HYDROGEN – The dawn of a heating revolution?
25th Oct 2016
The chemical element Hydrogen is the most common element in the periodic table and sci-entists estimate that it makes up 75% of the mass of the entire universe. The name hydrogen comes from the Greek name for water, because it only produces water when it is burned. Hydrogen may be easily found on other planets but here on earth it is bonded to other elements, such as oxygen, which then forms H20- water. Hydrogen gas is colourless, odourless, tasteless and non-toxic. Hydrogen gas was first produced artificially way back in the 16th century.
That’s the science lesson over. So why am I talking about Hydrogen, how does it relate to the heating industry?
We all know that we need to reduce the UK’s carbon emissions and to do so we must decarbonise heat, it’s tricky but necessary if we are to meet our climate change obligations. In our quest to reduce carbon, alternative fuel sources are being explored. Hydrogen- a ‘green gas’ is one of those alternative sources.
The gas grid currently delivers gas into the homes of over 85% of the UK population and there is little appetite to simply abandon gas and start again with a new system, not to mention the enormous costs involved.
UK Government has recognised the potential contribution of “green gas” in helping the UK meet its renewable energy targets. As a consequence considerable resources are being spent on ensuring better and more efficient delivery of gas, particularly in the Research and Development of biogas. Very recently however hydrogen has come to the fore. The Leeds H21 project is an exciting study where the city of Leeds would be changed over from natural gas to hydrogen, with the hydrogen made on Teesside, and the resulting carbon dioxide buried deep under the North Sea. This hydrogen could provide both heat and transport.
So is hydrogen the future fuel for the heating industry?
The automotive industry now has several hydrogen models on the market but a hydrogen car isn’t powered by an internal combustion engine in the same way that your current car is powered by petrol or diesel. A hydrogen car is basically an electric vehicle but instead of using power stored in batteries to run its electric motors, it generates its own electricity on the move. In effect this is a car that has the engine replaced by a fuel cell (a mini power station) that mixes the stored hydrogen from the fuel tank, with oxygen from the air to generate electricity. This is then used by the electric motors to make the car move.
Advancements in the heating sector may not have been as exciting as those made in the automotive industry but the prospect of replacing traditional combustion of fuel with hydrogen may just start to raise the pulse of the heating engineer. This prospect could become a reality using similar technology as the automotive industry-fuel cells, a device that converts the chemical energy from a fuel into electricity through this chemical reaction with oxygen or another oxidizing agent.
What is a fuel cell?
Fuel cells were first created in 1839 by William Grove. Grove was a British physicist, who discovered that four large cells, each containing hydrogen and oxygen, could produce electricity. NASA used fuel cells in the 1960’s to provide power during its space flights. It was essential for space travel to use a system that did not emit pollution so fuel cells were an ideal solution. As a result of NASA’s successful use of the fuel cell, private industry began to recognise its commercial potential.
A fuel cell is an electrochemical energy conversion device. The other electrochemical device that we are all familiar with is the battery. A battery has all of its chemicals stored inside, and it converts those chemicals into electricity too. This means that a battery eventually "goes dead" and you either throw it away or recharge it.
With a fuel cell, chemicals constantly flow into the cell so it never goes dead -- as long as there is a flow of chemicals into the cell, the electricity flows out of the cell.
There are many fuel cell types, but the principal ones are the proton exchange membrane (PEM) fuel cell, and solid oxide fuel cell (SOFC).
PEM fuel cells operate at relatively low temperatures, have high power density, and can vary output quickly to meet shifts in power demand. PEMs are well-suited to power applications where quick start up is required, such as cars or forklifts. They are ideally suited to using hydrogen. These offer the opportunity of a rapid response power station in every house.
SOFC fuel cells operate at very high temperatures, have high electrical efficiency, and have been used in to large stationary applications such as office buildings and retail stores. Interestingly they can also burn natural gas.
How are they fuelled?
Fuel cells need hydrogen as a feedstock, how can we supply the hydrogen? Well, as said above , in the long term the hydrogen supply to either the heat or automotive sector should be low carbon, but in the meantime some manufacturers are doing this locally as part of a fuel cell generator.
The opportunity for use of fuel cells in the residential market is via high performance micro combined heat and power units (microCHP’s). These produce both heat and electricity.
Fuelling the future
In the longer term we envisage hydrogen being produced on a larger scale either through natural gas reforming, or by renewable processes, and then distributed to our homes in place of natural gas.
The question is how much hydrogen can be used and in what manner? It is possible, within existing gas quality guidelines, to mix up to 2 per cent of hydrogen into the blend that flows through the gas grid. Some studies suggest that up to 20 per cent might be feasible – remember this makes the overall mix of gas “greener”. However, the Northern Gas Networks feasibility study is assessing 100 per cent hydrogen through the gas grid. Their Leeds 21 study is arousing considerable interest within the industry on the basis that it envisages using the existing gas grid, conventional heating systems such as central heating in the home saving about ¾ of the overall carbon emissions. It was launched on the 11th July 2016, and suggests a detailed route map of how to save approaching 1m tonnes per year of CO2 . A recent study for DECC has shown real enthusiasm by UK appliance manufacturers for the potential offered by hydrogen. The next few years should be exciting for the gas industry.
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