Written by: David McGuire – Gripfast Consulting
Over the last two years our advisory and project management team have been working with clients to develop business cases and to deliver state-of-the-art hydrogen production facilities. The facilities would not only be used for research and development but also to produce hydrogen to fuel long-haul vehicles.
To date most hydrogen vehicles are being used in mining and industry where vehicle speeds are low and terrain relatively flat. The use of hydrogen buses for regular, long-haul transport on the open highway is relatively new in Australia and would require the production of buses in Australia, or import them from overseas, the later option posing a range of dilemmas given the current geopolitical situation.
Central to the production of hydrogen via electrolysis is an electrolyser, a highly complex piece of equipment that, because of the rapid expansion of the hydrogen industry, has long lead times for purchase. Electrolysers are available in prefabricated, containerised modules to reduce CAPEX and installation costs. Through the process of electrolysis, an electrolyser uses electrical energy to convert water into its composite parts – hydrogen and oxygen. The oxygen is returned to the air (or can be captured and stored for use elsewhere) and the hydrogen is stored in pipeline assets for use. When the electrical energy comes from a renewable source, such as solar or wind power, the hydrogen has a small carbon footprint.
Electrolysis is energy intensive, with the vast majority of energy used in the electrolyser stacks, with the remainder used for compression, chilling, cooling and the balance for the plant requirements.
There are three main types of electrolysers: proton exchange membrane (PEM), alkaline, and solid oxide. These electrolysers function in slightly different ways. The solid oxide electrolysers operate at a much higher temperature (above 5000C) compared with alkaline and PEM electrolysers (up to 800C) and are still classed as ‘emerging’ technology, though they have the potential to become much more efficient than PEM and alkaline . Of these three main electrolyser types, the two which are the most commercially viable at present are Alkaline and PEM electrolysers, and it these two that were considered in detail.
Alkaline electrolysis employs a cathode, an anode, and an electrolyte-based solution of caustic salts, that are corrosive and toxic. When voltage is applied, water decomposes in the alkaline solution. Hydrogen is formed at the cathode and oxygen at the anode. Between the two electrodes is a membrane that only allows negatively charged ions of oxygen and hydrogen (OH-) to pass through, separating the gases. This group is called a cell. The cells are typically assembled in series in a “cell stack” that produces more hydrogen and oxygen as the number of cells increases .
The electrolyte is liquid, which means that the alkaline electrolyser requires more peripheral equipment, such as pumps for the electrolyte, solution washing and preparation. Alkaline electrolysers have the lowest capex on a nominal capacity (tonnes H2 per hour) basis but have relatively high operating and maintenance costs .
The alkaline electrolyser system, operating costs are increased compared with a Proton Exchange Membrane (PEM) electrolyser in several ways. When an Alkaline electrolyser is shutdown, for whatever reason, it requires a complete nitrogen purge to stop cross contamination of oxygen and hydrogen during shutdown / standby procedures. Further, due to its near-atmospheric operating pressure, it can only be turned down to 80 to 90 per cent of its operating capacity without affecting the life of the stack. Alkaline electrolysers use 30% potassium hydroxide solution as an electrolyte which hydroxide has inherent chemical handling hazards, increasing operational and maintenance costs compared to water.
Proton Exchange Membrane (PEM) Electrolysers
PEM electrolysers reverse the fuel cell principle and do not require liquid electrolyte. Water is pressed through a stack of two electrodes and a polymer membrane. The membrane only allows positively charged hydrogen protons to pass through. Platinum is usually used as a catalyst in the cell and the thin cells (membrane and a pair of electrodes) can be arranged in stacks to achieve better performance. PEM electrolysers are relatively small, which makes them more attractive. They can produce highly compressed hydrogen for decentralised production and storage at refuelling stations, offering flexible operation, including the capability to provide reserve and other grid services.
Compared with alkaline electrolysis, PEM electrolysis has the advantage of quickly reacting to power fluctuations typical of renewable electricity generation. They are able better able to ramp up and down in response to changes in the demand and changes in the cost of electricity. Further, they can operate at up to 160 per cent of capacity for limited periods if this has been factored into the design of the system. This technology is often used for distributed, modular and/or solar powered systems because the equipment is low-maintenance and delivers high quality gas suitable for use in vehicle fuel cells.
