Recent talk of a net zero target for UK carbon emissions by 2050 has put domestic space and water heating back in the spotlight. Gas boilers are likely to be banned in new homes built after 2025, with a combination of heat pumps, better insulation and ventilation reducing the demand for heating energy.
However, the gas industry is now responding to the threat to their business with innovative technology and proposals to use 100% hydrogen gas boilers. This provides an alternative zero carbon solution for both new homes and the millions of existing homes that currently use a gas boiler for heating (85% of UK households). Older homes are a challenge to decarbonise as many are not suitable for heat pump technology without significant spend, of the order of £20,000 – £30,000 per home.
As a result of manufacturers efforts, a new generation of gas boilers could soon be with us that can be used both with 100% hydrogen and natural gas (which is primarily methane, CH4). Assuming the natural gas network switches over to pure hydrogen in the 2030s and 2040s then potentially most gas boilers could be switched to using the new fuel with a simple adjustment to reconfigure it (maybe even automatically in some cases).
One of the UK’s leading boiler manufacturers. Worcester Bosch, has recently presented a prototype hydrogen boiler which could be used with existing central heating systems to heat homes whenever the switch to hydrogen occurs (See press release 14 Jan 2020: https://www.worcester-bosch.co.uk/about/news/making-essential-steps-towards-a-hydrogen-fuelled-future).
BDR Thermea, owners of Baxi boilers have also been active in developing a hydrogen boiler solution (See press release 25 June 2019: https://www.bdrthermeagroup.com/en/news/hydrogen). They also mention one of the other attractions of converting the gas network to hydrogen: the ability to operate small scale hydrogen fuel cells to generate electricity for use in the home. With access to a hydrogen supply there is potentially no need to have an electricity grid connection. One to watch in coming decades.
There are several technical challenges that manufacturers will need to overcome over the next few years. These include:
- Gas tightness: Hydrogen is a smaller molecule than natural gas (methane) so small changes to the way pipes are manufactured and sealed may be needed to maintain current gas leakage rates.
- Flame detection: Hydrogen burns with a near invisible flame so boilers designs will need other ways of detecting that the flame is actually burning. That could be by detecting its ultra-violet (UV) emissions.
- Condensate: Modern condensing boilers already produce condensate (water) but hydrogen boilers produce a greater volume, and this will need to be allowed for within new designs.
There will no doubt be other minor design tweaks to allow effective and efficient use of both natural gas and hydrogen, but boiler manufacturers sound increasingly confident that they can deliver the required products. In the meantime, work is going on within the gas grid to replace old cast iron gas mains with polythene pipe. This would allow every single one of the country’s gas pipes to carry hydrogen rather than natural gas.
The jury is still out on the best solution for net zero carbon emissions from homes and it will be fascinating to watch the gas boiler industry battle it out with heat pump manufacturers as both look to seize the opportunity.