Hydrogen boilers, Hydrogen fuel cells and the future of energy (UK focus)
25 January 2020
Hydrogen isn't just the most abundant fuel in the known universe, it is the most abundant element. Hydrogen is in everything, from the water in our seas to traditional fuels like gas and coal. Hydrogen can be used for very clean combustion with zero point of use emissions, it can be stored in bulk and it can produce high temperature heat as well as clean power for automotive and buildings.
So why don't we use Hydrogen more?
For the purpose of clarity I will attempt to stay on the domestic end of the energy industry, Hydrogen is much more commonly used in manufacture and the chemical field but the advantages for domestic and commercial buildings are the main interest for us.
Difference between Hydrogen Fuel Cells and Hydrogen Boilers
Hydrogen fuel cells have been widely used for commercial and military uses for over fifty years, they are a way to produce very clean electricity with a basic store of pure gas. Some fuel cells can be used for heat generation as well as power but the main uses are remote or mobile energy creation.
Current available domestic technologies
FCS have an array of fuel cells, mostly used outside of the home for monitoring, telemetry and marine purposes. Although some of their products could be used in the home they are prohibitively expensive, their main USP is the lack of emissions
A Hydrogen boiler is (as of yet) not available but highly regarded as one of the next big steps towards a Carbon nett zero emissions society. A Hydrogen boiler will be (for now) and adapted natural gas (Methane) boiler, there are some key differences in the combustion characteristics of Hydrogen but for the most part the boiler manufacturers don't need to completely redesign their flagship models.
A Hydrogen boiler adapted from a Methane model will need to have a UV sensor for the flame, Hydrogen flames produce no electricity like burned Methane. In modern Natural gas boilers there is often a electrode that creates a micro voltage from the flame, this process is basically ionised Carbon particles in the flame which conduct a current to the valve or control board to prove the gas is being burned. If the sensor does not have a voltage then it is either faulty or the gas is not ignited so the valve is closed to prevent unburned fuel from being sent into the appliance and out the flue.
Hydrogen when burned does not create a voltage because there is no Carbon in the combustion process, it may yield small amounts of Nitrogen Oxides but will predominantly produce simply water vapour. The flame is also invisible so a system must be implemented that uses the Ultraviolet, Infrared or similar to safely detect and control the combustion.
A standard gas boiler produces around 3.5 litres of condensate for every 30kw of heat (when running at optimum efficiency), Hydrogen boilers will produce vastly more due to the residual vapour as described above. Although the extra condensate volume should not be a problem if the boiler is installed correctly there are thousands of cases a year in the UK of freezing or blocked condense outlets due to installer error.
Nox - Nitrogen Oxides can be present in Hydrogen combustion and are a hot (sorry) topic in pollutant and emissions regulations worldwide, the combustion must be controlled to specific parameters around the flame shape, temperature and the airflow. More so than with current gas boilers the combustion and maintenance will be crucial and it should be the case that all boiler owners are required to provide certification annually to show they have been checked by a registered professional.
Hydrogen burns hotter and faster than Natural gas but as long as it is controlled and stable the majority of modern components should be compatible
Hydrogen is more prone to leakage, it is much smaller and lighter so any weak points in the supply line is more at risk with Hydrogen or a mix of Hydrogen and Methane than with pure (ish) Methane as we have now. Any potential leak will go up quick though as it is so light, unlike Propane for instance that will sink and cause a potentially dangerous trap in a basement or home the Hydrogen will try and find its way to orbit as soon as possible. If you're unlucky enough for it to be trapped at high level inside the property it will be an explosive risk so as with Methane an odour will be added. It is likely that stricter tightness legislation will be required as a small leak for a Natural gas pipe could release a lot of Hydrogen in a short time before it is detected.
Hydrogen does not react with the main components of a gas boiler, one thing worth talking about is that it does absorb into Aluminium under certain circumstances. With enough heat (over 100°c) and some pressure Hydrogen is naturally drawn into the metal to form a Hydride. I don't think it is likely that this process could occur in a domestic appliance as the pressure is not great enough but it is interesting nonetheless.
Future domestic Technologies
Although currently there are no Hydrogen combustion boilers, many of the big names are working on near future releases: