Two very different groups promoted hydrogen as key to a move to renewable energy:
- Promoters of Solar and Wind who see storage of energy as ‘green’ Hydrogen as providing reliability and a solution to the unpredictability of Solar and Wind.
- Oil & Gas companies looking for a new, ‘blue hydrogen‘ driven, market natural gas and oil.
These two almost opposing groups promote very different solutions that have the word ‘Hydrogen’ in common, but little else. This exploration provides also background for other pages such as: Electric or Hydrogen Cars?.
- Abundant and Sustainable?
- Sources of Hydrogen On Earth.
- Energy From Hydrogen: Nuclear, Chemical or Electrical? All are possible!
- Hydrogen for Stored Energy.
Abundant and Sustainable? Facts vs Myths.
Despite being the most abundant, and lightest, element in the Universe, there is no huge supply here on Earth. The Universe is around 70% Hydrogen, but the Earth is 0.14% Hydrogen.
Hydrogen is the most abundant element in the universe, at around 70% of all regular matter (regular as in ignoring dark matter). Hydrogen and helium together account for 98%. But most of the universe is also more than 200 degrees below zero, so clearly “most of the universe” is not how things are here on Earth.
Earth is around 0.14% Hydrogen, with Oxygen (47%), Silicon (28%) , Aluminium (8%) and Iron (5%) being the most common elements here on Earth. So Hydrogen is not as abundant on Earth as some sources suggest.
During formation, the Earth was is not sufficiently massive to have retain free hydrogen (or even helium) because it is so lightweight, so instead of being 98% hydrogen and helium like the universe overall, the earth started out with zero free hydrogen and helium, as both floated off into space. The only hydrogen on earth was retained by being bound to other elements, in chemical compounds, and that hydrogen is around 0.1% of the Earth. There was no helium at all, as helium does not form compounds, so was not retained in any form. Helium, is however a by-product radioactive decay of larger elements, and almost 5 billion years of radioactive decay means we now have some helium on Earth too, but nothing like the average for the Universe. Although hydrogen atoms will normally combine with other atoms to form compounds on Earth, in space there is so more hydrogen that any thing it can combine with, that most of the atoms in the universe exist as unattached hydrogen atoms. Helium does not form compounds, so given how hydrogen atoms so outnumber all atoms other than hydrogen and helium, most hydrogen atoms having nothing left to join with.
Hydrogen is ‘sustainability neutral’ in that Hydrogen being involved says nothing about whether a particular use is sustainable or not. Hydrogen project can be highly sustainable, but so far most are not at all sustainable. This is because most hydrogen in use so far, is extracted from fossil fuels in process just polluting as just using fossils for energy. Sustainability of the project is dependent of the source of the hydrogen, as discussed below.
Even use of ‘green’ hydrogen is not without sustainability risks. Remember how the Earth has insufficient mass to have retained free hydrogen when the Earth formed? Well, the Earth still loses hydrogen every year through Atmospheric Escape, and separating hydrogen accelerates that process, so any leaks of hydrogen can be the ultimate in unsustainability, as the material not just in waste form, it is gone forever. When burning fossil fuels, at least all the atoms are still here on Earth. Although Hydrogen is the most abundant element in the Universe, here on Earth, oxygen (47%), silicon (28%) , aluminium (8%) and iron (5%) are the most commonly available elements, with hydrogen down at 0.14%. Water is hydrogen and oxygen, so simply put, the less hydrogen, the less water. And we would miss the water if we lose too much hydrogen.
Sources of Hydrogen On Earth.
Unlike the space, Sun, or Jupiter and other massive planets where hydrogen can outnumber all other atoms (91% of the Sun), hydrogen on Earth (0.14% of Earths crust) exists almost entirely bonded into compounds with other atoms. The are three types of relatively abundant compounds containing hydrogen
- water (H20), from hydrogen and oxygen
- carbohydrates, from hydrogen, carbon and oxygen
- hydrocarbons, from hydrogen and carbon
Extracting Hydrogen from anything other than water, results in also extracting Carbon, in practice, in the form of CO2.
‘Mined’ or ‘Grey’ Hydrogen.
