Hydrogen - The Great Leveler
- Jul 19, 2021 3:05 am GMT
In Part I we saw how Hydrogen is used. In Part II now, we examine how Hydrogen is created and how some countries are seizing this opportunity to join the new energy boom
Hydrogen – green Hydrogen, is changing the global energy mix. A clear picture of winners and others will emerge by 2030 and beyond, but the stakes are so high already that countries are jockeying for space in this new energy race to be a major producer and supplier of green Hydrogen
Countries like Chile, Kazakhstan, Mauritania, Greece, Portugal, Spain and Denmark - not known as energy producers appear in this remarkable list. Big energy producers of fossil-fuel today like Saudi Arabia, Oman and Australia are joining this new race in earnest too. Hydrogen is presenting an opportunity to those who were net users till yesterday to be net producers tomorrow and for the producers of yesterday to re-align with the demands of the new energy scenario to stay relevant tomorrow
This re-arrangement of world energy matrix is occurring because countries are rushing to meet Paris Climate Accord targets and green Hydrogen figures high in the list. And the world needs a lot of it!
HOW MUCH HYDROGEN IS REQUIRED?
In 2020, 87 million metric tons of Hydrogen per year was produced, with less than 5% from renewable means. Its main use being in industry (oil refining and fertilizers mainly with food processing, etc. making up a tiny rest)
By 2030, 212 million metric tons of Hydrogen per year demand is expected to achieve net-zero. This extra Hydrogen demand is in addition to the industrial uses and will be from newer uses of green Hydrogen in power generation, transportation and building/heating
By 2050, 304 million metric tons of Hydrogen per year demand is expected which will be around 5% of the global energy demand (In 2050, total global energy demand is expected to be 18,757 Mtoe = 785 PJ ~ 6,544 kg of H2, so 304 mmtpa / 6,544 mmtpa = 4.7% ~ 5%)
Green Hydrogen produced using renewable energy is a clean fuel. It can be used as feedstock in current areas of application like industry, oil-refining and fertilizers as well as, as an energy vector in newer applications like power generation, transportation and heating to de-carbonize large
HOW IS HYDROGEN PRODUCED?
Overall there are many Hydrogen production methods, mainly these are:
- Electrolyzers running on renewable energy (also called power-to-gas) - green H2
- Electrolyzers running off grid electricity - yellow H2
- Steam Methane Reforming using natural gas (a fossil-fuel) - grey H2
- Coal gasification (a fossil-fuel) - brown H2
- Bio-gas from gasification / pyrolysis of bio-waste - turquoise H2
With variations on above, there are many more:
Hottest topic for Hydrogen creation these days is an Electrolyzer. This is because this is the only method that produces green Hydrogen
ELECTROLYZER PROJECTS IN THE PIPELINE
Electrolyzer space is running hot. Countries are setting up Electrolyzers now in order to reap the benefits of becoming Hydrogen suppliers in the future. In this fast-moving sector new project announcements come at a fast pace. Fathom this for a flavor of the trend (in ascending order):
If these reach fruition, that will be a whopping 217 GW! A few observations jump straight out:
- USA and India are missing. These economies, especially the US, have been dabbling with Hydrogen for some time (Fuel Cells, etc.), but on a national scale Hydrogen missions have only recently been announced in both, and no doubt both countries will plan own Electrolyzers accordingly
- As mentioned, new countries not associated with energy production appear in the list
- A number of projects plan to ship Green Ammonia. As an alternative to shipping Hydrogen, this has advantages as it is a Hydrogen carrier (Ammonia has more Hydrogen in a molecule than Hydrogen itself, 1 molecule of NH3 has 3 atoms of Hydrogen, versus H2 which has 2 atoms of Hydrogen) and is easier and cheaper to transport than Hydrogen, which needs cryogenic tanks or high-pressure cylinders plus cracking NH3 to obtain H2 is not difficult. However, a new process invented in Australia achieves the result even more easily at ambient temperature!
Electrolyzer is at the heart of the green Hydrogen revolution
In order that an Electrolyzer can rise up to this lofty expectation as above many questions need to be answered beforehand:
- Can the size and scale of Electrolyzers reach such yield and rate of Hydrogen production that the world will need?
