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