Engineering the hydrogen home

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Engineering the hydrogen home

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"A semi-detached show-home on the outskirts of Gateshead may seem an unlikely location for a technology revolution. But when this outwardly unremarkable looking building opens its doors in the coming weeks, it will mark a key moment in the UK’s accelerating transition to a zero-carbon economy.
When the programme began, it was as much about ruling out hydrogen as an option as anything else, but as the project team worked its way through key questions on everything from the feasibility of hydrogen appliances to public acceptance, the case for putting the gas at the heart of the UK’s energy transition grew stronger. “As the programme’s progressed we’ve discovered everything is feasible and found a way over various hurdles.” “Everyone’s beginning to realise this really could be a very real possibility.”
One of the keys to this has been the input from some of the biggest names in domestic heating, including the UK’s market leading boiler manufacturer Worcester Bosch, which has developed a prototype hydrogen-ready boiler that’s about to be put through its paces in a series of major trials.
Worcester Bosch CEO Carl Arntzen told The Engineer that when the company began seriously looking into hydrogen around five years ago, it set out to answer two key questions: can it be safely burned in a domestic boiler, and is it possible to make a hydrogen boiler that’s the same size as an existing system?
Artntzen’s team began by looking at what the differences between hydrogen and natural gas might mean in terms of engineering fundamentals.
An early win was the realisation that hydrogen and natural gas have a broadly similar Wobbe index. This is a measure of the amount of heat energy within a given volume of gas. Artnzen explained that whilst hydrogen has a lower calorific value than natural gas, its density is much greater, meaning the same volumes of hydrogen and natural gas will give roughly the same heat energy.
This provided early confidence that not only could a hydrogen boiler be physically the same size (and therefore wouldn’t require future customers to reconfigure their homes) but that it would also be compatible with the existing gas network. “The size of the existing gas network is roughly OK and supplies the same amount of energy whether you supply 100 percent natural gas or 100 per cent hydrogen,” he said.
Nevertheless, the properties of hydrogen did present a number of engineering challenges. For instance, it has a much faster flame speed when compared to natural gas which, said Arntzen, created some initial challenges around how to control the combustion process.
The team also encountered some early problems with “flashback”, a result of both the flame speed and shorter flame height of hydrogen. “The ignition was lighting the fuel upstream of the burner so we were getting a backfire,” he explained. “It was perfectly safe but of course your boiler going bang every few minutes is not really desirable!” Both of these findings prompted a redesign of the burner face to more effectively manage the flow of the gas within the appliance.
Another key challenge was around monitoring and controlling the flame. Whilst existing domestic boilers sense the presence of a flame by detecting the electric current generated by carbon molecules within the gas, the absence of carbon molecules in hydrogen meant they had to look at different solutions for flame detection.
At this point, said Arntzen, it became clear that it wouldn’t be possible to simply convert existing gas boilers to run on hydrogen, and the concept of a hydrogen-ready boiler was born, a system that would initially run on natural gas but which could be switched over to hydrogen with a minimum of fuss. “It goes into your house and burns natural gas, then, four or five years after you have it installed when you get notified that your area is going to be converted to hydrogen we come back in, quickly change a few components, and that boiler’s ready to burn hydrogen.”

The Full Article can be read here:- ... ogen-home/

(The posted readers comments after the 'Engineer magazine' article are not quite so positive....)
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