The following matrix compares the two technologies on key selection criteria:
Table 1. – Electrolyser comparative analysis
The CAPEX for Alkaline electrolysers is currently slightly less but PEM technology is reducing in cost. A 2017 European report estimated that an equivalent size PEM electrolyser is 20 per cent more expensive than an Alkaline electrolyser with this difference estimated to reduce to 10 per cent by 2025 . Recent investigations have noted that as the market for electrolysers increases there is greater variability in cost between vendors rather than between electrolyser types. Overall, the difference between the total cost of all plant costs associated with the electrolyser, including the electrolyser, are minimal at the same capacity rating .
However, the final choice between either PEM or Alkaline Electrolysers is affected by the supplier inclusions, the quality of the available water and the electricity source . These variables will need to be considered and validated in the approach to market. Currently, the procurement lead time for PEM electrolysers is slightly longer.
OPEX: there are notable differences in operational costs between the two electrolysers. PEM electrolysers have a distinct advantage as they are able to better respond to fluctuations in the electricity market, they have lower maintenance costs, and they consume less energy per kg of hydrogen produced. Further, a PEM electrolyser is less complex to maintain and does not require electrolyte maintenance and replenishment.
Durability and sustainability PEM represents latest ‘commercially viable’ technology and due to its construction will last up to 5-years longer than equivalent capacity Alkaline electrolysers. Both types of electrolysers require high quality water and a power source, however, PEM has lower overall power use and the ability to switch rapidly in response to the market cost of power.
As noted earlier, oxygen is a by-product of hydrogen production. It is possible to ‘capture’ the oxygen and store it for sale or alternative uses. Oxygen capture would increase the value of the project as a circular process – using recycled water and the ‘waste products’ of hydrogen production. However, it is not part of the core aims of the project and adds to the complexity and overall costs. ‘Capturing’ the oxygen would require equipment to process and store. The strategic working group felt that this was an option that may be considered by another UQ group at some point in the future.
This explains the science however hydrogen production is plagued by myths that must first be dispelled before projects such as this can gain popular support.
The following are some of the key myths that the team had to address with a wide range of stakeholders, many of whom were operating on old, antiquated opinions:
Myth: Hydrogen cell technology is new and untested
Fact: This myth is almost comic if given some context. The Diesel engine was invented in 1893, the Petrol (Gasoline) engine in 1876 and the first gas engine in 1858. The hydrogen fuel cell in fact predates them all being first described in 1838 by Sir William Grove, so twenty years before the first internal combustion engine and over fifty years before the first diesel engine.
Hydrogen was first produced by electrolysis in 1789 and was first used as a “fuel” when it was produced as a constituent of coal gas in 1792. The modern oil industry has roots dating back to 1847, so is youthful by comparison.
Myth: Hydrogen is too dangerous – it can explode and burn easily – remember the Hindenberg.
Fact: This is the greatest myth of them all.
The Hindenburg airship disaster and the explosive power of the hydrogen bomb (also known as the H-Bomb) have done little for hydrogen’s public safety image; but it’s an unwarranted reputation. The 1937 Hindenburg disaster, in which an airship lifted by hydrogen gas caught fire, killing 36 people, is still held up as an example of the element’s explosive properties.
It is thought that the accident was caused by a spark due to static electricity build up, that occurs when all aircraft travel through the air. The resulting visible fireball as the Hindenberg crashed was caused by the flammable aluminium and cellulose based dope covered fabric burning. Somewhat unbelievably the hydrogen bags were in fact made of a highly flammable material themselves. Unquestionably the hydrogen on board did burn but this is not what is seen in the film footage, as hydrogen burns with a clear flame. Clearly the use of hydrogen was a factor, but it was not the root cause, nor was it what’s seen as the flaming fireball.
Myth: Hydrogen is a renewable resource.
Fact: Hydrogen is the most abundant element, but using it first requires capturing it in its pure form. Once you have hydrogen, the combustion and electrochemical processes used to produce electricity from it are “clean” — in that these processes do not emit carbon and mainly result in water vapor as a by-product.
Hydrogen can be produced from burning natural gas and coal, among other sources often creating considerable carbon in the process, however given the advancements in renewable sources of power, ‘green hydrogen’ can be produced without the carbon emissions of old technologies.
Engineers have also considered ‘blue hydrogen’ which is produced from natural gas with carbon capture and storage, and ‘pink hydrogen’ which is produced using nuclear power, as other low-carbon options. Cost and resource availability as well as customer preferences and public opinion are major drivers in whether these options are viable in a region.