Hydrogen powered vehicles produce no pollution, only water, but producing the hydrogen itself can be produce more greenhouse gas per km to produce the hydrogen, than staying with fossil fuels and keeping gasoline powered cars. This is because most hydrogen available now is ‘grey’ hydrogen produced from fossil fuels.
There are four main sources for the commercial production of hydrogen: natural gas, oil, coal, and electrolysis; which account for 48%, 30%, 18% and 4% of the world’s hydrogen production respectively. Fossil fuels are the dominant source of industrial hydrogen. Carbon dioxide can be separated from natural gas with a 70–85% efficiency for hydrogen production and from other hydrocarbons to varying degrees of efficiency. Specifically, bulk hydrogen is usually produced by the steam reforming of methane or natural gas.
Steam reforming is a hydrogen production process from natural gas. This method is currently the cheapest source of industrial hydrogen. The process consists of heating the gas to between 700–1100 °C in the presence of steam and a nickel catalyst. The resulting endothermic reaction breaks up the methane molecules and forms carbon monoxide CO and hydrogen H2. The carbon monoxide gas can then be passed with steam over iron oxide or other oxides and undergo a water gas shift reaction to obtain further quantities of H2. The downside to this process is that its major by products are CO, CO2 and other greenhouse gases. Depending on the quality of the feedstock (natural gas, rich gases, naphtha, etc.), one ton of hydrogen produced will also produce 9 to 12 tons of CO2, a greenhouse gas that may be captured.Wikipedia
Natural gas consists of both carbon and hydrogen. Burning natural gas, as does burning gasoline, thus produces CO2 and H20, both dirty (CO2 ) and clean (HO2)exhaust. The CO2 is the problem, and ‘mining’ hydrogen from natural gas, is effectively burning only the carbon at processing plant, leaving the Hydrogen as the clean part of the fuel. The ‘dirty’ exhaust is produced in the same in the same quantities, but is all produced at the factory where potential for carbon sequestration is increased, leaving ‘clean’ Hydrogen as fuel for consumers. The level of improvement on simply burning natural gas is questionable.
The clear point is, that while hydrogen can be greenhouse gas free fuel supply, the production of the hydrogen is not necessarily green. When those promoting coal and gas also promote hydrogen, be wary, as it can be simply a way to promote future production of coal and gas.
Note, there are some, including the government of Australia (as of 2020) which is regarded by some as the last Western holdout on the climate crisis, that have goals to become a major international suppliers of ‘clean’ hydrogen, possibly by ‘mining’ hydrogen and then working to use carbon capture and storage to offset the greenhouse penalty. Hydrogen is not necessarily at all ‘green’, and can be promoted by coal and gas companies as their future.
‘Blue’ Hydrogen has been described as greenwashing by some, a great hope by others. The central idea is that the natural gas industry will have a significantly brighter future if Hydrogen produced from natural gas can be seen to be environmentally friendly, as opposed to being a huge emitter of CO2, CO and other harmful by products as is currently the case.
The label ‘blue’ is chosen to reflect that the process in not green, but perhaps the colour is just as attractive. Producing Hydrogen from natural gas is a well proven process, which, by removing the carbon from methane using oxygen, converts natural gas into Hydrogen and CO2. Since the CO2 is produced at the point of production, it is argued that sequestration of the CO2 will be easier that with natural gas. However, successful sequestration is still a concept, rather than a practice, and has not been demonstrated to be successful at this time.
So far, since the conversion process itself requires energy and increases energy requirements, Hydrogen from natural gas results in more CO2 for a given amount of energy than if directly using natural gas.
Clean ‘Green’ Renewable, sustainable Hydrogen.
Hydrogen can also be produced using green ‘energy’ sources. Even if there was abundant ‘free’ hydrogen on earth, accessing free hydrogen, and combining it with oxygen to form ‘water + energy’ would not be renewable, even if it was sustainable. The only way to have renewable hydrogen, is to extract hydrogen from water, completing the cycle. Fortunately for a sustainable planet, that is the definition of green hydrogen.
What makes hydrogen a big deal is the diversity of its potential uses. Green hydrogen — produced by splitting water into hydrogen and oxygen in an electrolyser, using renewable-powered electricity — can exponentially expand the use of solar and wind power. Right now, renewables can be used to pump the grid, but that’s almost it. You can’t put solar or wind power into your car or a plane. However, green hydrogen created by solar and wind power has the potential to do that.
