Surplus renewable energy could soon be converted to hydrogen and injected into Australia's gas networks to help decarbonise the nation's gas supply, if a trial in Adelaide proves successful.

Adelaide will next year host a trial of a new type of electrolyser, which uses electricity to split water molecules into hydrogen and oxygen.

Funded by a $5 million grant from the Federal Government's Australian Renewable Energy Agency (ARENA), the trial would inject hydrogen in small quantities into the gas distribution network owned by Australian Gas Networks (AGN).

"It turns out you can inject hydrogen into the gas main up to at least 10 per cent of the total gas in there, perhaps quite a bit higher without any modification," ARENA's chief executive Ivor Frischknecht said.

The hydrogen would be burnt alongside the natural gas molecules in the pipeline system — in gas power plants, homes and businesses.

But unlike the fuel source the pipelines were built for, the hydrogen produces no carbon dioxide — only water vapour.

"In the future we're going to have a lot of excess renewable energy on very windy days, on very sunny days, and we're looking for useful things to do with that energy," Mr Frischknecht said.

How renewable hydrogen is produced. ( Supplied: Renewable Hydrogen )

He said the Australian-first trial of so-called "power-to-gas" technology could complement other forms of storage like batteries and pumped hydro.

"What we think that will be good for is long-term storage," Mr Frischknecht said.

"You can easily store the hydrogen for days, weeks or even months and then run it through a gas peaking plant or use it to supply other types of services like heating hot water.

"A battery is really only good for seconds to hours of storage at very most, and pumped hydro you might be looking at hours through to days."

Mr Frischknecht said the hydrogen technology is also being trialled in Germany.

"It's certainly not a new idea. The challenge is that it's expensive. But we're looking to a future where renewable energy at certain times of the day is going to be free or almost free," he said.

Forecasts from the Australian Energy Market Operator show a high uptake of rooftop solar systems and other renewable energy sources mean SA could have a surplus of power on some days within a decade.

Pilot plant to be installed in Adelaide's west

The pilot plant to be installed at AGN's Kidman Park in Adelaide depot will be designed by Wollongong based company AquaHydrex.

Managing director Paul Barrett considered hydrogen to be "an outstanding energy carrier" with the potential to connect the electricity and natural gas grids and significantly increase renewable energy's storage capacity.

"This renewable hydrogen also opens up the possibility to exporting renewable energy, which Australia — with its vast renewable resources — is well positioned to exploit," he said.

AGN chief executive officer Ben Wilson said Australia's gas infrastructure could eventually store enough hydrogen to provide as much power as six billion household lithium ion batteries.

"This provides what is for all intents and purposes a 'bottomless battery' that is already in place and capable of storing and transporting vast amounts of time-shifted renewable energy," he said.

But Mr Frischknecht warned Australia's gas pipelines and appliances would need significant modification if the system was to shift to high penetrations of hydrogen.

"Years from now, if this takes off and it makes sense to put lots of hydrogen into the gas network, then we will have to change how the network operates," he said.

"The main change is changing the burners, but at some point you also have to upgrade the gas lines."