A Power system for all seasons- using hydrogen

A study by the UK Energy Networks Association (ENA) claims that production and storage of green hydrogen is a key to a sustainable energy future since it enables seasonal variations in renewable energy supply and demand to be balanced out. Moreover, it claims that this would dramatically reduce the need for so much excess generation capacity- by up to 76%.    

It says ‘a net-zero energy system that is largely based on wind but includes no green hydrogen storage could be a viable solution for the warmer months from a system resilience perspective, but in colder months the amount of wind capacity required to meet demand and maintain resilience would be extremely high and therefore less efficient. Our analysis indicates that 500-600GW of installed wind capacity would be required to deliver a resilient energy system without green hydrogen storage’. 

By contrast ‘Green hydrogen can be produced at times when renewable supply exceeds demand and unlike electricity it can be stored and discharged in large volumes for extended periods of time. Our analysis indicates that a system that includes green hydrogen storage would require significantly less amounts of installed wind capacity, in the range of 140 to 190GW and 115 to 140TWh of long-term storage via green hydrogen. Analysis of potential hydrogen storage facilities has shown that the UK has more than sufficient storage capacity to meet the the seasonal variations in demand for energy’.

It says that Britain’s wind and solar farms could generate between 60-80GW of renewable hydrogen, while the potential cavern storage volume from Britain’s salt fields ranges from >1TWh up to 30TWh. For disused oil and gas fields, the potential storage volume for individual sites ranges from ~1TWh up to 330TWh.

Overall then, ENA concludes that a system with green hydrogen and seasonal storage is resilient, providing confidence that there will be sufficient energy available during cold winter days, when consumers need it most, and efficient since it maximises the use of installed capacity. It says ‘without seasonal storage, a significant amount of additional wind capacity would be necessary to meet the winter peaks, and it is likely that capacity would be unutilised for much of the year’.

It also argues that the proposed system would be less disruptive than using heat pumps, since ‘it reduces the need for disruptive interventions in buildings that are not deemed suitable for electrification via electric heat pumps, and in the streets for network upgrades.’ That’s  a controversial idea- a new UCL study says that heat pumps can generate heat up to four times more efficiently and at half the cost compared to using green hydrogen. However, the ENA says ‘heat pumps are likely to be unsuitable for 37% to 54% of UK households and are only appropriate with the installation of highly disruptive and intrusive measures such as solid wall insulation’. 

There certainly are costs and installation issues, and it is true that heat pump heating efficiency can be poor in poorly insulated homes, making them inefficient in terms of meeting peak demand in winter. By contrast, ENA says, ‘the optimised energy system introduces flexibility because it includes the option to install alternative heating solutions that run on hydrogen, in buildings that are unsuitable for heat pumps or would require disruptive measures to make the building heat pump ready’. 

And it says, rather bravely, when considered holistically, in terms of total energy needs, ‘an optimised system that includes hydrogen for heat is much more efficient than a highly electrified system’, with it being possible to deliver hydrogen with minimal upgrades to existing infrastructure. So overall, ENA says hydrogen is cheaper to deliver, and is ‘the key enabler that allows a wind-based system to function effectively and is crucial to the creation of an energy system for all seasons’. 

While it is widely accepted that hydrogen can help with system balancing, the suggestion that electric heat pumps might not be a good idea is quite heretical. However, although it did not look at hydrogen heating, a new study of domestic heating costs for BEIS found that hybrid electric-heat pumps, that is systems combined with gas fired boilers, were significantly cheaper than electric heat pumps alone, so maybe there is some common ground!  Interestingly, it also found that installing battery or thermal storage in conjunction with heat pumps could provide some useful system flexibility, with thermal stores being the better bet at present, since they were cheaper. The BEIS study doesn’t say, but, as the ENA study suggests, hydrogen stores might be even more useful for flexible system operation.  

Wärtsilä’s new Net Zero scenarios

Renewable hydrogen certainly plays a role for balancing and decarbonisation in the ‘net zero’ scenarios for the UK, as well as Germany, India, Chile, Australia and California, produced by Wärtsilä.  It’s new ‘Front-loading Net Zero’ report claims that getting to a fully balanced 100% renewable supply is possible, and would not increase the cost of electricity- and can in fact slash total energy costs, in comparison to today. And, in the US context, it says ‘hydrogen-based renewable fuels can bridge the critical 10% – 20% gap to full decarbonisation of the electricity sector’. 

It is very optimistic about the prospects for rapid expansion. By investing in renewable power plants, it says companies are in effect buying in ‘unlimited’ amounts of green energy into the future, freeing themselves from the uncertain future of fossil fuel. Moreover, ‘we have all the technologies that we need for net zero. The transition to 100% renewable energy systems is set to accelerate at an eye-popping rate. It’s no longer a question of if we’ll make the journey, but when we’ll arrive at a decarbonised future’. 

It says that ‘in simplified terms, the capital investments needed in new renewable generation output and balancing power to deal with its intermittency are more than offset by the savings in fossil fuel use. Our country-level analysis clearly shows decarbonisation is not just possible – it is technically and commercially feasible with technologies that are already available at scale’. 

These technologies include wind and solar photovoltaic, as the main sources of primary energy, short-duration battery energy storage, Flexible thermal balancing power plants to provide firm and dispatchable capacity and sustainable fuels used in thermal balancing power plants, forming long-term energy storage. 

Sustainable fuels include ‘green hydrogen & hydrogen-based fuels, such as ammonia, methanol & synthetic methane produced from renewable sources’. But in the case of the UK, arguably a little oddly, it seems to condone 8GW of nuclear. Same for some nuclear in India. However, its hard to see how this would be used to balance variable renewables: it’s presented in their charts as inflexible base load plant. Although the ENA scenario (above) for the UK also retains a bit of ‘left over’ tech like this from the old agenda, its main concern and aim, as with Wärtsilä’s scenarios, is with flexibility. Though, to be fair, it is conceivable that conventional large nuclear plants could contribute to that, if used for hydrogen production, while Small Modular Reactors might be able to load follow, or even supply heat to meet local loads- at some cost.  

However, it seems more likely that renewables will provide the cheapest route forward across the board, as a new study from Oxford INET indicates. It says that ‘if solar photovoltaics, wind, batteries and hydrogen electrolyzers continue to follow their current exponentially increasing deployment trends for another decade, we achieve a near-net-zero emissions energy system within twenty-five years. In contrast, a slower transition (which involves deployment growth trends that are lower than current rates) is more expensive and a nuclear driven transition is far more expensive.’ And it says its fast track approach will not be expensive, given the progress of supply and storage technology, with, for example, hydrogen electrolyzers having ‘highly favorable trends for cost and production’.