Today a 1 MW Electrolyzer can output on average 300 kg or 0.3 tons or Hydrogen per day (this is dependent on number of factors eg efficiency of electrolyzer, operating hours). Several such Electrolyzers stacked together can reach a desirable size.
So, 217 GW x 1000,000 x 365 x 0.3 / 304 x 100% = 7.8% ~ 8%. Even with so many GW Electrolyzers as tabulated above, amount of Hydrogen produced will be only 8% of annual expected requirement in 2030.
Clearly, the world will need even more Electrolyzers to cater the massive demand for green Hydrogen. Will Electrolyzers rise to the occasion or will there be alternatives?
It is likely that blue Hydrogen will fill the gap, that is, Hydrogen production using SMR with CCS. In other words, to serve the huge demand the next best alternative to being carbon-negative will be to go carbon-neutral till commensurate green Hydrogen production comes online
- Are the materials used in the making of Electrolyzer efficient, stable, robust, economical and abundantly available?
This is an important consideration given attempts of some countries recently to thwart the trade of rare earths putting global batteries manufacture in jeopardy. Fortunately, in the manufacture of Electrolyzers the materials used as electrolytes (alkaline solutions or polymers) and electrodes (platinum, titanium, etc.) are easily available, stable and robust
- Do the input costs, R & M costs and service life of Electrolyzers support the business case of Electrolyzer use?
Electrolyzers, regardless of which type (see Electrolyzer Types below), are durable, have long lives, low input costs and low maintenance costs. So once the offtake agreements for sale of Hydrogen are in-place, the business case is expected to stay strong throughout
- Is the price of Hydrogen produced by Electrolyzer today competitive to price of Hydrogen vis-à-vis grey Hydrogen (cheapest today)?
Today there is a clear recognition that price of green Hydrogen must get competitive to grey Hydrogen before a large-scale switch to green Hydrogen will occur. Governments have come up with catchy slogans that are precise and inspiring at the same time. For instance, Australia has “H2 under 2” – that aims to bring price of Hydrogen to less than AUD 2 per kg, America has “1-1-1” – aiming for $1 for 1 kg in 1 decade called the Hydrogen Shot launched by the Biden-Harris Government
Until recently, owing to expensive electricity costs, Electrolyzers were not seen as popular platforms for Hydrogen production. With Solar and Wind crashing electricity prices, a key input cost to Electrolyzer, the focus has now shifted to bringing capital costs down. Over last 2-3 years, capital cost of Electrolyzers have dropped 75%. As research continues and size of Electrolyzers increases this will in turn lead to corresponding declines in capex (ala trajectory followed by Solar PV 10-12 years ago), which will drive down Hydrogen price/kg
It wouldn’t be a surprise if these goals are met well before target dates – Morgan Stanley thinks it could happen in 2023!
There are three types of Electrolyzer technologies:
- Alkaline – In alkaline electrolysis, two electrodes submerged in an alkaline electrolyte solution (such as potassium or sodium hydroxide) are kept apart by a non-conductive porous membrane or diaphragm. When electricity (from Solar or Wind) is applied at the electrodes and water is pumped in against the negative electrode, water (H2O) molecules take electrons to make OH⁻ ions and an H2 molecule. These OH⁻ ions travel through the electrolyte solution toward the anode, where they combine and give up their extra electrons to make water, electrons, and O2. These Electrolyzers operate at less than 100°C. Steps are:
- Anode: 4 H2O + 4e– → 2 H2 + 4 OH-
Cathode: 4 OH- → O2 + 4 e– + 2 H2O
Overall: 2 H2O → 2 H2 + O2
- Anode: 4 H2O + 4e– → 2 H2 + 4 OH-
- PEM – Proton Electron Membrane - In PEM electrolysis, the two electrodes are separated by a conductive solid polymer membrane. When electricity (from Solar or Wind) is applied at the electrodes, negatively charged oxygen in the water molecules gives its electron, resulting in protons, electrons, and O2 at the anode. The protons or H+ ions travel through the proton-conducting polymer towards the cathode, where they take an electron and become neutral H atoms and combine with other H atoms to make H2 molecule at the cathode. PEM electrolyzers usually operate at 70°–90°C
