How can gas contribute to a low-emission future?
This is a question often asked by industry and politicians alike, and one which is driving a variety of technological innovations to achieve this goal.
Power-to-gas is one of these exciting new developments, which is beginning to flex its power throughout the European Union.
An energy process and storage technology utilising existing natural gas network infrastructure to store electricity. The technology turns excess electricity, generated from renewable energy sources such as solar and wind, into renewable hydrogen gas through electrolysis of water. This effectively enables the storage of renewable power in the gas grid – a critical issue for renewable generation.
Efficiently utilising existing infrastructure
Dr Linke, an expert in the technology, says the unpredictability of renewable power generation leads to increasing uncoupling between power production and consumption and, as a result, the development of effective storage technologies is of increasing importance. This is where existing natural gas infrastructure can come in.
By way of example, existing infrastructure in Germany has enormous storage capacity available, due to the country’s huge gas consumption.
According the German Ministry for Economic Affairs and Energy, natural gas accounts for approximately 20.5 per cent of the nation’s primary energy consumption, with overall consumption of 85 Bcm in 2014, while the total length of the German gas network sits at around 510,000 km. More than 20 per cent of annual gas sales can be stored in underground storage reservoirs over a period of a month, or even years.
Given this existing capacity, surplus power from renewable energy sources can be used to power hydrogen electrolysis and feed hydrogen directly into the natural gas grid.
“The only method to store this amount of power is to convert it into a chemical substance – hydrogen – which we can then inject into the gas grid, or convert into methane,”? Dr Linke says.
“Our grid, the transmission compressor units, underground storage facilities and gas appliances are capable to operate with different gases. A blend with 2 per cent, or even up to 10 per cent hydrogen, is unproblematic. Higher hydrogen production rates can be absorbed as well if we convert hydrogen to methane.
“For this process carbon dioxide is used – preferable to renewable sources like biomass. That means that you can store an enormous amount of energy in the natural gas grid.
“Generally speaking, the storage capacity is sufficient to integrate the entire power production from wind energy of more than 30 GW installed capacity. Therefore, the natural gas grid can become the backbone of the power grid. This is what we call the convergence of two systems, or sector coupling, so coupling of the power sector with the gas sector.”?
Power-to-gas: energy storage for the future
“Many people believe we will still have natural gas in the system, despite government targets for 80 per cent renewables in 2025. And it is not a contradiction, given every energy system needs storage options and since power-to-gas is the path of step-wise decarbonisation of the gas industry,”? Dr Linke says.
“In addition, further options to improve the carbon footprint of the gas industry and to safeguard its role as a pillar of the future energy system is to increase the production of renewable gases from biomass.
“We have installed more than 8,000 biogas plants in Germany. The latest installations do not only provide the option to produce power from gas turbines but offer also the possibility to upgrade the gas to natural gas quality and to inject and storage it in the distribution or transmission grid.”?
The original power-to-gas projects are now around two years old, and presently Germany has more than 20 projects underway.
“The energy they produce is marginal compared to the gas demand in Germany at the moment. However, the idea is that future energy efficiency will see the demand for gas decline, that 10-15 per cent of traditional gas will be substituted by biomethane and an additional 10-15 per cent by hydrogen, so that a big share can come from renewable energy,”? Dr Linke says.
“If you also develop a strategy where oil is replaced by natural gas or LNG for heavy duty trucks, then the entire potential for decarbonisation in transportation and mobility is enormous, and that means we can really exceed these targets. Indeed, our next research and demo project is targeting the area of small-scale LNG appliances in transport.”?
Gas as a pillar of the energy system
Dr Linke says a big driver of the technology is that if governments want to increase the share of renewables in the energy mix, given the fact that renewables are unpredictable and the production of renewable energy is fluctuating and random, reliable storage capacity is needed.
Further, any significant increases to the share of renewable energy within the entire power system would effectively de-stabilise the system, hence the need for sector coupling.
Therefore, the overall cost of an integrated system would be lower than running two systems in parallel, which is the traditional approach.
This approach now means that the renewable terminology not only applies solar and wind, but also the creation of gas which can be put back into pipelines as storage.
Much like a gigantic renewable energy storage unit, which Dr Linke says will help secure the place of gas in the future energy mix.
“This is how we believe the natural gas industry can prosper, delivering the carbon dioxide reduction targets to the politicians while keeping gas as a pillar of the entire energy system.”?