Something in the water

Imagine a fuel source that could be burned to release energy, yet whose only by-product is water. Something non-toxic, non-corrosive and endlessly available.

Plenty have, including 19th century sci-fi writer Jules Verne (of 20,000 Leagues Under the Sea fame) whose Mysterious Island (1874) was powered by an element that “will furnish an inexhaustible source of heat and light, of an intensity of which coal is not capable”.

That utopian element may be Hydrogen, and today many consider it to be the single most important fuel for the energy transition. The most abundant element in the universe (almost all of it was formed in the moments after the ‘Big Bang’), it does not naturally occur on Earth. But ‘green’ hydrogen can be generated from electrolysed water using renewable energy – and that is exactly what Petrofac is helping Infinite Blue Energy achieve in Western Australia.

“People think you can just roll up with an electrolyser, plug it in - and make the world a greener place,” says Michael Czarnecki, Concept Development Consultant and FEED (Front End Engineering Design) project manager for the Arrowsmith Green Hydrogen plant. “If only it were that simple!”

When complete the plant will use a combination of wind and solar power to produce 25,000kg of green hydrogen every day. But the engineering and logistical challenges involved in getting it to that stage are immense. How do you work around the intermittent power supply? Or store and move in bulk a product that’s highly flammable and 14 times lighter than air, for example?

ARROWSMITH PROJECT

The Arrowsmith Hydrogen Project is a proposed green hydrogen production plant being developed by Infinite Blue Energy near Dongara in Western Australia, 320 kilometres north of Perth.

The plant will have a production capacity of 25 tonnes of green hydrogen per day, derived from renewable energy sources, including solar, wind and water. The plant includes around 100megawatts (MW) of solar power, supplemented by 114 MW of wind generation capacity, both generated on-site.

BALANCING ACT
“We engineer what’s called the Balance of Plant – thinking every detail through,” says Michael. “From the power that generates the electricity to electrolyse the water, to the roads, cables, substations, piping integration, nitrogen, buildings for people to shelter and work in. Safety and environment issues as well as regulatory requirements have to be considered. How you move, store and sell the final product. It all has to be engineered.”

Take the choice of power. Arrowsmith’s coastal setting is great for onshore wind and gets plenty of sun. But both sources are intermittent and fluctuate on a daily and seasonal basis – even in Australia’s sunniest state, the sun doesn’t shine 24 hours a day and the wind does not always blow. To be able to guarantee sufficient, reliable and continuous power, the design included a connection to green power from the grid – both to import and to export surplus power, creating an extra revenue stream and a way to mitigate low demand or market prices for Hydrogen. They also specified a battery storage system, to be used in case of emergency when there is no power to allow safe shutdown and to keep the essential power for lights, water and communications for up to eight hours

Water, a scarce resource, was another challenge. Electrolysers need demineralised water, and lots of it. To generate 25 tonnes of hydrogen a day you typically need more than 20 times that amount of water. The project is sited near an aquifer, but the water has to be stored, pumped to a water treatment package to remove minerals and salts and pumped into the electrolyser (the salts clog up the cells). About half of this water will be rejected as a concentrate. The concept design envisaged evaporation storage ponds covering a huge area of more than 400 square metres, but the Petrofac team applied a systems design approach that did away with them completely, sustainably returning the valuable water to the local environment while reducing the amount of reject water.

Anticipating ambitions to expand hydrogen production beyond the capacity of the freshwater aquifer, which would mean desalinating seawater (an energy hungry process), they realised that if they could find a way to conserve more water it would pay both environmental and financial dividends. The team retested the aquifer water, using the more detailed understanding of its composition to optimise the design of the water treatment plant and reduce reject water. What’s left will be reformulated so that it can be safely discharged into the ground water via a natural lake.

But perhaps the most complex engineering design challenges involved storage, as Michael explains:

“Hydrogen is the smallest molecule in the periodic table - it’s the least dense. As a result, it has one of the lowest energy densities of all conventional fuels by volume one kilo of hydrogen needs much more space than 1kg of methane. It’s like comparing feathers with bricks. And that makes storage a problem,” he says.

The colours of Hydrogen

THE STORAGE CHALLENGE: AN UNORTHODOX SOLUTION
Most of the Arrowsmith-produced hydrogen will be sold as road fuel. This means that the hydrogen has to be stored and exported either in liquid form or as a high-pressure gas. The first solution considered was gas-storage. “Arrowsmith needed a storage buffer of 2-4 days in case of production issues. To store the hydrogen as a high pressure gas we would have needed thousands of small diameter storage vessels to meet that, it just wasn’t practical. So the challenge was to increase the density. Part of the solution is to compress the hydrogen. It was like trying to fill up a balloon with hard walls, with mechanical design limitations – you can’t compress indefinitely.”

“We proposed a piping system to store the hydrogen as a high pressure gas to keep the volume down. We laid a few kilometres of large diameter 24-inch steel piping arranged in a line packing approach (like a busy airport security queue) – in effect hundreds of small vessels joined together and routed to a local truck loading station. The other benefit using piping code was that we could design the system to be at full design pressure and you would not require as many pressure relief valves as multiple pressure vessels require for example.”

