The Electric future meets its Partner in Hydrogen Grid and Storage
by Peter Bruce and Alistair Rennie
14 Mar 2020
Why is a Hydrogen Grid needed for the UK?
The graph below shows that domestic heating gas demand peak in Winter is 2.5x the electricity grid energy load (industry & power adds another 1x with more equal balance through year) and transport is 2x (N.B. 0.5x is aviation).
Thus if all this was switched to renewable electricity as some suggest it would mean expanding the electric grid and generation capacity to 4-5x current capacity (even with efficiency/ insulation improvements) which is just not credible. It is also not cost effective as there would be a 50% surplus generation capacity for 50% of the year. So how can the problem be solved cost effectively?
Hydrogen Storage +Grid Capacity Benefits
In the future there will be major overcapacity of renewable electricity in the summer (due to capacity to cover winter peak and because PV as a major renewable electricity provider produces 4x as much power in the summer as winter). Batteries can cope with some capacity matching across a day but not over a month to a year. Annual storage needs to solve the heating need in winter rather than expensive peak capacity investment and Hydrogen fits best for the next few decades as we have most of the infrastructure already in place. So the oil and gas currently being used in Heating and the (long distance) Transport sectors can be replaced by renewable hydrogen produced from electrolysis, stored over from summer thus saving grid capacity (Note EV cars best for short range transport).
Many claim hydrogen is quite inefficient compared to using electricity direct but the key is the storage efficiency of hydrogen using old North Sea gas fields to store it along with the existing grid capacity to deliver it. Summer surplus electricity will be very cheap once we have tripled renewable electricity capacity to cope with daily/winter peaks, EVs, etc making the relative inefficiency of conversion to hydrogen (c. 0.5p/kWh today) for storage cost effective.
How would this work for Heating and Transport?
The hydrogen can be retrieved from old gas fields in the winter and used for heat, transport and power at small to large scale to match demand using the existing gas grid. Garages would just take hydrogen from the grid and clean/compress it locally for delivery to longer range vehicles as quickly as a normal fossil fuel fill.
In the UK replacing 'Natural' Gas with hydrogen in the UK's gas distribution system is the least hassle, cheapest, and most universal way to decarbonise home heating and long distance transport as we aim for our Net Zero climate change objective. Short distance cars/local deliveries could be carried out by renewable Electric Vehicles (EVs) but for longer distance/high usage vehicles the recharge times/battery weights/costs are such that hydrogen will be competitive.
Hydrogen (which with a few additions including a colourant and odorant is called H-gas) is a viable generic fuel for future convertible heating boilers and existing CHP and heat networks to drastically cut emissions quickly and cost effectively as most existing buildings would be expensive and very inconvenient to upgrade to Passiv Haus standards. This covers us for the decarbonising phase to 2040/50 with competition beyond that between electricity and gas heating to determine longer term investments. Hydrogen has advantages in that it can be used in fuel cells or internal combustion engines which produce basically a water exhaust 2H2+O2=2H20.
The number of Hydrogen powered cars, trucks and buses is increasing and Hydrogen powered trains are already operational in Germany.
How are the techniques needed being proven in UK?
The gas grid is compatible with hydrogen (coal gas was 50% hydrogen) and heating equipments can be converted from methane to hydrogen as any grid changeover occurs regionally.
HyDeploy1 Trials are currently testing the gas grid at Keele University with 20% hydrogen mix in methane (CH4) with the hydrogen generated from an ITM electrolysis unit. The next stage in Hydeploy2 over 4years is to deliver hydrogen in gas mains to areas in the NW and NE at 20% hydrogen mix levels with it generated in bulk from reforming methane with carbon capture and storage underground (CCS) with some possibly from Electrolysis.
The long term plan would be to convert to 100% hydrogen generated from renewable electricity which will need the 'hydrogen-ready' heating equipment built into home heating from the early 2020s. Companies such as Worcester-Bosch are already designing heating boilers that can do this. As low carbon electricity becomes more available at cheap offpeak times then heating and long range transport can be switched from gas and oil to renewable generated hydrogen.
But how safe is a hydrogen network?
• Hydrogen is as safe as natural gas but different
• A Colourant is added so you can see the flame and an odorant so you can smell leaks
• Existing gas grid is suitable so low investment cost vs new electricity grid capacity
• Meters will need to be replaced with the system checked
• Gas appliances will increasingly be Hydrogen-ready or modified or replaced
Due to its low density but higher energy per kg hydrogen can replace natural gas in the UK gas distribution network with very few modifications. The iron mains replacement programme means most of the UK gas network is now plastic and ideal for hydrogen, and it is worth remembering that Town Gas used for 150years up to 1977 was about 50% hydrogen. The low density of hydrogen means it diffuses upwards quickly and readily escapes. Even if it catches fire it rises very quickly and is somewhat less likely to create burns/explosions spreading sideways like methane. Conversion work will address local choke points, transmission HP lines, change meters and equipment, and safety check all building systems and appliances. The various safety studies overseen by Regulators see plus and minuses compared to NG, but overall hydrogen is as safe as NG. Additionally there is no risk of carbon monoxide poisoning and unlike methane , hydrogen is not a greenhouse gas in climate change terms so leaks are not a climate issue. UK appliance manufacturers (for example Worcester Bosch and BAXI) are already working to design, build and certify hydrogen ready and hydrogen appliances.
Will hydrogen deliver Net Zero and Paris targets?
Hydrogen is part of the answer for the UK alongside renewable electricity from wind, PV, wave/tidal and nuclear (at least in short term). Renewable biogas from waste/biomass will also exist but it will be best placed to be used in Aviation and maritime transport to help them achieve zero carbon solutions. The UK has excellent gas storage in old gas fields or salt domes so will be well placed in winter to export renewable gas made with surplus cheap electricity in the summer.
By Peter Bruce
and
Alistair Rennie (Sustainable Energy Consultant YOenergy)
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From GLD Challenge Magazine 2019-20