Green hydrogen isn’t a stand-alone solution. It could answer up to 24% of our energy needs by 20505, and would be used along with electrification to head towards net zero carbon emissions by 2050. But what it does do is provide a green alternative for ‘hard-to-abate’ industries that can’t adapt to electrification.Bank of America Investment Notes on ‘green hydrogen’
The above extract from the Bank of America web site (not from a ‘green’ advocate), explains ‘green hydrogen’ in a nutshell. A solution, storing energy from wind or solar or other sources, applicable for ‘hard-to-abate’ industries that can’t adapt to electrification.
Any search on ‘green hydrogen’ should give many useful results. Another useful recent page, this time from CNBC:
Hydrogen is a clean-burning molecule, meaning that it can help to decarbonize a range of sectors that have proved hard to clean up in the past
But today, 99% of hydrogen is still made using fossil fuels, usually through a pollution-heavy process
Green hydrogen, which is produced using electricity from renewable resources, could be the key to curb our carbon footprintCNBC: Green Hydrogen is gaining traction.
Other Renewable Hydrogen?
Renewable sources have also been proposed for extracting Hydrogen from Hydrocarbons or Carbohydrates. While there would still be CO2 as a by-product of extracting the Hydrogen, the same amount of CO2 should also be consumed in producing the renewable source. For example, if extracted from vegetable oil, growing the vegetables should absorb at least as much CO2 as gained from extracting the Hydrogen. The negative is that in some cases, such as a proposal to use manure as a source, do mean liberating already captured CO2, that would otherwise remain captured. Overall, while there is research on other green sources of Hydrogen, they are all indirect use of solar energy and probably inefficient compared with solar panels. For example, growing a crop, which is a form of capture of solar energy by plants, to then process organic material to extract the energy in the form of hydrogen, requires far more land and more water, than using solar cells as an source of energy to extract the hydrogen from water.
Energy From Hydrogen: Nuclear, Chemical or Electrical?
So once the hydrogen has been obtained, (hopefully ‘green hydrogen’ obtained by electrolysis using green electricity), how should it then be used to produce energy? Hydrogen can be used in Nuclear Fusion, Hydrogen Fuel cells to produce electricity, or it can be burnt to produce heat.
Hydrogen can be used in nuclear fusion reactions, the same process that powers the Sun, and powers the H-Bomb. Despite the enormous energy potential of nuclear fusion, using hydrogen for fuel is not synonymous with fusion power. In fact fusion from Hydrogen requires so much head an pressures, the H-Bombs use an atom bomb to generate the energy to trigger the nuclear fusion. So far, fusion reactors as a power source require more energy to trigger the fusion than is generated by the reactor. There is promising research, but reactors are beyond current technology, and if/when they become practical, they require very little hydrogen, and produce ample energy to extract what they do need from water.
Chemical Energy: Combustion, or Burning Hydrogen.
The chemical reaction of burning hydrogen also produces significant energy, as well demonstrated when the Hindenburg caught fire. The best use of combustion, is when heat is what is wanted. A gas stove, or a gas room heater or gas hot water heater, all can use hydrogen as the gas, eliminating CO2 as by-product of the combustion. Natural gas, CH4, produces CO2 + water (H2O) when burnt, and instead, burning hydrogen produces only water. There is one trap, and that is the plumbing that has no leaks with natural gas, can leak with the far small hydrogen molecules. Leaks aside, hydrogen can replace natural gas as used in heating.
Internal Combustion Engines: A poor alternative to fuel cells & electric motors.
Hydrogen burns or ‘combusts’ in a manner suitable for the familiar Internal Combustion Engine, and there has been over a century of experience with these engines that burn fuel and convert the heat into motion. Not only is this familiar, but unlike with other fuels, which have both carbon and hydrogen and produce CO2 as well as H2O when burnt, hydrogen produces only H2O. This is a big step forward. A familiar process, with no nasty CO2! Except, that ‘familiar’, despite all that experience is only at best close to 40% efficient, and typically closer to 20%. In the end no matter how much you refine the process, combustion primarily produces heat, and will always be losses converting heat into motion.
