Green Hydrogen Breakthrough Uses Energy from the Sun, Water from the Air

Australian researchers have found a way to combine solar PV and water harvested from the air to produce low-cost green hydrogen, and are gearing up to put the zero-emissions fuel to the test in cars on Sydney roads.

The green hydrogen production system,  which is being tested at a pilot scale at the University of Newcastle Institute for Energy and Resources (NIER) precinct, is based on another University of Newcastle developed technology, the Hydro Harvester.

The Hydro Harvester is an atmospheric water generator which absorbs water from the air at night using silica gel. During the day, solar energy is used to produce hot, humid air – the hotter the air, the more water it holds – which is then cooled using ambient air as a heat sink to extract water.

The project was late last year awarded $330,000 from the NSW Physical Sciences Fund to prepare a prototype for commercial trial, and aims to deliver a technology that can be used at a residential, community, or industrial-scale to produce water at less than 5c per litre.

And while the team behind the Hydro Harvester, led by Professor Behdad Moghtaderi, primarily developed it to provide access to water for drought-stricken developing nations, they have since put it to use in a novel approach to green hydrogen production.

In this case, the air-harvested water gets fed into an electrolyser which – as University of Newcastle Research Associate Dr Andrew Maddocks explains in this video – uses solar electricity to split water molecules into oxygen and hydrogen, the latter of which can be used in fuel cells.

Professor Moghtaderi said the pilot plant was currently producing one kilo of green hydrogen a day, but that a commercial-scale system could produce thousands of kilos per day.

Most importantly, however, the technology is demonstrating some key advantages of cost and efficiency that could rapidly boost Australia’s domestic hydrogen production capabilities.

“By harvesting water from the air we aren’t placing added pressure on potable water supplies for drinking and household use, which in climates like ours is a long-term consideration for viability,” he said on Friday.

But the biggest advantage of using the Hydro Harvester is that water produced is so pure, it can be directly fed into the electrolyser.

“Sea water, wastewater or even tap water require multiple treatment steps to reach the level of purity required in electrolysis,” said Professor Moghtaderi. “By removing the need for treatment, we can dramatically reduce hydrogen production cost.”

Prof Moghtaderi says the Uni Newcastle team and its industry partners were currently in discussions with an international car manufacturer to demonstrate the green hydrogen at one of their Sydney-based locations.

“We’re very excited to test our first-of-its-kind green hydrogen fuel in hydrogen cars. We’re hoping to commence testing by the end of the year,” he said.

“Hydrogen is such an attractive fuel because its only by-product after oxidation (e.g. in a fuel cell or in an internal combustion engine) is water. It’s also the most abundant element in the universe – it makes up three-quarters of all mass on earth.”

The Uni Newcastle team has also partnered with Southern Green Gas on the technology, to work on ways to combine green hydrogen with carbon dioxide (also extracted from the air) as a ‘carrier,’ to readily transport the renewable fuel.

This part of the project, which has been funded by ARENA, combines CO2 with the green hydrogen to make renewable methane. This allows for both easy transport – via existing natural gas pipelines – and versatility; at the point of use, the green methane can be converted back to hydrogen or used as-is as a renewable form of natural gas.

The green methane technology will be demonstrated at a gas hub near Roma in Queensland where it will produce approximately 620kg of hydrogen per year, converting it into 74 gigajoules of methane that can then be injected into the existing network of natural gas pipelines across the East Coast gas grid.

“We’re leveraging Southern Green Gas and their partner APA Group’s expertise and energy infrastructure to transport green methane through existing infrastructure, which will significantly accelerate the adoption of this greener energy option. We expect to have this running by late next year,” said Professor Moghtaderi.

“At scale, renewable methane has the potential to be a significant source of Australia’s future natural gas requirements, and technologies like ours can help to realise this potential,” he said.

Source: Renew Economy
Date: Sep 9, 2020