In a guest blog for Energy Futures Lab, Charlotte Hartley examines the flexibility value that gas vectors and gas networks can provide to support the future energy system, the subject of the latest white paper published by the Sustainable Gas Institute.

Natural gas provides an important function in maintaining the flexibility of energy systems, helping them meet daily and seasonal variations in demand. But ongoing attempts to reduce greenhouse gas emissions and boost the market share of renewable energy sources cast doubt on the future role of gas. There is debate over whether flexibility can be maintained as existing gas networks are repurposed to support decarbonisation efforts. This debate is the focus of the Sustainable Gas Institute’s fifth White Paper review.

As nations strive to meet global climate change targets, such as the 2015 Paris Agreement, we’re seeing electricity take on a greater share of consumer energy demands. More and more of this is being generated from renewables, with gas generation acting as a backup to support the electricity system. The increasing interdependency between gas and electricity networks furthers the need for flexibility. Here, flexibility refers to the gas network’s ability to meet changing supply and demand over time and spatial scales. This could be by varying the rate of gas production, varying the pressure within gas pipes, storing gas for future use, or it could mean buying gas from other countries. A good example of gas network flexibility occurred on 1st March 2018 in the UK, when around 300GWh of energy was shifted from pipelines to meet extra demand on this uncharacteristically chilly day.

Challenges

When considering the future of gas networks, we first need to consider what kinds of challenges may arise. We will likely begin to see more from alternative gases, such as hydrogen or biomethane, carried either in pipelines of their own or blended with natural gas. These blends produce fewer greenhouse gas emissions, but also store less energy. But that’s only part of the story, says Dr Jamie Speirs, a research fellow at the Sustainable Gas Institute and lead author of the White Paper series. “The energy density of that gas and the way in which that gas network is operated can both reduce the energy stored.” He explains that the pressure within pipelines of alternative gas networks could be four times lower than their natural gas equivalent. Similarly, the storage capacity could be less than half.

Current natural gas networks are becoming increasingly interconnected, which is reducing the costs of shifting gas to manage seasonal changes in demand. It is, however, also reducing gas storage capacity in many regions. But the hydrogen and biomethane gas networks of the future are expected to be fragmented into smaller, less connected systems, with limited international trade. This might create an urgent requirement for underground storage, in order to maintain flexibility. “That’s certainly something we see in the proposals for demonstrations of hydrogen networks that are currently on the table,” says Dr Speirs.

The future of flexibility

So, how might flexibility change as gas networks evolve to become more climate-friendly? The review considers this question on a national, international, and global scale.

Modelling studies have found that overall costs are similar for hydrogen, electricity, and hybrid gas networks in the UK and Europe. Interestingly, costs may even be lower where electricity and gas networks are integrated. A greater use of renewables and a decreased, strategic use of gas can result in overall lower system costs for the same greenhouse gas emissions target. Gas networks can therefore continue to provide flexibility with a relatively low environmental impact. However, a more important contribution from gas networks to a sustainable future could emerge from low-carbon gases, like hydrogen and biomethane.

In some countries, this is just around the corner. An impressive 70% of Italy’s gas pipelines are currently ready to transport hydrogen. This was successfully tested on a smaller scale, by using a natural gas and hydrogen blend to power a pasta factory. “Our vision for the network as a whole, I suppose, is that over time it could be a segregated hydrogen network on the one hand, and a low-carbon biomethane gas network on the other,” says Camilla Palladino, Executive Vice President of Corporate Strategy and Investor Relations at Snam, an energy infrastructure company based in Italy.

Other nations, however, have ample opportunity for low-carbon gas networks, but simply lack the infrastructure. Brazil’s sugar cane industry could provide a steady source of biomethane gas, but this will rely on improving connections between sugar cane plants and existing gas networks. Brazil’s energy mix is already dominated by renewables. Its impressive geography of large rivers, substantial rainfall, and small mountain plateaus provides the perfect canvas for hydroelectric power generation. Gas could, therefore, play a key role in providing flexibility, while supporting the continued expansion of renewable sources.

What next?

The White Paper review highlights future avenues of research when it comes to improving our understanding of gas network flexibility. Firstly, safety demonstrations of low-carbon gas networks constitute a valuable opportunity to better understand how well they can provide flexibility. Whole systems modelling is another useful tool, allowing us to compare and contrast the flexibility value provided by low-carbon gas networks with alternative options for maintaining flexibility. And finally, the authors argue that examining how the switch to low-carbon gas networks will impact greenhouse gas emissions is an area deserving of more attention.

The flexibility services traditionally provided by natural gas are undeniably important for the functioning of energy systems. However, gas networks will clearly have to undergo considerable changes to meet targets for mitigating climate change. Making these changes could allow continued flexibility to meet traditional variation in demand, while also rising to the new challenges brought about by increasing electrification and the growth of renewables. Through using ongoing research to inform energy policy, the hope is that we can navigate the balancing act of making gas networks kinder to our environment, without compromising the value of their flexibility.