Fossil fuels, have a greater energy density by volume than hydrogen, which means there can be so much energy in a given space that we can live with the inherent inefficiency of using combustion to produce motion. It can be surprising to realise just how much energy is in a typically car fuel tank.
Not only are fossil fuels good in terms of energy density by volume, we have not found a better alternative to combustion to tap the stored energy. With fossil fuels, the volume is not such a problem, and we have no alternative anyway.
The lower energy density by volume means hydrogen tanks need to be larger for a given range than with fossil fuels. If you are going to burn the hydrogen in an internal combustion engine, than fuel tanks over six time (6x) larger will be required to achieve similar range to that of fossil fuel vehicle. Cars that burn hydrogen have been built, but the inefficiency of internal combustion when combined with lower energy density of hydrogen, made these cars impractical, with the range on a tank approximately 200km when powered by hydrogen.
The inefficiency result from energy lost as heat, which in internal combustion engine is quite intense. The intense heat can also lead to burning the nitrogen from the hydrogen/air mix, producing harmful, nitrous oxides, introducing pollution to what would otherwise be a clean fuel. Plus, if you use ‘green hydrogen’, instead of just digging up the fuel, making the fuel consumes energy that is expensive to waste.
We tolerate the inefficiency with fossil fuels because we have no better alternative for converting the stored energy of the fuel into motion, the size of the tanks was acceptable, and we had no alternative way to access the energy, but with Hydrogen, we do have a more efficient alternative. Which means smaller tanks, less heat, and far lower consumption of the energy used to make hydrogen.
Electrical Energy from Hydrogen: The Hydrogen Fuel Cell.
The electrical hydrogen fuel cell is far more efficient than even the best internal combustion engine, and produces electrical energy with far less heat that an internal combustion engine. Electrical fuel cells also combine hydrogen from on board tanks and oxygen from the air to produce energy, but as a more controlled reaction, the fuel cell is more efficient because there is very little heat. Less heat means less wasted energy.
The efficiency of hydrogen fuel cells combined with electric motors are the reason that car projects based on burning hydrogen ceased. There are still hydrogen based cars, but all current production hydrogen car models use electrical fuel cells, as the greater efficiency of fuel cells delivers far more range for a given amount of hydrogen. The problem of the large fuel tanks is reduced. Producing electricity in place of heat, the energy can far more efficiently propel a vehicle. Without wasted heat, or risks of pollution from burning nitrogen or other elements, the best electrical fuel cell vehicles in production can now deliver over 400km of range, or even with larger tanks 750km of range on a tank of hydrogen, although the Hyundai Nexo also claims to have the longest range of 380 miles or just over 600km. Not quite the range of the best battery cars from Tesla or the longest range Lucid Air, but still highly competitive, and the hydrogen tanks are far lighter in weight than other batteries.
If the application is not actually heating, electrical energy from hydrogen wins over combustion!
Hydrogen for Stored Energy.
How do you store Hydrogen?
Hydrogen can be physically stored as either a gas or a liquid. Storage as a gas typically requires high-pressure tanks (5000–10,000 psi tank pressure). Storage of hydrogen as a liquid requires cryogenic temperatures because the boiling point of hydrogen at one atmosphere pressure is -252.8°C.energy.gov
You can store hydrogen as a liquid, as a compressed gas, or using a hydrogen absorbing material.
Note that unlike LPG, which can become a liquid are ‘normal’ temperatures simply by compressing the gas, compressing hydrogen will not result in a liquid not matter how much compression is applied unless the temperature is kept below the critical temperature of -240°C. This means keeping hydrogen in liquid form for an extended time requires energy to run refrigeration. As with any supercooled liquid, (e.g. liquid Nitrogen), slow boiling of some the liquid and the resulting expansion of gas can provide some refrigeration, so using the hydrogen can itself aid in keeping the storage cold. This means that for a plane or a car or boat, or when used as rocket fuel, using liquid fuel is most practical if the vehicle will start using fuel immediately upon refuelling, as using some fuel helps keep the rest cold. This is the same process that can be observed with liquid Nitrogen, which although requiring to be kept at a similar temperature, can be kept cold when in an insulated container, by allowing some liquid Nitrogen to ‘boil’, thus removing sufficient heat.
