What are the chal­lenges when you want to make gas appli­ances ready for hydrogen?

Jürgen Schwalme, Head of Appli­ca­tion Regions & Certi­fi­ca­tion at ebm-papst Land­shut. (Photo: ebm-papst)

There are three main aspects here. Hydrogen is the lightest of all chem­ical elements with the lowest density. It perme­ates elas­tomers and plas­tics more easily than natural gas. This means the compo­nents in condensing boilers must have a higher density. In addi­tion, the compat­i­bility of the mate­rials must be ensured.

And the third aspect ?

The combus­tion behavior requires special atten­tion as the flame speed is eight times higher than with methane. The igni­tion para­me­ters in the combus­tion controller must be adapted to this. And because of the different calorific value and Wobbe index, the gas-air regu­lator must be designed to achieve optimum mixing and combus­tion that is as clean as possible. The normal flame moni­toring using the ioniza­tion current is also not suit­able for 100 percent hydrogen. Alter­na­tives include the tried-and-tested temper­a­ture measuring methods combined with state-of-the-art micro­elec­tronics.

How far is ebm-papst in the process?

Our estab­lished NRV 118 composite system is already designed for a hydrogen content of up to ten percent without any changes. In several inves­ti­ga­tions and field tests, we have shown that the system will be H₂-ready with a few hanges  — so it can be adapted to use with 100 percent hydrogen. Tests on temper­a­ture moni­toring are currently promising.

10%: The HS0118E1 already manages this hydrogen content in the gas mixture – without any changes. (Photo: Gernot Walter)

What changes are these?

We have increased the require­ments for the tight­ness of the gas valve and blower, and have tested and adapted the mate­rials used. The HS0118E1 Hydrogen compen­sates for the disad­van­tage of lower Wobbe index and calorific value, along with increased burner pres­sure loss. It does this using a special pre-mixing device to mix the gas and air upstream of the fan. Further­more, higher modu­la­tions can be run because the gas valve can be opti­mally controlled by nega­tive pres­sure.

What happens next?

Until the 100 percent hydrogen target has been reached, we will work with an increasing propor­tion of addi­tion. At our devel­op­ment center in Osnabrück, we are working on suit­able blowers and combus­tion control systems that ensure clean combus­tion even for changing mixture ratios. They will thereby increase the effi­ciency of the system and contribute to meeting the climate targets.