- The design of a PEM electrolyzer has the electrodes sandwiched between two bipolar plates, which transport water to them, transport product gases away from the cell, conduct electricity, and circulate a coolant fluid to cool down the process
- Anode: 4 H+ + 4 e– → 2 H2
Cathode: 2 H2O → O2 + 4 H+ + 4 e–
Overall: 2 H2O (l) + 4 H+ + 4 e– → 2 H2 + O2 + 4 H+ + 4 e–
- Solid – In this type of Electrolyzer, the electrolyte is a solid ceramic material. It is typical of such Electrolyzers to operate at very high temperatures (500°C-800°C) in order to work with the dense material, Zr O2 (Zirconium Di-oxide). At these temperatures hot steam is fed into the porous cathode. When voltage is applied, steam at the cathode combines with electrons from the external circuit to form hydrogen gas, H2 and negatively charged oxygen ions, O2- which move through the electrolyte to the anode where they combine with other ions to form O2
- Anode: 2 O2– → O2 + 4e–
Cathode: H2O + 2 e– → H2 + O2–
Net Reaction: 2 H2O → 2 H2 + O2
Alkaline Electrolyzers have a lower capital cost but efficiency-wise they are inferior to PEM which are more compact and with smaller area, can use higher current to produce same amount of Hydrogen. They are quicker to startup and react better to inherently variable Solar/Wind electricity. Solid-oxide Electrolyzers are newer technology and work at high temperature and therefore have even higher efficiency reaching 90+%
ELECTROLYZER BY NUMBERS
An Electrolyzer working in reverse becomes a Fuel Cell and vice versa. Switching the cathode and anode of a regular Fuel Cell in theory gives an Electrolyzer.
In Hydrogen by Numbers – Part I – Uses, we saw that an FC will oxidize 1 kg of Hydrogen completely, using 8 kg of Oxygen resulting in 9 kg of water vapor and a lot of energy
Doing reverse implies 9 kg of water plus energy will produce 1 kg of H2. Energy required is electrical, not thermal. So, upon electrolysis:
9 kg of water + 50 KWH of energy = 1 kg of H2
1 liter of water + 5.56 KWH energy = 111.1 g of H2
See section Hydrogen Equations for calculation of electrical energy required
Hydrogen produced must be captured ASAP as it tends to escape into the atmosphere rapidly. Using Ideal Gas Law, at standard pressure and temperature (1 atm, 0 ℃):
1 mol of H2 = 22.4 liters at STP
Extending the same law, it implies that at normal pressure and temperature (1 atm, 20 ℃),
1 mol of Hydrogen has a volume of 24.04 liters, (using V = nRT/P = 1 mol x 8.314 J/mol deg Kelvin x (273.15 + 20) Kelvin / 101.32 kPa)
1 mol of H2 = 24.04 liters at NTP
Since 1 kg of H2 is 1,000 g or 1000 / 2 = 500 mols of H2 = 500 x 24.04 = 12,020 liters
1 kg of H2 = 12.02 m3 (12,020 liters) at NTP
Total energy required in electrolysis must account for the latent water vapor energy plus overpotential (extra energy to overcome various electrochemical resistances in the cell), which causes a drop in electrolyzer efficiency. So, 142 MJ/kg / 3.6 = 39.4 KWH energy is required to get 1 kg H2. (since 1 KWH = 3.6 MJ). This is the theoretical minimum requirement
Electrolyzer efficiencies of up to 86% for PEM Electrolyzers and up to 70% for Alkaline Electrolyzers are observed today. Therefore, energy required for electrolysis
= 39.4 / 70% to 39.4 / 86% = 56 to 45 KWH, say 50 KWH on average
It is recognized by most Governments around the world now, how critically important hydrogen is to achieve a lower-carbon energy mix. Several countries are now in mission mode to join this energy re-alignment. With the right actions now, these countries will be able to shape their respective economies to meet Paris Climate Accord targets and by starting early will be able to achieve this transition smoothly
There will be new leaders in the new world of energy tomorrow and they will be ones who tap this emerging opportunity now
- grey Hydroghttps://www.esig.energy/electrolyzer-cost-performance-and-durability-status-and-prospects/?unapproved=7131&moderation-hash=35347ff90a7dcabfd65cf58ebca2de14#comment-7131en
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