Storage Comparison with Natural Gas, LPG, Gasoline and Diesel Fuel.
The main alternative to hydrogen as a chemical for storing energy are Hydrocarbons such as Natural Gas, LPG, and the core ingredients of Gasoline and Diesel Fuel. These hydrocarbons combine hydrogen and carbon into chains of Carbon, with hydrogen attached to the carbon chain.
The more carbon atoms, the longer the chain, and the higher the melting and boiling temperatures. Natural gas, which is Methane and has one Carbon (CH4). LPG which is mix of Propane (C3H8) and Butane have 3 and 4 carbons atoms. Gasoline has a mixture of hydrocarbons with between 5 and 12 carbons, diesel fuel has is hydrocarbons with between 10 and 15 carbon atoms, candle wax made from paraffin has 25 carbon atoms. As the melting and boiling temperatures increase as the chain get longer, the characteristics progress as follows:
|Natural Gas/ Methane||1||Always a gas unless kept below -150 °C|
|LPG/ Propane, Butane mix||3-4||Normally a gas, but liquid below -42°C or at pressure above 220kpa|
|Gasoline/Petrol||5-12||Normally liquid, but a percentage as vapour|
|Diesel Fuel/Distillate||10-15||Liquid, less vapour, but can become waxy when cold|
|Candle/paraffin||25||Solid at room temperature|
For internal combustion engines, a fluid is required, and liquids have better energy density than gases.
Comparison of gasses, and potential for long term storage as liquid without refrigeration.
|Gas||Boiling Temp||Liquid at Pressure?(kilopascals)||Combustion Temp|
|LPG/Propane or Butane||-42°C/-44°F,||Yes: 220kpa at room temp||1970 °C 3578 °F|
|Natural Gas/ Methane||−161.5 °C/−258.7 °F||only possible below -150 °C||1950 °C 3542 °F|
|Hydrogen||−252.879 °C, −423.182 °F||only possible below −240.21∘C||2111 °C 3831 °F|
A major use of ‘green hydrogen‘ is to add storage to electrical grids powered by renewables, acting as a giant battery. Renewable energy must be combined with storage to replace fossil fuels for electrical supply. Large scale hydrogen tanks for stored energy can be located anywhere, sometimes giving such tanks an advantage over stored hydro which is dependant on terrain, and often best located in mountainous terrain that hosts delicate ecosystems. Hydrogen tanks could be one way of restoring open cut coal mines, which are typically close to power plants and significant infrastructure for connection to the electrical grid.
For bulk storage, either compressed gas or storage using a hydrogen absorbing material are possible.
But how do you get hydrogen to the consumers for heating, or to fuel tanks for any cars, planes, and ships? One possible solution is to convert current gas pipe infrastructure from the normal methane to hydrogen. There are three challenges to be overcome:
- Pipes and valves that do not leak methane (CH4) may leak the smaller hydrogen, molecules so testing and an upgrade may be required.
- Current gas burners are optimised for LPG (propane) or natural gas (methane), but not hydrogen. Changes would be required.
- Burners for methane have to be adapted for propane, so it is likely burners will also need to be adapted for hydrogen.
For fuel tanks, research continues into hydrogen absorbing materials, but so far, the choices are:
- Liquid Hydrogen, where consumption can begin immediately and continue, or with refrigeration.
- suitable for: race cars, planes, ship engines, special purpose automobiles.
- Compressed gas, that can be stored indefinitely without refrigeration.
- all above uses, plus consumer automobiles, ‘gas bottles’, and home storage.
It is important to distinguish ‘grey’ and ‘blue’, hydrogen extracted from fossil fuels, from ‘green hydrogen’ made from water using renewable energy.
‘Green’ hydrogen one way of storing energy from intermittent renewables such as solar and wind.
Hydrogen is not a source of energy, but can work as energy storage.
‘Green’ hydrogen, obtained by using renewable electrical energy, is best used to produce electricity. Hydrogen is effectively best used as for stored energy that provides:
- Alternative, less efficient but very lightweight, battery alternative.
- Large scale storage of energy from Solar and Wind to provide on demand ‘baseload’ electrical power.