade, which works well when the measurement systems are in place, functioning, and unified.
However, some substances vary greatly in how they behave, making it difficult to measure the amount – and to carry out measurement, accounting and trade.
Green transition depends on accurate gas measurement
Hydrogen is the prime example of complicated measurements. How much gas actually flows past a given point in the pipe?
Research was needed to solve this problem, leading Cignus Instruments to contact SINTEF in Norway, which has extensive years-long experience with detailed flow calculations.
Svend Tollak Munkejord, a chief scientist at SINTEF, explains: “Energy carriers like natural gas and hydrogen hold their value in each molecule. For hydrogen, the world’s lightest gas, it is difficult to measure the exact quantity, and so far this measurement problem has been an obstacle to the green shift.”
“How can we know how much hydrogen is being sold, or produced by an electrolyser, if we can’t be sure that the measurements are precise?” he asks.
Nor does hydrogen behave quite like other gases do in pipes. It is so light, so sensitive and so compressible that even small changes in pressure and temperature have a big impact on existing measuring instruments. And if the gas with the smallest of all molecules is contaminated with something larger, the impact is enormous, and the calculation of the amount of energy is overestimated.
Thick, rigid pipes do not work well with vibrating tubes
The metres used today for measuring mass flow have tubes that wind around in a thin, small loop that vibrates. The flow of gas or liquid through the loop causes tiny changes in the vibration pattern. By measuring these changes, the mass flow in the piping can be found. These vibrating sensor tubes are called Coriolis flow metres. Often, several such Coriolis metres are needed in parallel, because they can only function with a precise diameter and wall thickness to maintain their effectiveness.
The problem with measuring the amount of hydrogen is that thick, rigid pipes are needed to maintain the high pressure required, and at the same time they must have sufficient pipe dimensions for the necessary delivery capacity. And that is exactly the opposite of what Coriolis metres are designed and made for. A new type of metre that has no pressure or size limitations, and which is at the same time very sensitive for measuring hydrogen and all other light gases, like natural gas, now solves this paradox.
Here Torquil Sørensen, senior technologist responsible for simulations, and CEO Martin Nese demonstrate the effect of the innovation. Photo: Cignus Instruments.
“These gases will release their energy later, and then the number of molecules is what counts. The question we had to figure out is how many molecules flow through the tube, but without using the existing metre design,” says Martin Nese, CEO of Cignus Instruments.
Like AutoPass for hydrogen molecules
The ingenious new solution divides the tube into four channels. The junction can be inserted into a tube of any size and thickness.
It’s like making the shift from pulling over at the toll booth to pay manually, to being able to continue driving on the highway and be registered automatically without thinking about it.
The new metre works according to the same physical principle as Coriolis metres, says Nese. The technology can be seen as a fancy “water metre” with special advantages for measuring gas in large-diameter pipes and at high operating pressures. But this metre measures mass – the number of molecules – and not volume.
“You can think of it as a combination of a speaker and microphone in one. Only that it is mounted inside a tube,” says Nese.
Digital design of the gadget’s details
At SINTEF, Eirik Holm Fyhn and Munkejord have been working on simulations to find the optimal design for the metre that will be fitted inside the pipe, long before a physical product is made. They are satisfied with the result.
“What we are observing is that this metre can be used to precisely measure how much hydrogen passes through,” says Fyhn.
“We have also simulated what happens when the metre is inserted into a pipe near a bend, for example a ninety-degree bend in the pipe.”
This is what the tube with the sensor looks like in the lab at SINTEF. It can measure the energy density in hydrogen gas – molecule by molecule. Photo: SINTEF
“In short, we’ve shown that the metre works well even if there is a bend directly upstream of the metre,” says Fyhn.
This means that planning pipe systems on the seabed will no longer require laying out the pipe geometry after placing the metres.
But the project is still under development. And before the new metre can become the gold standard for metres, it must itself be measured, verified and certified.
“The goal for the year is to get a hydrogen metre certified,” says Nese.
A key application for the new metre design is measuring how much hydrogen is produced in an electrolyser – both to verify the production process itself and to document the amount of hydrogen that is delivered.
The next step will be to adapt the metres for pipeline transport. Germany has many hydrogen producers, and there will be a need to take measurements at all entry and exit points along the pipeline network to ensure accurate control and settlement of accounts.
“We believe this will help make the hydrogen economy more efficient,” says Nese.