Myth: Green Hydrogen production isn’t really clean or green!
Fact: Hydrogen does not occur naturally as hydrogen in any great quantity, although it is an abundant element. As such, it is synthesized through a very simple process which can be powered by a variety of means. The latest electrolysis methods, if powered by renewables, are completely clean, meaning hydrogen production can only be considered green as the power source feeding the process. Green hydrogen is produced from renewable energy, such as wind and solar, meaning it remains a complete zero-carbon fuel source.
Myth: Hydrogen is an expensive renewable option.
Fact: The cost of hydrogen is coming down year on year as production is ramped up. The cost of production has dropped by nearly 50% over the last five years alone. Moreover, with the rising price of natural gas, the relative cost of green hydrogen produced from electrolysis is approaching price parity in some regions. It must also be considered that most green fuels cost more due to their carbon neutrality compared to fossil fuels. The fossil fuels have the extraction cost, refining cost, distribution cost and some notional duty, yet have no cost associated with the pollution they cause Therefore at some level fossil fuels only appear cheaper because we do not associate the environmental cost with the purchase cost.
Myth: Hydrogen is difficult to transport and store.
Fact: It is certainly true that hydrogen is more difficult to transport and store than diesel fuel, but this is also true of virtually every other alternative fuel. Diesel is quite a hard act to follow, but since it causes considerable pollution the idea that it is some sort of ongoing benchmark is false. Hydrogen therefore needs to be compared with other clean fuels.
In addition to the above hydrogen can be combined with other compounds so that they become a hydrogen carrier medium such as ammonia or methanol. Perhaps counter intuitively, although this increases their weight per unit of energy carried, it massively reduces their volume per unit of energy carried, approaching that of diesel fuel. If hydrogen carriers are used the transportation and storage of hydrogen can be much easier and cheaper than many people claim.
Myth: Using hydrogen at scale will require a whole new energy infrastructure.
Fact: This is fundamentally untrue. There was a concern that hydrogen could infiltrate the steel of pipelines, making them brittle. But experiments and analyses of existing pipes have shown that in softer grades of steel, this happens very slowly, and happily much of the long-distance pipeline grid in across Australia is made from such soft steel, with very thick walls, which can safely hold hydrogen for several decades.
For low-pressure distribution in urban areas, many States across Australia have been replacing metal gas pipes with yellow polythene pipes – which are butt-welded end-to-end for a perfect join.
This was started as a project to eliminate all the leaks in a natural gas distribution system, but it now turns out to be the perfect preparation to transmit hydrogen to businesses and homes.
Myth: Transport can be fully electrified so why worry about hydrogen fuelled vehicles?
Fact: Some forms of transport can’t be fully electrified. Airliners need to carry enough energy to take them thousands of miles, which is impossible using batteries for the foreseeable future. Liquid green or blue hydrogen, or fuels based on hydrogen, can be a solution to clean air travel.
Cargo ships will struggle to cross great oceans on battery power, and again hydrogen can be the answer, in the form of ammonia, which is easy to store as a liquid, and can be used directly as fuel in slightly modified diesel engines.
On the ground, vehicles powered by hydrogen fuel cells have some advantages over battery EVs. Hydrogen is very quick to refill – in minutes, rather than hours for a battery charge. It is also far lighter than batteries, an important asset when it comes to a vehicle’s range and decreasing road damage. This makes it appealing to replace today’s diesel heavy transport such as trucks and some trains, with Daimler, Volvo and Scania already looking at the technology
Myth: If hydrogen is so fantastic then why wasn’t it used years ago.
Fact:In the 1874 novel The Mysterious Island, Jules Verne imagined that water, decomposed by electricity into its primitive elements, would “one day be employed as fuel, that the hydrogen and oxygen which constitute it… will furnish an inexhaustible source of heat and light.” We’ve only recently started to make Verne’s vision a reality because, unlike ready-to-burn fossil fuels, clean hydrogen isn’t freely available: you have to put in energy to free it from its watery prison.
What’s changed over the last 10 years is that renewable power has become cheap, the technology of electrolysers has matured, and we have finally woken up to the profound global peril of greenhouse gas emissions.
Like any new technology it takes time and investment to make the dream a reality. Hydrogen power is no exception. It should be considered an additional tool in our renewable energy, clean power solution tool box.
Out team is proud to be working with some of the greatest and most innovative minds in the World on these projects. If you require any further information regarding renewable energy projects please reach out to our team.