The UK government has committed to meeting internationally agreed carbon neutral targets and as natural gas (used in domestic boilers) is a major contributor to carbon emissions, a low carbon alternative such as hydrogen, used in existing equipment, is a likely replacement in the future.

Leading boiler manufacturers including Worcester Bosch, Viessmann and Baxi are currently working on prototype heating boilers that will run totally on hydrogen, with some promising results.

Boilers that can run on 20% hydrogen and natural gas are available from Worcester Bosch and Viessmann right now, but developing boilers that would operate on 100% hydrogen are a little way off for full production, and there are other obstacles to overcome.

When hydrogen is burned it produces only water vapour and no carbon dioxide, so the possibility of delivering it into homes via the existing gas network is a very appealing concept.

Hydrogen is easy to produce and abundant in the natural world, being a constituent part of water along with oxygen (H2O), though it does take a lot of energy to separate the two. Advocates of using the fuel argue that it would be an ideal replacement for natural gas as the existing national pipework infrastructure could be utilised, while the next generation of gas appliances would be clean and efficient.

An easy and inexpensive switchover for home owners

From a user perspective burning hydrogen in their boilers would mean they don'�t notice any difference, and the only modification needed would be to the boiler itself, not the expensive equipment needed to heat a property with heat pumps and solar.

One school of experts say that there'�s no reason why repurposing the gas network and burning hydrogen in domestic heating boilers cannot be achieved, while others argue that there are engineering risks and uncertainties associated with swapping and using the existing gas network, burning hydrogen as a domestic heating fuel.

Whatever way you look at it, low carbon heating methods will in future become an essential means of achieving emissions targets and these will include technologies such as heat pumps, solar, biomass and hydrogen boilers. We'�re already headed down that path.

Existing residential boilers have already received substantial legislation, including the banning of the older type of non-condensing boilers. All new boilers must be at least 90% efficient, and there is to be a complete ban on gas boilers installed in all new build properties from 2025 and new natural gas boilers will no longer be for sale by 2035.

Ongoing trials

In Northumberland hydrogen boilers from Baxi Heating and Worcester Bosch were installed in 2020 into the first UK homes to demonstrate the technology'�s efficiency. These prototypes were trialled in specially built demonstration houses. Hundreds of tests have been completed to research and demonstrate the safety and efficacy of converting homes and gas networks to hydrogen.

The Northumberland trials aim to demonstrate how the existing gas networks can be easily repurposed to safely carry 100% hydrogen.

Homes fuelled entirely with hydrogen heating were part of a pilot scheme officially started in July 2021. Two semi-detached homes based at Northern Gas Networks' innovation site in Gateshead were powered entirely by hydrogen boilers for demonstration purposes, developed by Baxi Heating and Worcester Bosch. Hobs, cookers and fires are hydrogen-powered, and these are being interchanged so that different manufacturers can test and showcase their prototype devices and get consumer feedback.

Following this study, a hydrogen heating trial has begun in Wales which will test a hydrogen hybrid heating system. This system combines a Worcester Bosch hydrogen boiler alongside an air source heat pump, which will be managed using a smart electronic control system. It will automatically switch between the heat pump and the hydrogen boiler.

The National Grid in partnership with organisations such as OFGEM, SGN and the Scottish Government are trialling hydrogen use on the grid to help prepare for the UK's low carbon future. The pilot project involves over 300 homes in Scotland fitted with hydrogen boilers, cookers and appliances, to be fed with hydrogen gas at no extra cost by the end of 2022. It is being anticipated that eventually 1,000 homes could be included in the four-year trial.

Viable alternative

Given that most UK homes currently use gas boilers for heating, the economic viability of replacing all of them with solar and/or heat pumps is not considered achievable by many experts. If hydrogen ready boilers can be made available, along with sufficient supplies of the gas through the existing network, then it is though this would be the most viable alternative solution.

Pros and cons

Whilst hydrogen has some challenges to overcome, for example because it the lightest element, it is prone to leaking, it is highly inflammable and has no taste or smell without inserting additives. It takes as much energy to produce it as if gives off, therefore unless it is 'green hydrogen'� (produced by renewables like wind turbines or solar, off peak) it'�s not all that eco-friendly. Blue hydrogen gas is produced by burning natural gas.

There remain many barriers to the universal adoption of low carbon domestic heating of any stripe. Although technological developments look promising and manufactures are taking up the challenge, at the present rate of travel, according to the Environmental Audit Committee, it will take hundreds of years to achieve it.

In addition, the Committee on Climate Change has estimated that the cost of switching every UK home to a low-carbon heating system, of one form or another, would cost an average of �26,000.

So, hydrogen fuel offers one potential solution if the barriers can be overcome, because it uses the current gas infrastructure, a system that'�s connected to 8 out of ever 10 homes. Therefore, if the barriers to hydrogen'�s use can be overcome, if it can be produced cheaply in sufficient quantities '� as the oil moguls would hope - then it could be a real winner. Only time will tell which set of experts' arguments prove correct, the protagonists or the detractors.

UK government launches plan for a world-leading hydrogen economy