Storing the hydrogen as gas was not enough, cryogenic – liquid – storage was considered. Dry Hydrogen gas can be liquified and stored in insulated tanks at minus 253 degrees centigrade (the temperature at which the hydrogen gas converts to a liquid). Designing a process that keeps the hydrogen liquefied involved working with industrial gas liquefaction companies to engineer a liquid hydrogen plant along with it specially designed low temperature vacuum insulated tanks.

Compression and liquefaction of hydrogen is an energy intensive process, but is the only practical way to convert the abundant renewable power into hydrogen and to store it. The hydrogen then acts as the energy carrier.

STORAGE FACTS

The energy stored in one kilo of hydrogen is equivalent to the energy stored in a gallon of diesel. A kilo of hydrogen at standard atmospheric conditions occupies 11 cubic meters of space or 2,420 gallons (the size of a small office). One kilo of compressed hydrogen at 370barg (the unit of measurement of gauge pressure) can now be stored in an 8.5 gallon tank, and a kilo of liquid hydrogen can be stored in a 2.75 gallon tank.

IN SHORT SUPPLY
Until very recently green hydrogen production was a niche sector, with few original equipment manufacturers (OEMs). A key task for Petrofac was to identify and engage early with the suppliers it was going to need, reducing supply chain and lead time risk. These included wind turbine and solar PV manufacturers, electrolysis vendors and hydrogen liquification specialists.

“Petrofac acts as an integrator, we can be technically neutral,” says Michael, “which means we can generate competition in the market and with that, cost savings. We have a lot of expertise in procurement and supply chain management.”

The team included engineers from every discipline – process engineers, electrical engineers, instrument, piping and layout specialists, mechanical engineers, civil / structural engineers, metallurgists and risk and safety engineers. “We mobilised an interface engineer in Australia for two or three months to sit with the client and liaise between all parties, including local contractors for the civil scope of work.”

As countries accelerate plans to tackle the climate emergency, green hydrogen is likely to feature prominently when it comes to decarbonising residential heating, transport and flexible power generation. Petrofac’s engineering and project management expertise, and experience gained in delivering one of the world’s leading green hydrogen FEED projects, means the Arrowsmith plant is likely to be the first of many commissions to come.

And as a guide to what a hydrogen-powered future might look like, it seems Jules Verne’s vision in Mysterious Island is already becoming a reality on the tiny Orkney islands off the north-east of Scotland. They have their own wind and tide-powered hydrogen plant, and are looking to fuel their ferries and light aircraft, as well as homes and businesses, with zero-emission hydrogen. They are even looking at producing a local gin using hydrogen as a fuel. Utopia indeed.

SAFETY FIRST

Hydrogen is a potentially highly hazardous substance. Highly flammable, it burns with a pale blue flame that’s nearly invisible in daylight. And because hydrogen flames radiate little infrared heat, but lots of ultraviolet radiation, if you were very close to a hydrogen flame you wouldn’t actually feel a sensation of heat so you don’t get warning that you may be about to walk through a flame which could lead to serious injury.

Liquid hydrogen has different potential hazards, as the temperature at which it is stored can cause cryogenic burns. Leaks from piping or vessels can create a large vapour cloud that could quickly expand from liquid into gas and ignite.

Petrofac’s safety management framework in the design phase identified and modelled all major accident hazards and identified prevention measures, and specific engineering safeguards were built into the design. For example, all piping was fully welded to prevent leaks and metallurgists advised on the material for the pipes, as hydrogen embrittlement can cause some metal components to crack and fracture. Gas detectors were carefully placed in places where the hydrogen might accumulate (the lighter-than-air gas rises rapidly). Fibre optic cables can be used to pick up tell-tale vibrations that are emitted by a leak, and ultra-violet flame detectors used throughout.

SAFETY FIRST

Hydrogen is a potentially highly hazardous substance. Highly flammable, it burns with a pale blue flame that’s nearly invisible in daylight. And because hydrogen flames radiate little infrared heat, but lots of ultraviolet radiation, if you were very close to a hydrogen flame you wouldn’t actually feel a sensation of heat so you don’t get warning that you may be about to walk through a flame which could lead to serious injury.

Liquid hydrogen has different potential hazards, as the temperature at which it is stored can cause cryogenic burns. Leaks from piping or vessels can create a large vapour cloud that could quickly expand from liquid into gas and ignite.

Petrofac’s safety management framework in the design phase identified and modelled all major accident hazards and identified prevention measures, and specific engineering safeguards were built into the design. For example, all piping was fully welded to prevent leaks and metallurgists advised on the material for the pipes, as hydrogen embrittlement can cause some metal components to crack and fracture. Gas detectors were carefully placed in places where the hydrogen might accumulate (the lighter-than-air gas rises rapidly). Fibre optic cables can be used to pick up tell-tale vibrations that are emitted by a leak, and ultra-violet flame detectors used throughout.